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There is a Sony RX10 III camera which also has a external trigger for it. The goal is to send a signal from a micro-controller (Arduino & optocoupler in between) to release the shutter. I thought I could just short the GND to the shutter pin like with older cameras, but with this particular camera it didn't work. You can see the pin-outs made by some nice people here. I dismantled the external trigger and de-soldered the USB connector cables, but it seems there is more to it than just shorting.

What the trigger circuit looks like

I don't know what the circuitry is doing. From testing I was able to figure out, that the Green wire seems to do the focusing; this leaves the white for shutter. Just shorting doesn't work here though. I have read in the post I linked that there is resistors used sometimes for some custom protocol.

Here is a picture showing my interpretation on what is connected to what.

interpretation circuit

I hope some of you can help me figure this out. Unfortunately I only rarely have access to the camera, so I would like to do this with as little trial and error as possible. If more info is required please ask. Thank your for your help.

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  • \$\begingroup\$ What is the big white color thing? And what are the markings on the transistor? The red wire likely goes high (above 0.7V), which shorts the green wire to black, but I am not sure. \$\endgroup\$
    – Indraneel
    May 27 at 23:50
  • \$\begingroup\$ the three pin component may be a microcontroller \$\endgroup\$
    – jsotola
    May 27 at 23:52
  • \$\begingroup\$ @Indraneel The white cable is probably the shutter signal cable. Unfortunately I cannot identify the markings. They are too small and I don't have the tools to see them. I think it makes sense for the green one. But the white one doesn't make sense to me. \$\endgroup\$
    – RIJIK
    May 28 at 13:46
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Unfortunately I only rarely have access to the camera

You don't need the camera to diagnose this. Just use an ohmmeter to identify which switch terminals are shorted when the button is pressed. It may connect to one terminal when half depressed, and also to another one when fully depressed. The camera may require that both switch contacts be closed in sequence to operate the shutter.

Once you have determined which switch terminals need to be shorted, 'press' the switch from the Arduino using small PhotoMOS relays wired to it. These have the advantage that you don't have to worry about output polarity, so even if the camera does funky stuff on the trigger wires it should work the same as if you were pressing the actual button.

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  • \$\begingroup\$ "It may connect to one terminal when half depressed, and also to another one when fully depressed." did it for me. I didn't know that this button actually had two states. And thanks to your post I was able to figure out, that in fact red gets shorted! I will have an extra optocoupler ready, in case I need to add the sequencing like you said. Thank you so far. I will accept this answer after trying in two days. \$\endgroup\$
    – RIJIK
    May 30 at 23:09

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