An new twist on a LDR based envelope filter

[rankot]

Did anyone had success making one own's vactrols from 5539/5549 photoresistors and LEDs for this pedal? I have some VTL5C1, could I use those?

[rankot]

I finally made it:

[Kipper4]

How you like that?

Great is'nt it.
Good job

[rankot]

Yes, it's great! I used some kind of Chinese VTL optos. I believe my unit works fine, however, it seems that it is not so easy to use - hitting strings too strong doesn't trigger the effect, so I have to strum carefully. Or maybe I need to master controls a little bit more

[Kipper4]

That's funny cause my sens knob takes care of that.
But then again. I Mostly play with fingers,

[rankot]

I'll try to experiment with Sens a little bit more.

[rring]

wow that looks cool...not sure what your sensitivity issue could be...should be very adjustable over quite a range of input...if you still have trouble let me know.

[suryabeep]

Hello!
I'm very interested in building one of these. is the LED at the far right (connected to R14) the indicator led for the effect?
Also could someone please break down how this circuit works? I would like to try and understand
Thanks!

[rankot]

Yes, it is indicator LED for effect (shows what is going on inside LDRs), not on/off LED. You can see it mounted under sensitivity pot on my enclosure.

[suryabeep]

If I wanted to have send/return feature in this circuit, where would I put it? I want to be able to control the envelope with something like this: http://www.geofex.com/Article_Folders/LFOs/psuedorandom.htm

[Kipper4]

You would need some extra componants to bias the op amp but right before pin5 ic1b would be one suggestion.

Then it's a case of is the sudo lfo compatible.
there may be other issues but.

[suryabeep]

sorry for all the dumb questiosn but would I be able to use 3mm LEDs instead of 5mm?
In general, what is the difference between the two?

[highwater]

Aside from size, the bigger ones might (or might not) be able to take more current without burning-out, and/or be brighter at the same current. Or, they might be literally the exact same thing in different size packages.

Either way, they should both work just as well... you still might have to fiddle-around with diffferent values for R5 and R6, same as you would if you were using ready-made vactrols.

The only problem I could imagine is that it'll be easier to make a light-tight seal if the LED has the same diameter as the LDR, but that shouldn't be a deal-breaker.