Here we go again, here is a picture of the camera and flash trigger module I made for my arduino photographic projects:
It includes three 4N26 optocouplers. One (first one from the left side) to trigger a flash, as I did in the arduino controlled flash trigger project; and two more for triggering my Canon EOS 40D camera.
The trigger mechanism is quite simple in modern EOS cameras, they simply have three pins in the trigger plug, short-circuit one (the common one) with one of the others and the camera will focus, short-circuit the common with the other pin and the camera will take a picture.
My camera has a propietary plug, called N3, so I had to “canibalize” a remote camera trigger I bought somewhere in eBay to take the wire and the plug apart. This is the safest way to check which wire is each one, but you can get the wiring diagram in lots of sites around the Internet. Or you can check the site of Glacial Wanderer, that also this this hack.
This trigger thing can easily be accomplished with other models of Canon cameras (at least with the 350D and sisters, as they use a simple stereo mini-jack plug, easier to get) and may be with other brands too. I made myself a custom remote trigger for my old 350D, even before I knew about arduino
For more detail: Camera and flash trigger module
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