Any suggestions for improving this noise issue would be very welcome…
Application: This is for a lab instrument where annoying sounds will be an issue.
- a stepper motor (rather that a miniature gearmotor) suits the application because of reliability, simplicity, and easy accurate speed control at low speed.
I’m using the DRV8834 to drive a NEMA 8 motor (SY20STH30-0604A).
For prototyping, I’m providing the pulses to the DRV8834 with an Arduino Uno.
I’m trying to achieve continous rotation of the motor shaft at a constant 60rpm. The torque requirement is very low.
I have set the DRV8834 in 1/32 step microstep mode and I provide step pulses at 6400Hz (very simply by using the Arduino ‘tone’ function rather than playing with the timers).
The current limit has been set to a level a small amount above which the motor starts to jitter a bit (well below the rated current of 600mA per coil). Setting the limit low helps with the low frequency noise.
I use a bench power supply to supply the DRV8834 with 10V - it draws 0.2A from the supply which seems right. I have played with the adjusting the voltage - higher seems better from a low frequency noise perspective - and is also better for torque.
The resulting rotation is pretty smooth and at the right frequency. Functionally it does the job well.
The noise issue is really just the high pitched whine. My ears are not great and it annoys me - whereas my daughter cannot be in the same room as the instrument!
I should say that it’s only once the motor is mounted that the sound becomes annoying - ie it excites ringing in metal components. I have a number of options for acoustic isolation and damping but first I’d like to see if there is anything that can be done to reduce the source of the problem.
I’m thinking specifically of the following options:
- Capacitors across the motor coils? (does this just mess up the current control?)
- Can I adjust the current chopping frequency of the DRV8834?
- Is it worth me playing with ‘mixed decay mode’?
- Would increasing the microstep resolution help? (modulate using external DAC)
- Is it worth me trying a different stepper driver? (at the moment I’m just looking for the easiest solution to prove that using a miniature stepper is a viable option)
- any other suggestions welcome!
Thanks in advance!