I need to monitor the state of multiple relays carrying 110VAC and 60VAC using a microcontroller (I will probably use an Arduino) to ensure the relays are working properly. To do this I have figured out that I need a circuit with an optocoupler so when the 110VAC or 60VAC is on 5VDC is forwarded to the input of the microcontroller. Using an optocoupler with two LEDs in antiparallel, will also still leave me with 0V at the zero crossing, so some sort of stabilizing will probably be needed. But I need some help choosing an optocoupler and the accompanying components and designing the circuit.

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    \$\begingroup\$ This answer might help you. \$\endgroup\$ – m.Alin Dec 7 '12 at 10:49
  • \$\begingroup\$ Somewhat, but as this relies on using interrupts for resetting the timer, I would need an input capable of generating an external interrupt. As I need to monitor a total of 48 AC lines, I do not think this will be the most viable solution. Being able to just poll the input, without worrying about zero crossing would be the ideal solution. \$\endgroup\$ – Morten Grønkjær Jensen Dec 7 '12 at 11:05
  • \$\begingroup\$ The firmware might be different, but I recommended that answer for this part of your question: 'I need some help choosing an optocoupler and the accompanying components' \$\endgroup\$ – m.Alin Dec 7 '12 at 11:09

If you just want to detect if VAC is there or not, i can give you this example (see image below). We are using it to determine if some external relays are malfunctioning. This may point you in the right direction and gives some part examples.

230V AC detection


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