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.
.hc
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@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
sound card if you want DC output. AFAIK they all have capacitors on the
ouput 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.Martin
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