This is the build guide for my Touch Keyboard PCB.
Warning! I strongly recommend using old or second hand equipment for your experiments. I am not responsible for any damage to expensive instruments!
If you are new to microcontrollers, see the Getting Started pages.
Bill of Materials
- Touch Keyboard PCB (GitHub link below)
- Pin headers
Build Steps
There are just two key steps:
- Separate the two halves of the PCB. This can be achieved using a knife and metal ruler or a hacksaw. It takes quite a bit of scoring with a knife, but eventually, with scoring on both sides, the pcb will break in two. Just go gently and don’t force it!
- Solder on the pin headers.
The silver-keyed pcb can be used as a capacitive touch board or using the additional pin with a stylus.
The other pcb is for capacitive touch use only.
Both pcbs have 13 pins for the keys and an optional ground connection. The ground connection may or may not help with the sensitivity of the capacitive touch.
Both boards are designed such that the top note could be removed to allow several pcbs to be used alongside each other. In this case only the top-most octave would require the additional note.
To use the silvered board with a stylus, one connection pattern would be to connect all keys to INPUT_PULLUP pins and the stylus to GND. Some code to do that for a single octave can be found on GitHub here.
To use several keyboards together would require all keys to share the same connections (so C shares with C on all pcbs and is connected to one IO pin) and then to “scan” the stylus pin for each additional board in turn.
An example of that principle can be found here: Pi Pico MIDI Matrix Decode – Part 4. Additional diodes would be required if polyphony is required…
There are several ways to use either of the boards as touch sensors. Some examples might be:
There are more usage details here: Arduino Touch Music – Revisited.
Testing
I recommend performing the general tests described here: PCBs.
PCB Errata
The main mistake is not drawing a silk-screen line on the underside of the board where it can be cut! I also forgot to add a “diyelectromusic” label to the board. It might also have helped to include a silkscreen line connecting the stylus pin to the pin headers, just to make it clear what it is for.
If I re-designed them, then I might also include some edge cut cut-outs along the “cut line” to make it easier to separate the boards.
Closing Thoughts
These seem to work surprisingly well! I put two variants onto the same pcb as I wasn’t sure how they would perform, but I’ve been pleasantly surprised.
I don’t know how well the silvered pads will stand up to regular use. They look a bit thin. I suspect that to be a decent stylus keyboard, these would need to be much thicker plates to take some serious use. There might be options for different levels of manufacturing layers, I’ll have to seek some advice and see what might be possible.
But as a replacement for my copper-tape and button keyboards I’ve used in the past, I’m really pleased with how these have turned out.
These boards have been manufactured using the Seeed Fusion PCB service, which I am happy to continue to recommend. They have been supported with discount vouchers that I’ve been sent by Seeed for my previous projects.
Kevin
Simple DIY Electronic Music Projects 