[sdiy] A simpler LED/Optocoupler/Vactrol dimmer

Julian julian at 22host24.com
Thu Apr 3 21:02:36 CEST 2008



> Put the LED in the feedback loop of an op-amp. Makes it linear.


Ive been thinking of using vactrols to control some things, and Grant / Harry have just demonstrated how to get a controlled linear 
response, but what about a controlled antilog response, and a controlled log response?

Basically i want to use the same value control pot for every vactrol, and have some varying logarithmically between value a and 
value b, and some varying with a linear response from b to a, some from c to d etc.etc.  I want lots of different resistances and 
'tapers' from the same input.

In truth, i havent really thought about this very far, but its the antilog that seems the problem...


Julian 


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