[PD] Re: [PD-announce] PWM in Pd
hans at eds.org
Fri May 26 13:17:19 CEST 2006
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.
On May 26, 2006, at 11:39 AM, padawan12 wrote:
> Very true. The DC blockers in most s/c are going to be limiting.
> But there's no reason to assume people using Pd for more serious
> experimental applications won't use correct DAC hardware. I think
> its very exciting to see the emergence of Pd as an application
> for wider research in engineering, rapid prototyping etc and I
> applaud HC for thoroughness and attention to detail in the code.
> The beauty of sw over hw is extensibility, on a 64 bit system
> you could use this to position a radio telescope or whatever, far
> beyond the grain you'd ever get with 7bit microcontrollers.
> On Thu, 25 May 2006 13:24:16 -0400
> Martin Peach <martinrp at alcor.concordia.ca> wrote:
>> Hans-Christoph Steiner wrote:
>>> I should say, I forgot that PWM was used in synthesis some, so I was
>>> thinking about electronics and control when I was talking about PWM.
>>> That's why my PWM objects are tailored towards, but should work
>>> fine in
>>> the audio context too, unless you need the wandering DC offset.
>> For controlling things with PWM I think you'll need to modify your
>> card if you want DC output. AFAIK they all have capacitors on the
>> to block DC. I find it easier to program a PIC to do the PWM and
>> talk to
>> it from PD using MIDI continuous controller messages for 14-bit
>> resolution, or noteon with velocity meaning pulsewidth for 7-bits.
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