[sdiy] Digital encoders missing codes in many devices - why?

MTG grant at musictechnologiesgroup.com
Sat Aug 21 19:47:11 CEST 2021

What was the Dave Smith encoder debacle all about (and solution)? This 
was quite a while ago, I don't even remember what synth it was.

Someone in this thread also mentioned current and pull-up resistors. I 
think Moog had an issue around the time of the MemoryMoog or maybe the 
Source where the panel switches were oxidizing and getting intermittent. 
The ECO was to reduce the pullup resistor value substantially.


On 8/21/2021 9:04 AM, David Riley via Synth-diy wrote:
> On Aug 21, 2021, at 09:24, cheater cheater via Synth-diy <synth-diy at synth-diy.org> wrote:
>> Why does this happen? Why is it so spread out? Is this a programming
>> issue, or a mechanical issue related to the lifetime of the encoder?
> Having made these before at various different scales, I’d guess that it’s probably mechanical quadrature encoders using brushes to contact. If so, intermittent brush contact would do exactly that; a lot of decoders also don’t handle things like simultaneous transitions well.
> There’s a reason ball mice used optical encoders. They last practically forever. Most brushless DC motors and other servos also use optical encoders. For some military hardware I worked with (the carrier-side instrument landing system antenna motors), we used a magnetic encoder, which I’ve not seen elsewhere.
> Anyway, degrading contacts would be my guess. Either bent or dirty brushes. Does a hit of De-Ox-It help?
> - Dave
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