[sdiy] expo pair "heat shield?"

[Mattias Rickardsson]

Roman Sowa <modular at go2.pl> skrev:

> And one more thing to add - once I've seen internals of well known
> desktop analog synthesizer, and the only tempco was placed in the middle
> of the PCB, between voices. It was popular Panasonic PTC and it was used
> to tell the micro how to alter tuning scales on the fly. So in this case
> the term "encasing" referred to entire synth.
>

Interesting! If it's the synth I think, then the tempco is actually not
telling the micro anything, but it's in fact just changing the reference
voltage to one of the two CV DACs so that their CVs are compensated for the
temperature related errors in the 2164 VCAs that they control. Totally
behind the scenes - the micro doesn't know what the temperature is. :-)

Other products have temp sensors with digital communication to the micro,
where the compensation is done by number crunching.

Lesson learned: The temperature readings have interesting artifacts if a
digital temp sensor doesn't update both its MSB and LSB at the same time,
so that occasional readings have the MSB one value off after LSB
turnaround. If you think you're ready when the datasheet is studied and
followed, you're doing it wrong! ;-)

/mr

>
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