Circuit Bent Toy Keyboard Is MIDI Controlled

The [Tymkrs] crew has come up with a pretty neat circuit bent toy keyboard hack. It’s been a while since we’ve seen a good circuit bending hack. This project started as a way to demo the [Tymkrs] “MIDI In Me” kit. A cheap toy keyboard was sacrificed for its sound generator board. Like many cheap mass-produced toys, this board is based upon a COB (chip on board) package. The silicon die of the main ASIC is placed directly on the PCB and bonded out to pads. A round epoxy blob keeps everything protected.

The [Tymkrs] found a number of the chip’s pads were unused in their keyboard. The inputs appeared to trigger drums, possibly for use in a different toy. These inputs, coupled with the ‘demo song’ buttons turned out to be the basis of this hack. MIDI input is sent to a Parallax Propeller. The prop runs a program that will set its I/O pins based upon MIDI Note On/Off commands. The I/O pins then drive transistors which inject signals into the button inputs of the keyboard.

The [Tymkrs] even went so far as to use a voltage divider on the main clock circuit of the keyboard. Changing the main clock causes a sort of pitch bend effect often heard with circuit bent toys. As with the buttons, a MIDI signal commands the prop to enable or disable oscillator signal injection. A potentiometer is used to tweak the oscillator frequency.

The beauty of all this is that the entire hack can be controlled with a MIDI sequencer running on a PC. Sending fast note on/off commands results in some interesting effects.
The second half of the video is a jam session of the results. While it isn’t something we’d keep on our mp3 player, it’s definitely better than most of the Vogon poetry we’ve been listening to lately.

[Thanks Randy!]

5 thoughts on “Circuit Bent Toy Keyboard Is MIDI Controlled

  1. As I have ever been an opponent of circuit bending, this is not music and should not be considered such, although some of the sounds reminded me of the background noise in the original Tron movie so it’s good for special effects and should immediately go to a Foley artist. in keeping with the hitchhikers guide reference, I would rather be thrown out an air lock than listen to the music from this thing.

    Now that I have had my rant, this is a sweet build and the computer control is amazing, good job!

Leave a Reply

Please be kind and respectful to help make the comments section excellent. (Comment Policy)

This site uses Akismet to reduce spam. Learn how your comment data is processed.