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I am trying to use an ESP32 to remotely trigger my camera via WiFi, via the remote trigger outlet on the camera (which uses a 2.5mm audio jack.)

To trigger the focus, I need to connect the tip (3.3V) to the sleeve. To ground the tip, and to trigger the shutter, I need to connect the first ring (also 3.3V) to the sleeve to ground the ring.

So far I have this:

schematic

I would push the ESP pins high to send each of the tip or the sleeve to ground.

Will the transistor work in this way where the ESP is driving a completely different circuit, or will I need to link the ground of the ESP32 to the camera ground? Am I missing something all together here?

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    \$\begingroup\$ Current can't flow without the grounds being connected. So yes, you have to connect the camera's ground to the ESP's ground. You also need base resistors. \$\endgroup\$ Feb 2, 2022 at 22:32
  • \$\begingroup\$ Do you really have to pull these lines completely to ground, 0.0V? These transistors will not do that. You might need a relay instead. \$\endgroup\$ Feb 2, 2022 at 23:06
  • \$\begingroup\$ I want the digital version of a push button momentary switch \$\endgroup\$
    – bizzehdee
    Feb 2, 2022 at 23:19
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    \$\begingroup\$ mosfets would pull them all the way to gnd, a bjt will only pull them to 0.7v, which may very well be enough. i use FETs on my canon DSLR and they work perfectly. \$\endgroup\$
    – dandavis
    Feb 3, 2022 at 7:01

2 Answers 2

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There can be no base current unless the grounds of the circuits are connected. So the grounds must be connected for the transistors to work. And as mentioned before, without base resistors it won't work and something can be damaged.

If you want to be safe and want isolation between devices, maybe an optocoupler is an option.

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  • \$\begingroup\$ is 1k enough for the base resistors with the 3.3v logic from the ESP, given that the camera also runs at 3.3v, and link the grounds? \$\endgroup\$
    – bizzehdee
    Feb 2, 2022 at 22:42
  • \$\begingroup\$ @bizze as this doesn't carry any significant current, a 1k base resistor is probably good enough. \$\endgroup\$
    – Passerby
    Feb 3, 2022 at 4:44
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Given that the camera also runs at 3.3V you can just connect them directly. (any voltage equal or less than the ESP will work)

Set the ESP pins to high-impedance mode when idle. then set them to output and low to activate the camera features.

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