[sdiy] VCLFO and VCADSR details available online

[Tom Wiltshire]

On 18 Dec 2006, at 22:43, Adam Schabtach wrote:

> I built an ADSR using Tom's schematic and source code. It's a dandy 
> ADSR and
> the Scale and Exp/Lin controls make it more flexible than most analog 
> EG
> designs.

Thanks, Adam.

> One thing I've been wondering is whether anyone knows of a simple,
> low-parts-count protection circuit for microcontroller inputs.

My own thought about the matter was that I'd use an op-amp as a CV 
mixer. The op-amp would be supplied from +/-15V, which puts an upper 
limit on the output voltage. Overvoltage conditions at the inputs will 
just overdrive the op-amp, and I can't remember ever blowing one up 
doing that to it. I'll need an amp that doesn't latch up when driven to 
the rails, of course. We need to avoid negative voltages, so we can put 
a diode in the feedback loop or something. Then I was just going to 
stick a voltage divider on the op-amp output to ensure that when the 
PIC input sees the voltage it gets 0-5V instead of 0-15V. The PICs A/D 
convertor claims to be able to cope with source impedances up to 10K, 
so the voltage divider needs to think about that.

I haven't tested this idea yet (did you guess?), but maybe others have 
done something similar?

Tom

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