Wah sequencer, Vanishing Point, help?

[Michael Allen]

Alright, I've got the sequencer bug too! I havn't built anything since I've been away at school, Christmas break is coming up and man I need to throw down something major. I think a wah sequencer should be in the works.... but I'm lost.

Ideally, I want something that works like an Ooh Wah (I dont want to start any trouble here). So that entails a Sequencer with 4,6,8 stages, random sequencing. But what will it control? A filter or a wah circuit? There's RG's random wah that controls a wah circuit, or his Sing Wah that controls a filter, or the Vanishing Point that controls a filter as well.

Now, none of these designs have the option to select stages, so I think that will have to be an add-in. The VP is attractive because of the Up/Down/Pattern function, but I need more than 4 stages. Thus something like the Random or Sing should do. The problem is with the random function. From reading the random article you should control the random with another separate sequencer?  Where does this connect to the left/right sequencer?

All these questions seem overwhelming so I think that as of now I'm going to go with the Left/Right 8 stage sequencer controlling the wah circuit. Now my real questions come with the design. The values for R and C that control the Schmitt triggers are chosen to suit certain purposes of the circuit or are they just standard values for Schmitt triggers in general?

The pots that control the frequency... are they different values or the same value just adjusted to different freqs?

And finally, like the Ooh and Seek, I would like LEDs to indentify each frequency. How could I control these?

Thanks a lot for any help guys, this is definately my biggest project and I'm feeling a little overwhelmed with all these questions. But I WILL get it done one way or another. What do you guys think?

[The Tone God]

I belive you are refering to what I now call "The Original Vanishing Point". I have posted a new Vanishing Point which has 10 stages, a stage selector, a manual reset, and sequence/random modes. Everything you asked for but the wha section (or whatever audio you want to control). It also only uses two ICs for the logic. Both can be had for under a buck each or you could ask for free samples from TI.

Check it out.

Andrew

[Michael Allen]

Oh my word, I didn't know you had finished this. Checking it out right now!

[The Tone God]

I wrote an article explaining the operation. Feel free to post any questions and if you do build it send me/post a build report. I would like to know how well it works for others.

Hope you enjoy it.

Andrew

[Michael Allen]

What did you use for the optocouplers? Just various LEDs with photocells? Any reference numbers from distributors?

I think this is what I'll put together! Who needs to go up/down anyway? And especially since you already put together a layout!

[The Tone God]

What did you use for the optocouplers? Just various LEDs with photocells? Any reference numbers from distributors?

Yeah I just make my own optocouplers. I can then select the LDR and LED based on what parameters I want. For the HF clocks's optocoupler you want it to go as low as possible and not too high. I belive the LDR I used was in the range of 100 ohms to 1K. The effect optocoupler will depend on what audio circuit you want to use. I would assume at top of 100K for a standard wha circuit and probably as low as you can get it down. For the LEDs in the optocouplers I use green LEDs with roughly a 100-150 mcd output which would be most companies' "high brightness" LED.

Let me see if I can dig up some numbers later tonight.

I think this is what I'll put together! Who needs to go up/down anyway? And especially since you already put together a layout!

LOL. I will say the layout is not tested but I think it will work. Its even easy enough to perf too if you prefer that.

Andrew

[Michael Allen]

Andrew, on the layout the sequencing numbers do not line up with the pins given in the schematic. I'm a little confused here. Also, how do you connect up the reset and stage select switches?

[The Tone God]

on the layout the sequencing numbers do not line up with the pins given in the schematic. I'm a little confused here. Also, how do you connect up the reset and stage select switches?

On the schematic in the article the number outside the box representing the IC are the pin numbers which line up to the layout. The numbers inside the box are the pins' output/name. Yes there is alittle wire jumping that has to occur since the outputs are scattered about the IC. I belive the numbers on the layout represent the output stage number in the sequence so for example output number 0 is at pin 3, output number 2 is at pin 2, output 3 is at pin 4, etc.

The switches are wired as in the schematic so the stage selector has one of each it's poles wired to the output pin of the stage past where you want it stop at before the LED. The switch itself is a SPDT ON-OFF-ON switch which means it has a center posistion that is off/unconnected. The center off posistion will cause the sequencer to go through all ten stages. Each other position will select the number of stage you want. In the schematic I've set it to 4 and 8. You can choose whatever you want.

The reset switch just goes in series with the stage selector. A standard SPDT ON-ON switch. This could be a pole on a 3PDT footswitch so when you bypass the effect the sequencer sits at stage one or you can do an individual switch and reset on the fly. If you don't want the reset just leave it out and wire the stage switch directly to the reset pin.

Andrew

[Michael Allen]

Do you have any suggestions for the Pot values?

Also, with the reset pin that goes to Vcc. Is this Vcc(+) or Vcc(-)? Different people notate differently. When the reset switch is set to Vcc what exactly happens? It doesn't sequence right? You'd have to switch it back to the stage pole. That way you connect the reset to a 3pdt and can select stage when the 3pdt is on, and Vcc (non sequencing) when the 3pdt is off. Right?

[The Tone God]

The pot values depend on the LEDs you use. So there is not a fixed value. I suppoesed 100K would deal with most situations but it could be as low as 10K depending on your parts.

On the topic numbers I don't think Mouser is carrying photo resistors anymore.

Digikey carries a 3K-11K photo resistor which could be good for the HF clock and a 10K - 100K which could be used in the wha circuit.

PDV-P8001-ND (3K - 11K photo resistor)
PDV-P9007-ND (10K - 100K photo resistor)

Smallbear also has optocouplers although I don't know the specs for all of them.

I'll do some quick playing around later to see if I can give some okay range of values.

Also, with the reset pin that goes to Vcc. Is this Vcc(+) or Vcc(-)? Different people notate differently. When the reset switch is set to Vcc what exactly happens? It doesn't sequence right? You'd have to switch it back to the stage pole. That way you connect the reset to a 3pdt and can select stage when the 3pdt is on, and Vcc (non sequencing) when the 3pdt is off. Right?

Vcc is posistive on the power supply (+). When the reset pin is set high, either by the manual reset switch or through the stage selector, the sequencer goes back to stage one and will start counting again from there when the reset pin is either set to ground or left open. The 3PDT scenario you describe sounds correct.

Andrew

[Michael Allen]

So when the reset is on Vcc it stops sequencing?

[The Tone God]

Yep. When reset goes high the sequencer goes back to one and stay there until the reset pin is disconnected.

I just did alittle testing. The 3K - 11K photo resistor should be okay if you use a timing cap of less then 470pf. In the schematic its 0.01uF. I would go with something even less to be safe say 100pf. That should keep the HF clock out of the audible range.

I think a pot around 50K for the stages will work. You can change the 1K resistor at the end to dial in a range you like or if you decided to use a different size pot. These values were tested on some fairly bright LEDs.

I haven't tried any of these values in the whole circuit yet. I just quickly tested each section by themselves.

Andrew

[Michael Allen]

Andrew man, thanks for all your efforts! This is coming together man, I've almost finished my list at Digikey.

So, the pots value depends on the LED. What charateristic of the LED determines a good value? Right now I'm looking at 67-1102-ND a Lumex High Eff Diffused 5mm. 50k pots still sound good? I'm looking at the CT2267-ND for the pots. I'm going to try and line up a ZVex-esque line of pots across a 1590BB with an LED underneath. Might need to go with a smaller LED?

Anyways, just wondering how to determine the pot based on the LED. Thanks for your help Andrew!

[The Tone God]

Andrew man, thanks for all your efforts! This is coming together man, I've almost finished my list at Digikey.

No prob.

So, the pots value depends on the LED. What charateristic of the LED determines a good value? Right now I'm looking at 67-1102-ND a Lumex High Eff Diffused 5mm. 50k pots still sound good? I'm looking at the CT2267-ND for the pots. I'm going to try and line up a ZVex-esque line of pots across a 1590BB with an LED underneath. Might need to go with a smaller LED? Anyways, just wondering how to determine the pot based on the LED. Thanks for your help Andrew!

How much current the LED needs will determine the pot value. Look up the spec for the LED and check out the mA it needs then use ohm's law with 9v. That will give you the limit resistor (don't forget both LEDs in series) then figure out how much current you want to drop throw that into ohm's law to get the pot value. I just eyeball these things.

Don't forget your optocoupler LED. Make it bright and add its current to the indicator LED when calculating.

I would use a 3mm (T1) LEDs as I think 5mm will be a bit big. Those pots should be okay. Be aware of how you mount those pots. They don't have mounting hardware. If you do a board make sure it doesn't hit anothing inside the box that could short it. I just CADed the box and you will only be able to fit 10 pots across in the space of a 1590BB.

Andrew

[Michael Allen]

Well wait.... If the Pot is just to control the LED voltage, do you set each pot differently to get a sepearate sound? Technically, how am I going to use this thing?

[The Tone God]

The pot controls the amount of current going through both LEDs. The indicator LED and the optocoupler LED. As the sequencer goes through each output the pot that is connected to the stage is selected thereby control the brightness of the LED in the optocoupler which changes the value of the LDR.

Andrew

[Michael Allen]

So i set each individual pot to a separate brightness in order to get a different sound?

[The Tone God]

So i set each individual pot to a separate brightness in order to get a different sound?

Yep. Thats how each pot equates to a different sound/setting. Its like having ten wha pedals that you switch though. Each pedal can have its own setting.

Andrew

[Michael Allen]

Ah, but now. What to drive? Is this just feasible for just a wah circuit with a resistor to ground?

[Michael Allen]

I decided on using the Morley Power Wah, since there was a pcb for it in the Schematics 2 section. This should work out swell. I'm almost finished with a CAD drawing of the box layout (2D only, I can't tackle 3D) and it looks like it'll do well in a 1590BB.

Thanks for your help Andrew!