The SwoofTronic Pi is a small handheld device that allows you to change the frequency and duration of a basic sound wave using your thumbs to control light sensors.
This item consists of two small boxes joined by a cable. One box goes in each hand and each box has a light sensor in the top, as you let more light onto the Right hand sensor you increase the frequency (pitch). As you let more light onto the Left hand sensor you increase the length of the note played.

The interesting noises are made when you speed up the timing of the notes by blocking off all light into the left box. As the output is modulated between left and right output channels, speeding up the note repetition makes strange strobing effects.

Here is the MP3 demo of what the Swooftronic sounds like.
http://www.freewebs.com/rarebeasts/swoof sound demo.mp3

There are three ways to trigger the light sensors, each have different effects on the sound.
(1) You can use the ambient light in the room and control the level by blocking off the sensor with your thumb.
(2) You can use the built in LEDs in the centre of each box which can be used to trigger the sensor of the box on the other side.
(3) A small LED keyring can also be used.


  • Microcontroller: Picaxe 8M
  • 2x 10k light sensor inputs
  • 2x high intensity LED outputs (white, amber)
  • 3.5mm stereo output to earphones, computer sound card or mixer
  • Battery: 9v

The inside bits:

LHS Bits and Bobs


Both sides

RHS Ready for the battery