Stereo Memory Man w/ Hazarai mod?

All about modern commercial stompbox circuits from Electro Harmonix over MXR, Boss and Ibanez into the nineties.
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DWBH
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Post by DWBH »

As a Stereo Memory Man w/ Hazarai owner, I have one complain: the lack of a preset footswitch. One might think it's not necessary, but it totally is.
It's a very very powerfull pedal, and it's a shame to only use one preset for one song. On my Ring Thing (which does have a preset footswitch) you can scroll through presets without having to reach down.

These pedals use an encoder to switch presets. Rotating encoder - full rotation (360º are divided through 20 steps). It has an SPST (momentary) switch as well, and three lugs for the encoder, so I'm assuming 8 bits ( :scratch: )
My thought is that if I can get a system that, electronically, (maybe with an arduino) mimics a rotator encoder (maybe a momentary switch which increments the position on the "encoder"), and solder that to the existing rotating encoder (overriding it) it "will" work.

Thoughts?

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DWBH
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Post by DWBH »

People are hacking Playstations, why shouldn't we hack Hazarais? :P

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Post by Hides-His-Eyes »

I'm sure it's electronically possible. Is there room to work there?
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Post by DWBH »

Not really, but maybe a small jack - or a hole for some wires to pass through the box - may fit, so that the extra circuitry would be inside an extra, external enclosure.

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Post by Hides-His-Eyes »

well your first job involves a multimeter and the encoder
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Post by DWBH »

I think I need an oscilloscope for the encoder. I need to "see" how the square waves are output through the various positions of the encoder, right?

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Post by Hides-His-Eyes »

I expect that each 'direction' represents a binary output and the change in these is processed by a uC to interpret rotation.
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Post by DWBH »

From what I quickly read on my multimeter, when it turns left, it produces a positive voltage between the two outer lugs, and when it turns right it's negative - or vice-versa, not sure.
On a second look I think it's a 2 bit encoder, the outer lugs have traces and two resistors in series connected to the rest of the circuit. I think the center lug is to some voltage reference - ground most likely.
I'll have to make a voltage divider on a jack so I can put this through a software oscilloscope. Santa hasn't brought me a real one yet :(

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Post by tonymcbony »

A mate of mine has actually done this.
IIRC he mentioned programming his own controller, and something about the voltage controlling the preset.

It worked just as you'd imagine, he had two footswitches, one to scroll up, one to scroll down, and hit both to save a preset.

I told him he should take it to market, because there are heaps of people that'd be interested. I'll see if I can point him to this thread.

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Post by DWBH »

Awesome!
It'd be great if he could chime in.

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Post by DWBH »

Haven't had much look figuring out the output pulses from the encoder through a software oscilloscope. Frankly, I ran out of pacience, so I basically started staring at the circuit board. Center lug is connected to ground.
Each outer lug is connected to a 10k resistor, an from there they both connect to a single pin on a small IC (5-pin I think), which has either PFN1 or PFNI printed. So both resistors connect to a single pin of that IC. It has two pins on one side (pins 4 and 5) and the other 3 on the other side. There are 3 capacitors near it.
Image
Looking at this image, the IC and capacitors I'm talking about are right next to the encoder, on the top left corner. Part numbers U11, C31, C32, C33.

Hopefully, this is the decoder circuit which just outputs a CW pulse and a CCW pulse to the microprocessor. This means that if one can recreate those pulses, it can trick the microprocessor thinking that the rotary encoder has been turned to either side.

I've tried looking for decoder circuits for rotary encoders, but I haven't found much, particularly with the two resistor tied together.

Any hints?

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Post by DWBH »

Although I can't remove the board and check the underside of it, I managed to draw this from the top layer. Ignore pin number 5 on that image, it doesn't exist in the real IC.
At first I thought there would be a resistor between pin 2 and the 10k resistor junction that measured 982 ohms, but this value is simply the two resistors in series (258+726).

Image

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Post by Hides-His-Eyes »

IC1 is unpowered? Have you got a code?
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Post by DWBH »

It's either PFN1 or PFNI.
Yeah, regarding power I didn't have time to trace the rest, but I'll try to get that done today hopefully.

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Post by DWBH »

Idle voltages (without turning the encoder):

Pin 1: -6.17v
Pin 2: 6.35v
Pin 3 : -3.35v
Pin 4: ground
Pin 5: 3V

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Post by DWBH »

Image
Added some knot markings, this one's not as confusing.

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Post by dodgypete »

tonymcbony wrote:A mate of mine has actually done this.
IIRC he mentioned programming his own controller, and something about the voltage controlling the preset.

It worked just as you'd imagine, he had two footswitches, one to scroll up, one to scroll down, and hit both to save a preset.

I told him he should take it to market, because there are heaps of people that'd be interested. I'll see if I can point him to this thread.
Hi Tony. I used a microcontroller to effectively to the same job as turning the encoder and and selecting a preset. I added a 1/4" trs jack and made a a pedal with 2 momentary footswitches.
It allows you to step up and down through presets. To save a preset you still need to hold the encoder button. The encoder still functions with the footswitch plugged in.
The encoder is basic with 3 lugs for the encoder part and 2 for the switch. The 3 encoder lugs are A, common and B. Common is tied to ground, A and B are pulled high with resistors .
When you turn the encoder A goes low, B goes low, A goes high, B goes high. So basically A leads B. Turn it the other way and B leads A. The switch contact switches low when pressed.
I soldered transistors across the back of these 3 contacts and used the microcontroller to switch them.
I powered the microcontroller from an existing 7805 regulator in the memory man.

I'm away from home until 7th August, but when i get back I can post more info and photos.

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Post by DWBH »

Wow, thanks dodgypete! Looking forward to it!
How about activating the preset? Because besides scrolling through the modes you have to activate the saved preset. Do you use an extra footswitch?

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Post by coldcraft »

very cool
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Post by dodgypete »

DWBH wrote:Wow, thanks dodgypete! Looking forward to it!
How about activating the preset? Because besides scrolling through the modes you have to activate the saved preset. Do you use an extra footswitch?
It just uses 2 footswitches. When you press up or down it's like turning the encoder then pressing it to select the preset for that mode. It happens very quickly. If you hold a footswitch it will keep stepping through modes until you let it go.
I'll also post the simple arduino microcontroller code that I wrote.

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