I need an isolated closing contact, like a relay, but ideally solid state. Rating 24V 100 mA on the contact side would be plenty. 1 kHz operation would be enough as well. I will drive this from 5V 25 mA gpio pins. Ideally with a <10 mA draw!
I've looked at optocouplers, but the ones I can find put VCC on the transistor/contact side; I'd need one with that side having only contacts.
The application is a remote camera trigger with both pre-trigger and trigger inputs, so two channels needed although two singles is fine.
Is there some kind of component or variant I'm missing?
Best Answer
Let's assume this is for a Canon camera (other types are available).
The auto focus is the first switch (pre-trigger), the shutter is the second. Both are operated by taking the signal to ground. This can be done by a push to make switch, a relay contact or more simply by a transistor. Depending on the particular model you will require a 2.5mm jack plug or an N3 connector. A typical interface circuit using opto isolators is shown below that can be manually operated (Sw1,2) or controlled by 2 * 5V gpio lines.