A simple home-made light-operated camera trigger (camera trap)
This device is a very simplified version of the original CamTrig.
It has only 3 electronic components and costs less than $5 to build, but has some limitiations.
The device behaves like an reverse flash-slave unit, ie it will trigger a flashgun
immediately when it is shielded from a light source. This simple version has no
possibility for delay or for sensitivity adjustment, and will continually trigger
the flash when in the dark, though many flashguns will only flash once until
light is restored again. I don't know if continuously shorting the flash like this
can cause any damage, but I doubt it.
You don't even need to use a board - just solder the components together, and then drop a blob of epoxy glue over them
to hold them together and protect the joints from being torn apart.
If you want to add a power switch or a variable resistor to adjust sensitivity, feel free,
I just wanted to show the absolute simplest version here.
Unfortunately I don't have a good component code for the phototransistor I used,but I'm guessing that any PNP phototransistor will work, though it may require a different
value for the resistor.
Mount the device with the phototransistor pointing towards a pocket laser, connect your flashgun,
plug in the battery, and see what happens when you interrupt the laser beam. The flash should fire once.
This is what happens with the flashes I've tried (Nikon SB800, Sunpak 30DX, Metz 54 MZ3),
but some models may fire multiple times with this simple device.
For more information on using camera triggers, and more complicated devices, see the original CamTrig pages.
© Mark Harris 2008, but feel free to distribute without changes.