Hissing sound on low-ohm stepper motor

Hello all,

since I upgraded from Gen2 electronics to a Gen7 with Pololus, my stepper motors produce a hissing, high frequency sound when stopped. This sound is probably also there when they're moving, but it's not so clear, then. I adjusted the trimpot on the Pololu carefully, but putting this far enough down to have the motors quiet, tourque is barely sufficient to move them selfs, without belt or threaded rod.

Now, these motors are 4 wire types and rated 3 A at 1.53 V, so they have about 0.5 Ohms only. Obviously, current limit jumps in at a very high frequency and the voltage flanges are very steep.

Is there a known trick to make these motors quiet, like raising inductance somehow? Running the Pololus on the motor side with 5 V?


Thanks.

---

Generation 7 Electronics	Teacup Firmware	RepRap DIY

If it is a high pitched whine then it means the switching frequency is too low and you can raise it by lowering R4 on the Pololu.

If you use very low inductance motors the frequency will actually be high rather than low. Another effect of low inductance is higher ripple current, which may contribute to more noise.

If it actually a hiss then the frequency is probably ultrasonic and you are hearing the beat between the two coils. I get that on HydraRaptor with $800 stepper controllers, so I don't think there is a lot you can do about it. Some stepper controllers have a sync mode where the two coils are synchronised when stationary to reduce noise.

You can't add to the inductance without wasting power and you can't drop the supply below 8V. The only practical thing I can think of is to play with the value of R4.







.

Edited 1 time(s). Last edit at 10/08/2011 06:36AM by nophead.

---

[www.hydraraptor.blogspot.com]