Help selecting optocoupler DC input to AC output

Projects General Guidance
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@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!

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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

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@allanhurst - Interesting...hmm.

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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?

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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