[sdiy] Odp: PWM to voltage (was Re: wireless patching)

[Roman]

One can make PWM decoder that works as fast as lightning, basicaly straight from the first period of PWM wave. Just use the same ramp generator as in the transmitter, and alow it run only at positive level of PWM signal. Negative (or low) level of PWM resets the ramp and holds it at 0V. Also, the falling slope of the PWM signal triggers the FET of S&H circuit that is fed by the ramp, and S&H output is your PWM-decoded CV. Of course you need some filtering to remove possible glitches, but it can be tuned pretty high.  As a result you get CV that is lagged only by a period of input PWM frequency.   Roman    Dnia 27 maja 2017 12:31 Tom Wiltshire <tom at electricdruid.net> napisał(a):  On 27 May 2017, at 01:08, Quincas Moreira <quincas at gmail.com> wrote:   That's right, converting PWM to voltage requires filtering, so there'll always be a bit of glide.   This is true, but you can make it pretty minimal, depending on the situation.   I designed a PWM-based pitch transposer, which uses two PWM channels,  one to provide octaves, and the other to provide semitones. Since one channel only needs ten steps, and the other only needs 12, the PWM frequency can be very high (250KHz) and the required filtering can therefore be both effective and fast.   The project  finished up as this:   www.frequencycentral.co.uk www.frequencycentral.co.uk   It's a pity that the technique wouldn't work for a full MIDI-CV convertor, but that'd need more resolution to get between notes, and then the benefit of only a few steps is gone.   Tom    ______________________________  Synth-diy mailing list   Synth-diy at synth-diy.org  synth-diy.org synth-diy.org
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