Switchless wah?

[bancika]

Any ideas how to make switchless wah similar to Bad Horsie (I mean only "switchless" part, circuit would be either Tonepad wah of GGG Mod Wah)?
Tnx

[Transmogrifox]

Something I have been thinking to do to the Bad Horsie (and would work with the other wahs), is to make a proximity controller that automatically switches it on when you get within a few inches of the pedal.  Just like a copper plate on the treadle and some circuitry to play on its capacitance to ground characteristic.  I'll probably use a microcontroller, though there are analog proximity detectors that would work fine as well.

Hook this up to the switching driver circuitry and there ya go.

Look at this one:
www.geocities.com/transmogrifox/relay

There's a relay true-bypass--one for use with a microcontroller, and one that's analog.  They're in .pdf format.

You can also access the Morely schematics at their web site if you want to do it the way they do.  There's just a little bit of twiddling with the mechanical design of it to get things to line up right with the LED and LDR, and also the on/off delay ordeal.

[bancika]

That''s very good idea with proximity!!!
Just, I'm kinda new to this so I don't understand much on those schematics. If I understand well, this is bypass that should work with mechanical momentary switch, right? Now I guess there's proximity controller that works like momentary swith?
I tried with morley scematics, but don't understand much, can't tell which part is switching circuit
Thanks!

[bancika]

Damn, I just saw that proximity sensors at mouser cost about 50$, that waaaay too much :

[eetfuk]

We had a assignment at school using a JFET to turn on and of a LED.
The fun part about it was that i held a wire connected to the circut, and so did a classmate.
When i touched his hand. I were thinking of adding something like this to my Wah, so that whenever my foot is on the wah, it will... wah...

[Transmogrifox]

It's about time I get down to it and put this project together.

Proximity control:  For this you need not buy proximity sensors.  My first plan is based on the Theremin proximity detection.  Simple measuring of capacitance.  A similar thing can be found in the early capacitive stud finders for finding studs in your wall.

I understand now about the schematic thing being a problem.  I guess I should not be so quick to assume everybody knows electronics from birth. 


Here's the theory of what the Morley wah does:
Inside the pedal, there is a hard paper/plastic type thing mounted to the treadle.  On one side is an LED, and on the other side is a Light Depended Resistor (also referred to as "LDR", CdS Cell, opto).  As you apply light to the LDR, it becomes less resistive. 

Thus, there is is hole in this piece of cardboard.  As you move the pedal forward, the hole begins to align with the LED, and light is let through to the other side to the LDR.  When the LDR gets low enough in resistance, the CMOS inverter changes states on the output and switches the pedal on.

The parts related to the switching in the Morely pedal are:
http://www.morleypedals.com/vai-1es.pdf (for reference)
R1
LDR1
L1
U1
R2
C2
R8
R9
C3
C4
D3
D4

and finally, F1 and F2, which are the JFETs.  These are the actual switching devices.  For a positive voltage on the gate, they are low impedance.  When the gate is held at ground, it's a high impedance.  Those triangles with a ball on the tip (U1) are called inverters.  If the input is logic high (nominally 5V, but 9V in this circuit), then the output will be logic level low (0V).  Alternately, if the input is logic level low, the output is logic level high.

Not that if pin 10 on U1 is logic level high, then the gate on F2 is asserted high, and the drain-source (D, S) signal sees a low impedance.  Since the gate of F1 is driven by an inverter whose input is connected to pin 10 of U1, it always has the opposite state of F2.  Thus the drain-source signal on F1 sees a high impedance.   U2 is the final output buffer, and you can see that F2 is connected to the input buffer, so the pedal is bypassed. 

When the F2 gate is asserted high, then the output of the wah sees a low impedance to the pedal output buffer, and the input of the pedal sees a high impedance to the output buffer.

In summary, going through the circuit:
R1, LDR1 & U1 pins 13 & 12 give a voltage output "on" or "off" (+9V or 0V).  The diode and C2 & R2 set the turn-off delay after you engage the pedal (so it doesn't immediately bypass right when you zero the wah on the low end).  U1 (pins 11&10) buffer, or "hold" that on/off signal, and also turn it upside down.  Then the inverter of pins 9 & 8 makes the logic level on the gate of one JFET the opposite of the other.  Finally, F1 and F2 are the low impedance/high impedance elements to actuate the signal routing itself.  R8, R9, C3, C4, D3 and D4 are for preventing switch popping.

If you wanted to use my relay schematic to do true bypass switchless wah, you could copy the circuit from the Bad Horsie, parts
R1
LDR1
L1
U1 (only inverters on pins 13 & 12, 11 & 10)
R2
C2
D2

Use a CD4049 inverter instead of the 4069 (as Morley uses) and pin 10 would connect directly to the input of the relay as shown on the schematic on my page.  The indicator LED would be added to pin 10 with the cathode connected  to the pin, and the annode connected through a resistor to +9V.

Now to do this with a capacitive proximity sensor, we would have our proximity detector output a simple logic high or logic low signal and the rest is history.  As RG would put it "ASMOP" (A Simple Matter Of Programming)

[bancika]

Gee man, thanks for great explanation. Really appreciate it!.
Just few more small this:
what are those 3 leds with T1 and T2 in bad horsie for? And what about those 3 in series in your schematic going to PIC12F683 Vdd.
For a beginner optical sollution seems less complicated than proximity thing, so I think I'll go with that. I would use LDR only for switching part, I guess it's a bit more complicated for wah control because then there should be more holes with different sizes, right?
Also, if I'm about to incorporate morley's switching into my pedal where should I connect F1 and F2 to?
Thanks again

[Transmogrifox]

L1 is the LED that is hiding on the other side of the slitted cardboard/plasticy insert for the switching.  It's a diffused red LED.

One of the LED's with T1, T2 is the LED on the pedal that you see illuminate when the pedal is on.  The other one is the LED that supplies light to the LDR that controls the wah itself.  This LED is a very concentrated beam type.  It makes a round dot like a large laser on the cardboard/plastic insert.  For this one, there is a round hole in the insert.  As you move the treadle, the hole begins to aligh with the LED, and this beam of light is passed through to the LDR that controls the wah on the other side.  It works like a reverse lunar eclipse (to the extent that the analogy helps).  Being a concentrated beam, it provides a little more dependable relationship between pedal position and wah sweep.  I actually played on this to add an envelope follower to the Bad Horsie.  Instead of the LED being either off or on, as governed by the state of the on/off CMOS inverter, I connected the LED it the output of the envelope follower instead of the transistor.  Varying the pedal varies the "stop frequency", while the added sensitivity knob varies the sensitivity.  It works rather well.

If you're going to use active JFET switching, you'll want to add the input and output buffers like Morley does.  If you want true bypass circuitry, then use the relay driver circuit (not the microcontroller one) with the capacitor and CD4049's.  You could then drive the relay directly, and I think my schematic is clear enough about what are pedal inputs/outputs.

[bancika]

Your approach with relay seems very good, but the thing is I've never worked with relays and microcontroller, so I'm affraid not to screw up
Do I need to program microcontroller or it will work just like that? Also, which part of your circuit should I replace with R1-D4 switching circuit from morley?
Thanks again!

[Transmogrifox]

This is actually the schematic you want to look at:
http://www.geocities.com/transmogrifox/switchrelay.pdf

Electronic switching option is shown on the bottom half of the page.  This method doesn't require any programming knowledge.

As to the schematic you're referencing:  the microcontroller does need to be programmed.  You would need to spend a fair amount of time reading posts & interacting in the Digital/DSP section to get to where you could do this.  To answer your previous question, the 3 LED's are there to create a voltage drop of 4.5V.  The uC operating range is specified between about 3V and 5.4V, and will be damaged if the supply voltage on it is greater than 5.4V.  For those reading that intend to regulate voltage on a uC like that need to ensure that the supply voltage never exceeds about 9.6V for the pedal.

I'll have to look at one of the GGG wahs again to see what they show for switching, etc.  With the relay, you just hook it up like a regular mechanical DPDT switch as the schematic shows.

[tatems]

Heres an idea with the proximity sensor.



If you replace the Buzzer (BZ1) with a led, when you put your foot near the plate it should turn the led on which can then tigger a relay.
I haven't built this circuit before so i don't know if it would work, but its a start.

Tatems

[bancika]

At the moment, the best sollution seems to be combination of morley's LED switching and your relay "thing". I think I'll go with that.
Can some of relays here http://www.banzaieffects.com/home.php?cat=276 work for this?
Also, after pin 8 of U1 in morley's schematic, does it go directly to relay or it needs to go to CD4049 from your schematic?
Where should I put capacitor you mentioned. Also, where do Vdd and Vcc go on your schem?
HUUUUUUGE THANKS

[Transmogrifox]

You could connect direct from pin 10.  The Morley pedal uses a CD4069 for this application.  It doesn't have enough kick to trip a relay.  If you used a CD4049 instead, you could come directly off pin 10 (pinout is the same with the 4049 and 4069), and that's the beauty of it.

The relays from the page you referenced wouldn't do.  It really needs to be a latching type relay.  I think the 5V non-latching would work...but there's a chance it would be a little noisey...and it would kill your battery really, really, fast.  The latching relay only requires a little shot of current to make it snap, and then no more, so it's easy on the battery.

The capacitor is shown in the schematic.  Just pretend that the CD4049 output is pin 10 from the Morley schematic.  The NEC relays that I have specified have a printed strip that looks just like the diagram.  The schematic is almost a wire-for-wire representation of how you would physically connect it (as far as the relay goes).  For Vdd and Vss,  you'll want to consult a datasheet for the CD4049 for pinout information.  Just so you don't have to look, for both the CD4069 and CD4049, pin 1 is +9V, and pin 7 is ground (battery -).   

[bancika]

Do you know where can I find it (except for mouser, they don't ship here)

[Transmogrifox]

does DigiKey ship there?  How about Newark?  All-Electronics?  Allied?   PartsExpress?

These are the suppliers I'm familiar with.  Here's what you need in the relay:
5V single coil Latching
The rated tripping current should be at less than 20 mA.  The lower the better. It would be great if you can get one that switches at 10-15mA.  If not, then you'll need to used some of the unused inverters in parallel with the relay-driving inverter.

If you can find some other parts suppliers that will ship to you, then I can go looking to see if I can find an adequate equivalent relay in their stock.

If you can find somebody who carries NEC relays, you have it made.  You'll probably be able to get the exact one that I specified.

[victor nery]

Greetings,

Could anyone please repost the schematic? The links are broken. Thanks in advance.

Cheers

[R.G.]

Proximity switches are OK, but they tend to be touchy unless very, very well done. A simpler way might be to put a small switch like this:

under the treadle, and let that rounded part of the level stick up through a hole in the rocker's top. The lever makes it sensitive, longish throw, and relatively immune to abuse.

The switch can control an electronic switch like the CD4053, or a relay; or you can get a multiple-section switch in this format that can do DPDT.

[artifus]

stumbled upon this recently: http://www.ise.pw.edu.pl/~wzab/MIDI/pedal/index.html

[joegagan]

rg, you and i had the same thought. i have a dozen similar switches of slightly different  'leaf' etc  here that i haven't gotten round to.

here is phase one of a device i built to turn the wah or volume on when heel down is 1% off heel down. my approach was to sell it as an add-on to a wah pot, so i can sell more pots....( i know the roller is the wrong direction, this was first mockup)

[R.G.]

Nice work.

I messed with this whole "turn on the wah/volume" for a while. There are two styles: on when the foot is on the rocker, and on when you actually rock it forward. Both work, but they can be a pain depending on how the pedal is used. If the player wants to leave the rocker %^&*ed in a fixed position and take his foot off it, the "detect a foot" style is a problem. Volume pedals that did this would be a disaster; so would wahs if the player wanted to leave it in a middle position for voicing. But for ordinary "Polk Salad Annie" wah stuff, it's fine. The Univibe used the "rock forward to engage" style.

If I was doing the rock-forward-to-engage, I'd be horribly tempted to do it with a magnet and a reed switch.