LDR's and Wah?

[YouAre]

I read the technology of wah pedals at geofex

http://www.geofex.com/Article_Folders/wahpedl/wahped.htm#multfb

If you scroll down to "Cure for Pot Scratch, or Mod for Remote Wah (from Anderton)" It goes into detail about how you can basically use an LDR. I'm i'm not mistaken....essentially, the wah pot controls the amount of light emitted from the LED, which is fed directly to the LDR. That LDR goes to the 100k resistor, which is 100k because that is the value of the wah pot...am i right?

NOW, if i wanted to get saucy, could i replace that 100k resistor, with a 200k, so that it would be just like some vintage ICAR pots (and their repros)?

Also, would it be possible use 2 LDR's so that i can control 2 wah circuits with 1 wah pot?

thanks,
murad

[Seljer]

the pot in the classic crybaby type wah circuit is working as a voltage divider.
LDRs usually cover a range from bright->dark that is something like 1kohm to 800kohms.
That 100k resistor works as the top part of the pot.

So together with the bottom part you get:
bright = (1k)/(100k+1k) = about 1%
dark = 700k/(100k+700k) = about 87%
and everything in between makes up the "pots" sweep.
You might want to use a trimmer for the 100k to find the optimum range (if you have an LDR with less resistance you might want to try something smaller)


and yep, with this method you can control multiple wahs from the same controller, it doesn't even need to be a pot, you just need some kind of varying voltage that goes to LEDs, it could be something like an envelope detector or an LFO. Or with an simple inverting buffer you could reverse the control voltage going to through to the other wah and get 2 wahs working in opposite direcitions and other such stuff.