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Discussion Starter · #1 ·
I have a couple industrial valves that need to be changed out that currently have 120 volt readbacks to input to a PLC. The replacement valves that were ordered and received have 24 VDC readbacks. Does anyone know a means of converting the 120V at the valve to 24 VDC and then back to 120V after the readbacks? It would be preferrable to have the conversion means at the readbacks so we don't have to re-pull the wiring due to incorrect insulation color. The panel where the PLC is located does not have 24 VDC, and the PLC does not have 24VDC input cards. Trying to figure out a painless way to do this.
 

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Donuts > Fried Eggs
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What is "readback"? Is it just discrete valve status through some microswitches or is this actually an analog signal, i.e.: What signal is the PLC input looking for?

If it's just a discrete signal, I would use a 24V power supply to through the valve to run a relay in the PLC cabinet and put your 120V through the relay into the PLC input.
 

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i would change plc input output card for 24v version. what type of plc it is, there are some low cost used cards on ebay.
if not you will have to use a lot of relays for converting signals 120 to 24 and 24 to 120v
 

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Electron Flow Consultant
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3,309 Posts
What kind of valve? If it's a rotary valve, buy a new top works limit switch. If it's a gate valve install a couple tabs and use prox switches. You're just going to make it more complicated than it needs to be
 
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