Quote Originally Posted by mister_e View Post
Yeah that's what i thought too, hence why i buy few different model.

Well, yes i hear some little noise which is more or less louder depending of the model... but there's always some noise when you play around the minimum low-voltage threshold.

I tried higher PWM frequencies and it may cure some part of the problem on some voltage range and on some motor model. but it's certainly not perfect on ALL motor i have here.

To me, in this specific case, a better choice could be to use some kind of linear regulation. Something around the following.
<img src="http://www.picbasic.co.uk/forum/attachment.php?attachmentid=1396&stc=1&d=117175510 5">

it have some good point and some bad ones. But do you really a 0-100% regulation? mmm

Malc, don't worry... it's an interesting and funny thread.

An idea... we could skip the PWM and use some I2C DAC...
Hi, Steve

Your design is to try with a low input RC constant in order to produce some kind of trapezoidal wave ... instead of the beautiful square wave.

the problem lays in the slew-rate ... remember lentz's law ... the motor windings oppose an "electrical inertia" proportionnal to the slew-rate ...

that will create some dissipation in the ballast ... but make less noise and heat.

may be some "Mid freq" rectified sinus, used in burst mode could also do the job with minimal issues ( seen on the motor side ... LOL !!! )



Alain