[PD] Re: [PD-announce] PWM in Pd

Martin Peach martinrp at alcor.concordia.ca
Fri May 26 17:33:42 CEST 2006


Hans-Christoph Steiner wrote:
> 
> I just realized the answer to my question about getting positive-only  
> voltages from the sound card.  The DC filters will probably remove  the 
> DC offset, therefore, the output voltage on a PWM signal will  also be 
> centered again on 0, and therefore swing from negative to  positive.  I 
> do remember getting some very low frequencies out of a  computer when 
> testing speakers.  But I haven't actually tested this  [pwm~] object for 
> electronics.  But it would be nice to have a very  well implemented 
> [pwm~], so its great that this discussion happened.
> 
> I did use the [pwm] object with a MIDI-controlled relay box, worked  
> quite well at 30-60Hz on a biggish DC motor.

But that sounds like you're sending MIDI messages at a rate determined 
by the [pwm], so bandwidth is limited by MIDI  to ~1kHz. Better to 
program your relay box to do pwm with the pulse width controlled by 
MIDI, instead of using MIDI just to turn the motor on and off.

Martin




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