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My remote camera trigger has three wires (red, yellow, white). The white is shared, and the trigger can complete two different circuits by shorting it with either the red or the yellow cable. One of the circuits will tell the camera to focus, the other to fire the shutter.

I wish to sense these short circuits on a breadboard, but do not know enough about electronics to understand how to separate the common white wire. I can conceptualise two separate switches, each "pressed" by the pairing I want to use: enter image description here

But if I remove the two press-down switches here, and connect the common wire to the power end of the switches, it looks to me as though I would short both pairs of wires every time I try and short either of them.

Since the clever people at Sony knew how to separate the signals (before they removed remote trigger connections from their most recent bodies :-((), I am hoping someone here will be able to tell me what I need to add to my plan!

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  • \$\begingroup\$ You'll have to reverse those signals more in-depth before attempting to mess around with them. Sounds like you have ground, button driver and two button inputs. Measure them with your scope, is it on/off or some manner of pulsed system (more likely)? What voltages? \$\endgroup\$
    – Lundin
    Nov 24, 2023 at 8:00
  • \$\begingroup\$ @Lundin Remote camera triggers are passive devices with two momentary-close switches and a common wire. OP clarified in a comment on my answer below that it's the trigger device, not the camera, they want to connect to the Pi. \$\endgroup\$
    – TypeIA
    Nov 24, 2023 at 22:40

2 Answers 2

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You are risking damage to an expensive camera. To do this successfully requires some understanding of

  • the camera's control logic,
  • the maximum voltage the logic inputs can tolerate,
  • the logic switching voltage thresholds,
  • whether the common wire is common ground (typically the battery negative) or positive supply (battery positive).

You also risk damage by connecting the Pi to the camera and sharing its supply / ground connection.

Your best bet is to isolate the Pi from the camera using miniature relays or opto isolators. The opto-isolators are smaller and silent.

Procedure:

  • Get a multimeter and switch it to DC volts. Put the black (COM) lead on the white wire and using the red lead (V), measure the voltage on red and yellow. Hopefully it is a positive voltage - probably in the range of 3 to 5 V.
  • Get a couple of opto-isolator chips. These are an LED and a photo-transistor in the one package. Turning on the LED will cause it to emit light through an internal transparent insulator (good for 4 kV!) at an internal transistor. This will turn the transistor on and allow current to flow from its collector to its emitter (the pin with the arrow).
  • Wire up as shown below.

schematic

simulate this circuit – Schematic created using CircuitLab

I've written more on opto-isolators here.

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  • \$\begingroup\$ I think OP wants to hook the remote trigger to the Pi, not the camera. \$\endgroup\$
    – TypeIA
    Nov 23, 2023 at 23:13
  • \$\begingroup\$ @TypeIA, I'm assuming that the remote trigger is a wired remote plugged into the camera. If it's a wireless remote then why would it have wires? \$\endgroup\$
    – Transistor
    Nov 23, 2023 at 23:17
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    \$\begingroup\$ I don't think OP wants to trigger the camera. They want to use the trigger to control something on the Raspberry Pi, i.e. the Pi should be able to detect when the trigger switches are activated. No camera involved at all. But OP should clarify. \$\endgroup\$
    – TypeIA
    Nov 23, 2023 at 23:19
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You can easily do it like this:

(Note, I'm assuming you intend to hook up the remote trigger to the Pi, not the camera. DO NOT wire the camera to the Pi in the way I've drawn!)

schematic

simulate this circuit – Schematic created using CircuitLab

When the switches are open, the 10k resistor pulls the signals high (logic 1). When either switch closes, the corresponding signal is pulled to ground (logic 0). Ground is the common (white) wire. This is a very standard way of wiring buttons/switches.

The best part is, your Raspberry Pi even has those pull-up resistors built in. You can enable them when you configure your GPIO pins (refer to the documentation). (They aren't 10k - internal pull-ups have a much higher value - but it doesn't matter in this case.)

Note, Vcc here is your Raspberry Pi's I/O voltage, 3.3 V.

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  • \$\begingroup\$ Many thanks! Yes, i am connecting the trigger to the Pi. The onwards connection from the Pi to the camera will be via USB, using Sony's Camera Remote SDK libraries. I'm tied up for the next 48 hours, but will try this ASAP. \$\endgroup\$ Nov 24, 2023 at 8:55

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