To capture an instant on film or sensor with a camera, you usually need a fast shutter. But alternately a flash can be triggered with the scene in the dark and the shutter wide open. It’s this latter technique which PetaPixel are looking at courtesy of the high-speed class at Rochester Institute of Technology. They’re using a cheap sound sensor module and an Arduino to catch instantaneous photographs, with students caught in the act of popping balloons.

The goal here was to keep things as simple as possible. All you’ll need in addition to the Arduino (or really, any modern microcontroller) is the sound sensor — which are often sold as “microphone shields.” To trigger the flash while still providing electrical isolation is a reed relay. The write-up notes that higher performance systems would be better off with an optoisolator, but this provides a low-cost alternative to get started with.

We rather like the technique, and perhaps it’s a thing to try at a future hacker camp. Unsurprisingly it’s not the first flash trigger for water balloons we’ve seen.