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I'm trying to take photos with my arduino and a 4n25 opto. To trigger my camera you only need to close the circuit of the shutter cable, however the below simple circuit is not working. I've tried to change the shutter cable with a led and 3v and it works perfectly. I added a switch(SW3) to make sure it worked as expected when closing the circuit, which it does.
I've tried also changing the R2 resistor to 330, 220 and 84 Ohms, all of them work nice lighting a led but no luck with the camera.
Is there something I'm missing? Maybe a reason which makes impossible to close the shutter circuit with a transistor?
Any help would be greatly appreciated.

schematic

simulate this circuit – Schematic created using CircuitLab

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    \$\begingroup\$ A transistor isn't a switch. It only works in one direction for a start. Have you done any measurements of the camera's shutter control? Does it have one contact grounded and a voltage on the other, for instance? \$\endgroup\$ – Ian Bland Jul 2 '17 at 0:13
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    \$\begingroup\$ @IanBland You got it. I didn't think on the camera having polarity and I don't know how I always connected it the same way since I've got all free cables in a protoboard. If you add an answer I will accept it, just needed to turn the camera shutter connection. And to think that I spent 2 hours on this. \$\endgroup\$ – Mark E Jul 2 '17 at 0:17
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As an answer-

A transistor isn't a switch. It only works in one direction for a start. Have you done any measurements of the camera's shutter control? Does it have one contact grounded and a voltage on the other, for instance?

:)

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  • \$\begingroup\$ Please write the answer as an answer, not as a bunch of questions. \$\endgroup\$ – CL. Jul 2 '17 at 14:07
  • \$\begingroup\$ Sometimes a question is an answer. "Are you mad?" is equivalent to the statement "You are mad!". And "Have you done any measurements of the camera's shutter control? Does it have one contact grounded and a voltage on the other, for instance?" means "take these measurements in order to discover the polarity of the control circuit, and thus which way round to connect a polarised switching device". \$\endgroup\$ – Ian Bland Jul 2 '17 at 23:43

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