Automatic potentiometer

[cosy]

Is it possible to replace a potentiometer with a curcuit or some device, that can automaticly sweep back and fourth like you would the potentiometer manually.??

And if possible, can the device have a knob for selecting a time frame from A to B, "sweeptime"

[The Tone God]

There are several ways to do this but it depends on the function of the pot in the circuit and your particular requirements.

More information is needed to give a more accurate answer. What circuit are thinking about ?

Andrew

[cosy]

The potentiometer in a Wah!!!

[cosy]

Hmmmmm....... no idears...

[The Tone God]

The potentiometer in a Wah!!!

Why not look into various auto-wah circuits ?

Hmmmmm....... no idears...

You have to give people more then a hour to respond. Some people around here have lives.

Andrew

[Chuck]

Tone God,
I think you just digged yourself. 

Made me laugh anyway.

[Paul Perry (Frostwave)]

yeah, 24 hours is more reasonable! I'm only just awake!
For a wah, you could replace the pot with a light dependant resistor & a low frequency oscillator driving a led. As has already been done many times.
The "sweeptime" knob is in fact the LFO speed control.
It's been done.

[The Tone God]

Tone God,
I think you just digged yourself. 

Made me laugh anyway.

Good. That was my intention...I think.



Andrew

[cosy]

yeah, 24 hours is more reasonable! I'm only just awake!
For a wah, you could replace the pot with a light dependant resistor & a low frequency oscillator driving a led. As has already been done many times.
The "sweeptime" knob is in fact the LFO speed control.
It's been done.

That sounds like the thing.... but first off, I am not a wizard at electronics, so i need something with a walkthrough or a finished product that i can solder on my old crybaby curcuit. and i live in Denmark. so if you have a diagram blueprint or drawing of the curcuit, I'll have to find a guy here in DK to make it.....or die trying myself

[R.G.]

For how to do it, read "The Technology of Wah Pedals" at GEO (http://www.geofex.com) and look at the "resistor to ground" style wah. The simple way is with an LED/LDR and a LFO driving the LED.

Unfortunately, there are no layouts with parts lists and so on.

The old PAIA "Synthespin" project was exactly what you have in mind, a wah with an LFO driving it.

[col]

If you can get hold of them check out some of Penfold's books where he does just this with either a 555 or an op-amp oscillator. You might be able to get them from a library in Denmark and the one in "Electronic Music Projects" (ISBN 0-900162-94-5) works just fine.
The one he describes in "Practical Electronic Musical effects Units" (ISBN 0-85934-368-5) is a more advanced circuit which uses an LM13700 to trigger the effect. Mine didn't work too well but the DOD autowah which was posted on here and is a very similar circuit was a success and produces a good effect.  Also do a search on here for "cheap auto wah" which uses an op-amp oscillator and sounds very weird.

Col

[jonathan perez]

hmm...that just inspired me.

totally remove the pot, and place an LDR. stuff it all into a hammond box...hmmm...interesting...

[petemoore]

  I just ordered a PCB, I'm thinking of a second speed Lfo for the lfo on a phase 90.
  Spliced beside the existing speed pot, an LDR which slowly adjusts speed of ph90 lfo, so the sweeping would seem more random [this would eliminate the repetitive peak spacing].
  Speed could of course still be adjusted as 'average' or normal operation with a switch across the LDR . 
  Clock noise with a 555 in a phaser seems like it'd be a possibility.
  Some viewing of random LFO's at Geo seems in order.

[Sir H C]

Morley used LDRs and LEDs to drive a lot of their wahs.  If you can find those schematics, you should be on your way.  The problem is getting the light to "make sense" to the signal, that is to have the sweep match with what the oscillator puts out.

[Isaiah]

http://oikosulku.blogspot.com/2007/06/mempot-controlling-xoxbox.html

[Sir H C]

Morley has all their schematics on line.

Here is one:

http://www.morleypedals.com/slwaes.pdf

http://www.morleypedals.com/downloads.html

They used a wedge shaped piece of cardboard to limit the light from the LED to the photoresistor, something not seen in the schematic.