Peltier module voltage controlled ideas

Thread Starter

Dever

Joined May 2, 2022
35
I'm participating in project of create small thermal calibration chamber. I would like to get to know this topic. At this point I know that peltier module will be driven by voltage not PWM. That's because of provide general stability of the system.

How I can create such circuit? I don't think about temperature sensor just microcontroller that drives this peltier module. Let's say that my stm32 doesn't have DAC. Do any digital volrage regulator exist? Would it be nice to use adc and then drive voltage regulator or opamp? Do voltage regulator would be sufficient for peltier module?
 

MrChips

Joined Oct 2, 2009
30,986
STM32 MCU has DAC.
If you do not wish to use DAC you can use PWM and an integrator.
You can also use digital outputs and resistors to create a DAC.
 

BobTPH

Joined Jun 5, 2013
9,177
I have heard conflicting information about using PWM to control a Peltier device. But the document seems to cover it quite well.

Peltier FAQ

AsI read it, if you use a PWM voltage of Vmax, use a single sided driver so that the Pletier does not operate a a generator during the off portion and use at least 2KHz frequency, PWM is a good method of controlling Peltier performance.
 

ronsimpson

Joined Oct 7, 2019
3,149
That's because of provide general stability of the system.
How stable do you need?

There are many kinds of "PWM".
One kind, say you want 5 degrees. It turns on/off at 5/6 degrees. So it turns on/off every couple of seconds.
Another kind will run at 100% duty cycle until it is very close to temp then drop the on time back to hold at temp. It might be turning on/off 1000 time a second.
 

BobTPH

Joined Jun 5, 2013
9,177
Ron, check out the doc I linked. Turning the current on and off at a low frequency creates thermal stress. Using a higher frequency and having it operate at that frequency continuously would be better.
 

ronsimpson

Joined Oct 7, 2019
3,149
I just read that PWM is less efficient than using DC. This problem is not important to me because it only happens near 50% and not near 0 or 100%.
I had not though about thermal stress. I think if you hold the cells to within 2 degrees there will not be much stress.
 

Thread Starter

Dever

Joined May 2, 2022
35
I have found out a lot from your answers and document. I will talk about circuit and Peltier with employer. At this point, I have no knowledge about details. I hope he will easy share his knowledge with me.
 

Thread Starter

Dever

Joined May 2, 2022
35
does not operate a a generator during the off portion
Did you mean H-bridge can cause issues? (heat / cold option) What about the need of use LC filter on output? 8A is a quiet a lot for inductor.
 
Last edited:

MrAl

Joined Jun 17, 2014
11,587
I'm participating in project of create small thermal calibration chamber. I would like to get to know this topic. At this point I know that peltier module will be driven by voltage not PWM. That's because of provide general stability of the system.

How I can create such circuit? I don't think about temperature sensor just microcontroller that drives this peltier module. Let's say that my stm32 doesn't have DAC. Do any digital volrage regulator exist? Would it be nice to use adc and then drive voltage regulator or opamp? Do voltage regulator would be sufficient for peltier module?
Hi,

Wouldnt you want to measure the temperature and use that as feedback? That's the best way in thermal systems. You can get the temperature to be nearly perfect and if it is a constant temperature, really really near perfect.

If you decide to measure the PWM itself, that's probably easy because you are generating the PWM. Just use a little math. I would think you might measure the current too though or at least create a calibration table to look up the current with a given voltage. Since the PWM peak is constant, this should be easy. And with that in mind, the PWM peak should not and need not go above that which causes the maximum current you will get that with the PWM duty cycle set to 100 percent.
 
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