Raspberry Pi-Based Cable Shutter Release — Now with DIY Optocouplers

While a transistor-based cable shutter release does the job, it has one drawback. Grounding the camera to Raspberry Pi can cause the machine or the camera to have a negative ground. This might lead to a higher total voltage difference and could damage either of them. One way to solve this problem is to separate the camera and Raspberry Pi circuits using optocouplers (or opto-isolators).

While it’s possible to use a MOC3021 or a similar optocoupler for this, you can also build a simple DIY opto-isolator using a white LED and an LDR (light-dependent resistor). Basically, you need to align both components, so the LED’s light beam hits the surface of the LDR as shown in the photo below:

For better results, you might want to put heat-shrink tubing around the components to improve light transmission and prevent accidental light streaks (as well as make the DIY optocoupler assembly more sturdy). The LDR acts as a simple circuit switch: when the light hits the LDR, its resistance drops, thus closing the circuit. It might not be an optocoupler in the true sense of the word, but it serves well this particular purpose.


Replacing transistors with opto-isolators also simplifies the overall design, and you can use the diagram above to wire the circuits.

Tech writer covering Linux and open source software

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Posted in Hardware, Photography, Scribbles
4 comments on “Raspberry Pi-Based Cable Shutter Release — Now with DIY Optocouplers
  1. Howard says:

    This DIY article was okay, though there is no data as to what type of Sony camera or how to wire it to the camera, and no sample program to start with… I think you left out the “How-To” portion of your article..

  2. Well done, Dmitri! Opto couplers/isolators are a very good way to interface many circuit(s) devices as they rarely induce spurious noise, nor respond to false signals riding in noise, and simplifies impedance matching issues. Just my .000000000000001 kronor worth. ;¬)

  3. Oooops! It should have been:
    …..rarely induce spurious noise, nor respond to false signals riding in noise, and makes simple impedance matching issues.

    Sorry for the poor grammar of the first post.

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