[SOLVED] Pololu High-Power Motor Driver 36v9 Problem


I own a “Pololu High-Power Motor Driver 36v9” and just tried to get it work.
I connected the driver to a 12 Volt source and tested with a small low power motor. Everything works as it should.
But wenn i use a Power Motor (about 4 Amp continuous power) the driver wrongly detects a shortage.
In the datasheet i read that the driver can last 100A for a few milliseconds and i assume that the motor is not nearly taking that much at startup. Sometimes the motor runs… but at least when i try to change the direction the shortage-flag is set.

currently i am not using pwm, the pwm pin is always set high it the motor should run. Do you think i can prevent that behaviour if i use pwm so that the current is limited at startup?


Edit: Tried it now with PWM and it works :smiley:

Hello, avlbger.

I am glad to hear you got the driver working with your larger motor. Do you know the motor’s stall current? I expect it to be many times its free-running current, so the 36v9 high-power motor driver might be underpowered for your motor unless you are very careful to limit its acceleration (as it sounds like you are doing with PWM) and to avoid stalling it.

If you do not need to run the motor at a voltage higher than 12 V, the higher current capability of the 18v25 high-power motor driver might offer a bigger safety margin.

- Kevin

Hi Kevin,

I don´t have any specifications of the motor as it is one from an old car ( it was used to open/close the window )
As i measured with an old analog amperemeter it takes 1-2 A running and i saw a max of 7 A if the motor is blocked. At startup i think the motor takes more than this but i can´t measure it as the peak is too short to see it on an old analog amperemeter. All currents are measured at about 13V.

I don´t know whats the treshold of the driver to cut off the power and state an shortage condition but it seems that this treshold is getting reached mostly at startup and everytime when i change the direction.

But as i planned to use PWM anyway and i don´t need to startup or switch directions as fast as possible its no problem and i added a liittle “softstart”-feature when the pwm duty-cycle is at the upper third :slight_smile:
No shortage-condition problems from now :slight_smile: