How fast can you take a picture? Not as fast as you can illuminate a subject. James Hartnett wanted to capture events with fast movements, like the pop of a balloon, that a shutter camera simply can’t accomplish. Since a shutter doesn't move that quickly, he put the camera into a state where the shutter is left open. Then, in a darkened room, to avoid exposing the image, he illuminates the subject with a flash.

To trigger the flash at the right moment, he built a small circuit that sets off the flash upon the detection of an event. If a sound is detected or a moving object activates a trip wire, it will activate the circuit to trigger the flash with minimal delay.

James Hartnett's high-speed circuit can trigger a flash when movement or sound is detected.

The circuit consists of a few primary components: a siliconcontrolled rectifier (SCR), a trigger transistor (in this case, a MOSFET), and a sensor for the trigger.

Build Instructions