Mutron Flanger dissection.

[armdnrdy]

it will maybe provide a decent jumping off point.

That's exactly why I requested this voltage. If I'm shooting for the high/low voltage measurements taken from your unit....I might as well set up the trimmer for a similar output voltage. I can try different LEDs, LDRs, and distances until I get close to the actual unit.

I gave the trimmer adjustment some thought and as you would imagine, Mutron wouldn't set this trimmer to "taste".
Mutron would have a calibration set point....but what would they be looking for?

One practical answer would be to set the pedal to emulate the frequency/sweep of the LFO.

I'm making good progress with the LED/LDR test board. It was my girlfriend's B-day last night so....I didn't get a chance to work on it. Tonight I should be finished with the routing layout.

[digi2t]

One practical answer would be to set the pedal to emulate the frequency/sweep of the LFO.

That's basically where I have mine set at. I figured it only made sense that the pedal should emulate the LFO sweep.

And a very Happy Birthday wish to your girlfriend, and many, many more.

[digi2t]

OK, finally got to repackage the unit, and get the voltages. There is no drift in the voltages within a 10 second period. They stay rock steady. Here are the voltages;

Z10 pin3 - 5.50v
PC1 - 5.50v
PC2 - toe down (LDR shuttered from LED) - 11.60v
PC2 - toe up (LDR open to LED) - 2.29v

[armdnrdy]

My girlfriend thanks you for the B-day wishes.

Okay, so no voltage change from LDR dark to 10 seconds dark! I did not expect that....but that's actually good....no slight automatic change in frequency at toe down. I'll have to take another look at the pedal circuit....something in there is keeping things stable.

Speaking of pedal circuit, here's the LED/LDR test board layout:



I decided to leave the LED in a set position and give the LDR four position options for test purposes.

You'll notice the two switches on either side. Those are close approximate positions solely for lower board size reference.

Starting this board has caused a lot of ideas about the full board and layout to "fly" around.  

[armdnrdy]

I finished the LED/LDR test board yesterday, and today is all about trying different LDRs, LEDs, and positions.

If I don't achieve satisfactory results with the LDRs I have, then I'll have to order more varieties and the testing will continue.

Here's a shot of the test board mounted in the Morley enclosure:

[digi2t]

 

Wow. Like someone once said, "That's how Skynet started!".

Kudos on the test bed. Keep us posted on the results. If you want, I also have some LDR's that I picked up from Goldmine a while back. Are there any tests that I can do here to see if they might be good for the circuit?

[armdnrdy]

Wow. Like someone once said, "That's how Skynet started!".

Kudos on the test bed. Keep us posted on the results. If you want, I also have some LDR's that I picked up from Goldmine a while back. Are there any tests that I can do here to see if they might be good for the circuit?

I had to google Skynet. 

So far I've had mixed results with the components I have at hand.
The Waitronys are....not usable. I tried LDRs I picked up from Ebay....closer but with issues. I have a Radio Shack LDR pack with five different varieties....shows some promise. I'm able to get the lower range (low two volt range) but I discovered that I'm having a problem achieving the higher range.
I believe that I'm getting light leakage from outside of the enclosure and slight illumination from inside from the LED.
I think I know what the tubes are all about!
Since the tube I fabbed won't fit comfortably inside the Morley enclosure, I'm going to try to isolate the LDR in a piece of black Papermate ballpoint pen tube.
I'll report back.
I don't know how you can help short of ripping the tubes out of your Flanger  and trying the different LDRs that you have.....but if you did that.....I for one would be very upset with you!!!  You've already been more than gracious with your time and using that awesome flanger as a guinea pig for the cause!! Let's leave it intact!!

[Ronan]

I would replace R69 with a trimpot to get the higher voltage range.

I can get 20M under a Morley pedal from a Waitrony, but that does not include light spill from an internal LED. Try putting some black tape over the shutter to see what max dark resistance (higher voltage range) you can get with the existing values for R69 and R70.

If you can't get enough range (range not voltage) you could add 2 resistors to Z10B to get some gain, but I don't think that will be necessary.

[digi2t]

Larry, here`s a trick that might help.

I had similar concerns about light leakage from the adjacent LED on the Talking pedal. My solution was to wrap the LED with a piece of heatshrink, and with a razor, carefully trim around the tip of the LED leaving a small porthole for the light to shine through. This prevents most of the light from radiating out from the sides.

[Gus]

Instead of the led LDR and opamp why not try a potentiometer and a few resistors?

The circuit fragment is an adjustable voltage divider that is buffered and conditioned to get a control voltage

Find the voltage range the real unit uses. 

Use ohms law and the available travel of a wha body volume control etc to select resistors to give you the voltage sweep
Connect the wiper to the input of the buffer/signal conditioner.

[armdnrdy]

Instead of the led LDR and opamp why not try a potentiometer and a few resistors?

The circuit fragment is an adjustable voltage divider that is buffered and conditioned to get a control voltage

Find the voltage range the real unit uses.  

Use ohms law and the available travel of a wha body volume control etc to select resistors to give you the voltage sweep
Connect the wiper to the input of the buffer/signal conditioner.

We are way beyond that idea! I've already committed to the purchase of a Morley optical volume pedal and the rerouting of the Mutron flanger circuit to fit inside the Morley enclosure.

When this build is finished and verified, I might try fitting this circuit in a Dunlop sized enclosure.

[armdnrdy]

I would replace R69 with a trimpot to get the higher voltage range.

I can get 20M under a Morley pedal from a Waitrony, but that does not include light spill from an internal LED. Try putting some black tape over the shutter to see what max dark resistance (higher voltage range) you can get with the existing values for R69 and R70.

If you can't get enough range (range not voltage) you could add 2 resistors to Z10B to get some gain, but I don't think that will be necessary.

I'll try these ideas when I get home from work.

[armdnrdy]

Larry, here`s a trick that might help.

I had similar concerns about light leakage from the adjacent LED on the Talking pedal. My solution was to wrap the LED with a piece of heatshrink, and with a razor, carefully trim around the tip of the LED leaving a small porthole for the light to shine through. This prevents most of the light from radiating out from the sides.

Hey Dino,

I tried this today and it helped a little. The pen tube enclosure on the LDR helped too but still not where it should be.

I have seven different LDRs on the way.

[digi2t]

I think these are the ones I have from Goldmine;

http://www.goldmine-elec-products.com/prodinfo.asp?number=G15177

I`ll have to check to be sure. Light resistance less than 1K, and dark resistance over 4M. Now that I think about it, they sound like they would work wel on a Trem Lune too, but I digress.

[Govmnt_Lacky]

I am assuming we do not have the measurements of light/dark on the REAL LDRs as to not damage the Mutron right?

Is there any way around it to get the true measurments? Has this been done already and I am going to be exposed for my laziness? 

[armdnrdy]

I am assuming we do not have the measurements of light/dark on the REAL LDRs as to not damage the Mutron right?

Is there any way around it to get the true measurments? Has this been done already and I am going to be exposed for my laziness?  

I calculated the LDR on/off resistance from the toe up and toe down voltages that Dino suppied, the known voltage divider resistances and the voltage.

But....those resistances are only good for the Mutron "tube" configuration. We're adapting this whole optical voltage divider circuit using the Morley enclosure with it's foot pedal shutter.

What we're really shooting for now is the up and down voltages.

[Gus]

Measure voltages at pin 7 of Z10B at both ends of the foot control travel
Z10B is a buffer
The two resistors 220k and the 1 meg with the LDR in parallel are a voltage divider.

one side of the travel will be the LDR at max darkness(max resistance) the other side max light(lowest resistance)

Knowing this you can solve for the LDR resistance range
the LDR is in parallel with 1meg
so what combined resistance in series with the 220k will give the max and min voltage values?
solve for the LDR resistance in parallel with the 1 meg for the answer

[armdnrdy]

Measure voltages at pin 7 of Z10B at both ends of the foot control travel
Z10B is a buffer
The two resistors 220k and the 1 meg with the LDR in parallel are a voltage divider.

one side of the travel will be the LDR at max darkness(max resistance) the other side max light(lowest resistance)

Knowing this you can solve for the LDR resistance range
the LDR is in parallel with 1meg
so what combined resistance in series with the 220k will give the max and min voltage values?
solve for the LDR resistance in parallel with the 1 meg for the answer

You mean like this?

[Govmnt_Lacky]

@Larry

Im betting the GL5539 is your winner! 

[digi2t]

I checked the Goldmine G15177 LDR's under my fluorescent lamp. At 12" distance, I get about 750 ohms, and over 30M in less than 10 seconds dark. They react pretty quickly.