Hi All,

I've just assembled an L297 stepper driver configured for unipolar motor. When unit is turned on, I hear a high pitched whine from the stepper. everything works fine, but the sound is very annoying!

Anyone know how to filter this out? i've had the same problem with bipolar motors and solved by placing a .1uF cap across each coil. Tried that for the uniploar and it didn't work.

If this helps, chopper on l297 is running at about 24Khz.

Any help appreciated!

Thanks.

-A