How's about this? --> My wah with LDR

[Michael Allen]

http://www.freewebs.com/loudnoise/WahSchem.gif

Alright, this is the Mod-able wah from GGG. I've got a 500mh inductor to use, plus some Morley photocells. I havn't measured them yet but if they are not around 100k can I put resistors in parallel/series to compensate?

How about that LED driver. Is it suitable or is there something better I should use? What do you guys think?

Thanks a lot,

[Michael Allen]

Eh? Anyone?

So I was thinking, do I need the extra transistor to drive the LED? The only thing usefull is that the LED will be shut off to save power when the effect is off. Otherwise I could just tap off the 9v and use a limiting resistor....

What do you guys think? Please let me know, I think i might try and throw this together tonight....

[Rich G.]

Oops!  wrong thread...  :roll:

[Michael Allen]

Oops too! The schem is wrong. The LDR should be replaced with a 100k resistor and then the junction of the 100k and the .22 off the base Q2 should have an LDR to ground.

I threw it together and it works well! It doen'st sound too pretty but I'll get around to fixing all that. Now I have to do the mechanical section, in creating the shudder and all that working stuff.

Well, at least I have progress!

[RobB]

Michael, the link to your wah schem' doesn't work for me.  I'd like to see how you've incorporated an LDR into a wah circuit.

[petemoore]

PROBABLY MY COMPUTER>>>
 THE LINK AT THE TOP OF THIS THREAD OPENS A PAGE: THE LINK AT THE TOP OF THIS THREAD>>>

[brett]

Now I have to do the mechanical section, in creating the shudder and all that working stuff.

I made a similar wah once, and drove the LED with a hall-effect device (magnetic sensor).  That make the mechnaical part easy, because a magnet and sensor were easier to arrange than rotating a pot.  There must be other ways of adjusting the brightness on an LED too.  Pressure sensors come to mind...

have fun

[Michael Allen]

Hey guys, it's the Freewebs server that has issues. A copy and paste works but it's a PITA and I don't know why...

Brett, I've been trying to tink of a better way to do this and I think I might have to do something like that. This is to jerry-rigged to be feasable!! It makes me laugh that I would try it with this ghetto old pedal and the stuff I threw into it... but ah, it's all in the name of fun.

What I did was this: the pedal workings on the inside move about one Cm when the pedal is depressed. So I cut out a piece of tin to use as a shudder, and glued it on there. I used an LED and mounted it on the outside of the pedal, shining inside. The circuit board is screwed down to the inside of the pedal with the LDR kind of hanging off. I positioned the LDR so that when the shudder moves it is inserted between the LDR and LED. The thing is, there is not a lot of area on the pedal movement that has an affect, and when I get to that area it goes way to fast to really control. I want to spread it out a little bit. The other thing about this wah is that right now it dissappears when I use it with distortion. I think this is a common wah problem i've heard of so I'll try and get it cleared up sometime. Also i didn't have room for a bypass switch so I need to figure that out too.

Here's some pics. I hosted these on angelfire instead of freewebs so a copy and paste should do the trick.

http://www.angelfire.com/ia/foofighters/Mod_Wah_001.jpg
http://www.angelfire.com/ia/foofighters/Mod_Wah_002.jpg
http://www.angelfire.com/ia/foofighters/Mod_Wah_003.jpg
http://www.angelfire.com/ia/foofighters/Mod_Wah_004.jpg

[RobB]

The cut and paste worked.  
OK, your drawing + third post tell me your circuit is like the "Mod for Remote Wah (from Anderton)" as shown on The Technology of Wah Pedals by RG.
http://www.geofex.com/Article_Folders/wahpedl/wahped.htm
Seems the shape of your shutter will determine your effective pot taper.  The internal colour of your casing and shutter will also have an effect.  
It might be worth using a high brightness led if your LDR isnt producing enough of a change in resistance to mimic a pot (you seem to have done this).  
Shielding the inside of your wah from external sources of light will be essential if you plan to use it under bright stage lighting.  
I'll be interested to know how it works out.  It would be nice to do away with a component which has a limited life span.

[Michael Allen]

Yeah Robb, it's the Anderton retrofit but instead of the remote pot driving the LDR, it's just an LED. That's interesting about the color issue. I think i might try painting it black on the inside just to try and improve things. I'm going to also try and fasion a new shudder that sits flush against the bottom, then i'll move the LDR to sit right above it, so that there is an extreme of Total Brightness and None. We'll see!!

[Paul Perry (Frostwave)]

The cool thing about hall-effect pedals, is that you could play one while standing in a mangrove swamp. I'd pay to see that..
the other thing is, you could put magnets around the rim of the wheel on an exercise bike, and have a variable speed wah or trem. I'd pay to see that as well..

[brett]

They are very sensitive.  Imagine Angus Young with a magnet in his school cap and a sensor on his guitar.  Head-banging wah - yeah!!

Or on your chin and nose? :wink:

[Michael Allen]

Does anyone have any info on this Hall effect stuff?

I tried to add an output buffer to match the impedance (the buffer from home-wrecker) but I'm still not getting good results. There are two channels on my amp, one is bright which i use for clean and the other is normal which i use for distortion. The Wah works fine and sounds rad on the clean channel, but when i switch over to the normal channel the sound becomes distorted and blatty and fuzzy even with the amp (50w tube) on the lowest gain settings. But i can turn up the clean channel and it doesn't really overdrive it. It's only on the normal channel....Any ideas? It did this before I installed the buffer. That's the reason I put it on there actually...

Michael

[brett]

Does anyone have any info on this Hall effect stuff?

Simple Hall effect devices (UGNXXXX) have 3 legs.  One takes 5V in, one is ground, and the other is the output.  With no magnet near it, the output is 2.5V.  With south or north poles of magnets coming near the device, the voltage either rises towards 5V or falls towards 0V.  It's relatively easy to get it to drive an LED.  (In my case, I used an NPN transistor as an emitter follower to boost the current available to the LED).

This application note explains a lot
http://www.allegromicro.com/techpub2/an/an27702.pdf