best way to change voltage?

[daz]

It's a digital controller, not a signal if thats what u r suggesting. theres no guitar signal involved. I have no problem with the building end. I just want to know if anyone is familiar with the way these things operate with the sensor and whether i can remove the sensor and put in place resistance that i measure at the sensor at 2 different points in the pedal position and switch between them. i mean, is that all the sensor is, is a light sensing variable resistor?

[Enzo]

It is an LED, usually infrared, but sometimes visible, shining on a phototransistor. We'd have to see the circuit, as it alters the current conduction of the transistor.

So what is the damned thing, someone might even have the schematic?

[daz]

it's a fender EXP-1 expression pedal. It's not an opto because those use a light sensitive resistor and LED and this is what looks sorta like a chip with a glossy black surface thats apparently sensitive to movement. The pedal has a white strip of plastic about an inch long that swipe past it with pedal movement. Here's the sensor....

[Enzo]

Photo transistor, not photo cell.

See there are two devices side by side? One is an LED emitting light, the other is a photo transistor of some sort, I'll bet my lunch money. Light reflecting from one into the other is what the plastic strip controls.

There are two resistors and two semiconductor devices that I can see, but I also see plated through screw holes. making me think the other side of the board has tracery. Is there? In any case, you can draw out the schematic of this little board in a few minutes.

Digital cameras can often see infrared that our eyes cannot, so aim your phone cam or other digital camera you might have at this board while it is powered, and see if the smaller thingie looks lit up.

Or just measure for voltage drop across the smaller part, I bet the 560 ohm resistor is a current limit for it. Do you see an LED-like drop? Holding a white paper (business card?) right over them should reflect light into them, mesure for either resistance or voltage drop across the other device, whichever pins seem to connect somewhere. Now cover it with something opaque, does the reading change?

[J M Fahey]

it's a fender EXP-1 expression pedal. It's not an opto because those use a light sensitive resistor and LED

You should add: "the ones *I* know"

and this is what looks sorta like a chip with a glossy black surface

Plastic which is transparent to infrared may look like *dark* red or plain black to our eyes.

thats apparently sensitive to movement.

think how would it achieve that.

The pedal has a white strip of plastic about an inch long that swipe past it with pedal movement.

I think it´s a reflective distance/position sensor, which sends an infrared beam upwards, reads reflected light with an integrated phototransistor , that´s why it needs the reflective white plastic.
As opto as I ever saw.
You should ask Fender the schematic, and as a backup read any code printed on the IC, search its datasheet and suggested applications.
And tell us

[Jazz P Bass]

And please touch up the solder joints on the two left most wires.

[SoulFetish]

I think this is the best start to a thread I've ever seen in my life. LMAO.
I haven't even made it to the part that it's actually about yet.

[mikepukmel]

My friend Steve who used to repair old transistor and tube TV sets, back in the day, said: get 2 x 1000 foot extension cords. That'll drop the voltage. When you want to turn it on, just ask your neighbor to connect the two extension cords.

[Chuck H]

I just put a hose clamp on a standard extension cord and adjust the pressure.

[daz]

Then mounting holes are not part of the circuit on either side of the board. The small part DOES light up using my camera. As for voltage drops or resistance changes, i can't measure it. I can swipe my finger or anything past the sensor and it does change because i can hear the amp volume change. Anything i swipe by it changes that. But I tried but holding the probes on such tiny points and trying to swipe my finger by it while holding the probes but i just can't maintain contact while doing that so the readings are all just intermittent/wonky. I guess i'm gonna have to pass on this. Thanks for the help tho. Maybe they will add a firmware update that will make it do what i want because it does appear the firmware is not working exactly as it should. But for typical purposes i don't think they will care because no one pulls the circuit board and uses it out of the pedal, and when in the pedal the bug in the firmware doesn't matter. Long story that will probably bore you so i'll leave it at that. anyways, thanks for the info.

Photo transistor, not photo cell.

See there are two devices side by side? One is an LED emitting light, the other is a photo transistor of some sort, I'll bet my lunch money. Light reflecting from one into the other is what the plastic strip controls.

There are two resistors and two semiconductor devices that I can see, but I also see plated through screw holes. making me think the other side of the board has tracery. Is there? In any case, you can draw out the schematic of this little board in a few minutes.

Digital cameras can often see infrared that our eyes cannot, so aim your phone cam or other digital camera you might have at this board while it is powered, and see if the smaller thingie looks lit up.

Or just measure for voltage drop across the smaller part, I bet the 560 ohm resistor is a current limit for it. Do you see an LED-like drop? Holding a white paper (business card?) right over them should reflect light into them, mesure for either resistance or voltage drop across the other device, whichever pins seem to connect somewhere. Now cover it with something opaque, does the reading change?

[daz]

The mounting holes are not part of the circuit on either side of the board. The small part DOES light up using my camera. As for voltage drops or resistance changes, i can't measure it. I can swipe my finger or anything past the sensor and it does change because i can hear the amp volume change. Anything i swipe by it changes that. But I tried but holding the probes on such tiny points and trying to swipe my finger by it while holding the probes but i just can't maintain contact while doing that so the readings are all just intermittent/wonky. I guess i'm gonna have to pass on this. Thanks for the help tho. Maybe they will add a firmware update that will make it do what i want because it does appear the firmware is not working exactly as it should. But for typical purposes i don't think they will care because no one pulls the circuit board and uses it out of the pedal, and when in the pedal the bug in the firmware doesn't matter. Long story that will probably bore you so i'll leave it at that. anyways, thanks for the info.

Photo transistor, not photo cell.

See there are two devices side by side? One is an LED emitting light, the other is a photo transistor of some sort, I'll bet my lunch money. Light reflecting from one into the other is what the plastic strip controls.

There are two resistors and two semiconductor devices that I can see, but I also see plated through screw holes. making me think the other side of the board has tracery. Is there? In any case, you can draw out the schematic of this little board in a few minutes.

Digital cameras can often see infrared that our eyes cannot, so aim your phone cam or other digital camera you might have at this board while it is powered, and see if the smaller thingie looks lit up.

Or just measure for voltage drop across the smaller part, I bet the 560 ohm resistor is a current limit for it. Do you see an LED-like drop? Holding a white paper (business card?) right over them should reflect light into them, mesure for either resistance or voltage drop across the other device, whichever pins seem to connect somewhere. Now cover it with something opaque, does the reading change?

[Mick Bailey]

Whenever I get a 'not enough hands' situation I temporarily tack a couple of fine leads onto the solder joints and attach my meter to those via a couple of short clip leads.

Those phototransistors are usually connected internally to a collector-emitter junction. I think of them as the light controlling the base in my internalized 'flat-earth' model.

[mikepukmel]

I just put a hose clamp on a standard extension cord and adjust the pressure.

Chuck, what kind of torque wrench do you use on the hose clamp? Do you set the torque wrench to milli-micro-nano inch pound millimeters?

[J M Fahey]

Chuck, what kind of torque wrench do you use on the hose clamp? Do you set the torque wrench to milli-micro-nano inch pound millimeters?

Torque wrenches are for sissies.

We Macho men use our bare arms:

[Chuck H]

Those things are creepin' me out.