Ultrasonic distance sensor micro:bit theremin

I’ve tried to make really crude theremin-like noise-making machines before with an Arduino and an LED, and with micro:bits, and of course there’s my spooky bat theremin Scratch project.

sonar micro:bit theremin wired up

I had a HC-SR04 ultrasonic distance sensor lying around. You can buy these for under £4 and they’re common in robot vehicle projects to stop them bumping into things. I managed to hook one up to a micro:bit and not just get distance readings but use them to alter the pitch of sound too.

sonar theremin wiring diagram

You’ll need an external power supply for the sonar device – they need 5 volts and the 3 volts off a micro:bit board isn’t enough to make it work. I used 3 AAA batteries as a power source, but I imagine you could also use an old USB lead with the end chopped off instead. You also need a common ground, so make sure that the GND pin on the sensor is connected to the GND pin on your micro:bit as well as the negative terminal on its power supply. This ensures that the electrons that carry data between the sensor and the micro:bit have a complete circuit.

The code itself is very simple – just add the sonar block extensions and it’s as simple as this:

I added some buttons to turn it on and off as it can get a bit annoying after a while!

What else could you do with this? A commenter on my YouTube channel suggests attaching another one to control volume as well as pitch – micro:bit sound doesn’t have a volume function but it’s an intriguing idea, perhaps a second sensor could control something else like lights or octave shifts?

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2 Responses to Ultrasonic distance sensor micro:bit theremin

  1. Michael Dominic Horne says:

    I believe you can get 3v3 versions of those USD sensors now! :-)

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