I have recently started experimenting with an Arduino and would like to control a seperate circuit (for example, a small and cheap digital video camera powered by battery) from my arduino.
Basically my plan is to solder two wires to either side of a tact switch on the target device's PCB. Since I am new to the world of electronics and do not wish to risk any possible damage to my Arduino, I would like to isolate the two circuits from one another.
I have done some research to figure out how to switch one circuit from the other and the options I have come across are relays and optocouplers. I think I prefer the idea of using an optocoupler because they are small and completely separate the two circuits. I can also order some free samples to try them out.
My understanding of optocouplers is that I would not need to connect the ground of the arduino to the ground of my target device (operating on it's own battery source). Is this correct?
Also, considering I plan on using this to control only low voltage DC circuits, what would be a good choice of optocoupler? I plan on ordering several so that I can use them for various breadboard experiments where needed.