DC motor speed control NOISE

Forum 2005-2010 (read only) Hardware Interfacing
1

Hi,
I ant to control the speed of a DC motor with thr software Pure Data.-
For this I use the Standard Arduino Firmata and the so called PDuino in Pd. - A hardware control I use this Shield RN-VN2 :

499×773 46.8 KB

Everything works fine, except when I change the PWM_signal to run the motor with less speed - the motor produces a noise. Kind of buzzing noise.

Can I do sth. about this?

thanks
fränk

2

Does it move at all when making this noise?

It may mean that you are running too low (too few "high cycles") for the motor to operate properly. You can't say 1% PWM with all motors. One DC motor I have here will cease operating at 40% PWM, and another at 15%.

!c

3

Yeah thats common to hear a sort of high pitched sound when running the motor at a low duty cycle. Im not sure what causes it but from my experience I havn't run into any problems.

4

I had the same problem when controlling the speed of a cassette player motor. The sound even got into the output from the cassette player.

5

It is due to the chopping up of the DC signal. It is the noise at the PWM frequency and is caused by the magnetic field causing the coil windings to repel and then attract each other.
Two cures,

  1. Increase the PWM frequency so that it only bothers the dog.
  2. Add a capacitor across the motor to turn the choppy DC signal into a smooth DC voltage. Sometimes the motor will not run as well like this though.