Here is a simple Optoisolator Circuit (also known as an Optocoupler) that I use for my Nikon D750 camera, for an external remote Digital Shutter Trigger on my Camera’s Power Slider.
It is highly recommended that you isolate your Camera’s Trigger Control Circuit from any external voltage, even an Arduino!!! The only way to efficiently and effectively do this is via an Optical Isolation Circuit!!!
R1 and R2 are Current Limiting Resistors in this circuit and are designed for the 4N25 Phototransistor Optocoupler, driven from a Digital Logic CMOS Buffer IC, powered by a 12v Power Supply (I use a 12v Batt. for remote shoots to power my camera slider and the logic that controls the slider).
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