Electrolytic Cap Value on Super-Simple Dual-wave LFO.

[jamforthelamb]

Hey Everyone,

Just wondering what cap I should on the VB section of this circuit:
http://experimentalistsanonymous.com/di ... %20LFO.gif

I've already built it with a 100uf cap, but I was wondering if that's correct.

Thanks!
JFTL

[para]

should be fine - its just a smoothing cap


steven

[jamforthelamb]

Ok, cool.

I'm using this circuit to drive an LED+LDR vactrol for a effect pedal modulation device. When I have it set to triangle wave and have the LED brightness turned up it will stop oscillating, but keeps working fine on squarewave. That's why I was wondering.

Thanks!
-Kevin

[para]

that sounds like you might just be turning the voltage too high for the low swings for the tri shape to appear to have an effect. you can add a 1k resistor from the positive rail to the pot or led, which ever you have touching the power rail now, and that should start to clear it up. or take like a 1k or 5k pot and set it just right before the LFO seems to stop having an effect and then remove it from the circuit completely and measure it and use that value for the fixed resistor to make sure you get the full range of use

it doesn't happen with the square because it should drop all the way to ground on each cycle. the tri might not.

it might also help to have a DC offset cap on the output of the LFO right before the led to "re-center" the voltage ( not sure if there is one there now ? ). also possibly toss in a 100k or larger resistor to ground around there to help bias it a little.


seems like everyone is building LFO vactrol shit these days. lets hear it when you are done


steven

[jamforthelamb]

it might also help to have a DC offset cap on the output of the LFO right before the led to "re-center" the voltage ( not sure if there is one there now ? ). also possibly toss in a 100k or larger resistor to ground around there to help bias it a little.

Nope, no DC offset cap. Built it just like the Schemo. I don't even know how to implement one of those

I'll try this stuff the next time I open it up (and when I learn how to do the Cap thing). I have it housed in an old automotive tester box with the Osc out sent to the tester's needle so it swings back and forth with the osc. I set it up to be a modular thing for my guitar pedals. It has a course (10 meg) and fine (1 meg) speed control, larger shape pot to get the interesting patterns between tri and square (5k), and a brightness knob for the LED. The osc out goes to a 1/4'' inch jack so that all I have to do to use it on a pedal is add a 1/4'' jack to it, and wire it to the effect I want to modulate.

Thus far I've tried it on an "Ugly Face", "Crash Sync", "PWM" and "Thing Modulator" all with good results. I also tried it on a inductorless wah I built, but it didn't do as well. Fab Echo that's coming in the mail will be next to try it on. I've done one of those with a squarewave before, but not triangle.

seems like everyone is building LFO vactrol shit these days. lets hear it when you are done

I've used them quite a bit on circuit bent toys, but never effects before. I wanted to do something with a triangle wave when I built my first PWM with super simple LFO (it only does sqaurewave). The way it jumped the effect back and forth I knew it would sound a lot cooler with a trianglewave. I just didn't know how easy implementing it could be. Thanks Colin!

-Kevin

[para]

just add a big 10uf electrolytic cap on the output like you see on all the audio processing pedals.


steven

[jamforthelamb]

Oh, ok. That's simple enough.