DC motor 24V with elliptic gear at low speed


I have DC motor 24 V with elliptical gear, specification in attachment.
So, DC motor speed is linear to voltage which I generate with PWM.
I need slow motion for robotic arm movement and position control with encoder.

But at 8% of nominal voltage motor is noisy, sounds weird and do not even really move. I am afraid to damage a motor as it was quite expensive.

I am wondering if there is any minimal voltage for DC motor with gear to operate?
Is it problem with a motor or a gear?
Is there any danger for a motor at a such a low speed?

Thanks for help!


Image from Original Post so we don’t have to download it. See this Image Guide



It would be much more helpful if you post a link to the datasheet for the motor.

Also post the code you are using.

What does the noise sound like? Is it caused by the gears or is it an electrical noise due to the PWM frequency?

And I strongly suspect you mean "epicyclic" gearbox. I don't believe elliptical gears are a good idea. :slight_smile:


Elliptical gear is something like this: Non Circular Gears: Elliptical Triangular Square Multispeed Cam Gears

You want to implement a position control loop with your motor right? You’ll need a PID loop to control
output to the motor, using error between desired position and current position (as provided by the encoder).

Low speed is not a problem, position control loop does that for you (once tuned).

However you have backlash in the gears to worry about - placing the encoder on the motor shaft
won’t compensate for the backlash (but will be stable and can use a lower resolution encoder), encoder
on the output shaft automatically compensates for backlash but you might have stability issues.