I made a simple LED flasher based on the schematic below. The only difference is that I used two 22kΩ resistors instead of 100k.
Parts list: LED x 2, 22kΩ x 2, 470Ω x 2, 10μF x 2, 2N3904 transistor x 2, SPDT switch x 1, 9V battery x 1.
Originally I was thinking about laser cutting an acrylic case for the keyboard, but later decided to just use some cardboard and super glue (and some tape…) to make a rough looking case. I’m a complete noob at soldering. The soldering process took me about 8 hours, and designing & making the case took me one and a half. The dimension of the case is roughly 17.4 cm * 6.2 cm * 2.3 cm (front hight) ~ 3.6 cm (back). Under the protoboard is an Arduino and a 9V battery. I think the next step for this project is to figure out a way to replace the Arduino with just a single ATmega328 chip, making the keyboard even cheaper and thinner.
Inside the case:
In this version:
# Supports multiple simultaneous key presses (finally I can play some chords on it).
The code is available at the link below. I’m fairly new to C/C++, so it’s not one of the most elegant code I’ve ever written.
Serial Midi Converter from SpikenzieLabs:
Also, I’ll try to put the schematic up as soon as possible.