An Arduino can make a very inexpensive, and efficient, trigger for flash guns, and can be hooked up to a variety of sensors to enable impressive 'stop motion' pictures.
You can do this by triggering a camera and flash from a vibration sensor, in this case, a piezo element which is connected to a microcontroller, which by default is an Arduino.
These elements are cheap enough to be basically thrown away, so they can even be destroyed on each take if necessary. However, in the set-up below the sensor is taped to the base that the set rests on, and is thus away from the mucky stuff.
Also, the sensor is completely hidden from view, admittedly also by previous broken eggs :-), so it doesn't have to be Photoshopped out.
You can find details on how to detect vibration with a piezo sensor attached to an Arduino here : Knock Sensor Tutorial. Maplin here in the UK do cheap piezo transducers which work well, you can find them here
An optoisolator to actually trigger the flash gun. This keeps any nasty voltages from my old flash away from the Arduino. I used a 4N35 from Cricklewood Electronics, but most opto's will work. Simple treat it like a led, putting a 200 ohm resistor in series with the LED.
To illustrate the effects of delay, I’ve included shots at 0, 20 and 50 milliseconds after the event is detected.
The rig is pretty simple, and the pictures nicely show the photographic scaffolding system that I’m building up.
The set is pretty simple, two Vivitar 285's are positioned behind tracing paper to diffuse them. My equally trusty Nikon D70 is connected to the triggering rig by a hot shoe to PC cord adapter.