Driving Peltier with Pololu high power motor driver


I’m driving a peltier module with an Arduino microcontroller and a Pololu High Power Motor Driver I bought. Everything seems to work fine now, but I have noticed something that is starting to worry me in order to implement a PID control.

When I feed the Peltier (open loop) with some PWM values and I mesure with a voltimeter the output of the motor driver, I don’t get a constant voltage, I get values jumping all the time. I don’t have an oscilloscope so I’m not sure about the nature of this oscillation, ¿maybe the voltimeter sampling is in resonance with the PWM and everything is fine?

Or could it be related with the frequency with which the Arduino feeds the motor driver (490 Hz). There is a hughe difference between the max 40 kHz the motor driver accepts and the 490 Hz I’m working with, ¿maybe this is the origin of the problem? In the webpage it does’n say anything about the minimum frequency the motor driver accepts, so I’m lost now.


I have more info now.

Everything works OK if I disconnect the direction pin (DIR). But if I work with it plugged to the chip, it will prevent the whole thing to work.

With digitalWrite(LOW) on the pin, the output voltage will be 5,7 but suddenly it will start jumping from one value to another, and in the end it will end changing the polarity itself!!!

Any advice?

Describe how you are powering the system.


In addition to letting us know how you are powering the system, could you post pictures that show the motor driver and all of the connections to it?