A Simple Laser Harp MIDI Instrument
Craig Lindley, a technical author and passionate maker, embarked on his first project to create a laser harp MIDI device after being inspired by a three-string version he saw while on vacation. Determined to improve the concept, he expanded it to twelve strings. The operation is quite simple: twelve inexpensive diode laser modules direct beams toward light-dependent resistors (LDRs), which change resistance when the beams are interrupted.
The controller is built on a perf board featuring a Wemos D1 mini ESP32 module, along with some passive components, a barrel socket for power, and a DIN connector for MIDI output. Utilizing the ESP32 is a clever decision as it shifts configuration and user feedback to a web interface, making the physical setup more straightforward. After a few iterations, including an unsuccessful attempt with a triangular frame, Craig opted for a linear arrangement of beams enclosed within a laser-cut wooden frame. To ensure proper alignment and easier mounting, he machined aluminum rods to house the laser modules.
Unfortunately, Craig’s initial method of using magnetic attachments to secure the LDRs didn’t pan out, leading him to resort to hot glue—an all-too-familiar solution for many makers. As an interesting feature, he included an M5 Stack Unit-Synth module to provide sound when a dedicated MIDI synthesizer isn’t available, enhancing portability for performances. This thoughtful design choice makes it easier to transport the device to shows and events, where people are often captivated by the allure of laser harps.

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