Any Ideas of how using LDR as variable resistor?

[SuperGeo]

Hi

I built the Tim's Idiot Wah and used the LDR as a variable resistor. Put it outside of the box to use with my foot blocking or not the light but this way isn't very good because depending of the angle of the light it changes almost nothing and i can't use it in dark places...
searching in the forum I found some posts that say to use "shutters" but I don't know what does it means  :oops:  :lol:
have you got any ideas? thanks

[MartyB]

Could you put inside the box and attach a transparent greyscale that moves up and down in between the light and LDR?  IIRC, Morley pedals work in a similar way.

MartyB

[dpresley58]

I got inside a Morley volume pedal that has a LDR... I was expecting the throw lever to be connected to a pot, but instead it was attached to a black canvas flap that covered the LDR. The light was supplied by the "Power On" lamp just behind it. Being new to this sort of thing, the simplicity of it really impressed me.

Can't seem to get the "quicky sketch" inserted here. It'd explain it a lot better than I can with text...[/img]

[petemoore]

...just put something between/take something out from inbetween the light source and LDR.
 I [*disputed] came up with the spinning wheel idea, with holes in it...sizes and shapes of the wheels holes determine taper of sweeps, speed of spinning wheel [and # of holes in it] determines speed of sweep.

[Connoisseur of Distortion]

well, you could put a pot, an LED, a resistor, and an optoisolator to work to create a varying supply of light... but i get the impression that you're trying to avoid using a pot.

[NaBo]

Well, an external LDR is pretty much the only way you're gonna get a (simple) manual wah without having a rocker pedal of some sort.  I plan on having a little lamp nearby when i use it, and a pot in parallel with the LDR so i can adjust for different light conditions.

As a bit of an aside, have you tried Tim's photon filter?  That one is basically an idiot wah designed to be used with an LDR control...  you may have noticed that using an LDR with the idiot wah makes it more like an "aww" pedal...  a "backwards" sweep.  The photon filter doesnt use the LDR control as the variable resistor to ground... instead, it is used to control how much current goes to an LED to ground... so it will give you the normal "wah" sweep going from toe-up to toe-down.

It's definitely something you need to experiement with to get good results though...  try different LDRs if you arent getting a good sweep in typical playing conditions.  Try using different resistors in parallel to change the "taper" and range.  A good thing to have if you plan on using it in different conditions would be to have a little lamp with a dimmer switch, so you can have greater control over how much light is hitting the LDR.  Personally, I got lucky when I breadboarded it and the fluorescent light in my room allowed me to get a good sweep with the LDR i used (good enough to record this quick-n-dirty sample, anyway: http://geocities.com/nabotics/).  Of course, if I wanna end up with something I can use anywhere else, it'll be a bit of trouble.  There's certainly a lot of variables involved.  But it's worth it for a great sounding, cheap, touchless wah pedal...  Amaze the "normies"!  


Edit:

Oh, i just remembered some other ideas i had for finishing this project that I should share...

In order to both shield the LDR from ambient light sources and protect it, I'm going to be putting a little rubber gasket around it (think pete cornish stomp switches)...  This will probably also allow you to get closer to the max resistance of the LDR too.  And, to keep crap from the bottom of your shoe from getting in there, you could drill or glue a piece of plexi glass on top.  That way, I'm sure you wouldnt have to worry about stepping on the LDR and breaking anything.

[Transmogrifox]

Could you put inside the box and attach a transparent greyscale that moves up and down in between the light and LDR?  IIRC, Morley pedals work in a similar way.

MartyB

Actually, as non-intuitive as it seems, the plastic shaded piece in the morley pedal is part of the bypass scheme.  I traced the circuit board out as I did a mod to mine to convert it into an envelope filter and needed to determine which LED controlled the wah.

As it turns out, there is a very low-angle LED producing a concentrated beam to a single 1/4" hole through the metal and the LDR is aligned on the other side.  As the pedal rocks, the hole is aligned with the LED beam such that it allows the light through in a form similar to the phases of the moon.  It's actually more awesome than the shaded plastic deal--which uses a diffused LED.

I have had good results using a 3x4" copper plate and an RF oscillator as a capacitive proximity control like a theremin--but then that isn't simple like the idiot wah any more.  I guess ya gotta pay the trade-off somewhere.  It's a good design when somebody can make it idiot simple and genius performance.