A cherry-and-walnut laser harp with a tilt bend and a fog machine

Derrick Thomin (DJ Baja Blast)on Personal site

Lasers and photoresistors pluck notes, an accelerometer bends them, and a fog machine makes the beams visible. A Teensy 4.1 runs the whole instrument.

Build sheet

Controller: Teensy 4.1
Sensing: Photoresistors, accelerometer
Synthesis: Karplus-Strong
Frame: Cherry and walnut

Can I build this?Advanced · AI 3/5 · $150–300

Difficulty: Advanced
AI-buildability: 3/5
Time: A few weeks
Cost: $150–300

Parts

Teensy 4.1 photoresistor accelerometer ultrasonic distance sensor laser diode

Tools

soldering ironwoodworking toolslaser diode driver

Starter prompt

Based on "A cherry-and-walnut laser harp with a tilt bend and a fog machine" on Afterware: https://afterware.xyz/p/a-cherry-and-walnut-laser-harp-with-a-tilt-bend-and-a-fog-machine

Write Teensy 4.1 firmware for a laser harp. Read photoresistors on each beam as analog inputs and map the dip depth and speed to note velocity. Use an accelerometer's tilt axis to bend pitch, and output Karplus-Strong synthesized audio on the onboard DAC plus MIDI notes over USB.

Estimates based on the original write-up. How AI-buildability is scored. Building with an AI assistant? Connect it to Afterware (free MCP server).

Story

Most laser harps use photodiodes. This one uses photoresistors, so the Teensy reads the slow rise and fall of voltage as a hand crosses the beam. Pluck fast and hard and the note gets louder; pluck slowly and it softens. The velocity comes from the light, not a switch.

The extra inputs are where it gets strange. An accelerometer works as a tilt sensor that bends each note flat or sharp as it sounds, and an ultrasonic distance sensor offers a theremin-style control. An encoder wheel on the side adds a fifth input, and there are jacks for an optional looper pedal and an aux in. A Teensy 4.1 drives the synthesis, currently Karplus-Strong string synthesis, with an onboard speaker and MIDI out. The fog machine is plumbed in, so you can see where the laser strings are.

The frame is cherry and walnut. The write-up and GitHub files are there if you want to build your own.

Resources · 2

Full write-up GitHub files