Getting a DC input from an AC circuit

sumPLC · Oct 18, 2017

I am automating a COP tank. If you're not familiar with the term, it's basically a big dishwashing sink. I am using a level sensor to know when to stop filling the tank. The sensor is in a 120vac circuit. When the water gets to the level, it completes the circuit and triggers a relay that controls another 120vac circuit. I would like to use the second circuit as a digital input to the PLC. The best idea I've had is to use a transformer to transform the ac to dc. Is there a better, simpler, cheaper way to do this?

g.mccormick · Oct 18, 2017

Relay switching dc back to your plc.

damica1 · Oct 18, 2017

Is your PLC inputs 120vac or 24vdc? If they are 24vdc then just like "g.mccormick" has mentioned. A small 24vdc power supply ($20.00) then if your existing second circuit relay has a spare set of contacts.(Make and Break a 24vdc line through those contacts to an input on the PLC.)

That's about all it should take.

Bit_Bucket_07 · Oct 18, 2017

sumPLC said:
I am automating a COP tank. If you're not familiar with the term, it's basically a big dishwashing sink. I am using a level sensor to know when to stop filling the tank. The sensor is in a 120vac circuit. When the water gets to the level, it completes the circuit and triggers a relay that controls another 120vac circuit. I would like to use the second circuit as a digital input to the PLC. The best idea I've had is to use a transformer to transform the ac to dc. Is there a better, simpler, cheaper way to do this?

A transformer will not convert AC voltage to DC. You'd need a rectifier to accomplish that.

Two words... Interposing relay.

sumPLC · Oct 18, 2017

Thaks guys. Relay it is.

Getting a DC input from an AC circuit

sumPLC

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Bit_Bucket_07

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sumPLC

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