Synth / drum machine with Arduino
https://www.youtube.com/watch?v=Z5vrkXOSQN8
Bio-Contractor is a hardware hacking project that converts a 1990s electrostimulator into a playable drum machine / synthesizer using Arduino.
Instead of building an instrument from scratch, this project reuses the original enclosure, knobs, switches, and interface of an existing device, turning its physical controls into a sound engine.
- Arduino Nano R4 (UNO / UNO R4 WiFi also compatible)
- 5 potentiometers (reused from original device)
- 2 switches (reused)
- 1 LED
- 1 audio output jack
- DC input (optional)
The original electrostimulator electronics are not required for the system to function.
- Potentiometers → Analog inputs
- Switches → Digital inputs
- LED → Digital output
- Audio jack → DAC output
Power:
- USB-C or
- 5V via VIN and GND
Audio is generated directly from the Arduino:
- Samples encoded as raw, headerless, signed 8-bit PCM @ 16384 Hz
- Stored in Flash memory as arrays
- Playback handled with Mozzi
- Drum sounds from Boss DR-110
- Voice samples:
- “Arduino”
- “Open Source”
- Bottom-right knob → BPM
- Main switch → Play / Stop
- Remaining knobs → Pattern + sample triggering
- LED → BPM indicator
- Secondary switch → FM synthesis with random variations
Old potentiometers have inconsistent ranges.
A calibration script maps real min/max values to usable ranges.
(Not required with new components)
- Connect Arduino
- Open Arduino IDE
- Upload firmware
Audio output connects to:
- Mixer
- Amplified speakers
- Reduce output noise
- Add switches for distortion / modulation
- Replace unused panel elements
This project focuses on reusing existing hardware rather than designing new instruments.
The constraints of the original device become part of the sound and interaction model.
Roni Bandini