Hey all,
I want to build Tims Idiot Wah, and ive heard great things about it, build im not sure how to build the pedal. I heard one guy modded a sewing machine pedal for a wah, and he said it worked great, but wouldnt it scratch? Any ideas, as im not a great diy'er...
Alex

Hi.  One option is to use a light-dependent resistor (LDR) as the resistive element.  In a bright room you can cover it with your foot to get a wah effect.

I've previously used a magnet and Hall-effect device (magnet sensor) to light an LED on top of an LDR.

After building my own wahs, and always being a bit unhappy with their physical construction, I eventually bought a JH-1 off e-bay.  It's my *only* commercial pedal.  

Good luck.

Oh yeah.  

QuoteJimi blasts into his Hey Joe solo with the classy drum roll and the immortal cry of,"Then i gave her the gun...I shot her!". Too bad the pan happy producer sends the melodic lines a couple of kms past my right ear...

That solo would be in my top 3.  What on earth were they thinking when they buried it so deep?  I love the early bit (repeated at the end) with that four double-stop run, then the huge double bend (up and back) and double stop finish.  "do-do-do-do DWHOOW do"

The mechanical part is tough.
 I've done it, alot of work.
 I did it in a RACO [large] using a clock spring for a take up reel for the string driven pot.
 I used toilet seat hinges to get an axis point above the box for the pedal to see saw in.
 The string comes from near the tip of the pedal, goes in a Raco punchout hole, wraps around a pot with a 'square' knob [square when viewed from the side, a thread bobbin would work] then to the sprung takeup reel.
 Also did an easier one using a long box. this time using s straight take up spring.
 The spring keeps tension on the string enough to drive the pot, the pedal pulls the string 'up' and turns the pot one way, the spring pulls the string 'down' turning the pot the other way.
 I used counter springs on the Pedal, so that it would'nt be pulled back down, and will stay anywhere you leave it set.
 Gear ratios must be computed to get full throw from the pot. Smaller 'knob/drive pulley' means more pot range throw.

Sorry I don't have much for details but I'd think piezo element might be workable.  Then again maybe they just do sudden quick voltages?

How about Force Sensing Resistors http://fargo.itp.tsoa.nyu.edu/~hs420/pcomp/fsr.html

Wow!  That graph of a force-sensing resistor puts it right in the range to be a pot replacement.  Put it on top of an old mousepad and stand on it!! 100kohms to 1kohms.  Gotta get one!!

cool, thanx for the info. I think i might use an ldr like in the Phozer?

QuoteThat solo would be in my top 3. What on earth were they thinking when they buried it so deep? I love the early bit (repeated at the end) with that four double-stop run, then the huge double bend (up and back) and double stop finish. "do-do-do-do DWHOOW do"

Yeh, mine too. the annoying thing is my computers got like 7 different speakers, and the solo happens to be sent to the one accross the room, facing the opposite wall...He padded down the solo on purple haze too!  :x

brett: here`s an example of a Tube-Wah with FSR:


note however, that the "actuator", i.e. the actual little device, that presses
the FSR, is a problem to attach, again.
Pressing the surface of the FSR with your naked toe, socks on, or shoe - depending on rubber or leather sole - yields a different resistance variation each time.

I took the above chassis-design, so to be able to roll-on, -off or to pat on the sensor, which is placed under the black circle...

Concerning the Hall-sensor: were you unsatisfied with it`s function,
or with your mechanical design of the moving paddle itself?

Hi.  I found a Hall-effect device driving an LED/LDR pair a really good setup mechanically and electrically.  I just couldn't build a pedal as good mechanically as a Dunlop/commercial one.  Not even close.  And empty Dunlop shells on e-bay were ridiculous prices.  So I bought a JH-1, put an output buffer in it and it does everything I need.  

I look back on this this process (experiment first, go commercial later) as a way of having fun experimenting with circuits, inductors and all that, but ending up with something solid mechanically (and not much better or worse tone-wise than I achieved with my circuits).

But crikey PureTube, your pedal looks sensational.  A real work of art and engineering.

cheers

Hi Brett: that FSR-Wah ("P-Wah" for `pressure sensitive`)
was my answer to my mechanical-related problems
with gear & pinion pedals:
http://www.pure-tube-technology.de/NEWEST/T-Wah%20DSC00024.jpg

and with optical ones (hard to calibrate):
http://www.puretube.com/link-page-Dateien/Tube-Wah%202-0.JPG

Have purchased a bunch of broken/new/cheap shells over the years,
and am now experimenting with mechanic-inductivity solutions,
where you don`t have to sit in total darkness to adjust things...

There was a filter pedal, made some 25 years ago, called the "Patch of Shades".  It used some sort of pressure/force-sensing approach to sweeping the filter, rather than a foot treadle.  You can see and hear it here: http://www.tonefrenzy.com/2/stick_enterprises_patch_of_shade.htm

Anyone have any info on it?  The sound sample is not especially inspiring, but it DOES work, and may be improved upon.

the problem playing wah with the FSR, is the unpredictability of the
motion you do with your foot:
the fact that it reacts on the force you put on it, rather than a move (displacement), combined with the fact that it acts really quick,
lets each "rock of the pedal" sound a little different than the other,
and in the art of playing comes near the art of playing a Theremin:
takes some practice - is a different playing than a "gas-pedal" - but
is able to even let you express better and faster than conventional pedals.

Pressure sensors can be a handfull to use. Besides the mechincal issues of mounting and protecting the sensor depending on the circuit there is the noise that comes in from the sensor wires, calibration, and the slightly less traditional playing style that has to be developed.

Rocker pedals have the pivot point that provides a way of smoothly moving the pedal thus the sound. The foot can be removed from the pedal with the posistion of the pedal maintained by the mechinsim creating a foot adjustable filter. Using a non-mechinal pressure pad causes a loss of these properties making them alittle harder to become acustomed to for the average player. Even when a player is holding a posistion slight movement can cause changes in pressure. Try holding a setting with your foot for long periods of time without changing your foot pressure.

Hall sensors while interesting are sometimes hard to calibrate. Magnets differ in their strengths. Couple that with issue of users wearing steel toe boots, placing pedals near monitors, and other external background noise can make them a hassle at times.

Just a few thoughts.

Andrew

Hi.

I hadn't thought about the pressure sensor thing meaning that you gotta keep your foot squeezing just right.  That must be annoying.

RE:

QuoteHall sensors while interesting are sometimes hard to calibrate. Magnets differ in their strengths. Couple that with issue of users wearing steel toe boots, placing pedals near monitors, and other external background noise can make them a hassle at times.

With modern, strong magnets (alnico, etc...), there's virtually no interference from outside magnetic fields.  (A fellow I work with uses them for scientific measurements, and finds that solar flares are his biggest source of interference!!)  But I DID have to recalibrate each time I changed magnets or the position of the magnets.  I simply used a small trimmer (1k?) to divide down the Hall effect output voltage.  I'd push the wah all the way down, and trim for a nice, high filter sweep.  Easy.  Also, I could do the adjustment in normal lighting conditions, probably because I had a high-brightness yellow LED (6500mcd) right on top of an LDR.

If the pot ever gives out in my Dunlop, I'd definately go back to a Hall effect device.

The fact of getting drawbacks with FSR, LDR, and pot/pinion,
led me to the decision to release the Tube-Wah first
in its automatic (Envelope-FolloWah) form:

http://www.puretube.com/T-TRON-X-TT-L%20sml%20cor.2.jpg

now better known as the E-H Tube Zipper.