Here are some shots of the invisible instrument undergoing assembly.
It took a number of failed boards before we settled on this design (and even this is a bit messy - we still need to move a few 5v and ground pins to stop the cables for the LCD display getting everywhere) After a couple of failed boards, we finally managed to get one working that we were happy with! The main problem with the original PCB layout was the LDRs were mounted with the legs running east-to-west. No big deal? Not until we put the black tube covers over them and tried to bend them into position.
Because of the way the legs were facing, there was no give in them, to allow them to bend - they happily moved backwards and forwards, but not left-to-right.
This has been corrected in the latest PCB layout.
See photo (below) for the correct way to mount the LDRs:
Note also that the LDRs are unlike other components - they are not mounted flush to the board, but a few millimetres left on each leg. This allows the LDRs to be bent into the correct position once the black tubes are put into place.
Here's the board with all the cables for the LCD screen in place too.
We added the screen to allow the user to interact with the device (set ambient light levels, change chord sequences/scale modes etc) without having to refer back to the PC. The idea behind this was to allow the device to be converted into a MIDI instrument in future.
Note: the green LED does nothing special - I just ran out of 5v red ones!
We're off to BuildBrighton tonight and hope to spend a bit of time on the laser cutter there, making up a cool enclosure from 3mm acrylic. Then it's just a case of a few firmware updates, and another project will be officially complete!