Help selecting optocoupler DC input to AC output

@MorganS - My garage door wall buttons are 24V AC. The troubleshooting manual shows that, in event the door does not open, to place a wire across two terminals at the wall button (to short it?). If the garage door works, the issue is with the garage door wall unit, not the opener itself. I thought I could use a microcontroller to create that "short" and therefor have another way to control the opener. But I am dealing with 24V AC. Interestingly, pressing the door button sends the circuit voltage to 0 (a "short"?). The light button send the voltage to 12V and the security button to 6 volts. If I knew how, I could probably control all three with Arduino I bet.

@Lastchancename - You're right I'm sure, but this is a learning experience for me. I am going back to my childhood; putting together one of those Radio Shack transistor radio kits. Yes, I could buy a radio, but what fun is that? What is learned? I could buy a decently designed PCB relay too. This project is about exploring and ultimately it is going to refill my fountain when the water level gets low. A weather-tight electrical box is just next to it. If lightning strikes that, I will have issues to be sure!

Thanks everyone!

Professional irrigation controllers for commercial greenhouses using 24vac water solenoid valves just use ordinary triacs driven by processor ports - they don't bother with isolation.

Why should you ?

Allan

edit: I think the last one I mended used BT138's

@allanhurst - Interesting...hmm.

Professional irrigation controllers for commercial greenhouses using 24vac water solenoid valves just use ordinary triacs driven by processor ports - they don't bother with isolation.

Do they float the entire system on one side of the 24vac supply or is it earthed?

One side of the 24vac is earthed.

Of course there's a seperate dc supply for the electronics .

So 2 secondary windings on their mains transformer....

  • one to deliver power ( rectified, smoothed and regulated, and battery - backed for volatiile memory and RTC ) for the electronics,

  • and a seperate 24vac for the solenoids

Allan