I have a power supply that can be manually adjusted to increase or decrease power output from 0-100%. This is a manual variable resister (potentiometer?) that when turned reflects the % power. Is there a way to replace this manual pot with a remote 4-20mA receiver? There are many 4-20mA transmitter out there but not as a receiver to replace the manual pot. It's hard to explain, but basically, I want to be able to send a 4-20mA signal from my PLC to this "special device" and in turn the device will do the variable resistance. Any help, thanks

bnguyen [at] campbellap.com

 

http://en.wikipedia.org/wiki/Digitally_controlled_potentiometer

 

There are motorized pots for that application but that's pretty old school. To do it all electronically would require knowing how the CKT works. Generally the pot is just a voltage divider from a reference voltage. But it may or may not be ground referenced which complicates things. And the divider may be from the output and actually in the feedback circuit which would make simulating it much more challenging. It can probably be done, but most likely not in a simple general way unless it's a lab type supply. Many general purpose supplies have some provision built in. you could get lucky. Check what terminals there are.

You might see if the vendor has an interface, some do. Or you might consider using a programmable supply but that gets expensive.

Regards,
cww

 

It's probably a pot. If so, then you will need a voltage signal, not a current signal. If your PLC doesn't have a voltage output you can use a current to voltage signal converter.

You'll need to do some reverse engineering and measuring though to find out what that voltage is. However, I would suggest that you first check out whether the power supply is already designed to take a remote control signal. Many adjustable power supplies are and have input terminals on the back.