Two motors 37Dx52L with Encoder dead

Hi all.

Took a while doing a balancing robot project, as you can see in this video:

Use two motors 37Dx52L (29:1) with Encoder, VNH3SP30 controller, and an Arduino Mega. As I use a Lipo battery 11.1 V 2200mah 20C.

Today I changed the Arduino PWM frequency to 8kHz (10kHz max support VNH3SP30) and during testing, the two engines have died.

Specifically I put one motor at 8kHz and the other at 490Hz (default PWM Arduino). A full power and varying its direction every 25 milliseconds, first the motor at 490Hz dead, and later (1 or 2 minutes) the other. The controller VNH3SP30 was cold, but the motors burned and smelled horrible.

The code I used for the frequency change is correct:
TCCR3A = 0x00;
TCCR3B = 0x11, // TCCR1B = 0x11 -> N = 1; TCCR1B = 0x12 -> N = 8; TCCR1B = 0x13 -> N = 64, etc.
ICR3 = 1000;

I removed one of them and I found this:

Anyone know what could have happened?

Thank you.

A greeting.


I’m sorry to hear your motors were damaged. Can you clarify what you mean by the following?

Are you saying that you were driving the motors at full power but switching the direction every 25 ms? If so, please note that at full power (100% duty cycle), the PWM frequency isn’t really relevant because it’s basically equivalent to a steady high signal. Why were you doing this?

At any rate, if my interpretation of your setup is correct, then what happened isn’t all that mysterious. When you switch direction from full-speed forward to full-speed reverse (or vice versa) with no braking or delays in between, the motor will briefly draw almost twice the stall current, which in this case would be close to 10 A. These motors cannot survive that kind of current for long (from a current perspective, it’s like powering them at twice their rated voltage and then stalling them). You can see that the enamel insulating the copper wire in the motor coil has started to melt and is now probably causing a short within the coil itself.

- Ben

Hello Ben.

You understand good, 25 milliseconds with speed a 255 (PWM) and change of direction.

I tried this to see if I could see differences have changed the frequency of 490Hz to 8kHz, but from what I’ve said, I had to have tested a lot less speed.

Thank you very much for giving me an explanation of why have died relation to the intensity so high, I do not happen again :smiley:

A greeting.

PD: sorry for my english.