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[DPRG] Re: DPRGlist Digest, Vol 74, Issue 17

Subject: [DPRG] Re: DPRGlist Digest, Vol 74, Issue 17
From: David Jannke david at proboticsamerica.com
Date: Mon Jul 19 17:51:55 CDT 2010

PWM frequency choice

 From what I've seen the choice of PWM frequency is driven by the 
capabilities of your hardware plus or minus needs specific to your 
chassis, motors and electronics.  I used to use very low rate high amp 
PWM control for BikeBots because standard rate (under 10k or so at the 
time) was right in the heart of the audio band and whenever the motor 
was running at partial power it would actually hum/whine and create 
pulses in the power system at the same frequency which were promptly 
amplified through my audio system.  A low rate reduced it to a low 
grumble.  20-30Khz or more speed controllers are now far more common, 
but I still see the specs dropping back to the lower rates as the 
amperage controlled rises. From what I understand as the PWM rate rises 
there is more radio interference but I haven't seen it.  I've also heard 
higher is better for motor efficiency but can't provide the source just now.

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