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I feel like this has been beaten around the bush in a couple other topics, but I am hoping to find something a bit more definitive. I am looking to control a Peltier thermoelectric cooler.

I've got a 24VDC PLC with a couple tools at my disposal:

  • Analog thermocouple inputs
  • Analog outputs 0-10VDC, 4-20mA, 12 bit
  • Digital outputs 500 mA, 24VDC
  • PID ladder block in PLC software

I would like to use the PID in conjunction with one of the output types to drive the Peltier at full power (12VDC, 5A). I need some way to convert either of these outputs to a 0-12V controllable constant signal (As pointed out in other threads, the Peltier will wear out if cycled/supplied PWM input).

Some thoughts...

  • PWM controlled buck converter (haven't found one, but maybe I'm searching for the wrong things??, everything I have found is trimmer controlled) w/ 12V power supply
  • Use RC circuit to change PWM to analog (or analog output) and combine with MOSFET to control a 12V power supply
  • DC motor controller to step to required voltage, then RC circuit to smooth

Ideally, I'd love a box that takes 12V 5A in, and a 24V PWM duty cycle dictates the voltage % to an output. It seems like this should exist, but I don't know what to look for.

Also, lest it be too obvious, but unsaid, I am not super experienced with electronics design, nor am I seeking to be an expert. My intention is only to move what I have to move, heat what I have to heat, or in this case, cool what I have to cool. Therefore, I'm not looking to tinker too much, the most direct, robust solution is definitely the best here even if it's not the cheapest.

Thank you all!

GravyBagel
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  • Ideal regulation situation would be a buck converter controlled from your 0-10 V interface, but a straight PWM into a low side MOSFET and your pettier tied between + and drain will be the by far cheapest. – winny Apr 10 '18 at 20:59
  • Take a look at this one: https://electronics.stackexchange.com/questions/330471/low-side-n-mosfet-buck-converter Output L and C is most probably optional since the smoothing is done by thermal mass. – winny Apr 10 '18 at 21:02
  • @OlinLathrop I felt that it wasn't because I was seeking a specific set-up vs general guidance on PWM vs smooth direct current. Ideally, someone would have said, "Oh yes, just get this motor driver XXXX that runs @ 12V and has 24VDC input."

    At this point doing more research from Winny's comments, I have been able to move forward on this. I started a different thread regarding this as it seemed to go beyond the scope. If you feel that it is a repeat, I can delete it.

    New thread: https://electronics.stackexchange.com/questions/373400/peltier-circuit-components

     – GravyBagel May 21 '18 at 18:05

1 Answers1

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Perhaps I over simplify but how about using a mosfet transistor or similar with a thermal resistor that "chokes" the current when desired temperature is reached, that way it will alter cooling seamlessly depending on thermal load and the peltier should be happy to work like that. If calibrated right I believe it may also eliminate any over current problems if your power source is bigger than your load. Good luck in your project.

Anders_gbg
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