Light wah layout

JOHNO · Post by **JOHNO** » 30 Aug 2011, 04:41

Dr Tony Balls wrote:Man does anyone have the schematic for this that they can confirm WORKS? Ive got two drawn from different people that match but I cannot get the LFO to do anything at all. Breadboarded twice and checked all my parts and all I can get is an LED that says on constantly instead of pulse.

The schem Nocentelli posted looks to be correct. I have had the wah and dark light sections working but i havent yet built the lfo. But i did just troll through 23 pages at DIYSB and the lfo used in the light wah is the phozer lfo from runoffgroove. But robert changed the 10n cap to a 1m resistor. Comparing the two lfo schems it all looks good so it should work. I'm going to check over my layout for errors in comparison to the schem posted and build this circuit over the next couple of days and try to get this thing verified. Sorry this doesnt really help you Dr tony but it's all i have at the minute.

Nocentelli · Post by **Nocentelli** » 30 Aug 2011, 07:35

JOHNO wrote:
Nocentelli wrote:so tried doing a vero... FAIL AGAIN.
Did you use my layout?

No, I did my own layout.

doccom · Post by **doccom** » 11 Sep 2011, 15:54

JohnO or others, has anyone verified a vero yet? Can someone repost the vero JohnO pulled down? Come on people, lets do this.

DocCom

Dr Tony Balls · Post by **Dr Tony Balls** » 11 Sep 2011, 16:06

doccom wrote:JohnO or others, has anyone verified a vero yet? Can someone repost the vero JohnO pulled down? Come on people, lets do this.

DocCom

I have one but it's for a modified version of the same sort of thing. The correct LFO from the lightwah schematic (some of the schematics were wrong), and a colorsound-style wah. No foot control thing. that vero is here:

edit: wait....that has a problem....im fixing it
edit: k it's fixed now.

Nocentelli · Post by **Nocentelli** » 04 Oct 2011, 22:31

Finally got around to making this thing - Just the proximity wah part, no LFO - verified:

Nocentelli · Post by **Nocentelli** » 06 Oct 2011, 05:17

The footwah LDR (mounted externally) is the one hanging off the transistor, the other LDR and D2 form an optocoupler/vactrol.

hakanenlauri · Post by **hakanenlauri** » 14 Apr 2012, 17:20

Hi there!

I'm trying to breadboard this using the above schematic and the following is happening:

I get a wah sound which is controlled by the LDR hanging between the two capacitors connected to ic1 and ic2. The sound becomes brighter when the ldris covered and muddier when there's light. (Shouldn't it be the other way round, as in this video , for example: ) The other LDR does nothing but adjusts the brightness of the two leds in series. The sensitivity pot does nothing. Shouldn't it affect the sound somehow?

Thanks in advance,
Lauri Hakanen/Finland

Nocentelli · Post by **Nocentelli** » 14 Apr 2012, 18:10

hakanenlauri wrote:I get a wah sound which is controlled by the LDR hanging between the two capacitors connected to ic1 and ic2.

Have you tried this?

Nocentelli wrote:The footwah LDR (mounted externally) is the one hanging off the transistor, the other LDR and D2 form an optocoupler/vactrol.

hakanenlauri wrote:The sound becomes brighter when the ldris covered and muddier when there's light.

If you use the LDR that's connected to the transistor as the wah "foot controller", and shrink tube the LDR between the caps and one of the LEDs, covering the "controller" LDR makes both LEDS glow brighter. The shrink-wrapped LED illuminates the LDR between the caps and makes the sound brighter. Exactly how bright it goes (and therefore how trebly the wah effect) will depend on the sensitivity setting. The other LED serves as a visual indicator to set the sensitivity; Cover the controller LDR completely, and adjust the sensitivity until the LED is just lit, and the trebly-ness of the "wah full forward" is to your satisfaction. Now as you lift your foot/rock backwards on your heel to expose the LDR to ambient light, the wah sound should become more dull just like a real wah.

It works best when illuminated by plenty of natural ambient daylight, so I'm afraid it is not particularly suited to darkened stages!

fretzburner · Post by **fretzburner** » 15 Apr 2012, 11:54

Is it possible to use VTL5C10 for this circuit? LDR's here are not reliable because there's no specific value.From VTL5C10 datasheet it's impedance range is 400ohms to 400k.

mictester · Post by **mictester** » 15 Apr 2012, 12:19

It's really not a very good circuit - you can see that it's based on the Morley optically controlled Wah Pedals, but the values have been tweaked.

One of the problems is that it's going to draw quite a lot of current because you're running those LEDs all the time. The next problem is that the conversion from LED current to amount of light is in no way linear, and below a certain point LEDs emit no light at all - the "curve" of the frequency sweep will be very non-linear. The final obvious problem is that if you're trying to use ambient light with the thing, it's going to be affected by shadows, it will hum at mains frequency because of the "flicker" of mains driven lighting, and will be useless on stage with people moving about, lighting changing and so on. Morley use fixed illumination and a shutter attached to the pedal that interrupts the light path. It's a simple method, and gives a good range of resistance change, but requires a bit of mechanical work if you're going to replicate it.

You might get lucky and get a reasonable range of sweep out of the filter, but the values are wrong for a good Wah sound. It won't sound anything like a conventional inductor-based Wah - it's a twin-T filter and these have a very different response shape anyway. I gave up trying to use this type of filter a long time ago - if you get a sufficiently high Q for a reasonable sound, you run the risk of self-oscillation (especially with an unbuffered filter output), and if the Q is lower it just sounds like an ineffective treble tone control.

If you want a simple Wah circuit, spend out for a 500mH choke, and build a Cry Baby (or one of its variants) but be sure to add input and output buffering. I would especially recommend looking at the Colorsound Wah-Swell Pedal - it's a great way of getting two useful effects in the same pedal, but be certain to add buffering!

If you want a more complex (and much better) Wah circuit, consider the use of simulated inductors (gyrators) or state-variable voltage-controlled filters. I go the state-variable route by choice because it's trivially easy to set the "heel" and "toe" frequencies, the Q and select one of four outputs for differing sounds - bandpass (conventional), notch (interesting but less useful), highpass and lowpass (can be very interesting after distortion effects).... The only downside is that the circuits are more complex, but nothing worthwhile is ever easy!

Nocentelli · Post by **Nocentelli** » 15 Apr 2012, 15:23

All valid points, mic, yes there are much better ways of getting a good wah sound. I thought the range of sounds in that video was actually quite impressive for such a simple circuit. The biggest problem for DIY wahs is the mechanical aspect, not the circuit: This fun little project is a great way to get a foot operated wah in a standard 1590B enclosure.

hakanenlauri · Post by **hakanenlauri** » 15 Apr 2012, 17:35

Thanks, Nocentelli, for your reply! It works now as intended! Still have to build it though...

Zombie_Crush · Post by **Zombie_Crush** » 10 Aug 2015, 15:55

Hey all,

nocentelli

Looking at your verified lightwah lite diagram I would be lying If i said I couldn't quite understand just where some things should be wired. I am very confused about the green Foot LDR wire to sense 1? Can you explain how exactly this should be wired.

Also where does the LED Pos wire go ?

Thanks in advance for your clarifications.

Nocentelli · Post by **Nocentelli** » 10 Aug 2015, 19:30

Green wire goes to one leg of the control LDR (mounted on outside of box so you can cover it with your foot), the other leg of this LDR goes to ground; sens1 also needs to go to ground.

On-off LED pos goes to the positive leg of the on/off LED (the negative leg should be connected via the bypass footswitch to ground to give on/off indication).

Zombie_Crush · Post by **Zombie_Crush** » 10 Aug 2015, 19:41

Brill news!

Will get to work!

Big thanks! Nocentelli

Zombie_Crush · Post by **Zombie_Crush** » 11 Aug 2015, 15:23

Sounds great! But its inverted ... hmmmm.

I.e LDR darkness is brightness. Is there a way around this Nocentelli?

Nocentelli · Post by **Nocentelli** » 11 Aug 2015, 15:50

Zombie_Crush wrote:
I.e LDR darkness is brightness. Is there a way around this Nocentelli?

That's the design: Put your heel on the ground, holding the toes well above the LDR - lowering your toes over the LDR is like rocking a wah pedal forward, making the sound brighter.

To reverse the effect, you would just use the LDR that is part of the vactrol as the control element.

Zombie_Crush · Post by **Zombie_Crush** » 11 Aug 2015, 16:08

Shall perceiver.

Zombie_Crush · Post by **Zombie_Crush** » 11 Aug 2015, 16:58

Infernal 2n3904 and angry amber red LEDs ... Ouch! its not happy .. Oh well!

Your original version is fine however Nocentelli. 100% verified. On another note - shall get used to its arrangement.