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This might sound crazy, but bear with me ;)

I am making a DIY camera trigger, and I would like to see if I can trigger it remotely by plugging it into my Microphone or Headphone ports. It's a basic 2.5 mm --> 3.5 mm plug, and all I need to do is short the first and last, first and second, and all three to focus, trigger, and focus and trigger.

It's a bit hard to explain, but is it possible to send electrical signals directly through those ports? I'm up to some C++ or Python (heh) if I have to...

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closed as off topic by Gilles, Michael Mrozek May 9 '11 at 2:41


This question is off-topic here. Electronics doesn't want it either. SU, maybe? –  Gilles May 9 '11 at 0:56
You can just close it, if you wish. I didn't get a definitive answer from it, nor do I expect to. –  Blender May 9 '11 at 1:22

1 Answer 1

up vote 1 down vote accepted

You can use the audio port to create a time-varied differential voltage signal. You can't short the contacts together, though. In fact, you might even damage the dac in your computer if you connected it since doing that would force the dac outputs to whatever voltage level the hotshoe is.

If you really want to do this, you might want to use a USB gpio board (like this one) and make a circuit that shorts your contacts. The folks at Chiphacker (aka Electronics & Robotics) would be able to help you with any questions about that.

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It's not really connected to a hotshoe (if you're speaking camera terminology), but I'll see what I can find out. I can't see how to code this (or even find the appropriate device API), so I guess it's back to disassembling toys to find those switches! –  Blender Jan 18 '11 at 4:04
Oh, yeah; it's just the trigger. It's still not a good idea. The way those work is one works is one side is a high voltage and the other side is low; connecting them forces them to the same voltage, and the electronics detects that change. You'd still have better luck with a GPIO board. If you wanted to do it cheaper, you could use an opamp to make a Shmitt trigger that altered the voltage level when a certain amplitude signal is received from the audio. This can be done for a couple of dollars if you already have a soldering iron. –  Shawn J. Goff Jan 22 '11 at 13:06
