Electronics

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Exploring Electronics on a Budget

This page shares components and materials for exploring electronics and building interesting things on a budget. These are explored in our engineering, computing, and applied technology workshops in our face-to-face locations and online workshops.
We cover:

Electronic Circuit Fundamentals including resistors, capacitors, transistors (more useful than relays), diodes, physical user interface elements: switches, knobs, sliders and other controls, and basic interactive elements: LEDs, buzzer, speakers
Advanced Electronics including digital logic, integrated circuits (ICs), low cost microcontrollers, large scale integration (LSI) components such as application specific ICs (ASICs), and very large scale integration (VLSI) components including CPLDs and FPGAs
Sensors & Microcontrollers & Embedded Systems includes sensors, communications (serial, SPI, I2C, RF/RC, NFC, WiFi, Bluetooth, Zigbee), displays (OLED, TFT), motors/actuators, which are essential to building autonomous systems, smart systems, and robotics.

For more information about our programmes, email programmes-at-mathscitech-dot-org for our schedule of events across North London, Hertfordshire, and Buckinghamshire. Our active locations: Kings Langley, St. Albans, Harpenden, Welyn Garden City, Berkhempstead, Tring, Amersham, Chesham, Rickmansworth, Watford, Hemel Hempstead, Potters Bar, Chipping Barnet, and East Finchley.

Some examples:

Gallery 1 – kid-friendly projects,
Gallery 2 – 13-key piano based on tunable analog oscillators,
Gallery 3 – microcontrollers and sensors,
Gallery 4 – motors, actuators, and 3-D motion control (in prep)
Gallery 5 – complex sound effects generator, beats sequencer/drum machine, fully programmable digital piano on PCB (in prep)
Gallery 6 – talking sensors and voice-controlled hardware
Product Concepts (in prep)

What to Buy, When to Buy It

An initial investment of £90 (Kit 1 below) is enough to get started with electronic components, IC chips, sensors, and microcontrollers including essential equipment.
An additional £150 adds dozens of advanced components including ICs, OLED displays, WiFi, and motor control.
A further £200 includes equipment for a well-stocked electronics workshop including capabilities for prototyping (soldering, heat-shrink, hot-glue), signal analysis (signal generator, oscillosope), panel/enclosure construction (drill, saw).
Recommended references £60 covers basic electronics, programming in Forth, Digital Electronics, and Robotics.
If you go through all the capabilities here, you can get a comprehensive capability for approx. £500. As a hobby, this is similar to what you might spend if were serious about a sport such as tennis (multiple rackets, balls, shoes, case, club membership, and various accessories).
Suggestion is to start with Kit 1 investment and then gradually invest more as interest, workshop space, and available time/budget allow. Along the way you’ll be building some neat stuff you get to keep.
We provide all equipment in our courses. Just bring yourself/your child, with enthusiasm and the willingness to get stuck in!

Kit 1 – Entry into Electronics, Microcontrollers, and Sensors – £90

Electronics Kit £35 = £23 (kit) + £8 (9V walwort) + £4.20 (USB cable) – £23 – Excellent kit with enough common components to get started with. Includes 9V battery clip, MB-102 9V to 5V/3.3V power supply converter, requires to supply USB A male to A male power cable £4.20 or 9V 2A wallwart AC-DC converter £8 or both. Includes breadboard, jumper wires, resistors, capacitors, transistors, LEDs, diodes, tactile buttons, slide switches, buzzers, potentiometers, a few ICs (‘595 shift-out register), 555 NEC timer, a few sensor components (tilt switches, thermistor, photoresistor), relay, 7-segment displays, and some soldering elements (prototype boards, header strips, screw terminals), with parts storage box. USB A plug charger
Sensors Kit £26 for a kit of 37, or £4.99 each sensor
Arduino Nano (Atmega328P) breadboardable microcontroller platform with USB-mini programming cable, £27 for 4pc (£6.75 ea)
Lilypad 5V DC boost converter from AAA battery – £2.10
Mini Pliers £2.50 for bending component leads for insertion into breadboards/placing components
Multimeter £25 with Test hook mini-grabber multi-meter probe (banana plug) for electrical measurements and testing, and 9V battery
Software Arduino IDE (C-based Arduino compiler, 3-instruction Forth) — Free
3-instruction Forth for Arduino – Request via comment form

Extensions – £54

Head-aimable USB rechargeable light (£7) and 30x Lighted Magnifying lens (£11) for proper illumination/magnification.
Test hook mini-grabber cables 2 pairs double-ended £6.40 (2 pairs recommended per child for working with 3-8 year olds)
USB extension cable: M-F extension 1m £1.93 next day, USB-mini, USB-micro, USB standard 2.0 1m for £2.49
Universal DC USB buck-boost converter power supply with display — £6
Batteries – 9V for 50p ea. Later on can get targeted power supplies, batteries, holders, button/coin cells, AAA, Lithium 3V CR123,
Micro 5V DC-DC CE012 boost converter — 66p ea. Custom wallwarts (eg 5V 2A) etc.
Smaller microcontrollers ATtiny85, ATtiny84 — £1.70 ea, STM8/Trinket.
ATtiny Sparkfun Tiny AVR USB Programmer (£17) or Make Your Own for less than £5!

Replenishment of items can be made individually as needed from the list below:

Solderless Breadboards (x2 medium 400 tie-points, x5 small 170-tie points, £8), Jumper Wires (medium 20cm and short 10cm, £5), Solid Gauge Hookup Wire (3x, £2) — £15
LEDs small 3mm red, yellow, blue, green white — £3
Resistors 1/4W mixed values £7 and Trimmer pots £3
Capacitors — £5 mixed values
Switches — £5 for 4 basic types (1P2T slide switch, momentary tactile button normally open, latching tactile button, contact switch)
Transistors — £2, mainly 2N2222 and a few TIP122
Buzzers and Speakers (8-ohm, 0.5W, 1W, 3W, 5W)– £5.50
Diodes — £3
Parts Storage Boxes — £6

Advanced components and ICs can be selected based on particular projects:

Potentiometers £13 – including £4 Audio (A-taper) pots, £4 Linear (B-taper) pots, £2 knobs for 6mm shafts
Analog ICs: Timer Chip (555) Audio Amplifier (386) — £2
OLED Display — £3
Super Micro DC-DC 5V Boost Converter CE012 — 66p ea
DIP switches — £5 (5, 8, 10 switches, DIP-10, DIP-16, DIP-20)
Logic ICs — £25 Buy low power ICs — power budget grows quickly when using multiple complex ICs, and anything with total power >100mA will be consuming batteries quickly — a 3V, 1500mAh CR123 battery will last 900mA at 5V (ignoring conversion loss), which is 6hrs (at 140mA digi piano) and 5hrs (at 170mA digi piano+76477 synth) Normal ICs draw more than LS (Schottkey) which in turn draw up to 1000x more current than HC or HCT (CMOS) chips. TTL vs. CMOS chips explained. Integrated Circuits (ICs) – Sparkfun introduction. ICs come in chip families, with different attributes: TTL family are the original 74xxx chips. Then there are 74Sxxx and 74Fxxx. Then 74LSxxx TTL family (inputs float to high). Also CD4000 family were introduced by RCA in 1968 using CMOS technology as lower power alternatives to the 74xxx series. HC/HCT family are CMOS logic 74HCxxx or 74HCTxxx, inputs can float to anything. (Note – good design should leave no inputs floating no matter what logic family is being used.) (Note, HC and LS don’t mix well, so consider HCT). Then there’s AHC/AHCT which can also work with breadboards, and are half the power of HC/HCT and 3x faster. And then we get to chips faster than a nanosecond which are too fast for breadboards, e.g. AC or LVI For production designs best to source 74HC/74HCT chips. Further reading on logic familieis.
RF-Nano (Nano+NRF24L01) for 2.4 GHz remote control via wireless radio frequency (RF) – £10

Kit 2A – PCB Prototype Building Equipment- £80

Soldering Kit (including iron, safety stand, case, tweezers) – £17
Additional Soldering Accessories – £50 (flux pen 80p, swarf cleaner £1.30, tip tinner £6, copper alligator clips for heat dissipation £5, PCB-jib £8, thin gauge lead-free solder £9, rubber desoldering pump £3, curved soldering tips pencil point £7, soldering mat £11)
Wire strippers, £9
Wire cutters – £2
Safety glasses – £2.50
Wicker storage basket (heat resistant)

Kit 2B – PCB Prototyping Supplies – £40

Prototype PCBs for point-to-point wiring – £12
Wire Wrap wire (30 AWG) or Hookup Wire (22 AWG) – £4
Standoffs M3 and M2 – £5
Headers, PCB Jumpers – £10
Screw Terminal connectors, DC Barrel connectors and Plugs – £9

Kit 3 – Motor Components – £80

Power Resistors, 1/2W, 1W, 2W, 3W, and 6W low ohm resistors (5R to 100R), — £8 useful for audio and motor applications
Stepper Motors — £6
Darlington arrays (high current step motor driver IC) — £3.50
Gears and Pulleys — £4
Low-slip pulley bands and pulleys various sizes for amplifying transmission/drive ratio — £12
DC motors with reducing gearboxes – £15
Cams and Rack & Pinion, Steering assembly
Servo motors – £20
Wheels and Axles – £15
Candy Floss wooden sticks for chassis frame – £9 for 100pc
1.5mm and 2.5mm drill bits for drilling holders for 2mm axles – £5
Shaft couplers for mating 5mm step motor shaft with 2mm axle shaft – £5

Kit 4 – Signal Analysis – £32

Oscilloscope – £19
Signal/Function Generator – £9
BNC cables – £4

Kit 5 Equipment to build Prototype Assemblies, incl. Panel Mount, Enclosure, Wiring Harness – £81

Cordless drill, drill bits, step drill bit, Forstner bit, plug cutter bit – £50
Hot Glue gun – £17
Saws for cutting – £10
Heat shrink gun + Heat shrink warp – £11
Small screw driver set – £5

Computer Aided Design (CAD) and Manufacturing (CAM)

EasyCAD
TinyCad (schematic capture) (awesome: 20MB, quick, easy, no fuss, plenty of design library elements, creates PCB netlist, free). Orders of magnitude smaller than KiCAD, Eagle, or AutoCAD.
Kludge + MsPaint: quicker web-based one-off schematic creator. User interface is click-and-click instead of click-and-drag: clicking a tile moves it to “Current tile”, then you click in the grid (not drag), and whatever is in current tile snaps to the appropriate spot on the grid. Many more parts are available from its predecessor Klunky. Integrated tile editor would be best new feature to allow new parts. Second best new feature would be text tool to add part values and other annotations… I’m doing both in an export step (screenshot to mspaint). Could also export SVG to Inkscape. Using Kludge’s lamp symbol as generic placeholder, then dropping on top the desired symbol (eg. speaker) from stock schematic symbol images. Here’s an example (left image):

Example circuit created with Kludge and annotated in MsPaint.
FreePCB (PCB design) (download Portable Zip from MathSciTech.org)
VeeCAD (prototype layout). To export Netlist from TinyCAD that can be used in VeeCAD must use VeeCAD libraries in TinyCad, or make sure that the Package names used in TinyCad exists in VeeCAD.
TinyCAD webpage collects user submitted parts/footprints.
Schematic capture software, TinyCAD or KiCAD, then TinyCAD + FreePCB for complete schematic capture and PCB layout and TinyCAD + VeeCAD for schematic capture to breadboard layout. Discussion Netlist converter (opencad)
KiCAD: is designed around the following workflow: Make schematic & add values to symbols, annotate schematic symbols, Assign Footprints, import to layout editor. In EAGLE, every part has a footprint assigned or some variants. Once you add a resistor, you already chose its associated footprint. In KiCAD, the philosophy is different: You can pick a resistor from the symbol library and add as many as you like. After placing none of them will have a footprint assigned. You now can assign footprints to each resistor (This can of course also be done in a central place for bulk assignment). KiCAD also does not annotate for you. It keeps parts unannotated (eg L?, C?) until you annotate them. It makes sense, though: After placing, automatic assignment of names is not neccessary. It only becomes important when assigning footprints to symbols before the PCB routing. This can and should be done in bulk anyway. In KiCAD, symbols and footprints are intended to be separate in different libraries. This allows for re-use of standard footprints like SO8 or QFP32. (Jan Kruger, Hackaday)
Schematic and PCB layout software FreePCB or KiCAD
PCB Basics (Sparkfun enlightenment)
Printing PCBs in your home — for $4,000
eForth for STM8S gadgets
Forth cross-compiler for 8051, AVR, ARM Cortex-M, MSP430, PIC, and STM8 microcontrollers
TeachMePCB.com
PCB Checklist
Linkage Mechanism Designer/Simulator
One-Off Prototyping as a Service, from laser cutting to 3D printing
PCB Design & Board Assembly, Futurlec

The Equipment List

Items are grouped below by function and chosen based on capability and (low) cost. I have included links (UK based) where each item can be bought inexpensively, with the choice to accept longer delivery times for lower price. (Note: Since the COVID-19 pandemic, electronics component prices have risen 50% to 100% on many items. I show this by listing the lowest price at which an item had previously been sold, and current pricing. If the different is large, it is worth doing another search on both Ebay and Amazon, as there may be new sellers offering sharper pricing.)

0. Guidebooks

A. Equipment (long term investment)

B. Components & Supplies

C. Power Supplies (Batteries, Holders, Converters) Fuses, & Heat Sinks

D. Integrated Chips – Analog, Audio, and Digital Logic chips (incl. 555, LM386, 74xxx chips, ALU)

E. Microcontrollers and FPGAs

F. Sensors & Communications

G. Motors, Machines, and Robotics

H. Storage (Cases, Containers)

0. Recommended References

Make: Electronics, by Charles Platt, Maker Media, 1st ed. 2009, 2nd ed. 2015, 3rd ed. £20 Oct 31, 2021. This is an excellent hands-on, learning-by-discovery primer for the new electronics enthusiast: burn things out, mess things up; that’s how you learn. Audience: mature teen or interested adult, intended for self-study.
Make: More Electronics, by Charles Platt, Maker Media, 2014, £17.50 Journey Deep into the World of Logic Chips, Amplifiers, Sensors, and Randomicity
Easy Electronics, by Charles Platt, very easy starter book for children under 10yo, £7.53 next day, 50 pages.
Art of Electronics, by Paul Horowitz, £57 next day, or Third Edition free on Archive (digital PDF)
Mobile Robotics: Inspiration to Implementation, Joseph Jones & Anita Flynn, 1st ed 1997, £6, 2nd ed 1999, £3.50 — Get the 2nd Edition, it is much expanded!
Interfacing Microcomputers to the Real World, by Murray Sargent & Richard Shoemaker, 1981, £7 used, or $10 in US
Starting Forth, by Leo Brodie, £12.09, very easy self-starter programming book in Forth for smart children under 12yo. Forth (GForth) can be used to interface with microcontrollers using existing Forths, or my 3-instructions Forth for Arduino.
Principles of Computer Hardware by Alan Clements, 3rd Ed., 2000, Oxford University Press, £3.50 used An excellent introduction to Digital Logic and Computer Architecture. Uses Digital Works v2.0 (freeware, download here) to teach digital logic design. Fourth edition 2006 (£50 new/£17 used) appears to have essentially the same content as the 3rd edition, so you may wish to save the extra cost.
SparkFun Electronics Tutorials – comprehensive tutorials on many topics relevant to electronics makers
Comms Protocols:
UART (Asynchronous Serial)
I2C
SPI (4-wire, synchronous serial): my wiring convention: CLOCK=orange, LATCH=yellow, DATA=green (for shift registers). Arduino with Atmega328P MCU, ATtiny85 (SPI in software), ATtiny has USI in hardware which can be tweaked to use SPI protocol | SPI terminology – Controller / Peripheral. COPI/CIPO. Chip Select CS. Note: Historical wrongs need to be righted. See here for the Sparkfun initiative to rename SPI pins COPI/CIPO, CS Controller/Peripheral, Chip Select | Official Declaration — no more master/slave terminology in computing
| SPI comms – Excellent SPI bare metal tutorial (Steve Mansfield-Devine)
| I2C comms – Excellent I2C bare metal tutorial (Steve Mansfield-Devine)

New SPI pin names, righting historical wrongs: COPI/CIPO/CS
Controller Out / Peripheral In, Chip Select
STEM Summer Workshops
Article: How to Think about Engineered Solutions? (Sep 17, 2019)
Article: Electronics: Experiments & Exercises (Sep 15, 2019)

A. Equipment

How to use a Multimeter (Sparkfun)

Digital Multimeter – Budget (ESSENTIAL) You can get a lot of value in the sub-£15 category. Buy 2 units so can simultaneously measure current and voltage in a circuit. For advanced work you will need 3 units (unregulated voltage, regulated voltage, and current), still cheaper (<£30) vs. c.£100 for a multi-channel wireless multimeter Pokit-Pro £100 | How To Guide (Sparkfun)
What to look for: a) VDC down to 2V, b) R (resistance), c) ADC down to at least 20mA, d) VAC down to at least 20mA, e) F (capacitance), f) Audible Continuity check, g) diode test, h) manual ranging ¹ with dials coloured so DC are all one color, and AC are another, i) power button (to make auto-shutoff not irritating), j) hFE for transistor DC gain
- RECOMMENDED: DT-9205A £15.90 (Amazon) or DT-9205B
  Note, some of these are 2xAAA batteries, and some are 1x9V battery. Look after receiving. Also, some of these have an annoying beep after each rotary knob turn.
- NOT VERSATILE ENOUGH. Compact (but no capacitance measurement and AC voltage not for electronic ranges i.e. no 2mV or 20mV ranges, and voltage measurement is 4-5mV off): £8.00
- UNRELIABLE: Baoblaze AN819A (1star), £12. Two units each lasted less than a year, then started giving erratic measurements. Auto-power-off (APO) feature is annoying as it is based off a timer whether unit is in use or not. Once auto-power goes off (APO), it requires twisting the dial back to Off to restart, inconvenient when in the midst of measurements.
- GOOD. Out of stock since 2017: Ultrics UT0021D, £10, 5 stars, lasted 3 yrs.
- Advanced: Also does Temperature and Frequency, £42
- Advanced: PokitPro multi-channel multimeter
- Advanced: Combination o’scope & multimeter: Owon HD272 £140, HD242 £110 | Hantek 2D72 £151
Notes:
- [1] Multimeter probes require banana plugs on one end. Recommended probes are test hook clip (aka minigrabber or retractable hook clip), as these can grip thin resistor wires easily, and hold themselves in place, freeing up both your hands. (Less recommended options are pointed probe and alligator clip.)
- [2] Not critical to have frequency or temperature functions (see oscilloscope below).
- [3] How low-cost mass market multi-meters are made using How mass-market multi-meters are manufactured using chip-on-board COB technology to pot the electronics in an epoxy. The PCBs then have a glob/blob with the bare IC wafer underneath (picture).)
- [5] Yellow multimeters are apparently violating a Fluke trademark (2014, Sparkfun), which was resolved between Sparkfun and Fluke.
Test Hook Cable (aka mini grabber probe) (ESSENTIAL)
Test hook cables are excellent for securely gripping bare wire or individual IC pins to allow precise measurement in tight spots without shorting adjacent pins. They are able to be operated by general as young as 3.5 years unlike alligator clips which are too stiff for little fingers (until c.7 yrs). Grabber probe cables provide great hands-on circuit practice and visual demonstration of connections between components, for younger kids in a learning session.
1. for Multimeter (banana plug to minigrabber): Lowest price: £2.04/pair. Currently: £3.30 right-angle or £2.63 right-angle or £2.70 straight If your multimeter display starts to wobble/vary, check your cables. Cheap cables (not listed) can be problematic. If cables are fine, it may be your multimeter.
2. double-ended: £9 for 5pc, 50cm (£1.80ea).
3. grabber-breadboard: male or female end. £6.23 for 10pc (62p ea) or 56p ea (MOQ30), or £6.50 for 10pc (65p ea) or negotiate (seller1, seller2), £11.50 for 10pc (£1.15ea), next day, or £11 for 10 (£1.10 ea) or £16 for 10 (£1.60 ea)
4. probe only (no cable): Grabber Probes, 20pcs for £1.66 (8p ea.)
  Robust grabber probes with smooth action. Each grabber probe has a cap which can be removed to allow soldering any wire to the end to make custom test probles.
Alligator clips are harder for young children to open due to the finger strength required (appropriate for age 7+), their teeth are less effective in gripping unsheathed wire, and they cannot probe IC or PCB pins easily without shorting adjacent pins. for Multimeter: Alligator Clip to Banana Plug 70p/pair, double-ended: alligator clips (10 for £1.68 (17p ea.)
Wire Strippers & Pliers (ESSENTIAL)
1. Wire Strippers, ensure 20-30 wire gauge (AWG), Lowest price: £6.57, currently: £9 next day. Essential for building circuits using hookup or flexi-wire instead of pre-made jumper wires. Use with a twisting action for smooth cutting and stripping. Has a crimper slot as well for crimping wire into pin headers.
2. Mini-Pliers: Get the red & black ones, as these are safest for little hands. £7 Hilka red/black. Easily bend hookup wire into jumper wires, insert components into solderless breadboard, and as a crimp tool for crimping wire into header pins. As a 2nd pair, consider Needle-Nosed (Extra-Long-Nosed) Pliers: £2.50 or £1.18 (Add-on item) which are useful if you need to hold two ends in order to manipulate one end with force – e.g. when sliding insulation down a jumper wire.
3. Wire / Side / Flush Cutters: Lowest price: £1.63 for lower end (B3180) cutters that ended up getting blunt. Higher end: Amtech 8″ Pro Side Cutting Plier B0640 £4.25 or Amtech 6″ Pro Side Cutting Plier B0635 or Amtech B3180 (Mini Side Cutting Plier) – not recommended – (required when creating PCBs to snip ends left behind after soldering. Note! Wear safety eye-glasses when doing this, as the ends are often hard and fly off with force and at random directions). If it gets blunt after a time, discard and get a new one. (mine lasted 3 years of frequent snipping of soldered wire from PCBs)
4. Flush cutters – 4pc for £4 (£1 ea) next day or 2pc for £4 (£2 ea) next day | professional angled jaws £6.30
Head-aimable Worklight, Magnification & Safety Glasses (ESSENTIAL) £13 for 1 of each
Don’t cut corners on good aimable lighting. Electronics requires focusing your eyes on tiny parts and thin leads, and requires precision insertions. You will save your/your children’s eyes by having bright, aimable lighting. The portability of a headlamp means you can work anywhere with the same quality illumination. Recommend to buy two, so you always have one ready to use while the other is charging. Frustration = light giving out at a critical moment.
1. Work headlight/headlamp, USB rechargeable: 2pc for £14 (£7 ea) same day or gesture activated styles. Great for illumination while doing small precision work. Removes requirement for a bright desk-lamp. Recommend to buy two, so you always have one ready to use while the other is charging.
2. Magnifying Lens: Handheld – Needing something stronger. Trying this one: £6 for 30x, 60x, 90x in a compact, portable, lightweight form factor. Also have this one: Lighted 30x, £9 next day or £12 next day, 15x, £10.50 same day (integrated light helpful for reading ICs). Alternatives: (1) Trifold lowest price 15x £3, currently: 10x for £5.50, or (2) unlighted 6.5x for £6. or (3) Handsfree: LED rechargeable headset, 1-3.5x, £23 same day
  20x+ resolution is necessary to read the small print codes on some capacitors without which you cannot identify them without measuring the capacitance of each (slow!). 3x-5x Pocket magnifiers don’t have enough resolution. Illuminated lens is necessary to be able to make out etchings on electronics chips, tilting till the light catches it just right.
3. Safety Glasses: Children (2-16 yrs), £2 ea, Adult: lowest price £1.30, currently £2.93 next day. Better safe than sorry. A child’s eye would be a terrible thing to lose. Your own eye would also be a shame to lose.
Soldering: The Fine Art of Fine Soldering

Soldering well takes practice and requires some essential equipment. The following is some advice learned from dozens of hours becoming proficient.
1. Get a decent soldering iron and safety stand: Tabiger 60W adjustable temperature (200-400*C) soldering iron with on/off switch and LED indicator | It comes as a kit £17 comes with a nice carry case, safety stand, and a few extra tips (the rest is better assembled yourself, see list below). Iron only £9, but it is worth the additional £8 to get the carry case and stand. The iron is well balanced, reliable, and long-lasting (I’ve used mine for 4 years with no issues). Minor downside is the screw that holds the tips in place which is fiddly and seems to lose thread integrity, but overall this is a nice iron and recommended.
2. Set tip temperature higher than you think, e.g. 300-350*C. This allows soldering more quickly (2 sec total: 1 sec heat pin, 1 sec apply solder and remove), and heating the metal for less time, which minimizes unnecessary heat transfer into component (avoids e.g. switches fail from excesive heat).
3. Assemble your soldering kit to contain 15 ADDITIONAL COMPONENTS (besides iron, carry case, and safety stand above) — see links below
  1. lead-free thin gauge solder (0.6mm),
  2. curved pencil tip (0.5mm) soldering tips,
  3. tip tinner for protecting your tips after use,
  4. swarf cleaner (avoid water and sponge which introduces micro-cracks into the tips),
  5. soldering mat (to avoid burns to the table from dropping molten solder)
  6. 30 AWG super thin wire-wrap wire for point-to-point soldering,
  7. head wearable light for proper illumination (your eyes will suffer if you don’t have enough light!),
  8. flux pen (for smoother flow of solder from iron tip to components),
  9. copper alligator clips (for faster heat dissipation after soldering complete),
  10. rubber desoldering pump (for correcting mistakes, much easier than a solder wick, and more suction than the conventional solder sucker triggers),
  11. 170-tie point breadboard (to avoid need for helping hand),
  12. digital multimeter for testing connectivity.
  13. a PCB-jig once you start soldering PCBs,
  14. FR4 double-sided PCBs,
  15. M2 standoffs and nuts
4. Plan your DIY PCB board: 1) Prototype working model on breadboards, 2) Plan PCB design layout, 3) Place components (I use a drop of hot glue to keep them in position), 4) Solder components in place, 5) Bend intrinsic component wires and solder joints (use flux), 7) Measure, cut, strip, and add topside main bus/trunk wires using 22AWG hookup wire – keep stripped ends long to bend to connect to points/joints, 8) Measure, cut, strip, and add point-to-point wiring using 30 AWG wire-wrap soldering wire, 9) Remember to TEST AS YOU GO! (from step 5 on).
5. Invest in 30 AWG super thin wire wrap wire for point-to-point soldering – with conventional breadboard 22 AWG solid core wire, you bend the wires in your components to bridge between pins and make connections. (Don’t build solder bridges between adjacent pins.) For pin-to-pin connections I’ve come to love using thin gauge (30 AWG solid core) soldering wire instead of 22 AWG solid core breadboard wire. It’s quicker, easier, allows wiring in narrow spaces, making dense connections, and does not take up holes on the PCB. Everything goes on the back of the PCB keeping the visible top neat. In this way it’s akin to PCB routed wires, except that wiring errors are easy to connect – just tap the wire for 1/4 second with soldering iron and simultaneously pull the soldering wire away with tweezers copper alligator clips | Use wire-wrapping wire to do point-to-point soldering by attaching directly to soldered pins of components on back of proto PCB board.
6. Allow for time! Your assembly time will decrease dramatically as you get more proficient (practice!) Once proficient, rule of thumb might be c. 2 mins per soldered connection. So a 13-key keyboard takes (130 connctions) takes c.4 hrs. A 4 IC board with 32 LEDs (the shift register/programmable digital piano for example), with c.200 soldered connections on an Electrocookie PCB (one with some connected trace pattern), takes c.7 hrs. When starting out, it might take 6 min per connection to figure everything out, so a 20 connection project may take 2 hours of assembly time. By your 4th board you should be close to reasonably proficient.
7. Test as you go – If there is a connectivity problem, you can fix it immediately instead of troubleshooting later to find where the fault is (painful) | see digital multimeters. Fixing mistakes can take 3-10x longer than getting it right, so go slowly, methodically, don’t rush!
8. From DIY PCB proof of concept to turn-key assembly Once you’re happy with a DIY PCB, it may be more cost effective to lay out your own PCB and get it turn-key assembled (see eg JLC PCB in the References below).
RECOMMENDED ADDITIONAL SOLDERING COMPONENTS FOR SERIOUS DIY
1. Buy lead-free solder for for health reasons, even if it is harder to work with and more expensive. Buy 0.6mm for easier soldering of delicate parts. | Types of Solder, Lead Poisoning | Electronic Solder (rosin core): 0.6mm 100g for £8.50 Lead Free (Sn99/Ag0.3/Cu0.7/Flux 2.0%) rosin core.
2. Thin Curved Pencil End Tips: 10pc for £7 (70p ea) same day or 5pc for £7.60 (£1.52 ea) same day Standard tips: 10pcs T-I £6 (60p ea) or 15pcs mixed type £7 (46p ea). Replacement Tips: for normal soldering work 900M-T-B, for fine pin header soldering work 900M-T-I.
3. Use tip tinner to protect your tips from oxidation. Coat the tip after use before letting the iron cool. | Tip Tinner: £5.50 – reconditions iron tips to pristine condition by recoating the tip, prevents oxidation damage and provides even heat distribution. Must have.
4. Clean the tip with swarf not sponge and water. Between uses, or when the tip has accumulated solder, clean the tip by rubbing it (up and down motion) in swarf. Don’t use sponge and water as it can cause cracks in the tip due to the abrupt induced temperature change. | Swarf soldering iron tip cleaner, £2.87 pad and tin, £1.31 pad only Works brilliantly with tip tinner. Keeps soldering tip shiny and sharp. Much better than sponge and water. Have hot glued this and the can of tip tinner to the sponge location of my soldering stand for easy one-handed access.
5. Wire wrap wire 30 AWG, 8 colors, 15m each: £4 next day or £2.40 4 weeks. (Only downside is they are all wrapped together. Would prefer each color spooled separately) | Don’t use magnet wire which has insulation which cannot be stripped but must be burned with a soldering iron to remove, but insulation is gives off toxic fumes. | Magnet wire (0.2mm, #32 gauge), Red, £2 for 100m | How to Solder Tiny Things, example of wiring using copper winding wire, or here. Step-by-step here. | Extreme Soldering (highly recommended to learn advanced techniques) | Examples of Point-to-point soldering on Protoboard PCB using Wire Wrap wires | To use wire wrap wire you will need a pair of tweezers. I recommend copper alligator clips.
6. Learn how to solder without requiring complicated helping hands, which are expensive, take up space, and in my view are more awkward than they are worth. A simple copper alligator clip, a 170-tie point breadboard, and a PCB-jig for swiveling the pcb easily, are all you really need. | PCB holder Jig / vice £8. Useful for soldering PCBs and as a general third-hand. Can add a small breadboard to aid holding smaller parts, e.g. wires. Video tip for keeping components in the PCB while soldering. | Technique for using only your own hands: use copper alligator clip to hold tip-stripped soldering/breadboard wire raised (on a soldering mat to protect table surface from burns if molten solder falls), and apply solder to the exposed tip, apply solder flux from flux pen to improve the speed with which solder flows to where you want it, reducing sticking to the soldering iron tip. Do the same to the mating pin/wire (apply flux and then solder). Keeping one wire/component anchored, you can now bring the other in close and apply iron to heat both. The solder already coating both wires/pins should fuse creating a solid connection.
7. Solid Copper Alligator Clip Heat Sinks: lowest: Large 43.5mm, £1.23 ea. (MOQ4) or 50mm, £2.25 ea (MOQ4). Small Ones (<40mm) are not useful. These clips act as heat sinks when soldering sensitive electrical components (LEDs, ICs, etc.), as copper is a better heat conductor than steel. I attach these to the Helping Hand tool and then clip the components into these copper jaws. They are also very useful when running microcontrollers to drive motors or sensors until the current draws/settings are figured out, to prevent DC regulators and MCUs from overheating. Also for attaching copper plates/heat sinks to stepper motor casings, which heat quickly under constant load.
8. Rosin flux pen #951, Currently £5 (lowest price was 80p, Yosker; then £2.14!) Has solder in it (this paste does not). Helps speed up soldering, allows smooth and even application of solder to the wires, and helps it to flow into place before hardening. Use with a breadboard means can apply solder to each wire separately then briefly apply heat to hold them together melting their joint solder coats. In this way no third-hand equipment is needed, but the flux pen is necessary to get the solder to adhere to the individual wires.
9. Soldering Mat protects table/floor from burns due to molten solder drips. The mat has a non-stick coating which solder does not stick to (neither does hot glue!) | Soldering/Hot glue Mat £11. Or with built-in solder holder, £16
10. a solder sucker can be a lifesaver if you need to remove excess solder or separate pins that have accidentally been flowed together. | Removing Solder from PCB Holes | Rubber suction bulb, £2.50 or £3.00 for heavy duty desoldering. This versatile rubber suction pump has plenty of suction and works much better than dedicated desoldering pumps. The high suction pulls heated solder out of pcb joints instantly. Note, due to the narrow neck, cooled solder inside the bulb is too big to eject, so at some point this will fill completely with solder, and need to be replaced. But the price point works for this, and incentivizes fewer soldering errors.
11. use FR4 double-sided pcb boards instead of phenol single-sided boards (the rings around the PCB holes lift off with excess heat, and the board burns easily, rendering holes useless). | Get some M2 standoffs and nuts to stand the finished PCB above the table to protect the reverse side from pressure as the top side is interacted with.
  References:
  - Extreme Soldering (SMT chips onto a normal PCB)
  - Soldering Tutorial (Sparkfun)
  - Soldering tips, from equipment to method
  - Surface Mount Soldering with a standard soldering iron, key is to look for the larger SMT/SMD part dimensions: 0805, 1008, and 1206, etc., see Hackaday article
  - Common soldering mistakes (useful pictures)
  - Extreme Soldering (highly recommended to learn advanced techniques)
  - Examples of Point-to-point soldering on Protoboard PCB using Wire Wrap wire 30 AWG
  - PCB layout principles (for veroboard, but the general guidelines are true also for point-to-point PCBs).
  - See Soldering Tips (search solder)
  - Turnkey PCB production: Specifying the design for a PCB Contract Manufacturer, Gerber file format (Wikipedia), single vs. multi-layer PCB.
  - PCB Design for Contract Manufacturing and PCB Assembly: PCB Train £150 setup cost, £30 incremental board assembly cost), or Freelance PCB Design, Quoted Job 1711777. Ragworm, PCB Shopper (comparison, can get 5 boards from China for £10). JLC PCB Manufacture (fast, economical) also PCBWay
  - Schematic Layout Software: TinyCAD (awesome: 20MB, quick, easy, no fuss, plenty of design library elements, creats PCB netlist, free) VeeCAD (stripboard editor). FreePCB (via PCB netlist export feature). Or use Spice (for simulation). WALK-THROUGH, explanation #2
  - PCB Layout Software: Autodesk Eagle (Windows Download, free for 80cm2 board), KiCAD (open source) (Windows download, 478MB to install, lite version no 3D or help PDFs), FreePCB, other free softwares. Eagle to KiCAD conversion. Eagle vs. KiCAD comparison. FreePCB (original). FreePCB2 (50MB to install!), requires Java 8 to run FreeRoute autorouter. ViewMate (Gerber file viewer). Easy EDA. TinyCAD COMPARISONS
  - SparkFun – IC basics. Soldering Basics. PCB Basics. Parts List vs. BOM Making Parts Footprints Custom Footprints Schematic Design
  - Single vs. Double Layer PCBs: Explanation, Discussion
  - “Skywiring”, Breadboards, PCBs
  NOT NEEDED – Modelling clay (£2.12 for 56g) makes a convenient third hand for soldering. Softer variety (£2.60 for 56g)See this video on soldering spliced cable to pins for how.
  
  NOT needed – bulky, slightly awkward, and, once you get good at soldering, you can use the PCB jig with quick hacks for almost everything. Litebee Gooseneck flexible hands: 2 hands with C-clamp and soft-sleeve on alligator clips to prevent scratching, £11. Litebee two arm helper is perfect. 6 arms (£26.40) is overkill. The inflexible standard cheap 2-arm helper £5 is not recommended as it has insufficient flexibility (issue!) and alligator clip jaws that are too strong and leave marks on wire being held in place.
Heat Shrink Gun & Tubing
1. Mini Heat Gun, 300W: £9.00 WARNING: Do not block heat vents on the side to make the fan quieter. They are there to to prevent excessive internal heating which can damage the heat gun. GOOD NEWS: The heat gun has automatic overheat shutoff built in. If it does not appear to work, let it cool, then try again, keeping vents clear.
2. Heat Shrink Wrap / Tubing, various sizes: 1mm for bare 22awg wire, 2mm for insulated 22awg wire £2.11 for 328pcs, assorted colors, 8 sizes (1mm, 2mm, 3mm, 4mm, 6mm, 8mm, 10mm, 14mm) Single size: 2mm diam, 1M black for 50p, 2mm diam 4M white for 73p, 2.5mm, 1m length, clear, 52p and 3.0mm, 1m length, clear, £1.66 and 3.5mm, 10m length, clear, £1.24
  2mm diameter is appropriate for bare wire. 2.5mm/3.5mm are the right diameter for insulated 22 gauge wire.
  
  To wrap larger items: calculate flat diameter and round diameter and search accordingly (Amazon: “heat shrink 80mm”, sort by: price low to high). Formula 2*flatdiam = pi*roundiam. E.g. 85mm flat = 55mm round; 57mm flat = 36mm round. 60mm flat diameter can fit 170 tie-point board with nothing on it (8.5mm thick, 35mm wide – 3 points through a circle). 77mm flat = 50mm round can fit 170 tie-point board with components and 9V battery pack (35mmx35mm square inscribed in a circle). Buy 80mm flat diameter.
3. Heat shrink tube 85mm/55mm flat/round diameter, £3.53 for 5m This is large enough to fit 170 tie-point board with attached 9V battery, components and push switch.
Hot Glue Gun & Glue Sticks (RECOMMNEDED)
1. Hot Glue gun, 100W/11mm/on-off/carrying case, £16, or 60W/11mm/on-off, £13 or 60W/11mm glue sticks/on-off, £10 w/ 50 glue sticks. Replacement glue sticks 11mm diameter, £4.50 for 50pc (9p ea.)
  Important – there are two diameters of glue sticks, 11mm and 7mm, so check size compatibility with your glue gun.
  
  Video instructions on how to use your glue gun.
Oscilloscope, Function Generator, and Logic Analyzers (RECOMMENDED for audio/advanced signal work)
JYE Tech makes low-cost entry-level equipment
1. (RECOMMENDED) Function Generator, XR2206, runs off 9VDC. Note1: Output signal is 9VDC (use LM7805 step down converter to get to 5V if want to use with 5V circuit). Note2: pass output signal through 100kR resistor to get low current signal. Lowest price: £9 fully assembled, Current price: £8, unassembled, next day, £13, fully assembled, same day or £16, fully assembled. Biggest benefit: knobs for selecting frequency, jumper for waveform (triangle, sine) with amplitude for these and specific output port for these (bottom/yellow). Criticism: (1) no power on LED (you need a meter to check its working), (2) no markings on the pots (you need a scope to know what freq is being output), (3) awful documentation – figure out by trial and error, (4) amplitude only works with triangle/sine wave not square wave, (5) has two outputs instead of one, i.e. separate dedicated dquare wave output and a separate sine/triangle output. Chip 16-pin DIP: 2pc for £4.70 (£2.37 ea) (ebay) or £7.80
  XR2206 Function Generator board documentation. Using an oscilloscope, we can see that the generated waveforms are decent (sinusoid, triangle, square).
2. Function Generator, FG-100 DDS, 1 Hz to 500 MHz, Sine/Square/Triangle/Sawtooth, £18.20 Instructions here Works, but not user friendly: to change frequency requires lot of button presses. Would prefer a knob. Power is 5VDC but has USB interface. Would prefer a standard power jack. It is useful for precisely dialed in frequencies. Requires BNC to croc clip cable.
3. Function Generator, ICL8038, £6.50 unassembled next day | fully assembled | chip only 14-pin DIP, 5pc for £13 (£2.60 ea)
4. Function Generator, AD9850 Waveform Generator
5. Desktop Function Generator, dual/multi-channel, MHS-5200A £75 | JDS6600 £107 | FY6900 £130
6. ZK-PP1 square wave PWM pulse generator: lowest cost $4.50 or current price: £12 amazon
7. Velleman MK105 Function Generator,
  
  Oscilloscopes: Buy one with rotary knobs and not buttons (cumbersome to adjust). Cheapest adequate scope with 1 channel is £35 (DSO-150). Once you start working with signals, you’ll want a 2 channel scope to be able to compare two signals on the same grid. Cheapest here is £150, so a significant step up.
8. (RECOMMENDED) Oscilloscope DSO-150: 9V DC nominal input (8-10VDC rated), 100mA (1W draw). Can run off a 9V battery. Use 9V battery box with barrel jack. £36 fully assembled next day | £27 fully assembled, 3 weeks | £50 next day | Video review of features | Written review | DOS-150 (Shell) forum by JYETech | Hackaday article (Nov 2017) | Video how to start using | Disassembly/Assembly video | Product Info page | My experience: Bought my DSO-150 fully assembled (paid c.£15 extra for this). Initially did not work. Ultimately I was able to get it working but it required taking it apart and using a YouTube assembly video: https://www.youtube.com/watch?v=TqBRi2oHvbw
  Once that was done, I needed this startup video to get it configured right for use: https://www.youtube.com/watch?v=YMrM5D4O9mI
  
  Now that it’s working, I quite like it. However, not great that it required disassembly and fiddling about to get it to work. Here were the problems and fixes:
  
  Problem 1: Sec/Div button was erratic and then stopped working. Cause & fix: looked to be poor solder joint, re-soldered.
  
  Problem 2: No signal trace at start and analog board getting very hot. Cause & fix: not exactly sure if this was a short, or dodgy connection. Fixed by adjusting analog board connection.
  
  Was able to verify operation using integrated 1kHz test signal. Works fine now.
  
  Overall Review: Easy to use, works well for testing audio (<20kHz) and other low-bandwidth, regular, signals. Lagged (not real-time) for time divisions slower than 0.2 sec/div, so not great for analysis of transients.
9. DSO-068 – £40 3 weeks, kit. Single-channel, Advantages: built-in lithium ion battery. Spec sheet
10. DSO-094 – Dual Channel Oscilloscope – Amazon | £120 NooElec
11. PicoScope 2204 – £95
12. (tried, next gen DSO-150 is better buy) DSO-138 – Digital Signal Oscilloscope (DSO), JYETech DSO138, £27, pre-assembled with BNC to croc clip cable., £19 fully assembled. This is a useful little scope upto 20kHz (audio range). Above that be aware that sampling rate limitations make this scope inaccurate, so if you are working with >20kHz frequencies, look elsewhere. Outstanding value for low frequency use (<20kHz). Easy to use (small gripe: would be better to have knobs for tuning zoom window rather than buttons). Don't bother assembling the case - it's complicated and does not add anything. Just attach the LCD unit, connect the BNC cable, power up with 9VDC wall wart, read the user guide, and off you go. Kit website
  Usage Notes:
  - Built around STM32F (ARM-CortexM3) microcontroller
  - Boots upon powerup. RESET button reboots.
  - Interfaces from left top down and around to right top:
  - CPL: Gnd, AC, DC
  - SEN: 1V, 100mV, 10mV sensitivity
  - SEN2: x5, x2, x1
  - TRIGGED led flashes green when the signal passes above voltage threshold (adjust when right arrow is blue on screen)
  - SEL: toggles through 5 functions: time period (start at 10ms), AUTO/NORM/SINGLE trigger mode (default AUTO), TRIGGER EDGE mode (rising/falling edge), 3 graph modes: right arrow blue = trigger level (put to center of signal), top window blue, left arrow blue.
  - OK: pushes hold to freeze signal
  - Then plug the red/black leads into signal (into speaker) and ground to see the waveform.
  - OVERALL REVIEW: Works fine, but it’s fiddly to use with a function select button that toggles through 5 function. Better design would use adjustment knob (rotary encoder) which is more natural – see DSO-150 for exactly this!
13. Two Channel Scopes: Hantek DSO2C10 £190 | Owan SDS1022 £190 | Kiprim DS1202 £200 | Akozon DS212 £150 or £130 3 weeks|
14. Combination oscilloscope and multimeter, £70, nice piece of kit but pricier than the £50 getting them separately.
15. BNC croc clips test cable, 2pc for £4 (£2 ea.)
16. Tektronix 465B – the analog standard
17. Combination Oscilloscope & Signal Generator: £143 | £240 | £85. Note – it is often better to get standalone equipment so they can be upgraded separately when more is needed for that particular function.
18. Logic Analyzer, £100
Assortment of Craft Tools/Misc. (OPTIONAL)

B. Components & Supplies

Solderless Breadboards (2.54mm pitch). When not to use breadboards.
Features to consider: (1) Power rails down the side of the board (on 400+ tie points), (2) Attach/detach modularity (on 400+ tie points), (3) Central spacer for ICs (keeps pins separate on either side) (170+ tie points), (4) Two columns of horizontally connected rows (170+ tie points)

Use with 22-AWG hookup wire. Using thicker wire (20 awg or lower) can spread the clips apart for the whole row and cause loss of contact with smaller gauge wire

Fully modular means they can be clipped together horizontally or vertically to extend them. The power rails can be also unclipped to create double wide dimensions. Note the 170 tie point boards have just 1 modular clip per side which is not enough for mechanical stability without another strength member.)
1. Large: 1660 tie points: ZY-204, £11 next day, Vellemen VTBB4, £17. 2860 tie points: £11.20
2. Tall (MB102): 830 tie-points 4 power rails – £3 ea or
3. Medium: 400 tie points, w/ IC divider and 4 power rails: Lowest: £1.16ea, Currently: £1.70ea (MOQ6) or £1.67ea (MOQ6) or 3pc for £6.30 (£2.09 ea.) or 3pc for £7 (£2.33 ea).
4. Small: 170 tie points, w/ IC divider but no power rail: lowest price 36p ea. 5pc for £1.98 (40p ea) white with interconnect nubs, Ebay. | These were defective, requiring too much force to insert pins. Refunded.
  Excellent for little portable projects and preserving your prototyped circuits cheaply!. These are the smallest breadboards that can accomodate an IC chip because they have a DIP ravine electrically separating pins on either side of the chip.
5. Tiny (ZY-55): 55 tie points, no power rail: 7x for £4.80 (68p ea) ebay or 7pc for £3.69 (53p ea.)
6. ZY-001 baseboard: Red, £2.59 ea., Yellow, £2.59 ea., White, £2.69 ea
  The ZY series are excellent for little connections that don’t require ICs. The little nubbins on the back of the ZY series breadboards are like little lego attachments made to fit the ZY-55, ZY-35, and ZY-25 modules. NOTE: the spacing on the ZY series boards are not compatible with LEGO spacing — a pity!. Also note: The smallest breadboard (ZY-25) with 25 tie points 7pc for £2.70 (40p ea.) is not recommended and is not child-friendly, as the 5-rows and 5-columns mean there is no easy way to know which set of 5 holes are electrically connected, rows or columns. Stick with ZY-35 or ZY-55.
  
  References:
Prototype PCB for point-to-point wiring
2.54mm pitch same as breadboards aka Matrix PCB, Protoboard, Universal PCB, Paper PCB Check Amazon and Ebay for better prices.
vs. stripboard or Veroboard with interconnected strips like a breadboard.
Look for pre-drilled corner holes for nylon standoffs (most are M2, with single-sided paper PCB can expand to M3 with a drill).

Two types: single-sided phenolic, paper PCB DON’T BUY THESE TYPE: bad smelling, can’t take much heat before pads lift off. Better to buy these slightly more expensive: double-sided FR-4 fiberglass boards with tinned pads: higher quality, thicker boards, able to handle desoldering and resoldering. (Double-sided helps wire routing for more denser layouts). Thickness matters more for larger boards, where 1.6mm (paper PCB) may be too thin as there is greater flex in the center, especially if using heavier components, or pressing buttons, which can cause pcb joint failure.

Standard PCB sizes (cm): Small: 2×8, 3×7, 4×6, *5×7, 6×8, *7×9 (like 400-tie point breadboard); Medium: *9×15 (wider version of 800-tie point breadboard); Large: *10×22 (useful), 12×18, 15×18; Extra Large: 13×25, 18×30 (almost A4). (recommend to get 5 pc ea of 5×7, 7×9, 9×15, 12×18)
1. Small PCBs (7x9cm or smaller): Best value is 40pc kit for £12 (30p ea) + storage box, same day contains 2x8cm (10pc), 3x7cm (10pc), 4x6cm (8pc), 5x7cm (8pc), 6x8cm (2pc), 7x9cm (2pc). Other sets: 32pc for £11 same day, 16pc for £5 (31p ea), fewer sizes, 1 week, or 20pc for £10 (50p ea), same day, or 20pc for £10 (50p ea), more sizes, 3 weeks
  3x7cm: 10pc for £5.23 (52p ea) next day
  4x6cm (FR-4, 2-sided): 4×6 cm, 10pc for £5.80 (58p ea), next day, or 10pc for £6.50 (65p ea), same day
  
  5x7cm (FR-4, 2-sided): 10pc for £4.90 (49p ea) 30 days
  
  5x10cm (FR-4, NOTE one-sided NOT two-sided): 2pc for £4.67 (£2.33 ea) NOTE: This is a single-sided board. If you need the form factor, better to get the Electrocookie snappable (below).
  
  6x8cm (FR-4, 2-sided): lowest price: 86p ea.
  
  7x9cm (FR-4, 2-sided): 5pc for £4.50 (90p ea)
2. Medium PCBs (bigger than 7x9cm): 2-sided FR-4
  8x12cm (FR-4, 2-sided): 2pc for £3.40 (£1.70 ea) or 2pc for £4.38 three-day (£2.19 ea) or 10pc for £13.31 (£1.33ea)
  
  9x15cm (FR-4, 2-sided): 5pc for £6.16 (£1.23ea) or 2pc for £4.66 three-day (£2.33 ea) or 2pc for £5 (£2.50 ea) or 10pc for £18 (£1.80 ea) same day
  
  10x15cm (FR-4, 2-sided): 10pc for £25 (£2.50 ea) next day
  
  12x18cm (FR-4, 2-sided): 1pc for £3.28 (ebay)
  
  15x20cm (FR-4, 2-sided): 5pc for £27 (£5.40 ea) or 1pc for £10 or 1pc for £7 three-day (ebay)
  
  10x22cm (FR-4, 2-sided): 2pc for £9.20 (£4.60 ea), 1pc for £5.50 or 2pc for 15.60 (£7.80 ea), 1pc for £8.20
  
  13x25cm
  
  18x30cm/20x30cm (FR-4, 2-sided): £9 ea (MOQ2) 3 days or £9.20 ea (MOQ2) 4-6 wks
3. Electrocookie, snappable solder PCBs with solderless interconnections, for permanent fast prototypes, 9.7×8.9cm 6pcs 9.7 x 8.9cm, or 24 pcs 4.85cm x 4.45cm, £18 (£3 ea large, or 75p ea small), or 3pcs for £12 (£4 ea large, or £1 ea small) Excellent PCB when connecting many small components/ICs, reducing the number of solder bridges that need to be built.
4. Bendable PCB, 15x-18cm: 2pcs for £34 (£17 ea)
Nylon Hex Stand-offs / Board Spacers
1. Female 100pc Black Nylon 8mm M3 spacer, £1.86 (2p ea), 3 days or 5mm 100 pc for £1.99 (2p ea.)
2. Male 100pc Black Nylon M3 spacer (tall, 12mm+6mm), £3.01 (3p ea) (lowest price 2p ea) or (short, 6mm+6mm)
3. M3 (3mm hole) nylon screws 20mm height black, 50pc for £3.41 (6.8p ea) or 8mm height, 50 pc for 70p (1.5p ea), or 30mm height metal 8pc for 89p (11p ea), or 22mm height metal 20 pc for £5.49 (27p ea) next day
4. M2 Nylon spacer/standoffs Hex, Universal Standoff Ordering — all sizes and combinations! 4-5p ea buy: M2 black 100pc M/F 8/6mm and M2 black 100pc F/F 6mm (200pc for £9, 4.5p ea) (note, base length must be bigger than screw for securing PCB)
Wires / Wiring
Reference: Choosing wiring gauge (thickness, max current, resistance)

Reference: Wire gauge to mm conversion chart (e.g. 22-gauage = 0.6mm) and making sense of European wire measurements (e.g. 16/0.2mm and 24/0.2mm means 16/24 strands of 0.2mm diameter wire; solid core wire is 1/X)

Reference: Working with Wire – Sparkfun Tutorial | AWG to mm converter
1. Hookup wire, 22-gauge (0.6mm) single core , red (positive), blue (negative), yellow (signal), £1.77 (for 3 spools, 5m each). Add orange and violet for additional colors (£3.18 for 5m of each of 3 colors). (Spiratronics) This is the stuff for making short jumper wires for breadboard connections.
  Thin wire for prototype PCB boards: Note 22 AWG wire is 0.6mm, 28 AWG is 0.3mm, 30 AWG is wire wrap wire 0.25mm. Cellphones use 0.1mm wire (38 AWG). Thinnest is 40 AWG at 0.08mm
2. Magnet wire (0.2mm, #32 gauge), Red, £2 for 100m
3. Wire wrap wire (30 AWG), £4 for 8 colors, 15m each (Only downside is they are all wrapped together. Would prefer each color spooled separately).
  With wire wrap wire can do point-to-point soldering by attaching to the pins of an IC. No longer need the harder work with thin (0.1mm) copper enameled winding wire, 5 pc (15m long ea) for £4.70 (6p/m) same day, directly solderable without scraping off insulation. DON’T use magnet wire which whose insulation is gives off toxic fumes and cannot be directly soldered.
  
  How to Solder Tiny Things, example of wiring using copper winding wire, or here. Step-by-step here.
  
  Extreme Soldering (highly recommended to learn advanced techniques) | Examples of Point-to-point soldering on Protoboard PCB using Wire Wrap wires | To use wire wrap wire you will need a nice pair of tweezers.
4. Stranded flexible wire, 22-gauge, £1.81 in 2018 (red/black each for 3m, so 30p/m), £1.26 in 2016 or ebay at £4.50/10m red and black or 45p/m
  This comes in handy when creating leads for items you’ll want to move around flexibly, e.g. switches, or potentiometers that are user interface items, vs. inflexible hookup wire.
5. Jumper Wires (compatible with standard breadboard with 2.54mm pitch/0.1″ sockets):
  ProTip: Choose F/F wires and long header pins which can be used as grouping organizers (multiple cables), or gender changers.
  (short) 10cm: Lowest price: 1.6p ea, then 2.5p ea, Current: 5p ea, £2.06 for 40pc, 1 wk, or 6p ea, 80pc for £4.87, 4wks, or 7.5p ea,, 4 days).
  (medium) 20cm: MM/MF/FF mixed kit purchase – Lowest price: 1.3p ea., current price: 3.2p ea (MOQ400) or 4.8p ea or 360pc for £9 (2.5p ea, 120 pcs each type), or 240pcs for £16 next day (6.5p ea, 80pcs each type)
  
  These are useful for connecting between boards, whether breadboards, PCBs, or microcontroller dev boards (flexible, reasonable size, come prefinished in variety of terminations.
6. Jumper Cap Connector / Short Circuit Shunts (2.54mm pitch):
  With handle: 100pc black for £3.30 (3p ea) or 10 pc black for £3.25 (32p ea), or 10pc black for £3.86 (39p ea), or 60pc tri-color for £8 (13p ea), next day, or 200pc 4-color for £10 (5p ea) next day
  
  Cheaper, but require pliers to add/remove: 120 pcs for 97p (black) or 50 pcs for £1.16 (black) or 10 pcs for 63p (6p ea), blue
  
  Jumpers are essentially single-pole N-throw switches (1PNT) that you build manually to fit your application. Very convenient and cost effective when considering expensive switches. All you need are header pins and the jumper shunts. The rest is wiring.
7. Magnet wire (0.2mm, #32 gauge), Red, £2 for 100m
  Useful for wiring inductors of 1mH or higher.
8. Wiring inter-connection kit (Male/Female Crimp Pins, Female Header Blocks), 620 pc, £4.57
9. 2.54mm pin header strip (male) 10 pcs of 40 pins, 77p and 2.54mm pin header strip (female) 10 pcs of 40 pins, £1.27; or get both for 1.70.
10. Right-angle male header pins 2.54mm spacing, 40 pins per row: 30 rows for £4.36 (14p ea) *important* must have nub on the wire pin allowing flush pcb mount, not on the pcb pin which leaves a gap in height above board | 12pc for £6.00 (50p ea row) nub on wire pin
11. Double-long 8mm/8mm straight male header pins 40 pins per row, 10pc (40 pins ea) for £9 (90p per 40-pin pc) next day or 1pc (40 pins) for £1.42 (@MOQ2) 3-days, ebay,
  Note: typical male header pins have a needle length of 6mm on the connect side, and 3mm on the PCB side. These are 7.6mm on each side, so can be inserted easily into a solderless breadboard.
  
  Instructions for:
  
  Connector Basics: Everything you ever wanted to know about all possible connector types (Sparkfun)”
  wiring female connector block
  (video) how to use the male crimp pin
  (video) soldering pin headers and pins to boards using a breadboard as third hand
  (video) soldering technique to solder spliced cable to pins using modelling clay as third hand
  (video) using a d-sub crimper to crimp wire
Connectors
1. 2.1mm DC Barrel Jack / Barrel Plug / DC Power Pigtail Cable Male: Center positive: lowest price 19p ea., 20 pc for £6.00 (30pc ea), or ebay 10 pc. for £3.50 (35p ea). or with
  Amazon 10 pc for £2.93 (29p ea.), or 10 pc for £5 (50p each)
2. 2.1mm DC Barrel Socket: lowest price: 7.5p ea (10pc for 75p), or currently: £1.89 for 10 pc (19c ea.) WARNING: these are open mouthed (Ebay) to get them to insert into a standard breadboard pull out the middle pin with pliers, or 10 pc for £1.82 (18p ea), Ebay, or £1.66 for 5 pc (33p ea)
  These are fantastic and great also for general electronics repair or hacking into DC devices by splicing into power cable or battery terminals
3. IDC connectors, Ribbon Cable, and Board Headers, 10- to 50-way (Spiratronics). Installing Ribbon cables – demonstration, instruction. (IDC = Insulation Displacement Cables). Ribbon cables (Amazon)
4. IDC ribbon cables: 6-pin female for SPI / ICSP programming of Arduino, 5pc for £6 (£1.20 ea) 20cm next day, 20-pin female, 5pc for £8 (£1.60 ea) 30cm next day
5. Model & RC connectors (small molex)
6. 12VDC Car cigarette lighter FEMALE socket to wire terminals, £10 for 2
7. Power Inverter: 120/240V AC to 12V DC (10A) compatible with a car DC cigarette lighter connection. £20
  But first look amongst old computer power supplies you may have lying around.
8. Screw Terminal Block Connector for PCB: 2-pin terminal 40 pcs for £1.84 (5p ea.)
  These are bread-board or PCB compatible, and can be stacked to make 4-pin, 6-pin, 8-pin, connectors (a small tab on one side and a slot in the other creates the inter-connect)
9. Wire connectors (twist on), wire nut
10. Spring wire connector
LEDs
1. Standard LEDs come in two sizes: small=3mm, medium=5mm, but can be up to 10mm (large)
2. Note: Different LED colors have different forward voltages hence different brightnesses. Forward voltage (see table below) for most colors is 1.7-2.3V, with 3.2V for blue & white LEDs (super bright).
3. Tip: To get even brightness LEDs of different colors, use different resistor values. On 5V, try: Green: 33R, Yellow: 1.5KR, Red: 5.2KR, Blue: 20KR, White super-bright: 22KR
4. Tip: Why old stock green LEDs are much dimmer. “There are two types of green LEDs. Old green LEDs with forward voltage ~2V which are quite poor – the brightness @20mA is comparable to red LEDs @2mA. Also yellow LEDs are often poor. New green LEDs have forward voltage ~3.5V and are much brighter – about the same as blue and white LEDs, more than the red LEDs. Before the ’90’s most LEDs were extremely low brightness (about 1000 times less than today’s types). Check the forward voltage to be sure you are not getting old stock dumped. Source
5. Tip: Modern red LEDs light up at 1mA (5V, 5mW), shine nicely at 2mA and brightly at 4mA. So at 5V, a 2KR resistor is plenty fine.
6. Max forward current is 20mA. Protection with 1KR is enough for 3-12V (3-12mA), not including fwd voltage, which removes another 2-3mA. At 5V, 250R gives max allowable current (20mA). At 9V, 480R gives max allowable current.
7. Simplest circuit is driven by 9V battery with 1k ohm resistor, so resulting voltage is 6V (after LEDs forward voltage), so current will be 6mA. These are bright 3V DC 3mm diameter LEDs, perfect for DIY electronics. Easy to test with a test circuit in a few minutes (9V battery, 1 LED, 1k ohm resistor) using breadboard (but could also use test leads).
8. LEDs have polarity which is indicated with + being the longer leg. Brightness can be adjusted by lowering the resistor value (but be careful not to pass more than 20mA through the LED lest you burn it out, so min resistor is 330 ohms for max brightness, or 470 ohms to be safe).
9. LEDs come in two current types: std and low current. Low current LEDs provide uniform luminosity down to 2mA unlike standard LEDs whose luminosity decreases with current, but which are still reasonably bright down to 2mA. But low current LEDs are 10x more expensive at c.15p ea (vs. 1.5p std current) and appear to only be available in 3 colors for low-current LEDs: Red, Green, Yellow from Kingbright
LED forward voltage chart (courtesy of: http://stompville.co.uk/?p=37)
1. 3mm (std small) Size. | 5x color kit (white, yellow, red, green, blue): 750 for £10 (1.33p ea) next day, with 15 compartment box, 150pcs each color, | Single color packs: lowest price 0.82p ea (150pc. for £1.23).
2. 5mm (large) size | 5x color kit (white, yellow, red, green, blue): £4.89 for 100pc, 20 each color.
3. Small Low-Current: Kingbright 3mm, £3.50 (incl. S&H) for 25pc (14p ea).
4. Large Low-Current: 5mm, £2.62 for 10pc (26p ea.) (Spiratronics on Ebay)
  Note – the multi-colored special LEDs are auto-flashing, and make great wearable Christmas jumper LEDs
5. LED holders are sized to match: 3mm LED holder, 50 pc. £1.17, larger size: 5mm LED holder clip panel, 50p for 50 pc.
  1. RGB LEDs are able to make any color! They come in 3 flavors: auto-flashing LED, RGB LED, and SMD RGB LED
  2. KY-034 – 7-color Auto Flashing LED module, 5pc for £7 next day £1.40ea), or 3pc for £5 next day (£1.66 ea)
  3. KY-016 – RGB 3 color LED module (4-pins), 5pc for £3 (60p ea)
  4. **KY-009 – RGB 3 color SMD LED module aka Colour Mixer (4-pins), 5pc for £4 next day (80p), recommended for colored lighting work, as these have a very nice integrated miniature lightpipe in which the colors get mixed, to produce one color output.
  5. KY-011 – Dual Color LED Module, £5.40
6. Addressable LED strips (able to light any pixel with any color) – software control, SK6812 (RGBW) & variants – Products: 1m strip IP67 144 leds/m, SK6812, £22 6 weeks or £36 same day, or £25 for 10×10 matrix (100 LEDs)
7. Lens for Flashlights. Flashlight enthusiasts | Projection Flashlight | £5 Wilko Halloween Projection Flashlight with 5 lenses, or £0.50 direct from Wilko
Resistors & Potentiometers
1. Resistors are rated by power dissipation. Standard are 1/4W. Then you have 1/2W, 0.6W. Then the high power applications 1W+ rated.
2. Resistors are rated by tolerance. Standard carbon film (cream body) are 5% tolerance. Precision metal film (blue body) are 1% tolerance.
3. Resistors in series add rating.
4. You don’t need every value. These 3 values are the most needed: 1K (good for LEDs, get 50x), 10K (good for pullups, get 50x), 100k (good for audio signal mixing, get 50x), These 12 values are a sensible assortment: 100R (protects switches against surge capacitors, get 20x), For LED brightnesses: 33R, 220R, 470R, 1.5K, 2K, 5.2K, 20K- get 20x each. For high resistance, get 1M, 2M, 5M, 10M – get 10x each. The rest of the values are useful when creating e.g. precise frequencies for oscillations (using RC circuits/transistors, or 555 timer ICs).
5. Most digital electronics is low power. Fresh 9V DC battery (9.45V measured) with 470R resistor produces ~20mA current or 180-200mW of power. The resistor will get quite hot to the touch but can endure this without damage.
6. What happens if you increase power above the rating of the current limiting resistor? Doubling the power with a 220R (45mA current, 425mW power) gets the resistor burning hot to touch. Doubling again to 100R (90mA current, 800mW power) will literally smoke the resistor.
7. Bottleneck components: Resistors (standard 1/4W, but can go up to 6W rated), Transistors (2N2222 are rated at 1A but get hot at 650mA, can step up to TIP122 Darlington at 5A), 22 gauge single-strand hookup wire rated at 7A (XmA hot / xmA melt)
  For audio applications, keep in mind that speakers are often 8R, so no point in going below this if the desire is to maximize current (just remove the resistor and use speaker resistance alone).
8. Higher power resistors allow measuring higher currents through a circuit. Don’t forget that 22AWG also have a max rating of ~5A after which they will melt. Your multimeter likely also has a 10A fuse which will blow if you try to mass more current through.
9. High currents can be generated by shorting a 9V DC battery or 2x9V DC batteries in parallel. But be careful, either use a reliable fuse, or keep the flow time very small (1 sec max). More will make the battery burning hot and melt the wire harness. Wear safety goggles if you try this!
Resistor color chart for standard precision (5-10%, 4-color bands, tan body) and high precision (1%, 5-color band, blue body) varieties
1. Resistor Assortment Kit low power 1/4W (250mW) rated
  1. Standard 5% tolerance carbon film (cream body): 1500 pcs for £7 (0.5p ea.) next day dlvy w/ Prime, 75 values x 20 pc. ea, 5% tolerance. Values: Ohms: 1R, 2R2, 4R7, 5R6, 7R5, 8R2, 10R, 15R, 22R, 27R, 33R, 39R, 47R, 56R, 68R, 75R, 82R, 100R, 120R, 150R, 180R, 200R , 220R, 270R, 330R, 390R, 470R , 510R, 680R, 820R
    Kohms: 1K, 1K5, 2K, 2K2, 3K, 3K3, 3K9, 4K7, 5K1, 5K6, 6K8, 7K5, 8K2, 10K, 15K, 20K ,22K, 33K, 39K, 47K, 51K, 56K, 68K, 75K, 82K, 100K, 120K, 150K, 180K, 200K, 220K, 300K, 330K, 470K, 510K, 560K, 680K, 750K
    Mohms: 1M, 1M5, 2M, 3M3, 4M7, 5M6, 10M. Get the 75 value pack for £7 (0.5p ea) and then replenishment commonly used resistors individually (1K, 10K). These arrive in neatly labelled sheets of resistors.
  2. Low 1% tolerance metal film (blue body): Resistor Kit, 600 pc. for £3 (0.5p ea.), 30 values x 20 pc. ea (10R to 10M-ohm), 1% tolerance Values: 10R, 22R, 47R, 100R, 150R, 200R, 220R, 270R, 330R, 470R, 510R, 680R, 1KR, 2KR, 2.2KR, 3.3KR, 4.7KR, 5.1KR, 6.8KR, 10KR, 20KR, 47KR, 51KR, 68KR, 100KR, 220KR, 300KR, 470KR, 680KR, 1MR
  3. Individually (5p each with MOQ25), 5x more expensive (Spiratronics) but more cost effective for particular values: 1K, 10K, (common) 680R, 820R (substitutes)
  4. Bulk specific values: 10KR 500pc for £7.35 (1.5p ea) or 100pc for £2.80 (2.8p ea) | 1KR 200pc for £5 (2.5p ea) or 100pc for £1.69 (1.7p ea) | 680R 100pc for £2 (2p ea), 5 days or £4.44 (4.4p ea) next day
2. Resistors for high power/high current applications. P= VI = V^2/R.
  1. 1000 pcs 1/2W (500mW) rated carbon film resistors, clustered around low Ohm ratings, £20 Spiratronics
    Best value – power resistors, assortment, hand selected, 35 pcs for £8.25 (23p ea), 1/2W, 1W, 2W, 3W, and 6W resistors, from 5R to 200R
  2. 10-pack sheets 1/2W fixed value resistors: 10pc for 44p, individual values choose *100R (for 1/4W draw @ 5V), 56R (450mW draw @5V), 33R (750mW draw @5V),
  3. 1W metal film resistors, 16p ea. MOQ5, individual fixed values, get 100R, *33R (450mW draw @5V), 22R (1.14W draw @ 5V)
  4. 2W metal film resistors, 11p ea. MOQ5, individual fixed values, get 33R (5 ea)
  5. 3W metal film resistors, 19p ea. MOQ5, individual fixed values, get 22R (1.14W draw @5V), 10R (2.5W draw @5V), (5 ea), allows up to 600mA at 5VDC
  6. 6W wire wound resistors, 73p ea., individual fixed values, get 5R (2 pc), 150R (2pc), allows up to 1.2A at 5VDC.
  7. 150R, 1W, 10 for £1.97 (20p ea.)
  8. 10R, 10W, £1.02
  9. 1R, 100W, £1.37
3. Trimmer pots, single turn screw. Box kits with many values:
  Once you have prototyped your circuit with the screwdriver adjustable trimmer pots, then you can select the specific 6mm shaft diameter potentiometers with the right values and in the right quantity, either with rotary control knob, or separately. Article1 Article2
4. Potentiometer shaft diameter 6mm:
  Two types of potentiometers (pots) linear (B-taper) or logarithmic (audio, A-taper, or C-taper for reverse log) based on how the resistance varies as you turn the shaft. Audio (A-taper) pots are typically used for volume control since the human ear perceives loudness according to a logarithmic (dB) scale, so A-taper pots are perceived to vary volume uniformly throughout their range. B-taper (linear) pots will deliver what seems like 100% of the volume change within 5% of the pot range. Article 1 (with graphs), Article 2, Article 3.
  PCB pots are preferable for precise knob control– the chassis mounted pots have a phenolic pcb base which is heat-sensitive and prone to dodgy solder joint connections.
  
  PCB Pots – A (audio, logarithmic) taper
  BEST VALUE: Taiwan Alpha Breadboard/PCB pots with right-angle insertion and knurled shaft:
  All values – RV09 10k 4pc for £6 (£1.50 ea).
  Next best – some values
  Kit of 22pc for £32 (£1.48 ea): Values: 4x1K, 2x2K, 4x10K, 2x50K, 4x100K, 2x500k, 4x1M
  Knobs for this shaft (£1.75-2.75 ea)
  
  PCB Pots RV09 – B (linear) taper
  Most flexibility: any value, any taper, 10pc for £3.50 (35p ea), 10pc for £3.00 (30p ea), 100pc for 14.20 (14p ea)
  BEST VALUE: Ascot City/Sourcing Map Breadboard/PCB pots with right-angle insertion and knurled shaft:
  9 values, 5 each, £10.50 for 45 pcs (23p ea), 1K, 2K, 5K, 10K, 20K, 50K, 100K, 200K, 500K, 1M
  BEST VALUE: Any value, any taper, 10pc for £3.50
  10K: 10 pc for £6.50 (65p ea) next day
  100K: 10 pc for £6.00 (60p ea) next day
  1M: 10pc for £5.20 (52p ea) next day
  
  Linear Pots (B Taper)
  Small values kit 10 potentiometers with red knobs, 10 values, 1 ea., £6.50 next day (65p ea.)
  
  B1K ohm linear, 10pc for £3 (30p eah), 82p for 2 pc (41p ea.),
  B10K 10K £1.73 for 10 pc (17p ea.), SLIDE pot 10pc for £13 (£1.30 ea
  B100K 100K £1.14 for 5 pc (23p ea.),
  200K, £2.35 for 5 pc (47p ea.)
  B500K 500k, £1.32 for 5pc. including knobs (black w/ blue face and black stripe), (26p. ea.)
  B1M 1M £2.46 for 15 pc (17p ea.)
  
  Audio Pots (A-Taper, Logarithmic taper)
  4x A10K 60mm SLIDER pots, lowest price £1.78 ea, currently 4pc for £8.10, (£2.02 ea) Wiring detail
  
  Cylindrical PCB mountable (but not breadboardable)
  A1K – log (A) taper – 5pc for £2.75 (53p ea) or 5pc for £2.75 (53p ea) dual pins These A1K 6mm pots work great and deliver smooth audio response.
  My preference would have been for pins instead of solder lugs in order to use them directly for PCB/breadboard insertion, but this is stated in the description, and for the price it’s easy enough to workaround (solder hookup wire to the lugs). These comfortably handled measured 3W of power (2A at 1.5V in circuit measurement, powered by 5V DC wallwart). In tolerance test, they began to overheat at 11W of power (3.8A @ 3.0V, powered by 9V DC wallwart), and continued working for extended duration when 3W power restored.
  
  A10K – log (A) taper – 2 pc for £2.50 (£1.25 ea)
  A20K – log (A) taper – 2pc for £2.68 (£1.34 ea)
  A50K – log (A) taper – 2pc for £2.48 (1.24 ea)
  A200K – log (A) taper – 2pc for £2.48 (£1.24 ea)
  A500K – log (A) taper 10x 500K-ohm for £4.00 (40p ea.)
  
  Wiring – three circuit designs, two distinct choices: variable resistor (rheostat) or voltage divider (potentiometer). Both choices use the same hardware, which has a twist pole (6mm typical) and three pins so you can choose which direction you want the increasing resistance.
5. Rotary control knobs for Trimmer potentiometers 6mm shaft diameter:
  - Black w/ red top and stripe, 10 pc. for £1.30 (13p ea.)
  - Black w/ yellow stripe 10pc for 72p (7p ea.)
  - Black w/ white stripe 10pc for £1.10 (11p ea.)
  - Silver metallic dials, 5 pc. for £1.42 (18p ea.)
  - Red, with lettering “Volumex1, Tonex2”, £1.42 for 3pc. (42p ea)
  - Calibrated Knobs 4pc for £6 (£1.50 ea), 18pcs for £9 (50p ea)
Capacitors (1uF = 1k nf = 1m pf, so 0.1uf = 100k pf)
Two types: Electrolytic (cylinder) with polarity and Ceramic (disc) without polarity. For electronics work, get 16V rated caps (not 50V rated) to reduce physical bulkiness. Intermediate values can be reached by summing the value of capacitors wired in parallel.

Applications: (1) Smoothing capacitors reduce voltage ripple in a power supply, (2) Decoupling capacitors stabilize voltage against spikes and drops, (3) RC capacitors providing charge/discharge timing, e.g. for oscillators, (4) Coupling capacitors block low frequency DC and allow higher frequency AC to pass, e.g. in amplifier circuits for speakers.

Decoupling/Smoothing/Bypass capacitors (Wikipedia) reduce voltage ripple from a power supply, from 0.1uF (#104) to 10uF (to smooth a 30mV ripple) on up, observable on a scope, or calculated through an equation

Notes:
Capacitors voltage is often either 16V/25V/50V. No need for bigger 50V. 16V is fine. But higher does no harm.
1. Large (>470uF)
2. Medium Electrolytics (470uF-1uF, less than 1s charge time) from 1uF to 2200uF.
3. Lowest price: 120pc for £1.43 (1p ea). @25v/16v: 2200uF, 1000uF, 680uF, 470uF, 330uF, 220uF, 100uF, 47uF , 33uF, 22uF*, 10uF, 4.7uF, 3.3uF, 2.2uF, 1uF. Currently: 300pc for £8 (2.6p ea) 15 values, 20x each up to 470uF with storage case (next day).
4. Small Ceramics / Electrolytics Kit: 1000 pcs for £4 (0.4p ea.), 50 values (1pf-100nf=100kpf) x 20 pcs ea.
5. To replenish individual values, it is cheaper to buy 10-packs from Spiratronics and pay the £1.25 2-day shipping:
  100uF / 10V at 40p for 10 (4p ea)
  10uF/16V, 6p ea (MOQ10)
  100nf and below (Spiratronics)
  47nF = 47k pf = #473 10pc 26p
  10nF = 10k pf = #103 10pc. 26p
6. Custom value ceramic capacitors:
  10uF – smoothing capacitors for power supplies/batteries
  0.1uF = 100k pF (#104) – smoothing capacitors per IC – 100nF = 100K pf = 0.1uF = #104 10pc. for 26p (2.6p ea) or 100 pc for £3 (3p ea)
  22pF – pair of capacitors for 16MHz crystal oscillator, for use with Atmega328P standalone with standard bootloader fused for 16MHz external clock. 10pc for 31p (3p ea)
  3.3 uF capacitors, 30pc. for £1.25 (4p ea.)
  330nF (=0.33uF) 25 pc. £3.64. This is an important value for 9V to 5V DC to DC regulators, and is slightly more convenient than choosing 220nf + 104nf (324 equivalent capacitance).
7. Trimmer Capacitors 45 pc. for £5.00 (11p ea.), 5pF to 120pF, 9 values x 5 pc. ea.
Transistors are electronic switches which consume a forward voltage drop. Two types, BJTs (collector, base, emitter), and FETs (source, base, drain), each of N and P types. NPN is normally off and a current to the base turns it on; PNP is normally on and current to the base turns it off. Choose based on max rated current, gain, and max switching frequency.
- Max rated current: TIP3055 (Darlington array) upto 15A, TIP122 (Darlington) upto 5A, 2N2222 upto 1A, 2N4401 to 600ma, and 12N3904 to 100mA
- Signal frequency considerations (e.g. in audio or radio applications).
- RTL logic inverter application.
- SPST, SPDT, and DPDT switches
- RC oscillator circuit using caps
- variable current production by lowering the current through the base well below the saturation point of the transistor (ie where the gain must fall below max rated gain because the circuit limits the flow). E.g. a 5V circuit with 1K resistor and yellow LED, this means using between 100K and 1M resistors on the base signal. Anything smaller resistance, and you’re essentially saturing the transistor anyway.
1. 2N2222 Transistor (Amplifier), NPN (normally open)-type, 100 pcs for £1.59 (<2p ea.), forward voltage drop 0.7V, current gain 100x hFe, max current 1A , Component Notes and Pin Diagram
  
  2N2222 Transistor, 600mA rated, With flat side to the right, collector leg is on top.
  
  Darlington transistor arrays can be obtained in an IC package (ULN2003A) as they are common in stepper motor driver applications.
2. TIP122 Darlington transistor TIP122, rated to 5A, forward voltage drop 1.4V, 10pc for 1.08 (18p ea) Component notes and pin diagram
  PUT (programmable unijunction transistor) offers another approach to building oscillator circuit, with fewer components.
3. 2N6027, 10pc for £6 (0.60 ea) Datasheet: 2N6027 datasheet
4. B521 MPF102 Transistor £2.63 for 10 pc. (26p ea.) for use with LM386 Audio Amplifer chip.
Inductors Understanding inductor parameters SMD Inductor packages are specified by a max plane dimension and height, e.g. CD54 is 5mm max width/length and 4mm height, CD43 is 4mm width/3mm height, CD103 is 10mm width/3mm height. Inductance is indicated by standard electronic terminology for resistors, capacitors, inductors, e.g. #470 means 47uH, #101 means 100uH, #4R7 means 4.7uH.
1. Inductor Cores: Green Toroid Ferrite Cores: 10mm x 6mm x 5mm, 79p for 10pc (8p ea)
2. CD54 series SMD power inductor wire wound chip, various values, 5pc for £2.77 (55p ea.)
3. CDXX series SMD power inductor wire wound chip, various values and formats, 50pc. for £2.50 (5p ea)
4. CD43 series
5. CD75 series
PHYSICAL USER INTERFACE DESIGN OPTIONS:
1. LEDs: When only binary (on/off) input is needed
2. Display: OLED display (I2C comms) – 2 pins. Or TFT display (color). When linguistic information is needed.
3. Switch: More than 4 way switch becomes clunky – (4 pins)
4. Buttons: More than 6 buttons becomes clunky (use a shift register to reduce to 3 pins)
5. Rotary Encoder: When have between 5 and 15 choices
6. Rotary Encoder with Coarse & Fine Grain selection: when have between 10 and 100 choices
7. 12-key Keypad (10+2) & 4-way selector switch: when have up to 48 choices
8. 16-key Keypad (4×4) & 4-way selector switch: when have up to 64 direct driven choices
9. 16-key Keypad (4×4) & 4-way encoded switch: when have up to 256 choices
10. Larger Keypad
11. Macro Keypad: Hackaday 18 concepts, 51 more and a few more (413) | stream deck | bluetooth with ESP32 | shortcut keypad | full tiny keypad for under $5 using CH552 uc
Switches
1. EXCELLENT: Momentary push-button tactile switch, normally open, SPST, momentary, non-latching: 100pc for £3.49 (3.5p ea). Notes: Long 5.5mm pins better for breadboarding. Button height 5mm preferred to 4.5 or 4.3mm. 9mm can have button caps 6x6x9mm with caps (£10 for 50 pc (20p ea). 4 pins preferable to 2 pins (2-pins are mechanically unstable and hard pushing breaks solder joints on PCB or removes from breadboard). Better to have 4-pin variety. These buttons make a clicking sound when pressed.
  Momentary on switches (non-latching) that let current flow when pressed down. Other type is normally closed.
2. Conductive Silicone soundless tactile button, 4-pin or 2-pin DIP, 20pc for £3.50 (18p ea)
  Debouncing switches is a fine art. Jack Ganssle’s excellent white paper (PDF). using software – excellent discussion of mechanical bouncing. Summary: Sample twice 10ms apart (1ms is typical bounce period, 10ms to be safe) and check to see that the value has settled, then act.
3. Caps for 6x6x5mm Tactile switches. 55pc for £2 (4p ea)
4. EXCELLENT: Micro limit switch SW158, markings on pins: Common (C) closest to hinge, then normally open (NO ), then normally closed (NC). Lowest price: 13p ea (60pc for £8 next day) | Current price: 20 pc. for £3 (15p ea), prime. EXCELLENT for low-force repeatably reliable pressing, e.g. for piano keys.
5. Latching Push-Button Switch. 2-pole OFF/ON – Assorted buttons, select individually, 50pc for £8.60 (17p ea). Or individually: KAN112D black 2-pin 10pc for £2.15 (22p ea), KAN1208D black/white 2-pin 10pc for £2.10 (21p ea), KAN1288BM black/white, Ultra-Thin 12*12*9.4, ebay or red button 2-pin 5pc for £2.72 (54p ea) or Red 5pc. for £1.51 (30p ea.), 2-pin or Black 5pc. for £1.91 (38p ea) 2 vertical pins 3-pole OFF/LEFT/RIGHT Black 5 pc. for £1.71 (34p ea.) 3-poles OFF/LEFT/RIGHT 3-pins right angles 3-pole OFF/ONE/BOTH 4-pins Red 3-poles OFF/LEFT/RIGHT or OFF/ONE/BOTH 4-pins, 10pc. for £2.22 (22p ea)
6. Latching Tactile Switch. 9 pcs DPST for £1.09 (12p ea.) with DIP-6 pins or 25 pcs DPST for £3.11 (12p ea.) DIP-6 pins.
  Note: there are SPST switches with 3 pins on the same side for half price (6p ea) but would recommend to avoid these. While the pins make them breadboardable, the asymmetric location (all 3 pins on the same side) and the fact that the pins are a bit short, means that these switches tend to pop out at the slightest disturbance. Remedies (none ideal) (a) hot glue in place (b) solder some hookup wire to the pins to lengthen them; (c) use panel mount buttons instead and mount elsewhere with jumper wires or cable, (d) use DIP switch instead, (e) use a bit of BluTac when seating them; (f) jam in one of their pins into sharing a hole with the other in-feed wire to tightens the fit; (g) use DPST switches (twice as pricey at 12p ea.) which have 6 pins, 3 on either side, giving the switch stability in breadboard use.. Panel mount: Fancy colored latching push-button switches, 10 pc. for £7.86 (79p ea.)
7. EXCELLENT: SPDT slide switch: Breadboardable: Lowest: 50pc. for £1.04 (2p ea.). Currently: £4.68 for 100pc (4.7p ea)
  Panel Mount: 20 pc. for 13p (<1p ea!)
8. Slide Switches:
  Excellent for building custom UIs for HW configuration, combined with shift registers. 1PxT switches can be used instead of more expensive rotary switches, or microcontroller solutions.
  
  WARNING! Panel Mount switches are not likely to have pins that fit standard breadboard pitch of 2.54mm. Even PCB mounted switches may not have standard pitch (e.g. 2.0mm or 1.5mm). Be sure to check with the seller/vendor!
  - (tried) 1P2T slide switch (see above)
  - (tried) 2P2T slide switch on/on 10pc for £3.14 (31p ea) or for £7 (70p ea) next day, or for £6.50 (65p ea) right angle switch next day
  - (tried) 1P3T (4 pins): PCB Mount: Panel Mount: 20pc for £6.50 (33p ea), or slide switch 5pc for £4.50 (90p ea) next day or right angle 10pc for £4.20 (42p ea) or 20pcs for £5.34 (25p ea)
  - (tried)2P3T (8 pins): PCB Mount: 20pc for £7.70 (39p ea)
  - 1P4T rotary switch £6.12 for 2pc (£3.06 ea),
  - (tried) 1P4T slide switch: 10pc for £10 (£1 ea), 3 days (ebay)
  - (tried) 2P4T slide switch: PCB ready (2.54mm standard pin pitch), 5pc for £4.35 (87p ea) ebay, or 5pc for £6.50 (£1.30 ea) 2PxT switches can implement any $2^n$ choice. WARNING 1 When using in breadboard, this will be a 1P4T as the pins are not separated far enough apart to straddle the IC chip divide to keep the two poles separate. WARNING 2 The case is metal so be frugal with soldered connections to avoid shorting to the case (test that this has not happened before live test).
  - (tried) 3P4T £1.30 ea
  - 1P5T £8 rotary
  - (tried) 2P5T rotary switch 2.26ea
  - 8P5T rotary 6mm, £5.24
  - 8P5T rotary 6mm, £5.24
  - 1P6T £3 with knob, or £3.12 (was £1.30)
  - 1P7T £6.37 or £7.50
  - 2P8T, £9
  - 1P10T £9.50 next day
  - 1P12T £7 next day
  - 1P16T – cool rotary hex entry switch $3 ea
9. DIP switches:
  Kit of 35 pcs for £5.27 (7 varieties, 5 each, 15p ea.)) or Kit of 44 pcs for £7 (6 varieties, 10ea. of 2-,4-,6-,8- position and 2ea. of 10-,12- position, 16p ea.)
  or Individually:
  1-bit (DIP-2 pins), 10pc. for £1.11 (11p ea.) Note: you’re better off with breadboard-able SPST slide switch at 2p ea.,
  4-bit (DIP-8), 5pc. for 89p (18p ea.),
  5-bits (DIP-10 pins), 8pc. for £1.35 (17p ea.),
  8-bit (DIP-16 pins), 10pc. for 98p (10p ea.) or 10pc for £3.20 (32p ea.) or 10pc for £2.20 (22p)
  10-bit (DIP-20 pins), 10pc. for £1.87 (19p ea.)
Relays
Relays can be latching (with memory) or non-latching (without memory), or momentary. Dual-pole Relays allow connecting independent circuits, one to each pole. The number of poles indicates the number of basic states. While a dual-throw switch may also have a center off position for relays this requires adding another relay to manage power. Connecting DPDT relay
1. DPDT 8 pins – wiring diagram
  12VDC 10 pcs for £3.51 (35p ea), mini size, 10 pc HK19F for £10.07 (£1.07 ea), 10 pc HK19F for £9.90, three days
  
  9VDC Omron G5V-2-H1-DC9 DPDT 1A 9V NON-LATCHING (DigiKey UK), £4.96 (for 2 pc) – All DigiKey (16 relevant) – these aren’t cheap UK sources: RS-Online, Omron G5V-2 9DC £2.81 ea. in pack of 5 and Farnell, Schrack RT424009, £2.88 ea. in qty x1 or Jameco Electronics, Kemet UA2-12NU
  
  5VDC Omron G5V 5 pc for £4 (80p ea) ebay
2. SPST
  5VDC 10pc for £4.40 (44p ea), or £6 for 5x KY-019 relays (£1.20 ea.) w/ Prime Delivery or £5 for 3x KY-019 relays (£1.66 ea.) or £5.50 for single board with 4 channels
Buzzers (Active) and Speakers (Passive)
1. Active Buzzer (DC): Lowest: 11p ea (£1.06 for 10pc, 5V 85dB). Or: £5.65 for 20pc (28p ea.) or £7 for 7pc (£1 ea.), 6V-12, 10mm, 85dB@5V
2. Siren/Alarm (Active) Buzzer (DC): BJ-1K 100dB, 40mA draw at 5V (200mW), externally mountable alarm speaker, £3. BJ-1K is a definite ear-splitter even at 5V.
3. Loud PASSIVE Buzzer, 1300+/-500Hz (1 full octave), 85dB, rated to 12VDC., 2pc for £5 (£2.50ea). Note requires oscillation circuitry.
4. Mini Speaker, 8-ohm load (measure resistance/impedance directly and round up to 4,8,16 ohms) :
  ASSEMBLY TIP: when soldering wires to a speaker, or if it comes with wires attached, use hot glue gun to put a drop around the solder points. This provides strain relief against the speaker wires. If those come off or pull off the solder pad, the speaker is unrecoverable.
5. 0.25W 2″ speaker sounds much better than 1W PC mini speaker. | Advice on sounding better (avoiding clipping and distortion).
  1. 0.25W speaker: Lowest price: 2″ (50mm) diameter ultra-slim, £1.01 ea. (Spiratronics). Current price: 1.6″ (40mm), £2.90 (Spiratronics) comes with attachment points for cables or clips
  2. 0.5W speaker 28mm, 4 pc. for £1.08 (27p ea.) or 28mm, 4 pc. for £1.30 (33p ea.) attachment points are solder pads – requires a soldering iron
  3. 1W speaker, Lowest price: 29p ea (10pc for £2.91) | Current price: 28mm, 10 pc. for £7.50 (75p ea.), 3 weeks
  4. 1W PC Speakers: 10mm diameter: 5pc for £2.54 (51p ea.) or 5pc for £2.66 (53p ea.), each with “PC” speakers, 1W,
    w/ pigtail wires 26 AWG (need to use grabber probes and 22 AWG wire to use with breadboard, or solder onto 22 AWG wire – note the wires have limited strength; if they break off the speaker is toasted — see ASSEMBLY TIP above)
  5. *good* 2W speaker, round:2pc for £5 (£2.50 ea) 3 weeks, 22mm/1.1″, 2pc for £6 (£3 ea) next day, or 2pc for £8.50 (£4.25 ea) next day, or 36mm 10pc for £13 (£1.30 ea), 6 weeks
  6. *best* 5W speaker (no need for amplification IC): Oval broadband speaker 70mmx30mm 4pc for £10 (£2.50 ea) next day or 4pc for £8.50 (£2.12 ea) or 4pc for £5.62 (£1.40 ea) incl. S&H (lowest price 90p ea)
  7. 10W speaker: 2 for £7.01 (£3.50 ea.) 30-day shipping
  8. Bluetooth Wireless speakers (consumer product not electronics component): Ewa, £10, IP67 (Waterproof) or Lenrue £13, IPX5 (Shower/Outdoor)
    Note, sub-1W PC speaker (10mm diam.) does not need amplification to be heard when testing, provided use a 100uF coupling capacitor and voltage to speaker is large enough. In applications an amplifier chip will be useful (LM386 IC is easy to use, supports 9V input, and is inexpensive). A 5W speaker does not need anything to be heard quite well.
    
    Be careful of applying too much heat — if the solder pad comes off, the above inexpensive speakers are likely toast. Scraping back the black seal with a knife does not reveal a wire to connect to.
    
    I use hot glue to provide a protective seal around the solder pads/wires once they are soldered on, to prevent mechanical pressure lifting the pads up.
1. KENABLE audio store @ Amazon – good prices, deliver in a few days, all things audio
2. Mono TS (tip sleeve) audio cable, M-M, right-angle/regular: 0.5m £1.94, 1m £2.05, 2m £1.78, reg/reg 0.5m, 1.0m, 1.2m, 2.0m, 3.0m, 5.0m, £1.91-£3.03
3. Audio Adapters: 6.5mm mono coupler F-F (socket-socket), £1.80, | F-M (socket-to-plug) **6.5mm mono socket to 3.5mm mono plug, £1.94 or 5pc for £7.30 (£1.46 ea) next day works great for plugging into electronics 3.5mm female pcb mounted socket to allow the device to be connected to an amp using standard amp MONO TR cables (6.5mm M-M) | 3.5mm stereo socket to 6.5mm mono plug, £1.76, WARNING: this shorts the two stereo channels and sends them to TIP, 3.5mm mono socket to 6.5mm stereo plug, 3.5mm stereo socket to 6.5mm stereo plug, 3.5mm separate mono sockets to 3.5mm stereo plug (c.£1.80 ea, £2.30 for latter – Kenable store)
4. Behringer MX400 4-channel line level mono mixer – £18 next day – perfect for combining multiple electronic instruments and sending into a single amp! 🙂
5. Breakout: 3.5mm mono socket to 2-pin terminal block, 5pc. for £9 (1.80ea)
6. PCB mount: 3.5mm stereo socket to 4-pin pcb mount connector (non-breadboardable), 15pc for £4 (25p ea)
Diodes The stripe indicates the negative terminal. Forward voltage drop of 0.7V.
1. Rectifier Diodes – 1N4001 50V 1A 25 pc for 50p (2p ea.) or 50 pc to £2 (4p ea.), 1 week (note, under magnifying glass can see 1N4001 written around barrel)
2. Signal (Switching) Diode – 1N4148 300mA 50 pc for £2.00 (4p ea.) (reddish glass with black stripe)
3. Zener Diodes – 0.5W rated Lowest price: 0.8p ea (300pc for £2.40), 1W rated: £3.95 for 250pc (1.6p ea) 3V-33V 25 values 10pc ea
  Used to ensure a minimum voltage supply / detect a MINIMUM voltage violation (e.g. low battery, and shutdown). Can use to build your own buck (stepdown) voltage converter and regulator circuit | Calculate the current through a Zener like this: V_source – V_Z / R = I_eff | Maths for working with Zener Diodes | why it doesn’t work on real (non-constant) loads (I tried it with the analog piano) – the battery sagged less than the diode! | Similar explanation – zener diodes only regulate at low current with fixed load, i.e. they are useful to provide reference voltages | Remember you need an adequately sized resistor to dissipate the delta between V_source and V_z or if the load current varies between max and min (e.g. volume control on audio), or the zener diode will run hot.
Display Elements / Lights I recommend getting 4x 7-segment displays (for a basic 2 digit calculator, 1 serial (16-pin) 1602-LCD display to understand such displays, but then use OLED I2C displays for all of your standard display needs)
LCD (liquid crystal display), TFT (thin film transistor) LCD, OLED (organic LED), MicroLED, and QLED (quantum LED) display technologies. Gist: LEDs are lower power light-emitting diodes. OLEDs, MicroLEDs, and QLEDs use these as individual pixels which means no backlight required. By contrast, LCDs require an always-on light source (backlight) which is blocked or allowed to shine through the liquid crystal interface using electrical charge. By creating granular spatial control of the LCD surface, the technique can get pixel-level control instead of the usual calculator-like segments.
1. 7-segment display, Red LED 0.5″ 10-pin, 10 pcs £1.15 or Kingsbrite SC56-11EWA 0.56″ height, low current, red common cathode (Digi Key), £3.20 (3 pcs)
2. LCD display 1602-module (16 characters per row, 2 rows), 5VDC, HD44780 LCD controller chip, 80x36x10mm:
  - 16-pin (serial) 1602-model requiring 7 I/O ports to control: £2.02 (without pins) or £6.68 for 5pc (£1.34 ea) without pins, or £4.00 Prime Delivery
  - 4-pin (I2C) 1602-model, I2C interface requires only 2 I/O (data) pins to control. Backlight & contrast can be manually controlled with potentiometer and/or jumper pins: £1.96 or £9.78 for 3pc (£3.26ea) with Prime Delivery
  - 4-pin (I2C) 2004-module (20 characters per row, 4 rows): £3.50
  Reference: Connecting the serial 1602 to a breadboard
3. OLED Display: Organic LED is a high luminosity self light-emitting technology that does not require backlight and so uses lower power than LCD. High pixel resolution allows displaying graphics through individual pixel manipulation, and text. Device driver readily available (see below) Note, all OLED displays below use the SSD1306 driver IC chip. These are about half price vs. those that use SH1106 driver chip (advantage of latter is Tiny Graphics Library that does away with buffer writes, so can fit on ATtiny85 MCU). | Tiny Tetris demo with real-time (unbuffered) drawing and detailed post here | Default address is 0x3C. Can change to 0x3D using SMT resistor to back of board, or using I2C multiplexer, or custom library with one SDA line per display
  1. comprehensive catalog on Ebay – all sizes and comms types
  2. 128×32 pixels (4 rows of text) 0.91″ I2C interface (4 pins): Low: £2.10ea £8 for 2pc (£4ea, without pins) with Prime Delivery
  3. 128×64 pixels (8 rows of text), 0.96″, blue, white, or yellow-blue: lowest price: £2.13. Currently: 6pc white or blue for £18 (£3.00 ea) same day
  4. 128×128 pixels 1.5″ (16 rows of text: cheapest price: £5.86 (expired). Active: £12.82 next day
  5. 128×64 2.4″: £10.50 (SPI)
  6. 128×64 2.7″: $50 (SPI)
  OLED Display is driven by SSD1306 display chip. Driver for use with Arduino is Adafruit’s ssd1306_i2c.ino. Tutorial for connection and use.
  
  These 128×64 pixel I2C OLED displays are crisp, sharp, and bright. Easy to display text or turn on individual pixels (graphics) by using device driver software (Adafruit_SSD1306.h/.cpp and Adafruit_GFX.h/.cpp) for the integrated SSD1306 driver chip. Because they are I2C controlled, you need only use 2 pins on your microcontroller (not including 5VDC power/ground) instead of 4 pins for SPI control or more pins for standard LCD.
  For advanced users, it’s also possible to control the OLED display directly through I2C by sending byte commands and graphical data to the SSD1306 chip without requiring a software buffer reducing memory consumption. I’ve written an Arduino Forth to make this easy. One neat feature built-into the SSD1306 is software configurable scanning direction control which means the display can be mounted in 4 different ways and the content can be screen flipped on the fly. Watch-out: careful you check whether you are buying single color or dual color display (e.g. Yellow/Blue). The colors can’t be changed. (For that you need a TFT display.)
  Bottom line: this is an elegant, aesthetic, and highly versatile device, easy to use for beginners and advanced users alike.
4. TFT Full 18-bit color Display with SPI (4-wire) interface, SD Card Reader, and ST7735 image controller:
  1. 1.8″, 128×160 pixels, SPI: £4.20 next day or 5pc for £20 (£4 ea)
  2. 2.4″, 324×240 pixels, SPI: £9.80 next day or 3pc for £23 (£7.60 ea) or 5pc for £34 (6.80 ea)
  3. 3.5″, 480×320 pixels touchscreen/touchpen, SPI: £18
5. Flashing Lights: £16 for 7.5W, 12V, (1.6A), (short cable) or £20 for 12V, 25W, (2A), 30 LEDs, magnetic mount, configurable flashes or £9.28 for 10V rotating beacon or £12 for 12V rotating beacon
6. LED Bargraph Display (aka fuel gauge indicator). 10-segment Green only, Yellow only, or Red only, £1.07 ea. (Spiratronics) or 10-segment Greenx7/Redx3 – £3.37 for 2pc. (£1.68 ea.); 10-segment Red, £1.40 for 1pc. or £1.46 for 1pc.; 10-segment Red/Yellow/Green/Blue, £1.50 for 1pc.;
7. LED 10-segment IC Driver Chip LM-3914 £2.66 (Spiratronics) or LM-3914 £5.20 for 1pc. (linear display) and Instructions from Sparkfun
  Three common 10-segment IC driver chips are LM-3914(linear)/3915(3dB)/3916(-20db to +3db). The latter two are usually used in displaying audio signal strength. Video example and skywire demo
8. LED Tower Light RYG with Buzzer on flexi-mount, $27.50, Adafruit

C. Power Supplies (Batteries, Holders, Converters) Fuses, & Heat Sinks

Barrel Jack notes:

2.1mm barrel jack – default is center positive, i.e. inside is positive, shaft is negative. Read to see if center negative (opposite polarity) is specified.
Polarity reversing barrel jack cable 2pc. for £5.60 (£2.80 ea) – useful for centre negative guitar effects pedal and other musical equipments
3-way barrel jack connector cable £4

DC Power Supply (wallwart, 110/220V AC to DC) with 2.1mm barrel jack
Notes:
1. wallwarts are unregulated power supplies. Use 100uF capacitors across their inputs to smooth them. E.g. 9V wallwarts measured at 9.19V and 9.13V (not bad).
  Wallwarts & Brick Basics | How Power Supplies are built: Transformer+Rectifier+Smoothing+Regulator
  1. Breadboard Power Supply MB-102 – convenient form factor plugs into 400+-tie points breadboard (watch out to align +/- with red/blue power stripes), takes 5VDC USB power input or 9VDC wal-wart, converts down to 5V or 3.3V, or both to have two power rails, £4.67 next day, or 3pc for £3.79 (£1.26 ea)
  2. 9V DC 1A 9W £3.95 (two weeks), £4.77 (five days), or 2A 18W for £5.79, five-days, or £8 next day. Also: Center negative 1A £9.74 next day (for e.g. guitar pedals and other musical equipment).
  3. 5V DC 2A 10W: £4.03ea 1 week (ebay), or £3.38ea (MOQ2) ebay, £3.41ea (MOQ2), or £4.69 in 2-3 wks, or £7 next day
  4. Converter cores: 5V DC switching power supply 2A, 10W, no cables, £2.39 2.8″ x 1.5″ x 1.2″ compact
2. Batteries and Holders
  References:
  1. AA have better energy density than 9V batteries: 4.6x more energy, for 3x worse weight and 2x worse volume
  2. Camelion battery information | Table: Internal Resistance of Batteries Used batteries have higher resistance, upto 5x | List of Battery Types Thought all 1.5V batteries were the same? They’re not. Read to understand the properties of different types of batteries. | Zinc Carbon batteries can be 25% cheaper per unit than Alkaline batteries (18p vs. 23p), but you’re typically getting less for your money electrically, except in low drain, intermittent use applications. | When a Lithium battery gets hot… remove, put in open air, cover, let cool. Do not use again | Battery descriptions and stable voltages | CR123 safety | Manually recharging Li-ion/Li-Po batteries with a desktop power supply – punchline, first run at CC (constant current) and the voltage will rise, then charge at CV (constant voltage) and the current will drop trickle charging the last bit of the journey | Li-Po slim high density various shape batteries – charging/building tutorial
    Other batteries: 18650 15969
  3. Table: Power Specs of Common Batteries
    
    Electrical capacity of common battery types.
    Source: https://daycounter.com/LabBook/Battery-Capacity-Comparison.phtml
  1. Battery contacts kits for direct PCB insertion (instead of holders): Contact plate spring kits, 10 pairs for £2 (20p each pair), ebay, Leaf spring kits,
  2. LiPo batteries, high density, thin – example: 3.7V $12 next day
  3. 9V batteries:
    1. Standard current: Current price: 15 for £11.15 (74p ea) 4 for £5.50 (£1.38 ea) or 4 for £6 (£1.50 ea) or 8 for £7.50 (94p ea) or £20 for 24pc (83p ea)
    2. High current: 9V battery high current, £1.59
    3. 9V Battery Clip Connector (Wiring Harness), RECOMMEND: Hard Plastic not Faux Leather which has poor connectivity: £3 for 5
    4. 9V Battery Holder (open), two types. With loose wire £3.55 for 10pc (35p ea, 4 weeks), or £5.00 for 10pc (£50p ea., 4 weeks) or £5.55 for 10pc (£55p ea, 4 weeks), or with DC barrel plug: £11.50 for 10pc (£1.50 ea, 4 weeks),
    5. 9V battery box with barrel plug, Lowest price: 80p ea (MOQ1). Current price: 10pc for £6 (60p ea) or £4.40 ea (MOQ1)
  4. 3V Coin Cell Battery:
    1. CR1220 3V coin cell (smaller), Li ion: £1.65 for 5pc, (33p ea) or £1.60 for 5pc, (32p ea)
    2. CR2032 3V coin cell (button) batteries (thicker than 1220), Li ion: Low: 10 for £1.79 (18p ea). Now: £4.60 for 20pc (23p ea) or 20 for £5 (25p ea), or 20 for £6 (30p ea) or 10 pc for £4.00 (40p ea.), or 10 for £4 (40p ea.)
    3. CR2032 holder: open-holder lowest price £1.08 for 20pc (5p ea) or 82p for 10pc (8p ea), or £4.50 for 20pc (22p ea), or £5.40 for 20pc (27p ea, 3 wks), or £6 for 20pc (30p ea, next day), polarity: + is at the raised neck of the holder; (to see how to remove the battery from the holder later, see here) Enclosed-holder: CR2032 holder with wire lead and button 68p (need voltmeter to identify polarity of the lead wires as they are both white). Vertical open holder: Lowest: 56p ea, Now: 5pc for £4 (80p ea.)
    4. CR2032 6V double coin cell holder: Dual holder enclosed case (6V) with on/off switch and wire leads, 3pc for 90p (30p ea)
      Using the double coin cell holder is not obvious: Cell 1 (closest to wires) goes in with + side up; Cell 2 (furthest from wires) goes in with + side down.
  5. 1.5V Button Cell Battery: LR41, LR1120, LR1130, LR43, LR44=AG13 from 30mAh to 120mAh
    1. LR41 button cell (1.5V): 10 pc for £1.86 (19p ea.)
    2. LR44 button cell (1.5V): 10 pc for £1.85 (19pc ea.)
    3. LR1130 button cell (1.5V): 20pc for £1.88 (9p ea), or 10pc for £1.84 (18p ea), or 10pc for £2.30 (23p ea), or 10pc for £3.25 (33p ea) same day
    4. Holder for LR41, 100pcs for £8 (8p ea.) and alternative
  6. MN21 23A 12V wireless doorbell battery, 2 for £2.28 (£1.14 ea) same day, or 5 for £3 (60p ea) 2 days
  7. Li-Ion 3V Safety Precautions for Lithium batteries
    1. CR123A (CR17345) (3V) Li ion: 2pc for £2.48 (£1.24 ea) or 2pc for £2.55 (£1.28 ea.) or 18pc. for £17 (95p ea) 960 mAh batteries boosted to 5V. These deliver high current and maintain stable voltage for the duration of their life (10 years), so are essential for battery powered motors, and other projects with sustained current draws of 150mA or more. Design details WARNING: If you drop this battery you should assume it is internally damaged, and discard. If you use it, you will find erratic voltage, and it will start to get hot, and a chain reaction may start that causes it to get hotter slowly even if not connected. In this case, put it outside and cover it with a saucepan for a few hours and then you can safely recycle it in a battery recycling center.
    2. Battery holders for CR123A: Best price 24p ea. (2019). Currently: 10pc for £3.88 (38p ea), or 6 pc for £2.50 (42p ea.) or 5 pc for £6 (£1.20 ea.) next day or 20 pc for £10 (50p ea.)
  8. AA and AAA batteries: Zinc Carbon 30pc AA and 20pc AAA for £8.50 (18p ea)
    1. AA Zinc Carbon (14500, 14mmx50mm) batteries: lowest Zinc Carbon was £4 for 28pc (14p ea). Currently Zinc Carbon £4.60 for 20pc (23p ea) or or £4.00 for 10pc (40p ea.) Camelion
    2. AA Alkaline batteries: Lowest Alkaline was £7.45 for 40pc (19p ea). Currently: Alkaline
      32 for £9.79 (31p ea.) Maxell (Same Day delivery), or Amazon Basics, £13.50 for 40pc (34p ea.), or or high current, 74p (for 2 pc)
    3. AAA Zinc Carbon 1.5V batteries (low current capacity): Low 10 for £2.07 (21p ea). Now: 28pc. Alkaline for £6.23 (23p ea.) or 10 for £3.33 (33p ea). WARNING: Not all batteries are the same — LR03 (alkaline) and R03 zinc carbon are the same nominal voltage but R03 have typically half the current capacity as LR03.
    4. AAA 1.5V batteries Alkaline: Low: 32 for £8.46 (26p ea). Now: 16 for £5 (31p ea), or 20 for £9 (45p ea), or 32 for £12 (38p ea.) Maxell (Same Day delivery)
    5. Battery Holder with Flying Leads:
      - Assorted sizes and combinations: Spiratronics;
      - 1xAA, 3 pc for 61p (20p ea);
      - 2xAA, 24pc for £9.00 (38p ea.) w/ Next Day delivery.
      - 3xAA: 2pc for 70p (35p ea;
      - 4xAA: 3pc for £1.02 (34p eac) or 2pc for £2.39 (£1.20ea) or 3pc for £5.29 (£1.76 ea) next day;
      - 1xAAA: 15pc w/ flying leads for £8 (53p ea) next day or 35p ea (Spiratronics) not including shipping £1.49, or 10pc for £4.00 (40p ea) incl. shipping
      - 2xAAA: £1.04
  9. High Capacity AA batteries: Amazon Basics 8 pack for £15 (1.88 ea), 2400mAh, pre-charged, rechargeable, + charger for £8 w/ Same Day delivery, or Tybatt 12 pack for £20 (£1.67 ea), 2800mAh, pre-charged, rechargeable, w/Same Day delivery, or EBL 16 pack for £23 (£1.44 ea), 2800mAh, not pre-charged, rechargeable, w/ Same Day delivery
  10. 18650: rechargeable 3.7V Li-ion battery (up to 3500mAh). 20700, 21700, and 26650 batteries (up to 6000mAh). Example: 18650 used to replace CR2032 batteries
  11. Block battery 6V Carbon-Zinc battery, 4R25, £5.20 w/ Prime delivery
3. Fuses Automotive Blade fuse 3A @ 14p ea. from Spiratronics, these blow immediately (< 1sec) when tested by inducing a short circuit with 2x9V batteries in parallel or Assorted glass quick-blow fuses 100 pc. for £2.77 (3p ea.), 0.2A to 20A, 10 kinds, 10 ea., 5x20mm
  Worth testing a batch of fuses before assuming they’ll blow in case the fuses are defective. These cheaper fuses (3p ea.) did not blow despite batteries and wire harness getting hot, smoking and finally melting, and the fuse still had not blown. Better to spend more on quality protection than risk a fire.
4. Fuse Holders: 5 pc. for £1.47 (30p ea.), clear plastic cover, two-pins, for 5x20mm or 10 pairs for £1.06 (10p ea.), 4 pin per pair
5. Heat Sinks / Cooling Fins: Heat exchanger can exude heat faster by heat exchange through contact with air. Pure copper (401W/mk) has higher thermal conductivity than pure aluminum (237W/mk).
  1. 8x8x5mm Aluminium 5x for 50p (10p ea) (needs thermal adhesive) or thermal conductive double sided tape
  2. 14x14x7mm Aluminium 5x for £1.70 (34p ea)
  3. 16x8x2mm Copper w/ adhesive tape, £1.35
  4. 8x8x4 Copper w/ adhesive tape, £1.31
  5. 50x25x5mm Aluminium w/ thermal tape, £10 (£2.50 ea), w/ Prime delivery
  6. 13x12x4mm Copper, £4 for 8 (50p ea)
  7. Copper Plate: Foil 10x10cm x 0.2mm – £4.09 or £2.98 for 10x10cm x 1.0mm or £2.43 for 0.5mm (10x10cm) or £6.05 for 10x10cm x 1.2mm
  8. Copper wire: 10m x 1.0mm – £3.74
  9. Thermal Conductive Tape, Double Sided: 20mm for £4.74 or £7.59 w/ Prime Delivery
6. DC to DC Voltage Converters / Regulators / Power Supplies
  Four types: Wallwarts (AC to DC converter), Boost converter, Buck converter, Boost-Buck simultaneous conversion.
  Two flavors: Fixed output voltage, Variable (selectable) output voltage.
  Two designs: Switching regulator, and LDO (low dropout, non-switching) regulator
  
  Supply source: selection direct from Canton Electronics (maker of CE012)
  
  Go-to components: LM2596 (blue rectangle) inefficient, NCP3063 (good but SMT), Wurth 173010542 7805, MC34063A[std temp range] or MC33063A[extended temp range] (dip8), HT7133 LDO (Low-Dropout Regulator has no switching noise)
  
  Why not to use MC33063 / MC 34063 chips:
  (1) No built-in thermal protection, no built-in over-current protection/fuses: 25V to 5V step-down using MC33063A IC DIP8 when a short-circuit fault happened outside the regulator.
  (2) Inefficient design, ancient chip. Much better chips and designs out there for battery to 5V boost conversion.
  (3) Requires external inductor, schottky diode, proper heat sinking/thermal management to prevent overheating and damage to the IC, external fuse at 500mA at the input voltage to prevent catastrophic short circuit failures
  (4) The higher the switching frequency the better response rate required from the external capacitors used. Switching frequencies anywhere from 50-200kHz.
  (5) Consumes 4mA while idle (wasteful, considering the ATtiny85 consumes 3mA when running at 100% duty cycle.
  WARNING: This is also why not to buy cheap wallwarts that get very hot. If they have the MC33063 inside, would not be good.
  
  Analysis of NCP3063 (good)
  1. Boost converter (step-up) with input from 0.8V to allow using 1.5V batteries (AAA, AA, C, D, LR41 button, etc.) to power TTL logic circuits even with depleted batteries.
    Fixed output
    - Super Micro DC-DC 5V Boost Converter: CE012 / WTI-0833 / T64, 5V Boost Converter, 0.8V to 5V input generating 5V output, variable max current output from 7mA to 100mA (1-1.5V) to 480mA (3V and 5V inputs) (verified no problem drawing 130mA from 3V CR123A battery, plenty sufficient to power Arduino Nano be sure to use 10uF smoothing capacitor on the output/ground to provide steady current for chips. Switched mode power supply operating at 150kHz with 85% conversion efficiency. Size: tiny at 1cm x 1cm, or precisely 10.8mm x 10.5mm x 7.2mm. Lowest price: 72p ea (2019). Currently: 10pc for £6.60 (66p ea) next day, or £1.90 ea, 8 days, or 10pc for £6.83 (68p ea.) or T64 10 pc for £10.79 (£1.08 ea). Device uses just 5 parts: the ASIC ME2108A (1831/50 – 5.0V version) switching voltage regulator (ASIC), a Schottky diode SS14, a #220 22uH CD54 series SMD inductor, and two 12uF capacitors in parallel (to obtain 24uF). REVIEW, DESIGN ANALYSIS. CE012 are smaller than a postage stamp, and, similarly to a joule thief, can take a “dead” 0.8V battery and boost up to produce 5V (obviously current depends on deadness of the battery, but at least 7mA). Wiring: V1 is V_in (battery) and V0 is V_out (5V). The PCB comes without pins, so you will need grabber probes to test and a soldering iron and 2.54mm pin header block to use in production.
    - HW-553: 17mm x 25mm x 6mm, input and output pads, 500mA Sources (best price 36p ea MOQ 5): 5 for £3.50 (70p ea). Ignore the D+ and D- pins. They’re useful if you want to wire a USB connector to the output.
    - LilyPad boost converter 1.5V-5V input boosted to 5V output, max 200mA current, 1W (@5V), default with AAA battery clips, but can attach any battery up to 5V (I frequently use low cost 3V CR123A lithium batteries for even voltage supply through life of battery, longer life battery, and higher current draw). Be careful, if you draw a lot more than 200mA you will release the magic smoke from the CD43 series 47uH (#470) SMD power inductor on the board. Boosting is done using NCP1402 Size: 70mm x 10mm Current: £2.07 2 weeks
      - NCP1402 boost converter chip max 200mA, shutoff at 350mA, surface mount, requires 4 external components: an inductor, a schottky diode, input/output smoothing capacitors, 10 pcs. for £2.63 (26p ea) ebay, or 10 pcs. for £3.10 (31p ea), surface mount or £3.73 for 10 pc (37p ea.) ebay, or 10 pc for £3.30, 33p ea. Amazon. Datasheet.
      - Inverting Buck/Boost Converter: MC33063AP DIP-8 buck/boost converter chip outputs 5V from 3-40VD at 1.5A. How does this work? 10pc for £13 (1.30 ea), £1.43 (MOQ4) to £1.68 ea, and 6p ea. (50 pc for £3.36) | Datasheet
    - Pololu 2564 (U1V10F5): High quality with thermal regulation, over-voltage protection (up to 5.5V), and ultra-high efficiency. 5V output from as low as 0.5V input (works down to 0.3V) $4.89 or £12.60, Amazon or £9, Ebay
  2. Adjustable output
    - MT3608: 2v-24v input, adjustable through pot, max output voltage 40v. Current handling typical up to 1A, max 2A. 6pc for £2.72 (45p ea) Features thermal protection and over-current circuitry. Seems solid. Optimizing for minimal idle current usage.
    - XL6019 – £2.50
  3. Buck-Boost converter
    - Pololu 2836 (S9V11F5), £7.76 next day. 5V out, from 2V to 16V in, ideal for battery power where starting voltage is above 5V before discharge, e.g. 9V cell, or two CR123A in series. High quality name-brand product.
    - Type 3A: w/ USB input interface and LED display. Input: 3.5V to 12V, Output: 1.2V (buck) to 24V (boost) up to 3W power (or 600mA at 5V), with display, USB powered, 60mm x 20mm x 10mm. Lowest price £2 ea. Currently: £6 same day, or 3pc for £10 next day (£3.33 ea). These buck-boost converters are fantastic. On/off switch, smooth potentiometer control, LED display to 1 decimal digit precision, ability to take Vin from pins (you need to solder in female headers) or USB micro or USB A. Can take Vout from screw terminals or pins. Stable reliable power, up step up or step down. Great for regulated output without having to use lower efficiency linear converters
    - Type 3B: 60mm x 40mm x 14mm. Source: £4.00
  4. Buck converter (step-down), Adjustable 4V to 40V with voltage regulator and LED display
    - LM7805 5V Regulator (input 7-35V): lowest price 50pc for £3.53 (7p ea). Currently: 50pc for £6.57 (13p ea.). Datasheets
      
      LM7805 5V voltage regulator (input 7-35V). Pin 1 (input) shown.
    - LM2596 fixed output – 6-12V down to 5V fixed: £1.79 with easy access pins,
    - LM2596 adjustable output – 6pc for £7.70 (£1.28 ea) next day
      start with c.20 turns CCW (buck, stepdown), CW is boost.
    - Type 4A: 120mm x 60mm x 30mm, 4-40V input, 1.25V to 37V output, i.e. 3V step-down voltage drop, adjustable power out, with display. Source: £1.75
    - Type 4B:5-16V input steps down to 1.25V to 5V fixed voltage output, £4.69
7. Solar Power
  1. Solar Engine for harvesting weak solar energy – 1000uF to 4700uF capacitors have quick charging cycles (seconds) and can then deliver pulses for twitchy movement.
  2. Tiny Solar Cells 3mmx3mm. The smallest generate 1/2V / 2mA. So you’d need 6-10 of these in series to generate 3-5V, and then arrays in parallel to increase current.
  3. Decent Solar Cell 2.4cm x 2.2cm – generates 3.4V / 12mA. One would be enough for an ATtiny powered computing device.
  4. Beefy Solar Cell 4x6cm. 6.7-8V and 30-44mA
  5. High-Density (Aerogel) Super Capacitors: 0.35F $5 or 1F $5
  6. BEAM Robots using solar power — what are BEAM robotics?
D. Integrated Circuits (ICs) – Analog (555, LM386, etc.) and Digital Logic (TTL, incl. 74xxx chips, ALU)

References:
1. History of ICs and their evolution: SSI (up to 10 transistors), MSI (up to 500 transistors), LSI (up to 20K transistors), VLSI (up to 1M transistors), ULSI (beyond 1M transistors)
2. GIICM (Generalized Internet IC Manual) has a of all 7400 and 4000 series of IC chips, their pinouts, and notes.
3. Discussion of ICs and numbers of transistors
4. Digital Logic and Circuit Design (article with resource links)
5. 7400 Series of ICs, and sub-family designations
6. Integrated Circuit (IC) packaging types and history
7. DIP and Skinny-DIP ICs have standard pin spacing of 0.1″ (100 mils)/2.54mm, compatible with solderless breadboards.
  Shrink-DIP ICs have a 0.07″ (70 mils)/1.78mm pin spacing.
  
  To go between them, you need a pitch changer. ProtoAdvantage has a wide range of these!
  64-pin 1.78mm to 2.54mm pitch changer – 10 EUR ea. (wire wrap pins, pins assembled) + S&H extra — Note this one doesn’t work with YM2608 — the chip IC is too wide
  32-pin 1.78mm to 2.54mm pitch changer – 6.40 EUR ea.
  With 5 EUR minimum shipping
1. IC Socket DIP 8-pin 50pc for £3 (6p ea), 16-pin 50pc for £4 (8p ea), 28-pin 50pc for £6 (12p ea), 14-pin, 16-pin, £3.26 (10 pc + 34 pc + 30 pc)
2. 8-pin SOIC to IC Test Clip $18 Sparkfun, or £3.00 with 2 adapter boards
3. 555 Timer Chip, 8-pin DIP IC (TTL version, not CMOS version): Lowest price ever: 11p ea (MOQ40), Current price: 22p ea. no MOQ (Spiratronics) 1-2 days delivery, or you could consider this ATtiny85 with a mod that allows it to function as a 555!
4. 556 Dual timer chip, 14-pin DIP, 10 pc. for £2.60 (26p ea.) (Spiratronics) or 25p ea., no MOQ but £1.29 delivery for 1, £3.49 delivery for 10, so 10 for £6.00 (or 60p ea.)
  The 555/556 timer chips can be used to create an oscillation when run in astable multivibrator mode (flashing lights, or a sound tone). They’re cheap, take 9V input, and are easy to use. 556 chip is a dual 555 in a more compact 14-pin DIP package.
5. Op-Amps | Op-Amp basics & 13 circuits | Summing Amplifier | General Purpose & Specialty Op-Amps | Top10 op-amps
  1. IC741, LM741, or uA-741 single op-amp 8-pin DIP IC chip – standard – 20pc for £7 (35p ea) next day
    
    LM741, UA741, IC741 op-amp, 8-pin DIP chip.
  2. LM358 dual op-amp 8-pin DIP IC chip – 50pc for £7 (14p ea) next day
6. Audio Chips – Sound and Speech
  1. Audio Amplifer IC chip: LM386 8-pin DIP: Lowest price: 10p ea (MOQ5) | Current price: LM386 IC chips x5 for £3.70 (74p ea.) | LM324 14-pin DIP with dual LM386 onboard (useful for stereo applications): Lowest price 5p ea (MOQ10)
  2. Audio Amplifier board, based on LM386, with 10k variable resistor to provide volume control, and pins for speaker: Kyrio 10x for £10 (£1.00 ea) next day good for quick applications instead of making your own board, but removes the ability to modify the produced sound (gain, bass boost, etc.)
    LM386 IC chip is a audio-amplifier that is low-cost, low-power, and requires few external parts to work. It is a differential amplifer (op-amp) amplifying the difference in voltage between V- (usually set to ground with a 10K R pullup resistor) and V+voltage delivering gain from 20-200x. accepts 4V-12V input but best at 9V separate power source from the logic circuit; can drive loads of 4R to 32R, consumes 4mA to 65mA (at 5V), voltage gain from 20-200x or 26-46dB, drives a 0.2W 2″ speaker to be loud enough for personal use in a quiet room, and a 5W speaker plenty loud. Datasheet: National Semiconductor, Excellent explanation and usage reference (hackaday), Arduino instructable
  3. MP3 Sound Chip (download, playback, 4MB/4min recording time, USB upload, USB rechargeable lithium battery), £13 next day with speaker and 4.5V battery module, 4MB/4min recording time, £7.50 4MB/4min recording time, (tried) WT2003S programmable MP3 recorder/player, £4.18 storage 4MB, with USB interface for download of MP3 files, rechargeable battery, Example usage of WT2003S and ATTiny (sparkfun): one, two Instructions: Connect to micro-USB, copy MP3 files, press button to play or stop playing. Press volume while playing to toggle through 5 volume levels. Hold button down all the way through end of one file, then index will shift to next file in queue for next button press. Otherwise will repeat the same track. Have not figured out how to programmatically select which track plays. Better instructions here
  4. Record/Playback Modules/Chips
    - Gift card style. LXB-15B – separate record/play buttons – 10s recording time – £3.66ea (ebay) or 40c ea (MOQ2000) or AliExpress or ebay (search “recordable voice module 10s”) or £2.90ea (ebay) negotiated £2.30 (20% off) for MOQ5 | 30s two button module £2.78ea
    - (tried) YS41F 30s Record/Playback module, event triggered playback of single-message, powered by 3x LR1130 button cells (can squeeze in LR41 slightly thicker). Capability based on 16-bit multimedia processor TR16F064B (chipsourcetek.cn) – Lowest Price: £2.47ea (MOQ3), Currently: £3.24ea (MOQ2) triggered by opening/closing action, or £3.59 ea (MOQ4) triggered by photoresistor
    - (tried) ISD1760 (60 sec. recording) single-chip, multi-track playback, SPI interface for uC control. Programmer + chip: £8.50 next day, £4.72 3-4 weeks (ebay), Chip only ISD1760: 10pc for £23.28 (£2.33ea) or 5pc for £12.78 (£2.56ea) or 2pc for £6.26 (£3.13 ea) | Programmers (Design) Guide, including for SPI control| Chip Datasheet
    - IC Station’s Voice Playback module
      Usage tips for the breakout board:
      + SP+/SP- connect directly to an 8R speaker
      + Mental model should be two pointers
      + The recording pointer points to the memory after the last recording, so that pressing REC adds a new recording.
      + The playback pointer points to the current message. Pressing PLAY plays it, and again if pressed again. FWD is the only thing that advances playback pointer to next message, or circular back to first message (same message if only one)
      + ERASE – global erase if press and hold. Deletes current playback pointer message if press erase hold down and press and hold Play briefly and then let go of both.
      + The breakout board is great for programming. A programmed chip should be able to be placed in the ciruit.
      + SPI interface should allow full control using microcontroller of which message to play. See this Instructable for how to do this, and two diodes to protect your uC. Make COPI, CS, SCK, pins outputs. Make CIPO pin an input. Use the Design Guide to design your software. This is where my 3-instruction Forth for the Arduino Nano will prove invaluable in real-time test/debugging.
      + Applications: (1) Makes complex microcontroller debugging in real world operation much easier. E.g. can state — “Turning left. Stopping” etc. Which helps listen to the controller informing you of its choices/decisions while it is making them. (2) Instructions — e.g. Piano keys – vocally lists the key. (3) Questions for interactivity with a child/device, e.g. Turtle Logo. (4) Sensor detection information, e.g. Sonar — vocalize range. If bump, say “Ow!” (5) Recommending decisions – e.g. Warning: Battery low. (6) Immerse Sound Effects – e.g. car FX, low gear, rev, next gear, rev, etc., then down-shifting, etc. So could have 10 different sounds, and microcontroller chooses which to play. Example: Space Invaders — alien sounds, etc. The sounds could be sampled from the 76477 CSG board and then played back as desired/needed under software control. E.g. Warfare sounds.
    - Other variants: ISD1932 multi-message with addr and direct triggers (latest chip) – features here. ISD1820 (10 sec. recording), single-chip, single-track £1.77 (ebay) | Datasheet/User Guide, VCC 3.3V power supply
  5. Speech Synthesis IC chips
  6. Sound Effect ICs: HK6xx chips (HK628 8 sound effects, HK625, HK637-x specific sound effects), HT2884 sound effects,
  7. Honsitak Sound Effect ICs: Catalog, can listen & download datasheet, HK620 (siren, alarm sounds), HK623 (gunfire, laser, bomb, alarm, telephone), HK628 (rifle/bomb/laser gun), HK629 (3 emergency vehicle sirens and machine gun burst), HK637-5 (car sounds), HK637-4 (truck sounds), HK637-3 (baby sounds), HK637-2 (train sounds), HK637-1 (animal sounds), more from Nightfire
  8. UM3561 DIP8 – 4 sound effects (3 sirens + machine gun): Lowest: £1.40 (MOQ2), £1.80ea (MOQ3). Currently: £1.83ea (MOQ2) / £1.53ea (MOQ6), or £1.95ea. (MOQ10), datasheet, schematic, £2.75, good tutorial video. NOTE: This is like HK629 (above).
  9. Music ICs, UM66T-XXX chip (3pin IC + buzzer + battery, video), catalog of chip tunes, UM66T-19L Fur Elise 5x for £1.75
  10. Complex Sound Generator ICs:
  11. Texas Instruments sound generating chips: Heritage TI sn76477 (mixed analog/digital) -> sn76488 (mixed analog/digital + internal audio amplifier) -> sn76489 (purely digital)
    1. (tried) TI sn76477, See my article Modular Sound Synthesis (forthcoming, 2021). £6 ea MOQ of 2 £8.27 GOOD – this is the N pkg with standard 2.54 mm pin spacing. WARNING: be careful that the chips are not the SDIP-28 (skinny DIP) package with 1.778mm pin spacing vs. DIP-28 (standard DIP) package with standard 2.54mm pin spacing. The SDIP-28 package does not fit into standard 2.54mm spaced breadboard/PCB, and therefore is unusable without a custom PCB pitch-changer adapter which costs £12 ea. While datasheet says N denotes standard package and NF/NE denote SDIP-28, this seller has an N chip marked on case but pin spacing is SDIP! list of many sellers, or Another NF, Another NF, £21 converted to 2.54mm pin spacing compatible with standard breadboard. Video demonstration, narrow pitch (will need a breakout board setup, Wikipedia description and schematics. Press coverage in Popular Science (1978 to 2008), Other designs.
      
      Sound Generator IC SN 76477, £6.08, 28-pin miniDIP (1.78mm irregular pitch spacing)
      
      Datasheet
    2. (tried) TI sn76489, Sound (Tone) Generator IC. Low: 5pcs for £3.60 (72p ea), Also: 5pcs for £7.44 (£1.09 ea). Article on driving this with code, Excellent description/dev discussion, Hackaday articles. Heritage
    3. (tried) AY-3-8910 (DIP-40) – £2.79 4 weeks, or 2pc. for £4.50 (£2.25ea) 2-4 weeks, or £4.60 10 days or £5.40 4 days, £4.60
    4. AY-3-8913 (DIP-24) – this variant has no I/O ports, which are not needed for sound generation. 5pc for £12 (£2.40 ea.)
    5. Yamaha YM2151 DIP-24, £2.78
    6. (tried) YM2608 DIP-64 – Yamaha sound chip £2.38 WARNING: This is a Shrink-DIP with non-standard 1.78mm spacing. Needs a pitch-changer to use in a solderless breadboard. (This one doesn’t work! Chip is too wide)
    7. Yamaha YM2612 DIP-24, 2pc for £5.08 (£2.54 ea)
    8. RP2A03 – Nintendo sound chip – £38
    9. SID 8580 (9V), MOS6581 (12V) for Commodore 64. On Nano SwinSID form factor selectable by jumper. £13.50
  12. Guitar effects pedal chips – MN3007/MN3101
    Reference: Experimentalists Anonymous: Schematics and Datasheets for Audio effects creation
7. Digital Logic IC chips
  1. 7400 ICs from Spiratronics, specifically 74HCxx logic ICs. Plan your shopping list ahead of time as shipping is flast rate £1.50 for an order of small size items, whatever quantity. For a budget of £20, one can get 5-10 pcs ea. of ~10 common ICs below, enough to make a range of applied digital logic projects.
    ICs on a shoestring For ~£20, 5-10 pcs of each of the below parts to enable a reasonable selection of digital logic applications.
  2. 7404 – 6 x inverters 33p ea, 27p for MOQ 10
  3. 7400 – 4 x 2-input NAND 25p ea., 20p ea. w/ MOQ 5, 18p ea. w/ MOQ 10 (Spiratronics)
  4. 7410 – 3 x 3-input NAND
  5. 7420 – 2 x 4-input NAND
  6. *7430 – 1 x 8-input NAND
  7. 74133 – 1 x 13-input NAND
  8. 7408 – 4 x 2-input AND HC family – 27p ea., 24p ea w/ MOQ 10
  9. 7411 – 3 x 3-input AND
  10. 7421 – 2 x 4-input AND
  11. 7402 – 4 x 2-input NOR 30p ea., 25p ea.w/ MOQ 5 (Spiratronics)
  12. 7427 – 3 x 3-input NOR 22p ea., 19p ea. w/ MOQ 5 (Spiratronics)
  13. 744002 – 2 x 4-input NOR
  14. 7432 – 4 x 2-input OR 23p ea., 19p ea. w/ MOQ 10 (Spiratronics)
  15. 744075 – 3 x 3-input OR
  16. 744078 – 1 x 8-input OR/NOR 44p ea., 38p ea.w/ MOQ 10 (Spiratronics)
  17. 7486 – 4 x 2-input XOR
  18. 747266 – 4 x 2-input XNOR
    
    DETECT. Encoder – Use case: You have a bunch of 1-bit input signals, and you want to detect which went high (priority order) using an encoded address
  19. 74148 (DIP16) – 8-lines-to-3bits priority encoder, with cascade logic included to allow building 16-, 24-, 32- to 4,5-bit encoders. Takes 8 line inputs (active low inputs) and encodes the ID in binary (active low output). 32p ea. (Spiratronics), but if out of stock then 2pc. for £3.20 (£1.60 ea.) 5x more expensive, or £2.75 ea. (4 days) 9x more expensive, Note, a single 16-to-4 priority encoder chip does not exist, but one can be built from 2x 74148s and a 7408 (quad 2-i AND chip) which preserves the active low outputs. See Figure 2 in the 74148 datasheet. Usage example: keypad – which key is pressed without needing to reserve 8 i/o lines.
  20. 74147 – 10-lines-to-4-bits priority encoder, £6.00 for 2x (£3 ea.)
  21. 74922/74923 – 16/20 key encoders (available since 1995) providing 4×4/4×5 matrix keypad encoding logic. Datasheet
    TRANSMIT. Decoder – Use case: You have a bunch of 1-bit output channels/signals, and you want to dial up using binary code which channel to output to, and then you will set the output value with 1 pin (hi/lo).
  22. 74138 – 3bits-to-8-lines decoder
  23. 74139 – 2x 2bits-to-4-lines decode
  24. 74141 – 4bits-to-10-lines decoder
  25. 74154 (DIP24)- 4bits-to-16-lines decoder, LOWEST POWER (but slower) LS series: 88p ea (best price), now: 10 for £10.74 (£1.07 ea), or 4 for £10.11 (£2.52 ea) or 5pcs for £14 (£2.80 ea). HIGHER SPEED (but higher power and more expensive) HC series (74HC154): £2.10ea (best price) 5pcs for £13, or £2.60 ea.. Usage example: 16 leds, indicate which ID to light up without needing to reserve 16 i/o lines, note only one can be lit at a time; to light multiple LEDs use a shift out register. Datasheet
    To activate multiple lines, can use a shift out register instead, or complement with an addressable latch that stores the state
    
    RECEIVE. Multiplexer/Data Selector – Use case: You have multiple 1-bit signals (channels) coming in (hi/lo), you only want to use 1 input line, and you want to dial-in which line you listen to.
  26. 74150 (24 DIP) – 16-to-1 data-selector/multiplexer (4-bit channel selection + 1 input line). Usage: use 5 lines to listen to 16 inputs, 4 lines as channel selector and 1 line as shared input to the MCU. 4 pc for £6.90 (£1.70 ea MOQ4, £2.25 ea unit), or £2.48 ea. Usage example: 16 in-feeds, which one to sample from? Usage 2: sample all 16 lines from 2x 8-bit DIP switchs
  27. 74151 (16 DIP) – 8-to-1 data selector/multiplexer (3-bit channel selection + 1 input line). LS family – 10pc for £3.33 (33p ea), or £3.18 ea
  28. 74153 (16 DIP) – Dual 4-to-1 data selector/multiplexer. Use: 2-bits to select which of 4 one-bit channel/signals to listen to, 1 I/O line from chip to MCU. So each of the devices uses 7 I/O lines, for total of 14 for the dual chip, + 2 power). HC family – 10 pc for £2.16 (22p ea) or £2.96 ea
    GPIO Expanders
  29. Use Decoder – only 1 line active at a time
  30. Use shift register – use 3 i/o lines (data, latch, clock) – to independently control 8*N lines, daisy chainable indefinitely
  31. PCF8574 IO Expander – adds 8 i/o lines via 2-wire I2C, daisy-chainable to 64 i/o lines individually addressable. Example
  32. TCA9548A MUX board – can multiplex 8 channels, so multiplexing 8 channels of 8x PCF8574 ICs, one can control 512 (=8×64) line independently — LED display arrays
  33. Other clever techniques also possible
    Note: can use Darlington Array of transistors to avoid pulling high current through logic decoders
    
    Flip Flops/Latches/Buffers
  34. 7474 – 2 x 1bit D flip-flop with set/reset
  35. 74174 – 1 x 6bit D flip-flop
  36. 74125 – 4 x 1bit tri-state buffer with active low enables
  37. 74126 – 4 x 1bit tri-state buffer with active high enables
  38. 74244 – 2 x 4bit tri-state buffer
  39. 74259 – 8 bit addressable latch – allows to maintain state and set state one bit at a time using a decoder chip e.g. 74138Example
  40. 74273 – 1 x 8bit tri-state D flip-flip
  41. 74374 – 1 x 8bit tri-state flip-flop
  42. 74574 – 1 x 8bit tri-state D flip-flop Spiratronics 81p
  43. 74373 – 1 x 8bit tri-state latch
  44. 74573 – 1 x 8bit tri-state latch
    Shift Registers for independently controlling N GPIO lines (daisy chainable) with 3 pins
  45. 74164 – 1 x 8bit SHIFT OUT register WITHOUT LATCH *NOT RECOMMENDED, see 74595* –SIPO (serial in/parallel out), 14-DIP, HC family – 5pc for £2.21 (44p ea)
  46. 74595 – 1 x 8bit SHIFT OUT register WITH LATCH SIPO (serial in/parallel out), 16-DIP, HC family – 20pc for £1.80 (9p ea), 50pc for £3.30 (6p ea). Pair with ATtiny85 microcontroller for dedicated monitoring service, I2C interface with controlling CPU, and Arduino compatibility
  47. 74165 (DIP16) – 1 x 8bit SHIFT IN register PISO (parallel in/serial out), lowest price HC family – 20pc for £2.85 (14p ea). Current price: 10pc for £2.82 (28p ea) or 10pc for £3.52 (35p ea). Pair with ATtiny85 microcontroller for dedicated monitoring service, I2C interface with controlling CPU, and Arduino compatibility
    Note: Shift registers require 3 lines to control: data, latch, and clock. There is no actual clock required, rather the shifting works when the clock pin is toggled LO/HIGH.
    
    Excellent Tutorial Video (Sparkfun) on SHIFT Registers
    
    Counters, Adders, and ALUs
  48. HCF4017BE – Decade Counter, 10pc for £2.62 (26p ea)
  49. 74163 – 4bit binary synchronous counter
  50. 74393 – 2 x 4bit asynchronous counter 47p ea., 41p w/ MOQ 5 (Spiratronics)
  51. 4008 – 4bit binary full adder with carry
  52. 4585 – 4bit magnitude comparator
  53. 74181 – 4bit 16-function ALU Amazon, $16 (£13.16)
  54. 74381 – 4bit 8-function ALU
  55. 74382 – 4bit 8-function ALU with ripple carry and overflow
  56. 74881 – 4bit 16-function ALU
    
    7-segment display driver ICs
  57. 744026 – (4026B) Decade Counter w/ 7-segment out driver, 16-pin DIP 60p ea. (no volume discount, Spiratronics, Ebay £3.34 for 3
  58. 744543 – BCD-to-7segment decoder/LCD driver with input latch Spiratronics 91p
  59. Hex Driver for 7-segment displays (0-9 and A-F): MC14495P or MC14495P1 – hex to 7-segment out driver, 10pc for £20, or £2/ea, or DM9368: £18.50 for 4pc (£4.63 ea).
  60. Or use ATtiny84 as a lower cost 7-segment driver or ATtiny85 with shift register as 7-segment driver.
    
    Misc
  61. MC14490 – Hex Debounce Circuits
  62. Memory chips: EEPROM Atmel AT28C16 2KB (2Kx8bits=16K bits), DIP24 package, £13.30 for 2 pc.
8. Converters
  1. Breakout Boards:
    1. DB15 Parallel Port to 15 pins, £1.66,
    2. DB9 Serial Port to 9 pins, 86p,
    3. RJ11 Telephone to 4 pins, £5.18 (incl. S&H),
    4. RJ45 Ethernet to 8 pins, £5.69,
    5. USB 2.0 Male plug to 5 pins, £2.62 ea. or £4,
    6. USB 2.0 Female plug to 5 pins, £2.62 ea. or £4
  2. TTL Logic to RS-485, £6 (incl. S&H)
E. Microcontrollers and Dev Boards

Microcontroller Comparison table: Arduino Nano, Attiny, ESP, etc.

Sources:
1. Arduino Nano – 5 board variants
2. Microchip (owner of PIC and Atmel) Parametric Search
3. ST Micro MCU finder software
4. Technido, supplier of 8051, AVR, Arduino, Atmel, and PIC learning/starter kits with dev boards and sensors
References:
1. Programming Microcontroller Chips
2. Forths for Micrcontrollers: To run Forth in a microcontroller, you have a few options: ideally the uC is a von Neumann architecture, not Harvard (most modern MCUs are Harvard architecture, with a few notable exceptions) OR if serial is supported at bootup time you can write a 3-Instruction Forth (I’ve written one that I use for Arduino / Atmega328 MCU).
3. Make: FPGAs, by David Romano, 2016, £17.30. Read partially online
4. Making things Move, by Dustyn Roberts, 2011, £14
5. 8051/52 Microcontroller by Craig Steiner, 2005, £11.50 in Aug 2018 Architecture, Assembly Language, and Hardware Interfacing
Arduino Nano/Uno (contains Atmega328P)

References:
1. Wikipedia: ATmega328 | Arduino Nano | Arduino Uno
2. Low power consumption for Arduino
3. 10 ways to destroy an Arduino
4. Arduino cheatsheet (PDF)
5. Arduino IDE (using C/C++) (for Windows get the ZIP package (182MB) for portable installation)
6. RealTerm, billed as “an engineer’s terminal program specially designed for capturing, controlling and debugging binary and other difficult data streams. It is the best tool for debugging comms.” Essential for tethered development and rapid development/debugging.
7. Forths for Atmega328 and Arduino: Go Forth, Forth on Arduino, CH Ting’s paper on eForth for 328, CH Ting’s slides, GitHub code
8. AmForth for AVR/Atmel micros.
9. 3-instruction Forth for Arduino Atmega328 (request in the comments)
10. Basic for Arduino (Robin Edwards, c.2005)
Nano
Arduino Nano V3.0 CH340/Atmega 328 (30 pins, 14 digital i/o, 8 analog), program via Arduino IDE (free) using C. Built in FTDI interface to allow programming directly from PC using usb cable (no programmer required). Note: there are now three types: type MINI, type MICRO, and type C depending on the USB connection. I recommend either MINI or type C as the connections are chunky. Micro connectors tend to get damaged over time and with repeated insert/removals.
Arduino Nano is small, cheap, versatile, installs onto a solderless breadboard for easy prototyping, and has plenty of expansion possibilities (see below for Ethernet and 2.4G wireless versions). Fully functional Arduino compatible microcontroller, able to be programmed directly from your PC using the Arduino (free!) IDE, and has three advantages over the Uno or Mega: (1) can be plugged directly into a solderless breadboard for easy electronic prototyping, (2) USB connection is via lower profile USB mini port instead of standard size USB port, (3) power is direct via pins or USB instead of a standard size barrel connector.
Pinout:

Arduino Nano board, 30-DIP form factor, with ATmega328P microcontroller, 22 i/o lines + UART, SPI, and I2C serial comms, 5V regulated, or 7-12V unregulated (VIN), and 3.3V.
Note: User needs to ensure that no more than c. 20mA is sourced from a single pin, with no more than 200mA total sourced across all pins.
1. Nano v3 board, MINI, ATmega328P, welded, with bootloader, without cable. Currently: £3.68 (MOQ10) with 2 USB cables | £4.12ea. | £3.13 welded without cable (MOQ4) or £3.70 welded MINI or £6.75 ea (MOQ4) next day
2. USB mini cable for standard Nano CH340 V3.0, 30cm: Best: 99p ea., 95p MOQ4 (incl. 2-wk shipping), Now: £1.37 ea or 5pc for £6.79 (£1.36ea).
3. USB A Extension cable (Male to Female). Best: £1.93 (1m). Now: £2.00 (1m), £4.00 (1m), or £4.49 1.8m, or £2.5, 2m
4. Nano to UNO Adapter board, $3.70 ea, £18.71 for 3 boards including £11 shipping (£6.25 ea) w/ 5-7d shipping or £2.70 ea (Ebay)
5. Nano terminal adaptor shield – no need for a breadboard, solid screw terminals breakout each pin. Without Nano uC £12 for 5 (£2.40 ea) w/ Prime Delivery. With Nano uC integrated 2 for £8.90 (£4.45 ea.), or £12 for 5 pc (£2.40 ea.) next day
6. Nano ethernet server adapter board –
7. RF Nano, with integrated 2.4G wireless chip & antenna. Lowest cost: £1.50 ea (AliExpress) or £4.77ea (MOQ 4) | Currently: £2.28 (AliExpress) | £2.70 ea (Ali Express) | £7.50 ea (ebay) or £8.75 ea (ebay) or £9.50 (ebay) or £13 (amazon). Note: needs minimum two for applications. Uses micro-USB cable not mini-USB as with Nano (warning: be sure your micro-USB is a full cable with both power and data lines, not just a power charging cable. To upload code in Arduino IDE for Arduino Nano, be sure that you’ve not selected “Old Bootloader” – this is different than the standard low-cost Nano’s that require “Old Bootloader”.)
8. NRF Short Range Transceiver NRF24L01, 80m range module, standalone boards, config/comms through SPI (pins 9-13), 2.4 GHz band, 125 channels, WARNING REQUIRES 3.3V POWER and Nanos 3.3V out pin is NOT sufficient so USE 5V breakout board, 14mA max power consumption (2Mbps receiving mode).
  “Module includes interrupt request (IRQ) pin which can be used to wake the host microcontroller, from sleep when the module receives a transmission providing great power conservation in battery devices”: Lowest price: £1.35 pair NRF+breakout boards 67p ea | £1.52 pair NRF+breakout 76p ea board MOQ4 (Ebay) | NRF board only: 10pc for £11 (£1.10 ea) or Kuman: 10 pc for £20 (£2 ea) next day, or 5V Breakout Board for transceiver (accepts up to 12V input using AMS1117 voltage regulator to step down to 3.3V): 5pc for £6.60 (£1.30 ea), or 10x NRF24L01 modules for £10 (£1 ea.) next day 5x for £5 (£1 ea).
9. NRF Long Range Antenna NRF24L01+ 800m range module, 2pc for £8 (£4 ea) or 2pcs for £9 (£4.50 ea) or 3pc for £17 (£5.70 ea), or 3 pc. for £13.60 (£4.50 ea.) or 3 pc. for £13.60 (£4.50 ea.) or ebay
Atmega328P uC IC
This chip has 23 GPIO lines (8 pin port PB and PD, 7 pin port PC).
References:
1. Wikipedia: ATmega328
  The cool thing about these chips is that they contain an in-circuit programming (ICP) feature using which you can download code into them using some simple hardware and connecting to 6 pins on the chip (1,7,8,17,18,19) and using the built-in SPI (4-wire synchronous serial) comms capability of the chip.
2. Programming 328P with Tiny AVR Programmer over SPI, or Hookup & usage with AVR toolset (Sparkfun)
  
  ATmega328 8-bit microcontroller chip in breadboard friendly DIP28 package, c. £2 ea.
  Pinout & hookup schematic/picture.
3. AVRDUDE command line utility for reading, writing, and manipulating AVR chips
4. Atmel 328P datasheet (294 pages)
1. ATmega328P DIP28 chip, breadboard friendly (328 is cheaper and consumes few mA more, 328P finer process allowing SMT and uses few mA less):
  - Without bootloader: Lowest price: £1.75 each, then £1.90 (MOQ10). Current: 5pc for £19.50 (£3.97 ea) (50% higher).
  - With bootloader Lowest price: £1.75 each, then £2.50ea (MOQ10). Current: £3.48 (MOQ4+) w/ bootloader, or £3.55ea (MOQ2)
  - 28-pin DIP insertion socket, £2 for 5pc, 3 days
Related chips/boards:
1. Arduino Uno R3 running Atmel AtMega 328: Lowest price: £8. Currently: £9 same day
2. Arduino Mega Atmega 2560 R3 running Atmel AtMega 2560 R3: £13
3. Atmega4809 – available in 40-pin PDIP package, successor chip to Atmega328P
4. Arduino Uno WiFi (Atmega4809 processor) | Nano 33 IoT (SAMD21, Arm Cortex M0 processor) | MKR 1010 (SAMD21, ARM Cortex M0 processor)
5. MCP2221A – USB to serial converter chip
  See Atmega4809 on a breadboard
Atmel ATTINY85/84

References:
1. ATTiny Adventures (getting started with ATTiny)
2. Using Arduino IDE for ATTiny microcontrollers requires ATTiny board files for Arduino by David Mellis (Download ZIP, copy attiny\ to ..\arduino\hardware\.) | Sparkfun ATTiny Quick Reference Sheet & PDF
3. Device Driver for TinyAVR USB Programmer (Windows) for ATTiny chips: Zadig Device Driver: libusb-win32 (v1.2.6.0). Then ready to program from within Arduino IDE (see Board files above) or AVRDUDE utility
4. Sparkfun Hookup Guide for Tiny AVR Programmer for ATTiny85. Sparkfun documentation for Tiny AVR Programmer.
5. Datasheets & Application Notes
6. ATtiny85 cheatsheet (PDF)
ATTiny85 is an 8-bit MCU (2005) with 8-bit timer/counter, 2x PWM channels, USI (Universal Serial Interface), 10-bit ADC, Programmable Watchdog Timer, Temperature Measurement, On-chip Analog Comparator, In-System Programmable (ISP) via SPI port, External and Internal Interrupts, 5x programmable I/O lines + reset, 2.7V-5.5V operating voltage. ATtiny84 is also an 8-bit MCU but with 11x programmable I/O lines + reset. It can be programmed using the ATtiny85 Tiny USB Programmer and wiring to connect via SPI (see diagram below).

From programmer standpoint, ATTINY85 is a RISC (reduced instruction set chip) with 120 instructions, most executed within a single clock cycle, providing up to 20 MIPS (20MHz at 5V, 1 instruction per cycle). Memory model is Harvard architecture with separate Program Flash memory and Data SRAM memory. There are 32 8-bit registers, of which 6 can be used in pairs for 3 x 16-bit indirect addressing (X,Y,Z) into SRAM data memory.

Wiring diagram for programming a Tiny85/Tiny84 on a breadboard using Sparkfun’s Tiny AVR programmer — you will need 6 wires
1. Atmel ATTINY85 20PU microcontroller chip, DIP-8 package: lowest price £1.30ea (MOQ10). Current prices: 10pc for £16 total (£1.60ea, offer accepted) or £1.94ea MOQ5, £1.70ea MOQ10 (ebay) or 5pc for £10.64 (£2.12ea, amazon) or £2.30 ea. (amazon) or 5pc (+ 5x 8pin DIP sockets) for £18 (£3.60 ea).
2. ATTiny84 DIP14 chip (2005): £10.80 for 5pc (£2.16 ea. MOQ5) or £3.52 (Amazon) | Datasheet
3. ATtiny2313 DIP20 chip: 18 i/o pins. £6 for 4pc (£1.50 ea.)
4. ATtiny85Programmer Board (can also program ATTiny84, see wiring diagram above): Sparkfun 11801 Tiny AVR USB programmer: £16.73 from proto-pic UK or $16 from Sparkfun US or Make Your Own for less than £5!
5. DigiSpark ATTiny85 – an integrated Arduino with ATtiny85 at its heart, powered by USB, programmable over USB, having I2C and SPI available directly, with a built-in voltage regulator (though unfortunately not a boost converter or a buck-boost converter). Usage discussion | 3pc for £8 (£2.66 ea) MicroUSB Spark – £1.70 or £3.00 for one (auction)
6. ATTiny85 Trinket uC (Adafruit), £7.34, this is a fully-fledged USB programmable, Arduino-IDE compatible microcontroller built around ATTiny85 uC.
32-bit ARM core uCs

Espressif’s ESP boards
1. ESP8266-12 NodeMCU WiFi: 4pc for £21 (£4.25ea) next day or 3pcs CP2102 for £16 (£5.33ea) same day | 3pcs ESP-12F Lolin for £13 next day (£4.33 ea) | 1pc for £7.85 | 4pc for £14 (£3.50 ea)
2. (tried) ESP8266 32-WROOM WiFi + Bluetooth: 3pcs for £19 same day (£6.33 ea) | chip only £2.10
3. (tricky to use – needs 5V to 3V level converter, and fiddly upload instructions) ESP8266 ESP-01/-01S Serial to Wifi Transceiver Module: 4pcs for £12 same day (£3 ea) | Information from Sparkfun ($7) | Usage discussion
  ESP8266 Wikipedia, and ESP32 (successor product of ESP8266 with ESP32-C3 using a RISC-V open-source firmware chip)
  
  Difference between ESP8266 and ESP32. Toolchain for ESP32, ESP-IDF, or ESP-Arduino.
4. ESP8266 Thing Dev Board (Sparkfun) or ESP8266 Thing (Sparkfun) or ESP32 Thing (Sparkfun)
5. ESP8266 WiFi Module add-on for any microcontroller ($7 ea) (Sparkfun)
6. ESP8266 dev board, w/ WiFi, w/ pins. £10 for 2pc (£5ea) with Prime Delivery
7. WeMos / Lolin dev board & system based on ESP8266, w/ WiFi & Bluetooth. Overview & Possibilities, Main page, Lolin store
  Forths for ESP8266, PunyForth
8. Seeeduino – smallest Arduino compatible board with SAMD21 microcontroller chip (32-bit ARM core) – c.£4 ea., or 3pc for £22 (£7.33 ea)
Raspberry Pi
1. Raspberry Pi: v4 desktop power for $35
2. Raspberry Pi RP2040 – £9 from Sparkfun, £9 from PiHut
3. Arduino Nano RP2040 – latest uC board with RP2040 (dual-core ARM Cortex M0+with WiFi and Bluetooth integrated, 22 I/O pins, 16MB memory, programmable from browser or Arduino. Article
Retro CPUs
1. 25 Microchips that Shook the World, IEEE Spectrum, Bryan Santo, 2009
2. Motorola/Freescale (6811) MC68HC11xx (48-pin DIP) : Lots of board options, and Forths for them, the MIT Robot Builder boards, with detailed info on the Motorola 68HC11 chip | Mosaic QCard – with integrated Forth RTOS, datasheet, product page, $150 from Mosaic
3. RCA/Harris 1802: CDP1802ACE, £2 each (Qty 1), or £1.64 each (Qty5). Details here. Neat builds here. 1802 on FPGA. 1802 FigForth.
4. Motorola 6809 (or faster 6309): MC68B09EP £12.50 qty 1. Example project. Hackaday writeup.
5. 6502: R65C02P. Hackaday project page. Opcodes page.
8051/8052
1. 8051 Self Learning Kit, Technido, £74 with 8052 chip (Atmel AT89S52 24PU 1732A), programmer (ATMEGA 8AU 1804 KTG 35469L), 12V power source, expansion board, starter kit of sensors (IR, DC motor, …), and all necessary cables. Comes with experiments/manual that can be downloaded.Video showing how to connect programmer and install first program
2. 8052 USB ISP programmer, £1.76
3. USBasp AVR Programmer, get Windows drivers v3.0.7 (digitally signed) here.ProgISP.exe flash programmer
4. 8051 C compiler (KEIL). Launch UV4.exe for the IDE.
5. Atmel AT89S52 (8052) chip, 40-DIP format, £6 (=£5.40 chip + 60p S&H)
6. Crystal Oscillators for uC: 12 values, 60 pcs, 5pc/ea for £10 same day (16p ea), incl. 12MHz for 8051/2, 16MHz for ATMega328P, more. Individual values: 16MHz 10pc for £4.50 (45p ea) | 10pc for £2.65 (27p ea) 45 days | 10pc for £2.42 (24p ea) 45 days | 20pc for £2.84 (14p ea) 60 days |
7. 8051 Reference Book: 8051/52 Microcontroller: Architecture, Assembly Language, and Hardware Interfacing (bought new for £11.50 Aug 2018); Craig Steiner (2005)
STM8s (8-bit ARM chips)

Why this chip? Because it has a Serial UART capability built-in and has an untetherered Forth available (STM8 eForth).
1. ST Micro STM8S chip: STM8S001J3 8-PIN SOIC-8 package. £8.50 ea. (Ebay) or 46p ea with MOQ of 10 (Digikey UK) but £2 ea with VAT & Shipping.
2. STM8 Chips and Dev Board (DISCO) for STM8S00001J3: £8.50 from RS (next day delivery) + 3 programmable breadboardable uCs (£2 ea)
3. STM8 Microcontroller board: STM8S103F3P6 ARM STM8: £6 for 2pc (£3ea), Prime delivery, or £1.40 ea
4. STM8 USB programmer, £2.10
PICaxe chips
1. Overview (Wikipedia) | PICaxe description | Chips with the PICaxe bootloader | PicAxe language reference |
2. PICaxe 08M2 (£4.50 or £4.50 option 2)| 14M2 | 15M2 | 18M2 £6 | List of Chips for purchase from Spiratronics UK
Other small Microcontroller boards
1. BBC Micro:bit – cool new computing platform with ARM Cortex-M0 for $18 (Sparkfun)
2. Raspberry Pi Pico ($4)
3. M5Stack platform for rapid development of IoT applications | About | Low Power Long Range (LoRa) and M5Stack | ESP32 prototyping M5Stack |
Ultra Low Power & Low Cost uCs and Custom ASICs
1. Microcontroller’s under $1 ea. (qty 100), by Jay Carlson
2. EM Microelectronics: EM6580 (4-bits) | Custom ASICs (list) | EM6812 (8-bits) – ultra low power 8-bit uC
3. CH552 8-bit microcontroller with USB connectivity for $1, and an example full tiny keypad for under $5
4. GreenArrays-GA144 (Multi-core) – Chuck Moore’s latest chip, 144x F18A computers connected in a mesh network, programmable using ColorForth, ultra low power consumption (from 100nW consumption per idle node so 14uW for all nodes idle to 4mW running one node at top speed of 700Mips, to 650mW running all 144 nodes at top speed generating 100 total Gips), means dedicated circuits for sensor controls. Programming the GA-144 (video by Chuck Moore, 2013), GreenArrays site, $20/chip, $30 dev board, Breadboarding Example | For large-scale ubiquitous computing, the ultra-low power GA-144 multi-core controller with 144 individual controllers, invented by Chuck Moore, the father of Forth and of ultra-low power MISC (minimal instruction set computing) hardware designs, offer intriguing possibilities. The GA-144 has 144 independently programmable F18 microcontrollers, interconnected in a defined topology, on a single-die. Ultra-low power. Usage: Wherever there is a need for dedicated continuous real-time monitoring and control, instead of multiple discrete components and a lot of communication interconnects, this chip allows integration. Application: Piano-25 PCB (small scale, 3 dedicated controllers, 1 coordinating controller), smart sensored car (many dedicated controllers, 1 coordinating controller). Sort of like CAN bus in automotive control.
5. #GreenArrays news & community on Twitter
6. PIC Micro 8-bit: with UARTs in DIP-8 packages: PIC12F 1572 for £2.34/1822 for £2.73/1840 (£2.40). These are also PIC16F 15313/18313. I chose PIC12F1840 (7K program memory) Datasheets 1840
7. TI MSP430: F2012IPW £6.40
For high volume applications, the ultra-low cost category can be worth a look: there are the sub-30p reprogrammable ISP microcontrollers and the sub-10p one time programmable (OTP) microcontrollers. While these are really inexpensive and quite powerful, they are not easy for hobbyists to use, typically requiring specialized high voltage programming equipment, assembly language coding using proprietary toolchains with limited documentation. Examples: Padauk PMS150C example, full review);

Ref: [Cravotta, 2010] 4-bitters
Ref: [Ebrahim, 2021] Programming Microcontrollers – Ultra Low Cost / Power Options

FPGAs and friends Overview (Wikipedia)

PAL – Programmable Array Logic – MSI chip (medium scale integration) that allowed doing away with SSI (small scale integration) logic chips e.g. those in the 7400 series.
PLA
GAL – Generic (or Gate) Array Logic – improved upon PAL.
CPLD – Complex Programmable Logic Device – Max V Kit (Altera)
FPGA – Field Programmable Gate Array made by Alterra (acquired by Intel) and Xilinx
Numato Labs Elbert v2 – $30 (entry level with Xilinx Spartan 3A FPGA), $20 shipping to UK
Numato Labs Mimas v2 – $50 (mid level with Xilinx Spartan 6), $20 shipping to UK
Not to be confused with
PLC – Programmable Logic Controller – which are devices that do large scale monitoring. E.g. Atmel4809 can be an effective PLC.

F. Sensors and Communications

Sensor Modules – £4.74 ea pc (MOQ2). or £26 for Kit of 37 pc.. Download the datasheets/tutorial (download, 50MB)
Camera module, OmniVision CMOS camera modules: recommended with capable 32-bit uC e.g. ESP boards instead of relatively low processing power Atmega328s (Arduino). ArduCam CMOS camera interface on ASIC. Arducam Mega SPI interface requiring 6 pins: 2x I2C pins (sensor configuration) AND 4x SPI pins (camera commands, datastream), camera multiplexing possible using I2C and SPI interface IDs. 5MP has auto-focus. 2MP and 3MP has fixed-focus adjustable manually. 3.3cm square. 120-160mA when operational, c.50mA idle.
- OV7670 – without FIFO – 640×480 pixels = 307k pixels – don’t get, cheap but have to write your own driver and build the image with your micrcontroller from the 4 blocks captured and stored by the module. Lowest price: £3.33, current price: OV7670 £5.64 WARNING this has no FIFO
- OV6948,
  Arducam include 8MB FIFO buffer
- OV2640 – Arducam board – 2M pixels – image board, I2C/SPI interface – integrated controller ASIC, £21.
- OV2640 – ESP32-CAM – 2M pixel w/ WiFi and Bluetooth integrated – £10, £11 w/ external antenna, £18/ ESP32 Camera OV2640 + WiFi/Bluetooth module £20
- OV5642 – Arducam 5MP Autofocus with 1080P video, w/ 1TB onchip memory, £32, or with fully sealed ABS enclosure £40
- OV5647 – Arducam 5MP CSI bus for RP with mounting bracket, £12, works on CSI bus for use with Raspberry Pi, which can be converted CSI to HDMI, £11 for 2pc
- Low Power QVGA (320×320 pixel, 32FPS) camera, £19, possible to use with Arduino.
- Arducam VGA camera, 640×480 pixel, 60FPS, £31
- Pan/Tilt motor platform, £32
GPS, £21 or £13
ESC (Electronic Speed Controller board), £11.30 or £10 same day
Pinion Engine Gear 5pc for £10, next day
Motion Sensing / Human Intruder: use Passive Infrared or Dippler Microwave Radar
- Doppler Microwave Radar Motion Sensor (rcwl-9196 / 0516): £6.80 for 5 (£1.36 ea) with Prime
KY-001 – Digital Temperature Sensor D18B20, £3.06
KY-002 / SW-420 – Sensitive Vibration Switch (for less sensitive Knock sensor see KY-031): Lowest cost £1.31 ea, then £1.90, currently: 5pc for £5 (£1 ea). Or buy the components directly: SW-18010 sensor and KY-002 Arduino board
- SW-18010 high sensitivity: lowest: 34p ea (MOQ10), currently: 80p ea (PiHut)
- SW-18020 ordinary sensitivity: lowest: 31p ea (MOQ10), currently: £7.50 for 10 pc (75p ea.)
- SW-18030 low sensitivity: 10pc for £7 (70p ea)
- HDX-2 SW-420 normally closed, high sensitivity: lowest price: 17p ea (MOQ10), or for Waterproof components: 40p ea (MOQ10).
KY-003 – Hall Magnetic Sensor, £1.70 ea., 5 for £3.00 (60p ea)
KY-004 – Button Switch, 65p
KY-005 – IR Transmitter, £1.70
KY-006 – Passive speaker, £4.80
KY-008 – Laser Transmitter, low-power, 650nm (red) works with 3V button cell battery, or 5V TTL from MCU. Lowest prices: £1.62 ea (Qty1) or 65p ea (MOQ10), or for laser head only without circuit boards 35p ea (MOQ10)
combine with photoresistor (10x 90p ea.) with spectral peak at 540nm (GL5539),
WARNING: use red laser protection goggles £10 (30 days delivery)
KY-010 – Light Break Sensor, Photo-Interruptor, £9.70
KY-012 – Active Buzzer, Lowest: £1.44 ea.
KY-013 – Analog Temperature, £1.35
KY-014 – Heartbeat Sensor Module, £2.79
KY-015 – Digital Temperature and Rel. Humidity, £3.00
KY-017 – Mecury Switch £4.45 for 2pc (2.22 ea.)
KY-018 – Photoresistor module (analog board): lowest: £1.38ea. Core component is the LDR (Light Dependent Resistor) aka Photoresistor (Darkness/Daylight Sensing), datasheet here: Assortment Kit: 6 value x 20pc ea. (120pc total) assortment kit, £3.20 (2.67p ea.), GL5506/16/28/37/39/49 (least sensitive) or individual values from GL5528, 20 for 69p (3.5p ea.) or GL5516, 20 for 77p (3.9p ea.) or GL5539, 88p for 20pc (4p ea.).

Light sensitivity (in ohms) for common LDR photoresistors, from GL5506 (most sensitive to light, least resistance) to 5549 (most resistant to light)
Phototransistors
Photodiodes
KY-019 – 5V DC Relay module with Opto-Isolators rated up to 250VAC: 86p or £8 for 5x KY-019 relays (£1.60 ea.) w/ Prime Delivery or £5 for 3x KY-019 relays (£1.66 ea.) or £5.50 for single board with 4 channels
UL Listed 120VAC Relay controllable with 5VDC, 10A switching, $125 ea.
KY-020 – Tilt Switch, £2.00 or professional grade
KY-021 – Mini Magnetic Reed Sensor, £1.70
KY-022 – IR Receiver, £1.70, or 10pc for £2.05 (21p ea)
KY-023 – Dual Axis Joystick, Lowest: £1 ea (qty1), 80p ea (MOQ5), or 60p ea (MOQ10)
KY-024 – Linear Hall Effect Sensor, £2.10
KY-025 – Large Magnetic Reed Switch, 2.60
KY-026 – Flame Sensor, £5.40
KY-027 – Magic Light Cup Sensor, 95p
KY-028 – Digital Temperature Sensor, 2.60
KY-029 – Bi-color LED (RG), £2.40
KY-030 – Sound Detection Module, Lowest: £1.84 | MT02-02, 95DB-75DB (AT-SK-04, 6LUX) £1.81 pre-packaged sensor (to build yourself, get microphone and LM386 amplifier chip) |
KY-037 – High Sensitivity (small mic) Sound Detection Module, Lowest: 80p, currently 92p (MOQ10)
KY-038 – Standard Sensitivity Sound Detection Module, Lowest: 80p, currently £8 for 5 (£1.60 ea)
Microphone: Lowest: £3 for 3pc. (£1 ea.), Mini Electret Microphone Condenser (Capacitor) with Pickup: £7.50 for 10pc w/ leads (75p ea, 6mm diameter x3.5mm thick, next day) Technical description of an electret circuit.
Microphone + Amplifier: MAX4466, £9.60 for 5pc (£1.92 ea) or higher end MAX9814 £19 for 5pc (£3.80 ea) with automatic gain control
KY-031 – Knock Sensor, £5.50 for 3pc.
KY-032 – Obstacle Avoidance, £6.30 for 3pc.
KY-033 – Tracing Line Hunter, £1.40
KY-035 – Analog Hall Magnetic Sensor
KY-036 – Metal / Human body touch sensor, £9
KY-039 – Heartbeat Sensor, £5.50 for 3pcs. (£1.80 ea.) or £1.88 singly (heart shaped) or £1.86 singly (rectangular)
KS-039 – Real-Time Clock DS3231 or AT24C32, I2C: Lowest £1.43 ea
KY-040 – Rotary Encoder/Encoder module, £6 for 5pc no knobs (£1.20 ea) next day, £10.85 for 8pc w/ knobs (£1.35 ea), next day, £8.85 for 6pc w/ knobs (£1.50 ea) next day | Useful for: parameter selection (user interface), fine-grained control of many options (more than a switch would provide), does not require a keypad for entering multiple IDs. | References: Discussion & Implementation
KS-007 – Rotary Encoder, 6mm shaft, £2.90
KS-040 – Smoke Sensor, lowest: £2.17
KY-041 – Big 12mm Button Module, £2.70
KS-041 – Alcohol Sensor, Breathalyzer, £4.50
KS-042 – Methane Sensor, £4.60
KY-043 – Passive Buzzer
KS-044 – Propane Butane LPG Combustible Gas Sensor, £4.50
KS-045 – Carbon Monoxide Sensor, £4.60
KY-046 – LDR (Light Dependent Resistor)
KS-046 – Hydrogen Gas Sensor, £4.80
KY-047 – Thermistor Temperature
KS-047 – Pollution Sensor, £4.60
KS-048 – Rainwater, Water Depth Sensor £3.30
KS-049 – Moisture Detector, £3.30
KY-050 – Ultrasound Ranging Sensor, HC-SR04 £4, or £9 for 5 (£1.80 ea), or £10 for 5 (£2 ea) w/ mounting bracket
PIR Motion Sensor – HC-SR501 fully configurable, large lens – Design/Online Reference – Lowest Price: 80p ea (MOQ5), £1.10ea (MOQ10), Currently: £13 for 10pc (£1.30ea, next day) or £12.70 for 10pc (£1.27ea), 1 wk, or £7.50 for 5pc (£1.50 ea), 1wk, or HC-SR501, £2.45 ea, or £1.10 ea when purchasing 10 (£11) same day. Powered by BISS0001 dedicated PIR controller ASIC, £1.20 qty 1 DIP16
PIR Sensor – MH-SR602 Techtonics Mini Motion Sensor – £8 for 5pc (£1.60 ea, next day) | Datasheet online
PIR Sensor – AMS312 – £9 for 10pc (90p ea, 3 weeks), or £8.50 for 5pc (£1.70ea, next day) | Datasheet online
PIR Sensor – KS-052, 3-12V mushroom form factor, £2.86 ea
HC-SR312 2.7-12V mushroom factor, smaller lens, non-configurable, 5x for £8 (£1.60 ea) next day, Susceptible to false triggering

HC-SR505 mini lens, reduced range, non-configurable, 5pc for £9 (£1.80 ea)

Notes: Conversion to run on 3V/3.3V for use with ESP8266 wifi, Comparison of variations

The directions for turning the potentiometers are when they viewed from the top, i.e. facing you and ready to be turned. Critical one to adjust is the timing delay – maximum CCW turn sets to 3 seconds delay.
Non-Contact Infrared Thermometer, £13
AMG8833 – Infrared Thermal imaging Camera available as a component to be integrated as a sensor, £22
Camera product with screen on top of the AMG8833 infrared thermal imaging camera sensor, £30
KS-053 – Colour Sensor
KS-060 – 4×4 Matrix Micro Switch Keypad, (used to be £2.40ea ebay) |5 pcs for £7 (£1.40 ea) next day (no hardware debounce). 4×4 matrix keypad usage: connect 8 pins to uC, treat 4 as transmit pins (output) and 4 as receive pins (input), with a scan/interrogate logic to determine which key is pressed — see 3iSensor.fs and 3iSensor.avr code. Because the keypad must be driven using both Tx and Rx, an SPI hack could simplify the interface.
K62103BS – MODAL KEYPAD: 4×5 Matrix (16-key + 4 mode selection keys) keypad. HIGH POTENTIAL Using each as a bank of commands gives 64(=16×4) commands. Using each as a binary selector gives 256 (=16*16) commands. Since it has a bank of 8 LEDs, could be used as a high speed 16-bit hex input device: keypad inputs hex a nybble at a time, and modes which nybble and display.
£3 ebay or £3.50 ebay
4 Direction Keypad with 3 buttons £2.50 ebay
5 Direction Joystick Keypad with 2 buttons £3.00 ebay
TTP229 4×4 capacitative touchpad £4.50 ea.
4×4 Matrix Membrane Keypad, 5 pcs for £6 (£1.25 ea) same day, £2.39 (picclick)
KS-088 – IR Remote Control and Receiver, £4.60
Eye Blink Sensor using InfraRed
KS-097 – Bluetooth Serial for Arduino, £6.90ea, 12 EUR, or 2pc. for £10 (£5 ea, next day), KS-393 Bluetooth/WiFI Choices for Bluetooth: ESP32 (and Android smartphone), HC-06 Bluetooth module. Bluetooth uses the standard serial protocol. Setup. DSD Tech Blue Tooth specialists. Bluetooth primer: HC-05 (master/slave mode, Bluetooth 2.0), HC-06 (slave mode only, Bluetooth 2.0), and WF-05 (WittyFox) (dual mode, but Bluetooth 5.2, so can connect to smartphones and laptops). WF-05, £5 ea for HC-05, HC-06, and JDY-31
KY-098 – Ambient Light Sensor, £3.60
KS-143 – Bluetooth XBee, £7.90
KS-148 – Ethernet Breakout, £7.30
KS-167 – Weight Sensor
KS-168 – Fan Motor, £4.60
KS-171 – Heartbeat Finger, £8.70
KS-186 – Current Sensor Module
KS-196 – Optical Dust / Smoke Sensor, £12.30
KS-203 – Steam Water Vapor Detection, £3.30
KS-204 – UV Sensor Module, £5.50
KS-272 – Ceramic Piezo Vibration Sensor, £5.70
KS-279 – Slide potentiometer, £7.90
KS-280 – Breadboard Mini Power Supp
Mini-Voltage Sensor, 4.30
Barometric Pressure, Temperature, Altitude, £7
Weight sensor (24-bits), £8 for 6pc (£1.50 ea)
Gyroscope/Accelerometer/Magnetic, £9 for 2pc (£4.50 ea)
Temperature, Barometric Presssure, Altitude, Humidity, £17
Gas Sensor Module, £20 for 9 (2.11 ea)
16×2 I2C LCD Display, £4.40
Color Sensor Module, £5.50
Luminosity Sensor TSL2561, GY-2561, £1.73
Gesture Sensor / Proximity Sensor: £3.40 using luminosity sensor
GPS (excl. battery): Neo-6M-GPS-Module-GY-GPS6MV2, £4.28
Gyroscope/Accelerometer: 9DOF-MPU-9150-3-Axis-Gyroscope-Accelerometer-Magnetic-Field, 3-axis, £8.79
Light Intensity Sensor: LM393-Light-Sensor-Module-3-3-5V, 29p ea (MOQ5)
Barometric Pressure BMP280 (hw-611 e/p 280), I2C interface: 82p
Traffic Light module: £15 for 30pc (50p ea, 3 wks), or £5 for 5pc (£1 ea, 1 wk) or £6 for 6pc (£1 ea, next day), or sj-3wgj-h6md Or: KS0310 model. Or real traffic lights. Reference 1, Reference 2 Note: The LEDs are nice and big (10mm?) and the module looks good. However, the green LED is much dimmer than the others. In interior light, the green LED is faint when lit; in daylight, it’s practically undetectable. This due to the designer applying the same surface-mounted 330R current-limiting resistor to each LED, instead of using a lower value for green. The workaround is to solder a 33R resistor across the terminals of the surface-mounted 330R resistor, creating a parallel bypass leg with lower resistance, hence providing the green LED with higher voltage.

To increase the brightness of the Green LED, solder a 33-ohm resistor across the surface-mount 330R resistor to create a lower-resistance, higher-voltage/current parallel path.
Ultrasonic Sensor: Lowest: 59p ea, currently: £4 ea.
Soil Humidity/Dryness Sensor/Hygrometer: 51p ea. (MOQ5), or £1.20 ea.
Full automated irrigation system – £74
Magnetic Reed Switch / Magnetic Induction Switch (Normally Open) Lowest Price: 17p (MOQ10), Currently: £2.40 for 10pc (24p ea), or 22p ea for 40x, 0.5A current or £2.45 for 10pc (25p ea), or 23p ea.)
Video: How to make an N/O reed switch and convert to N/C?
NO/NC, £12 for 4pc (£3 ea), door alarm kit, magnetic reed switch sensor or £9 for 10pc NC only (90p ea), pre-wired with 25cm cable,
Tilt Switch / Ball Sensor: SW-100 (KY-020 board), 100 pc. for $9.50 (9.5c ea.) or SW-200D, 10pc. for £1 (10p ea.), max 12V input
Photo Interruptor (Light Blocking Sensor): Board, £1.03 or Slotted Optical Switch, £2.49 for 10pc (25p ea.)
Temperature Sensor: Analog board KY-013, £1.35 or Digital board KY-028, £2.75
Capacitative Touch Switch: TTP223B, 5x for £1.28 (27p ea.)
Metal/Human Touch Sensor: KY-036 board, £3
Linear Hall Effect Sensor: Board, £3 or sensors £1.60 for 10pc (16p ea)
Flame Sensor: £2.43 (red board) or 78p (blue board, MH Sensor Series, Flying Fish)
Serial Communications
1. DB9 female / RS232 to TTL: £1.61 for 1pc, fully assembled, with 4pin cable, or £1.17 as above or 5 pc for £4.00 (80p ea.)
2. Cables: USB to DB9 Male73p
3. Gender change adapters: DB9 F/F, 25p; USB A F/F, £2.22 (Prime) this is a cross-over coupler (the top pin goes to the bottom, and so on)
4. USB / RS232 to TTL: Lowest: £1.18 for 1pc, Now: £3 for 1, or £1.10 for integrated cable with 4 TTL leads
5. USB C to USB: 4pc for £2 (50p ea)
References:
- 50 low-cost sensors for interfacing to the real-world
- Sensors Online Magazine
- Sensors Catalog 1 or Catalog 2
- RS-232 communication
Remote Control (RC) and Radio Frequency (RF) Communications
1. [tried] 4-channel wireless remote control modules, QIACHIP 433 MHz Radio Frequency (RF) Tx/Rx pair, TX-118S-4 transmitter, receiver with 1527 learning code, 3V-24VDC operation 3 pairs for £9 next day
  Pinouts for 433MHz RF transmitter and receiver pair, £3 ea. pair
2. STX882 433 MHz Rx/Tx pair for £8
3. 27MHz 4-channel RC Remote Control, 4 pc. for £10 (£2.50 ea), or £6 controller, 40 MHz 2-channel remote control, £2.50. Discussion on pros/cons of 27 MHz/40MHz/2.4 GHz…
4. How Remote Control RF radio works…
5. 27MHz 5CH controller (5 buttons) + receiver + antennae, (XN-AR11R-V4) £5.71 delivery in 10 days, 4CH Rx/TX boards £2.48 3 weeks, £5 option, £8 for controller with 2 button joysticks
6. 33 MHz EV 1527 TX/Rx board pair for £2.50
7. 40MHz 4CH Rx/TX board components £2.54 3 weeks
8. DO NOT BUY THIS 433 MHz RF transmitter/receiver – 5 pc for £6 (£1.20 ea) next day, Receiver 1527 module for £4.30, Transmitter EV1527 module, 7 pc for £7 Tx/Rx pair DO NOT BUY THESE – many reviews on incomplete or poorly made boards being sold by many sellers.
9. 2.4 GHz controller £10, or 2.4 GHz 4CH controller £35, or £11, 4CH £7 ebay
10. 2.4GHz with antenna for £1.19 or 315 MHz x 5 pc for £2.65 (53p ea.) or 2.4GHz ESP system or 8266 WiFi Module, £8 for 4pc (£2 ea);
11. RF Sensors, can detect fluid flows and dynamics of objects: How RF sensors work. Example: VIPER field disturbance sensor
12. RFID (Radio Frequency IDentification) / NFC (Near Field Communications)
  1. RFID Reader / Writers
    1. Passive LF (125kHz) £28 or just the module £8; up to 1m, £69, 125kHz Sparkfun Kit for $52, 125kHz ID-20LA Innovations, £28.07
    2. Passive HF (13.56MHz, RFID/NFC), Reads @ max 20mm: (1) RC-522 Module + S50 Card & KeyFob £1.94 or £4 (with chip manuals) (instructable here); or KS-204 at £5.19 (2) Reads @ max 50mm for UNO R3 (PN532), £13
    3. Passive UHF (860-925 MHz)
      1. Chip (IC): ThingMagic M6E-NANO (surface mount) $125 with multi-tag read capability. (ThingMagic was a brand of Trimble Navigation, makers of GPS systems.) Needs a carrier board to use it..
        Based on Atmel SAMD21 32-bit ARM microprocessor. Note that the M6E-NANO is the low end of the ThingMagic M6 (Mercury 6) product line (watch video). At the higher end is a 31.5dBm, 1.5W module capable of longer read distances and up to 750 simultaneous tag reads/second.
      2. UHF RFID Reader Carrier Board: SparkFun SEN-14066 based on ThingMagic M6E-NANO, $225 with excellentsetup documentation or £232 from Amazon.co.uk or £212 from CoolComponents.
        Key specs: (a) simultaneous (multi) tag reader (max 150-200 tags/second), (b) can write to tags, (c) max read distance is 16ft (4.9m) with adjustable power output 0 to 27 dBm, (d) is an Arduino UNO shield, i.e. compatible wwith Arduino form factor/pinouts, and the Arduino toolset/ecosystem/coding platform/open-source libraries, (e) reads standard Gen2 UHF RFID tags, (f) 5V operation, (g) UART 5V for TTL serial communication (9600 to 115200 baud), (h) serial selection switch toggling between HW serial (Rx/Tx on pins 0/1) to SW serial (Rx/Tx on pins 2/3), (i) firmware compatibility with Jadak’s ThingMagic UHF RFID line including 2- and 4-port reader modules< and specalised or custom-designed antennas, (j) USB to PC connection through FTDI breakout board to use Jadak’s URA (Universal Reader Application) software for easier exploration of all ThingMagic features and configurations.
        
        The Sparkfun board works, but is of medium difficulty to setup: requires a soldering iron, FTDI serial to USB breakout board to test using PC uRA software, R3 stackable pin headers for use as UNO shield, external antenna for long range reading, 2 auxilliary antenna cables to enable connection , and Sparkfun Redboard UNO compatible main board for direct / headless connection without collision of the integrated antenna with UNO components. Have not been able to get it working headless with nano because of the incompatbile pin to pin connection and the difficulty of high speed (115k baud) serial communications over jumper wires.
      3. Alternatively: AtlasRFIDstore, $263 or JieTong, £101 (incl. £21 delivery), a small size short range UHF tag reader w/ UART interface, or 3m-6m reader with 8dbi integrated long range antenna, £177, 10-1000mm, £145; 10-500mm, £140
        References: (1) Hookup Guide (2) Video illustrating usage
  2. Tags: Passive long range UHF tag: Alien H3, 20pc for £8, 1-6m depending on reader, Monza Tag, 20pc for £9
  3. Passive UHF RFID Laundry Tag, 5pc for £11, or UHF passive laundry tag $1 ea, machine washable.
  4. Antennas: Passive Long Range *UHF RFID External Antenna: 860-930MHz:
    1. WRL-14131 6dBi gain, linear polarization (for reading fixed orientation tags) RP-TNC (reverse polarity) female connector: $35 (Sparkfun) or £48 (CoolComponents UK) or 1m-4m, £60 Antenna Only 6dbi gain (Sparkfun);
    2. MTI Wireless, MTI-262041, 85*x85* beamwidth, 5.0dBic gain (circular, with circular polarisation), $565
    3. MTI Wireless MTI-242043, $140, 8.5dBic gain (circular), with circular polarisation, 65*x65* beamwidth, pre-certified by FCC for use with M6E-NANO, or MT-262062, or MT008S08LH, 65*x65*, 9.0dBic gain (circular), or MT009S08LH for , or MT-262006, 63*x63*, 9dBi
    4. MT-243005 Dual polarization 120* x 16* beamwidth, 3dBi gain, 10W, 1.2m x 0.5m base station antenna for $1800, or 263004 Sector Antennas, $860-1360
    5. MTI Wireless, MT-263018, 65*x40* beamwidth, 10dBic gain, 6W
    6. MTI Wireless MT-263020, $460 (US price) (11dBic circular gain / 8dBi linear) with circular polarisation, 63* x 30* beamwidth (elevation x azimuth), highest gain antenna already certified by FCC for use with M6E-NANO
    7. Extronics IANT217 Omni-directional (no predictable orientation) UHF antenna, 7dBi gain;
    8. 1m-4m, £90 Antenna Only 6dbi gain, circular polarization
    9. Custom Design, Wide Selection: MTI Wireless Edge selector, 32 UHF MTI Antennas (list), 865-928 MHz, 8353 antennas with parametric search (Everything RF), 10 RFID circular UHF antennas (all directional); 900MHz Patch, Directional, Omni, Sector, and Grid; 243 RFID Antennas from Arcadian; 23 RFID Reader Antennas
  5. Antenna Interface cables
    (note – antenna cables have a confusing mix of gender and polarity — see this guide)
    1. *RP-TNC male to RP-SMA female cable: £15.12 Amazon Prime or £14.40 from 4GLTE.eu
    2. *RP-TNC male to RP-TNC female coaxial extension cable: 6′ for $16, 15′ for $19
    3. *RP-SMA male to U.FL cable: £18.52 Amazon Prime or £16.80 from 4GLTE.eu (WiFi nation)
    4. RP-SMA female to U.FL Sparkfun WRL-00662 or £3 in UK and
    5. U.FL to SMA £3.50 in UK
  6. Data Interface Boards: FTDI interface (serial to USB): £15 (Amazon), or £15 (Cool Components) requires USB mini (not micro) B cable.
  7. Universal Reader Assistant (URA) software
    RFID Notes & References
    
    RFID systems.
    
    The simplest RFID system consists of three parts: Reader + Antenna (for radio transmission and Tags (receiving antennas that backscatter ID information).
    The tags can be passive (powered by the interrogation signal from the reader), battery-assisted (semi-)passive, or active (self-powered).
    System is classified by radio frequency used — readers, antennas and tags have to match:
    
    low frequency (LF) less than 132 kHz (40€-70€),
    high frequency (HF) 13.56MHz (40€-1000€),
    near field communications (NFC) which is a subset of HF that additionally features encrypted data exchange (e.g. bank cards), and
    ultra-high frequency (UHF) 860-960MHz (140€-2000€)
    
    Readers have different levels of integration: chip, modular, or finished. Finished readers are off-the-shelf ready to operate; modular readers are components that are lower cost, customizeable and can be integrated into an engineering product solution. Modular readers can be an individual chip, or a development board which onto which the chip is integrated.
    Ranges: passives tags have a range of 1-7m depending on tag size and reader power; battery-assisted passives: 50+m (150+ft)
    Encoding data into RFID tags
    RFID Tag specification, Gen2 Air Interface Protocol
    
    Antenna Concepts
    
    Excellent explanation (Mobile Mark Co.): antenna theory basics made accessible
    Antennas are classified by various parameters, and selection is critical for a desired application
    
    Frequency: higher frequency means longer range, higher power, smaller wavelength hence greater detection, better detection grain. UHF is 865 to 928 MHz.
    Polarization: describes the geometry of the radiated fields produced by the antenna. A linear polarization means that the electric field oscillates in a plane, and is constant in the direction of travel. A tag whose orientation is not aligned with the polarization suffers polarization loss in its backscatter. Cell phone antennas are often linearly polarized, which is why signal quality varies point to point. Circular polarization means that the electric field oscillates radially, so a tag will reflect regardless of its orientation. GPS satellites are RHCP for this reason.
    RHCP and LHCP (right- and left-hand circular polarisation) – no difference, just match transmitter and receiver for maximum signal strength and least interference
    Amplitude: signal strength
    Radiation pattern: the geometry of the wave pattern, omni-direction or directional, based on angles vs. various amplitude levels, measured azimuthal in the plane and elevation in the z direction
    Wavelength & detection grain: related to the wavelength (e.g. UHF is 860-930MHz [cycles/sec], so each wave travels for 1.075×10^-9 seconds. Since light travels at 3×10^8 m/s (300M meters per second), the wavelength [distance between waves] is 32.2 cm to 34.5 cm (=300/930 and 300/860)
    Phase: relates to the parts of the wave, and determines potential constructive or destructive interference. For UHF, half wavelength is about 16-17cm — this is the destructive point (minimum energy). Quarter wavelength is about 4-5cm — so could put a ground plane (reflective metal sheet) at this spacing to enhance the signal.
    VSWR (Voltage Standing Wave Ratio): smaller is better
    
    Examples
    
    White Papers. Guide to UHF tags (PDF)
    Battery assisted passives (BAPs) – case study: Vaillant boilers
    The battery in BAP tags are usually not replaceable, and once it dies out these tags need to be replaced.
    Hybrid passive/BAPs for pervasive sensing: “RFID is the cheapest, lowest-power RF communication protocol currently out there. When generic RFID chips can be deployed to sense the real world through tricks in the tag, pervasive sensing can become reality.” (Sarma, source)
    Other case studies
Electric Door Lock / Door Solenoid: 9mm stroke / 15N force, 12VDC, 16W (1.3A) £11.10 or JF-S1670DL, 10mm stroke / 40N force, 12VDC, 2A, 24W, £13.23 or JF-1264B 55N, £20, or JF-1250B, 60N, £21
Strike locks are normally closed and use power to draw back the strike mechanism (stroke). Need enough pull in force to counter friction/resistance on the bolt. Lots of choice here (Locks online) and The Solenoid Company / Impulse Automation

G. Motors

Start here for everything you need to work with, fabricate, mount to, and mount on motors! ITP Fabrication

Next here for inspiration on Engineering Design of small autonomous motorized robots built by students in 13 weeks as part of ELEC 201 Intro to Engineering Design, Rice University, Instructor: James F. Young and Course 6.270 Autonomous Robot Competition, MIT, Instructor: Fred Martin and Randy Sargent

Selecting a motor: 4 types of motors to choose from: (1) can DC, (2) geared DC, (3) servo DC, (4) stepper motor.

Mounting a motor: custom 90* assembly for motor and worm gear £4.80 (spiratronics), dc motor base mounting bracket (20mm), 25 pc. for £7 (28p ea), mounting hub or £8.50 (34p ea) Amazon, or 10pc for £4.86 (48p ea), or alternate screw type £2.20 ea

Attaching to a motor drive shaft: ideas: hot glue, drill bit/press fit, shaft coupler, hose tubing, heat shrink tubing, coupler to universal drill bit coupler, end of plastic/wood rod/dowel, drill & tap metal, weld, pin, solder, clamp, clamping collar, adapting bushing, terminal blocks (150 for £7, or 5p ea)

Mounting a motor:

Controlling a motor (feedback loop):

Stall/Free current, Stall/Free torque.

Gearing down a motor to create torque – torque increases linearly with gearing ratio

Making things move: Gears & Propellers

Uses for small motors: hovercraft, propeller cars, helicopters, etc.

Powering Motors – I use CR123 3V lithium batteries. These are cheap, long laster, and provide steady voltage over their life. They also hold their power up to 10 years (per spec, not tested of course).

Wheels / Moment Arms / Propellers

Wheels and Axles – 50 wheels (42mm) and 25 axles (2mm shft) for £9.59 (38p per axle) Note: can carefully expand shaft diameter to 3mm using two steps, first expand to 2.5mm then to 3.0mm.
Eye Caster Wheel (cow eye/bull eye) – 5pc. for £5.62 (£1.12 ea) ebay, or 5pc. for £6.20 (£1.24 ea) ebay, or £1.72, £1.98, Lego Caster Ball (£6), Lego Caster Wheel on a rotating platform using “landing gear wheel” (#2415, 4pc for £2.75, 67p ea.) attached to swivel platform (“turntable”) (#3679,3680, 10pc. for £2.90, 29p ea.)
Simple Lego caster wheel made from a single “landing gear wheel” attached to a swivel platform (“turntable”) which is in turn attached to the baseboard with a 2×2 brick.
Propellers – Drone flight and propeller selection, Modeling Thrust FancyWhoop 3-bladed props, 16pc for £9 (56p ea) next day 2.5″ for Emax BabyHawk Race Pro (video) using F15 1106 6000KV motor £16ea. Understanding quadcopter motors. Flight forces calculator: weight, lift, thrust, drag (motocalc.com) DRONE KNOWLEDGE

Motors

DC Stepper Motors:

28BYJ-48 5V DC Stepper: 5 pc for £5.83 (£1.17 ea.) ebay
Motor + ULN2003 driver board: Available singly @ £1.32 for motor + driver board, or 5 pack at £7 (£1.40 ea.), or 5 motors + 1 driver board for £11 (2.20 ea) next day or 5 pack + 10pin male-female jumper wires, £14 (£2.80 ea.)
ULN2003A IC chips – this is all you need to drive the motors – you don’t need a driver PCB as the Darlington Arrays are very straightforward to hook up – the chip is itself the interface. Note – power goes to pin 9, ground to pin 8., 20 pc.for £4.80 (24p ea.) 1 month, 10 pc. for £3.80 (38p ea.) 4 days, 10 pc. for £3.40 (34p ea.) 4 days, 10 pc. for £2.48 (25p ea.) 1 month
ULN2003 motor driver surface mount PCB with surface mount LEDs (note, these are good for test but not production, as they consume additional power and are always on). 5x for £6.40 (£1.30 ea) next day
Shaft 5mmx3mm, motor wire red=power, a step is a signal to the motor, max gear ratio is 1:64 (1 revolution = 64 steps) when driven in half step mode, so half step angle is 5.625 degrees (=360/64). Micro-step mode has 64 micro-steps per step 1 revolution = 4096 microsteps (=64×64) of 0.088 degrees each (=360/4096), 5V rated, noise < 35dB, slower rotational speed means higher torque, can do up to 25 rpm, at 4 rpm can open heavy curtains. Tip1: Put a relay between the power pins to ensure that software can cut power to the motor (not spinning does not mean unpowered). Tip2: bolt motor to copper plate as heat sink to dissipate heat buildup.

28BYJ48 Step Motor cheat sheet.
4 phase 5V stepper motor with internal gearbox providing max 4076 micro-steps per revolution in half step drive mode. (2038 steps in half power wave drive mode)

Driving 28BYJ stepper motors via Darlington arrays ULN2003A IC which provide 500mA max current each (2A max total, 10W drive at 5V).
- Download Datasheets & Instruction Notes (ZIP),
- Explanation of Motor & Driver Board, usage with Arduino,
- micro-stepping mode with integrated gearbox of 1:63.68395 ratio (4076 steps per rev).
- Motor deconstructed and explained,
- Video showing 3 modes to drive the motors: (1) wave drive, single coil, half power (160mA, 5V, 800mW), half torque, 32 steps/rev (ungeared), (2) full step drive, double coil, full power (320mA, 5v, 1.6W), full torque, 32 steps/rev (ungeared), (3) half step drive, combination of both, 64 steps/rev (ungeared).
- With a suitable modification, the motor can also do micro-stepping.
- Nanostepping.
- The motor has a gearbox which applies a further 1:63.684 gear reduction, giving a total of 4076 steps to turn the shaft 1 revolution (=64*63.684): ” 64 steps per revolution of the motor rotor, and the motor has an internal gear ratio of 63.684:1, so effectively we have 4076 steps per revolution of the motor shaft.”
Micro steppers: Mini Micro (smaller than a coin), 2 phase, 4 step, 3V microstepper 10 pc for £5.22 (52p ea.) or 10x 2 phase 4-wire microstepper motors for £10.90 (£1.10 ea.)
Attachments 5mm x 3mm shaft: (1) Polymorph coupler to 2mm axle, (2) 5mm drill bit, (3) 5mm to 3mm shaft coupler £3.83, 5x multi-couplers max to 5mm,for £8 (£1.60 ea.) (4) Variable angle 5mm to 5mm coupler with set screws, 5 for £10 (£2 ea.), (5) plastic gear adapter, 2mm to 5x3mm,
NEMA17 high-torque stepper motors

DC Motors:

Small DC Motors, 12 kinds, for £8.40 (70p ea.)

Micro 130 DC motor – no gearbox, high speed (9500rpm)/low torque, without gearbox good for experiments and propellars (datasheet), only good for propeller without gearboxDC 3-6V 16.5k rpm motor: 10pc for £4.50 (45p ea.) ebay or 10pc for £10.50 (£1.05 ea.), or 6x kit with motors and motor brackets (holders), £11
RF 300 DC motor – without gearbox, low torque, good for propellers and spin launchers 1.5V-6V, 1700-7300rpm, 50p ea.
Using Gearboxes: Warning: when using a motor without any other speed/current control mechanisms you will need a high current resistor, capable of handling up to 2A, i.e. dissipating up to 1-10W of energy, as the motor itself is low resistance and the shaft will typically spin >2K RPM with little torque strength which is not useful for most applications. A gearbox slows down the RPMs and delivers stronger torque:
Article1, Article2, Article3, Article4, Article5

Geared Motors (with integrated Reducing Gearboxes)- 3mm shaft (except as indicated):

2x motor drivers, 4x geared motors, and 4x wheels – £15 These are large wheels, great for a robotic platform with differential steering. Enough for 2 such robotic platforms (need 4 caster wheels)
Micro Mini N20 motor 3V-6V, ebay £2 ea. with PH 2.0 female connector 55rpm [tried 8x]
GA-12 N20 motor ebay, £2.25ea (MOQ 8x), 30-2000 rpm, tried 2x ea. in 30rpm/3V, 70rpm/3V, 150rpm/3V and 30rpm/6V flavors
Geared DC motor + wheels, 4pc for £7.20 (£1.80ea), 6pc for £14 (£2.33 ea) 3 weeks, 90/200 rpm at 3/6V.
Geared DC motors + wheels + L298 dual axis PWM motor driver, 2pc. for £10 (£5ea) next day, 4pc. for £15 (£3.75ea) next day
4x Geared DC Motors – £10 next day (£2.50 ea.)
Motor Driver chips – Overview of all choices
L9110 chip: £2
L298 chip: H-Bridge dual channel DC Motor Driver (with built-in polarity reversal) Instructions (Sparkfun)
L298 boards: 5 pc. for £11 (£2.20 ea) 3 day, 5pc for £11.50 (£2.30 ea.), or singly at £2.50 ea
5 RPM (full rotation once every 12 seconds), £8.65 next day;
10 RPM (full rotation every 6 seconds) £8.90 next day;
20 RPM (full rotation every 3 seconds);
40 RPM £6 next day
100 RPM, £8 with mount next day
130RPM Sparkfun, micro gearmotor
600RPM £4.60 next day
12V motors 5-700 RPM sealed, 12V motors 5-700 RPM £3.50 30-days
5mm shaft – 18 RPM £3 (30days);
Decent torque, but 30rpm is too slow for a car. [tried]6V 30 RPM (full rotation every 2 seconds) £6.30 next day open construction, £7 next day, £9.79 next day with long threaded screw shaft
Dustproof design: 60-600 RPM, 6V 100 RPM £3.10 (30 days)- tried, too little torque

DC Servo Motors:

MicroServo SG90 (torque 1kg/cm, plastic gears) Best price was: 10pc for £13 (£1.30 ea), 5pc for £9 (£1.80 ea), 5pc for £10 (£2.00 ea), Datasheet/connections. Not recommended for general use.
MicroServo MG90S (torque 2kg/cm), or 5pc for £12 (£2.40 ea), or 10pc for £24 (£2.40 ea) or 10pc for £27 (£2.70ea) or 5pc for £18 (£3.60ea)
MicroServo MG996R (torque 13kg/cm) or MG995, 10pc for £36 (3.60ea) or 4pc for £18 (£4.50ea) or 4pc for £19 (£4.80ea)
DMS15 (torque 15kg/cm) or LD-3015MG
LDX-227 (torque 17kg/cm), £17
SR-6120MG (torque 20kg/cm) or LD-220MG or LD-27MG or LD-20MG or A202-81 £11
A202-81
Servo Motor PWM Driver Board: PCA9685 board, 16-channel, I2C, free-running with built-in clock £5 next day, or £4.50 3 weeks

Robotic Platforms

6 DOF Robotic Arm £140 or $179 or £190

6 Degrees of Freedom – Robotic Arm £140, with 6-channel wireless bluetooth controller for each motor separately
Hydraulic Robotic Hand £120

Hydraulic Robotic Hand
DC Motor PWM Speed Controller: 3-35VDC, mini with 6mm knob, £1.43
Electric gearbox
one
two
three
four
Steering rods/mechanisms:
one
two
three
Steering Theory
Timing Belt Toothed Pulley
Motorized Wheel
one
two
Chassis & Robotic Car Kit
one
two
Robotic Devices & STEM toys
one
two
three
four
five
six
Robotic Arm
one
two
three
four
five
six
seven
High Performance RC Cars
wall climber £11
Lambourghini Black £13
Lambourghini + Batteries £15
Hi Speed £15
Example wooden toy RC motor car driven by simple pulley, forward/backward only, 27MHz remote control and antenna, £4.52 (ebay) or £13 on Amazon (with better pictures for helping with assembly)
Steerable remote control car, 27 or 40 MHz control frequency, £7 ea.

Motor Couplers
A coupler allows connecting motor shaft to something else. A shaft of 5mm x 3mm requires a 5mm coupler. The set screws are used against the 3mm side to keep the coupler in place.

2.3mm/3mm to 5mm shaft coupler (for wheel axles): 3mm for 65p (best price anywhere), 2.3mm for 99p (ebay)

Gears, Gearboxes, and Pulleys

Basic Machines / Mechanical systems: there are SIX fundamental mechanisms for automata: (1) Pulleys, (2) Crankshaft, (3) Camshaft, (4) Gears, (5) Ratchet, (6) Lever, (7) Screw (converts rotational to linear motion).
Motor driver to screw for precise linear alignment – 5pc. for £7.81, 10pc for £18 (£1.80 ea.)

Mounting Platform: 2x screws, platform (wood or copper plate for heat dissipation), DC motor bracker

What are you pulling?

Gear & Pulley Kit, 2mm aperture (shaft diameter), 78 pieces for £3.85 Simple & Compound Gears, Sprockets, Simple & Compound Pulleys, Axles, Bevelled Gears. 58 pc. for £3.10, 2-3mm aperture, 64 pc. for £3.51, 2-3mm aperture
Steel Axles/Rods: 2mm diameter 10x 100m for 5.26
Pulleys: Reducing slippage in pulley systems (article 1): (1) more tension (smaller belt, pulley wheels further away), (2) more friction (sandpaper pulley surface), (3) gear mechanism, (e.g timing belt GT2 pulley, wheel, and belt, closed loop, for £16), (4) run the pulley faster. Belt slippage theory
1. Assorted plastic pulleys (Spiratronics), 15p ea., from 10mm to 30mm, for 2mm shafts to 3.2mm shafts
2. 4 pack of mixed pulley sizes to illustrate pulley ratio, £3.90 (Amazon), or direct from Spiratronics
3. 2mm shaft, 6mm dia, axle drive pulley: 50pc for £2.29 (4p ea.) or 20pc for £4.60 (23p ea.) next day
4. 2mm shaft, 10mm dia: 10pc. for £1.09 (11p ea.) Spiratronics
5. 2mm shaft, 17mm diameter: 30 pc. for £4 (13p ea.) next day or 30pc. for £2.40 (8pc ea), or 100pc for £6.20 (6.2p ea.)
6. 4mm shaft, 25mm dia: 10 for £5.80 (58p ea.),
7. 10pc for £2.50 (25p ea.), 5mm D-hole shaft 36mm dia
Pulley bands Drive belt theory (Wiki) Belt drives Basic Machines theory
1. Lego Rubber Bands – Round cross section: White 15mm 5 pc for £3 (60p ea), Red 25mm 5 pc for £3.30 (66p ea), Yellow 33mm 5pc for £4 (80p ea)
2. 100mm unstretched normal rubber bands for 2mm pulley (stretched 400mm) 100pc for £5 (5p each)
Wooden rods/dowels/bars, 5mm rod can be drilled with 2.3mm drill bit to hold a 2mm axle comfortably:
1. 5cm balsa wood square: 10 for £1.80 (18p ea.)
2. 6cm pine wood squares: 50 for £4 (8p ea.)
3. 7cm balsa wood square: 30pc for £3.67 (4p ea.)
4. 11cm balsa wood square: 50pc for £6 (12p each)
5. 12cm balsa wood square: 5pc for £4.00 (80p ea.)
6. 20cm wood rods: 20pc for £5.50 (28p ea.)
7. 28cm (11″) candy floss sticks: Lowest: 5.5p ea (£5.50pc for 100pc), Currently: 100pc for £8.90 (9p ea) next day. These are excellent! Easy to snap off cleanly, and lightly sand to remove sharpness/splinters, wide enough to use a 2.4mm drill bit to drill a hole for a 2mm axle shaft to rotate within, great for making frames for lightweight items using hot glue.
8. Craft Stocks – Jumbo: 19mm wide x 150mm, £4 for 100pc (4p ea, 1wk), or £4.20 for 50pc (8.4pc ea). Narrow: 10mm x 114mm
9. Bamboo Paint Stirring Sticks: 40cm long, 10mm wide (1/2 width of wide craft sticks), 3mm thick £10 for 100pc (10p ea)
2mm beads – 1200 for £1.30 (c. 9 beads fo 1p) great as axle spacers, and chassis frame rods to stay in place
Pinion/Sprockets 4x 18-24T £8 next day

H. Storage Solutions (Cases, Containers)

Low-cost, compact, secure storage solutions are essential for the amateur enthusiast. There are 4 main types: small components, medium project boxes, rugged cases, and hardshell/pelican boxes.

Small components: For £6, get 5 boxes: 2x 10-compartment, 2x 15-compartment, 1x 24-compartment, providing a total of 74 compartments.
1. 24 compartments (deep, good for holding ICs): Lowest price: £2.50. Currently: £3.00
2. 15 compartments (thin, good for holding shallow electrical components): Lowest price: 99p ea. Currently: 4pc for £9 (£2.25 ea) next day or 4 for £10 (£2.50 ea.) multi-colored same day
3. 10 compartments (compact, good for same part with less than 10 variations, e.g. switches): Lowest price: 69p ea (MOQ2). Currently: £1.00 ea.
Project Boxes:
1. The best medium project boxes I’ve found are the deep height plastic Chinese take-away boxes with lids. These just about fit a BB830 breadboard (800 tie-points) at the mouth of th ebox, so flipping the board upside down both protects the components and puts the widest part of your design against the widest part of the box. Cost: 30 min in the dishwasher after your next takeaway.
2. 4 x 1.5L Whambox boxes with lids, Lowest price: £1.25 ea (MOQ5). Currently: £7.00 for 4 (£1.75 ea.) from Amazon.
Rugged stackable cases. Recommend to get one of the following to hold the larger, odd-shaped items
1. Stanley, £6
2. Empty Raaco £8 + additional for inserts This is a spacious storage case as it is able to accept double stacked half-height inserts and singly stacked double-height insert. The issue is that the inserts are only available from Raaco, and have a £12 S&H fee
3. Raaco inserts for blank Raaco storage boxes or workbench organization:
  1. RECOMMENDED: Raaco Insert A7-8 42p ea. x2, 8 compartments each Great for screws, tactile switches, header pins, and other small parts
  2. RECOMMENDED: Raaco Insert A7-5 42p ea. x4Half-height with 5 compartments
  3. RECOMMENDED: Raaco Insert A7-3 42p ea. x4. Half-height with 3 compartments, great for pre-cut hookup wire ready for use as jumper wires, of different colors.
  4. Raaco Insert 80 BA8-2 £1.30 ea. x2 Good for sheets of 20-25 resistors; one for >5KR one for <5KR
  5. Raaco Insert 55 A8-1 38p ea. x4Good for medium sized parts such as brackets, LED bags, fuses, switches, large capacitors, etc.
  6. Raaco Insert 55 A9-2 48p ea.Not used: For resistors, one folded sheet, need a minimum 70x35mm insert
Pelican/hardshell cases:
Pelican cases are able to withstand punishment (being stood on, dropped from height, etc.) Aluminium case not so much, and would not expect to survive flight in baggage hold.
1. Pelican 1150 (24x19x12cm), £40, 1300 (26x24x17cm outside dims, 23.5x18x12cm inside dims), £70, 1120 (21x17x9cm), £35 Amazon Basics Medium (44x34x16cm)
2. Max 23x18x10cm for £30
3. Aluminium Flight Case 46x33x15cm for £29 or Perel 1829 (43x30x12cm) for £25, or (33x23x10cm) inside dimensions for £29

References

Electrical Symbols Reference and Periodic Table of Electrical Symbols
Partfinder (Lady Ada’s reference) – This is a neat, comprehensive list with a similar intent to the above, organized in tables with pictures (note links are US-based).
Spiratronics – Electronics Hobbyist Supply – UK (a.e; B*a) – Shipping £1.50 per order
BitBox UK – excellent organized component catalogue
Hobby Electronics
Langrex Vintage Electronics, stocklist of Transistors, ICs, and Diodes (40,000 lines)
Bits Box – Electronics Hobby Supply – UK
Quasar Electronics – UK
Rapid Online Electronics – UK
Where to buy Electronics Hobby Supplies – by main countries
AliExpress – Source direct from China(ae*0;r0*0)
Sparkfun account (USA); (ae*0; r0*0)
Flux Workshop
Pololu Robotics & Electronics
Switch Terminology
Metric Prefixes Reference
DigiKey – UK
AWG to mm conversion
Wire Gauge Size Chart
Worldwide Voltage, Plug, and Socket Reference
Understanding & Working with Capacitors
Perforated Board
Elegoo Device Datasheets and Instruction Notes – Downloads page
Physics of Sound/Music; Frequencies of Musical Notes; C0 (16Hz) to B8 (7.9kHz)
Online Tone Generator, for tuning various instruments
Online Tone Generator, any musical note

Inspiration

Browse the cool projects of these intrepid builders:

Hackaday – a site for experimentalist folks who like to play with microcontrollers and build cool things!
Frank Sargent’s 3-instruction Forth (1991) for microcontrollers having serial UART capability at bootup. Frank wrote this for the Motorola 6811 which has a von Neumann architecture. I’ve written a version for the ATmega328P (the uC Arduino Uno/Nano) that works in a Harvard architecture chip by using a precompiled table of function pointers stored in SRAM (data memory) making the chip’s capabilities available over the serial line. You can request the code in the comments!
Viktor Toth – 4-bit computer and the W programming language (his physics page, his Maxima page, his audio page)
Dejan Nedelkovski – Mechatronics with Arduino Nano
Petteri Aimonen – Essential Scrap, including steering mechanism, and some nifty inventions
TurtleBot
Karan Shaw – Trybotics – astounding array of Arduino projects
Willow Garage – ROS – the Linux of Robotics
Leon Maurer – AmForth for Arduino
DF Robot.com –
FX-Creations – Making it real
Petapixel – Light and BitDepth
Leah Buechley – Electronics in Art, Design, and Fashion, designer of the Lilypad product set.
Pololu Robotics & Electronics
Articulated Finger Extensions by Adrien R.
Andrew Huang – Modular Synthesis demonstrated, Endorphines Shuttle System – Incredible Synthesizer demo! Andrew Huang, $2500 – modular synthesis
Thomas Henry – Birth of a Synth designs – check out his SN-Voice samples using SN76477 complex sound generator IC as the core
What’s Next? A hardware accelerator / incubator.
Fantastic remote controlled car using Arduino Nano, SAMD21, and 3-D resin printed chassis
Aiden Lawrence – a fully functional MIDI programmable sound generator system – developed from July 2017 – Mar 2019 – writeup
Tindie Synths
For $99, can get an SBC with an Intel Celeron, 4GB RAM, capable of running Windows 10 Pro
Surface Mount memory chips
Garage Projects from CMU students
Easy Surface Mount Soldering using Schmart Boards
Ben Eater’s 8-bit programmable breadboard computer from scratch using ICs. Complete kit of all parts $295, or 4 kits bought one at a time.
Garage Build Week – Carnegie Mellon
App controlled Flamethrower using ESP8266 (Sparkfun)
Electronic music generators – arpeggiators
Paul Bleisch, Remote controlled Arduino tank
IC Station’s gadgets
Paper Circuit cards made from copper tape (Sparkfun)
e-Textiles (Sparkfun> and examples
Hacking a Matchbox/Hotwheels car to make it an RC car!
Awesome Fidget Spinner Rube Goldberg machine
How to Get what you Want — ATTiny adventures
Andrew Huang – Hologrm Electronics’ Microcosm Desktop Effects Pedal, for article see Engadget Review. Available direct from Hologram, $450.
Kevin – 50 projects in musical electronics using Arduino Nano culminating in his lo-fi orchestra.
Building a 3D Zoetrope: Mechanical Design, CAD, Motor control, Maths, Animation. – 3D Zoetrope Explained (video), Embroidered Zoetrope example (video)
BroHogan (John) – Home Automation network with Arduino/X10. Also ESP8266 and control via Alexa. Solar charging, wireless, valve control garden watering system.
David Touretzky (Carnegie Mellon University) 3D Printing – the next industrial revolution –
Calypso intelligence framework for the Cozmo robot
AI studies for K-12
Drum Computing
Norbert Heinz (Homofaciens) shows an impressive pick and place robot arm constructed from wood battens and long screw rods, run with an Arduino UNO with CNC extension board, controlled from a laptop running a Python positioning script. The explanatory video is efficient at explaining the design and is worth the watch! “This is fantastic. Great to see that cheap wood battens and long screw rods can provide a suitable frame for mechatronic experiments of the kind of precision shown in the video. Impressive indeed!”
John P. Miller’s – Robotic Xylophone – Came across this nifty robotic xylophone built by John P. Miller (https://buildmusic.net/). Looks like a tidy 25-key affair, with nice solenoid action per key, allowing for simultaneous strikes of the bars. Especially noteworthy is the care John has taken in the build – a nice wood case, transparent plexiglass window exposing the inner workings (and that can be opened up for access or adjustment), and a “no solder” build approach. He’s clearly into transferring skills – evident in his rigging up a simple 8-key experimental version that children can play with at Maker Faires. I was most impressed with the PC software interface he built making it easy to curate and upload MIDI files to create playlists that his Robotic Xylophone can play. Well done to John!

manual-range-select (not auto-ranging). Manual ranging instills the useful discipline of selecting the appropriate measurement range and there is no software delay in the measurement ↩

Mathematical Science & Technologies

Electronics

Exploring Electronics on a Budget

What to Buy, When to Buy It

The Equipment List

0. Recommended References

A. Equipment

Soldering: The Fine Art of Fine Soldering

RECOMMENDED ADDITIONAL SOLDERING COMPONENTS FOR SERIOUS DIY

B. Components & Supplies

C. Power Supplies (Batteries, Holders, Converters) Fuses, & Heat Sinks

D. Integrated Circuits (ICs) – Analog (555, LM386, etc.) and Digital Logic (TTL, incl. 74xxx chips, ALU)

E. Microcontrollers and Dev Boards

Arduino Nano/Uno (contains Atmega328P)

F. Sensors and Communications

G. Motors

H. Storage Solutions (Cases, Containers)

References

Inspiration

Leave a Reply

Dear Readers:

Reading List…

Mathematics History & Philosophy

Topics in Mathematics: Pure & Applied Mathematics

Technology: Electronics & Embedded Computing

Technology: Sensors & Intelligent Systems

Maths Education

Explore…

Timeline

Mathematical Science & Technologies

Electronics

Exploring Electronics on a Budget

What to Buy, When to Buy It

The Equipment List

0. Recommended References

A. Equipment

Soldering: The Fine Art of Fine Soldering

RECOMMENDED ADDITIONAL SOLDERING COMPONENTS FOR SERIOUS DIY

B. Components & Supplies

C. Power Supplies (Batteries, Holders, Converters) Fuses, & Heat Sinks

D. Integrated Circuits (ICs) – Analog (555, LM386, etc.) and Digital Logic (TTL, incl. 74xxx chips, ALU)

E. Microcontrollers and Dev Boards

Arduino Nano/Uno (contains Atmega328P)

F. Sensors and Communications

G. Motors

H. Storage Solutions (Cases, Containers)

References

Inspiration

Leave a Reply

Dear Readers:

Reading List…

Mathematics History & Philosophy

Topics in Mathematics: Pure & Applied Mathematics

Technology: Electronics & Embedded Computing

Technology: Sensors & Intelligent Systems

Maths Education

Browse…

Explore…

Timeline