Turntable sequencer scratches with coins


[tvst] has an interesting take on a sequencer. His design uses coins on a turn table to trigger midi events in a loop. There are four tracks available, each having its own sensor above the spinning platform. The sensors consist of an IR transmitter and receiver setup as a voltage divider. When something passes below the IR transmitter and reflects the infrared waves back up to the receiver, the output of the sensor moves to digital high. The four sensors are connected to an Arduino which is used in conjunction with ttymidi, which converts the Arduino data into midi events.

We like projects that provide a more tangible interface for the user. Coins work well for this setup. They reflect infrared enough to trigger the sensors, and they’re easy to pick up and move without upsetting the rest of the tracks. It would be great if this could be expanded to differentiate between coins (pennies versus dimes, etc.) in order to increase the resolution from four different events to eight or more. Check out the video after the break.


  1. strider_mt2k says:

    I didn’t quite understand until I saw the video.

    That’s pretty neat right there man.

  2. Wraith says:

    The turntable should be divided in such a way that it can show a measure of music. It would be easier to get precise times for a good loop.

  3. nek0 says:

    Maybe it could be improved with a metal disc, with marks, and replacing the coins with magnets

  4. Jack says:

    @Wraith he is spinning the turntable himself though, so the measure could be 1 revolution, or 1/2 or 3 or any number of revolutions depending on the speed he is turning the turntable, and the tempo of the song.

  5. Wraith says:

    That’s pretty neat, with two of those and a crossfader you could make some cool music.

  6. craig says:

    similar idea, but with pepperoni on pizza:

  7. 36chambers says:

    This was done DIY using cuecats years ago….


    Theres also the EJ Midi Turntable

  8. strider_mt2k says:


    “It’s always the magnets with you…”

  9. Jussi says:

    What if the turntable would have RGB-led switches or if the turntable surface was some moldable mass?

  10. I love my Crosley CD Recorder.

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