QWIIC Motor Driver squeals and doesn't drive above ~200

Robotics
1

Hi guys. I’m trying to drive a small DC motor (nominally 6V) with the QWIIC Motor Driver.

Motor power is two Li cells (currently at 7.5V). I’m using a Teensy 4, and at low drive levels (under 150 or so) the driver seems to work fine, the motor spins, both directions are OK. However when I get to around 180-200 for drive level (motor voltage around 4-4.5V) the motor stops turning and something (possibly the motor) makes a high-pitched sound and the voltage drops to a small value (0.1V or so). I then have to lower the drive level to a low value (around 20) before the squealing stops and the motor runs. However going back up to 180 brings the problem back.

I have two motors, both do the same thing. If I drive the motors directly from the battery pack they spin normally, so I think the motors are OK. The code is a cut-down version of the example program. I have attached the recommended heatsinks and they are toasty.

Any suggestions for debugging this? The driver does not have a motor voltage limit I suppose? (I have multimeters, oscilloscope, etc.)

2

How big are your motors and what kind of current are they pulling when connected directly to your battery? It sounds like they are pulling too much current and that’s causing the driver to shut down.

Can you try running them up to about 150 and then making small increases from there to see if that gets you above 200?

3

Thanks Chris. I had that thought too, so I’m adding an ammeter to see how much current they’re actually drawing. (I don’t know anything about the motors’ specifications except “6V” :slight_smile: