Replacing optical sensors with pots?

DIY STUFF
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Hello everyone :slight_smile:

I’m trying to rehouse my zoom bfx-708 bass multi effect pedal, to make it a bit sturdier :slight_smile:

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The expression pedal works with this (unknown) 4 pin optical sensor. Using the diode mode of my multimeter gives me the following results:

Pin 1-2 Vf= 1.3 volt
Pin 2-1 Vf= 0.93 volt
Pin 2-3 Vf= 0.85 volt
Pin 4-3 Vf= 0.85 volt
Pin 4-1 Vf= 0.93 volt

Pin 2 and 4 are connected to ground.

Moving the pedal does not change the relative voltages, however, there is an empty variable resistor spot on the pcb. The 3 pads are connected together, but swing between 0.4 and 0.8 volts when moving the pedal.

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(You can see the 4 conductor ribbon cable and the VR connections in a triangle shape)

I’m trying to find a way to make this work with a potentiometer or external expression pedal.
Can it be done?
I was thinking to create a 0.4 to 0.8 volt reference and connect a pot as voltage divider between it.

Any help would be so appreciated :slight_smile:

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Numerous Zoom pedals use the same tech - and I’ve been wondering about a similar issue - did you sort this in the end? :slight_smile:

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Sadly not.
I use the pedal a lot so i put it back together and never really looked at it again.

I’m still interested in fixing it so i might take a look at it soon. Going to do some reading up on optical proximity sensors :slight_smile:

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