The other day I taking apart this old organ from the 60's (one of those furniture sized play organs they would have in theatres and things, all electric, no pipes), and I was looking at the volume pedal and noticed that it used an odd system to measure the pedal's position. Moving the pedal up and down pushes a small piston back and forth that has a small light bulb at one end. the light bulb on the piston is enclosed in a small cylinder which lets out into a small, closed off area populated with two photo-resistors that sense the amount of light coming from the bulb, depending on how far it is in the cylinder. When I wired it up to a breadboard, I noticed that the bulb is very dim, which helps with light accuracy, I guess.
I was messing around with it and when I wired the photo-resistors up to analog inputs on my Arduino Uno and read it with the serial monitor, it was actually pretty accurate, but because it is constantly spitting out values, I can't figure out how to turn the outputs into something useful. The numbers fluctuate heavily, but depending on how much the pedal is depressed, some numbers show up more than others, larger or smaller depending on what position the pedal is at. Because of this fluctation, I can determine what position the pedal would be at based on the numbers, but I cant imagine writing a script to read it and try and figure it out. I am turning the organ into a desk (thats another story) and would like to keep the pedal to do something cool, like change the volume of windows, but until I can figure out how to read the input from these photoresistors its pretty useless.
Any thoughts? Thanks!
Could you have a certain value equal a volume? Perhaps if you look at how the organ operated, you could see how it used the pedal, and give you an idea on how it used the pedal so you can create something based off of that.
Can you elaborate more about what numbers you are getting? If the pedal isn't moving, you should be getting the exact same value always. If not, I think you wired the arduino wrong
c4ooo wrote:
Can you elaborate more about what numbers you are getting? If the pedal isn't moving, you should be getting the exact same value always. If not, I think you wired the arduino wrong

I wrote the code so that it is constantly reading the analog input and then writing it to the monitor, with a 10 msec delay. Because it is the analog input of two different photo-resistors, even in a dark space it is going to have fluctuating numbers because of the nature of the sensor. I need to figure out a way to make it stay at one number when the pedal isn't moving.

Caleb_J wrote:
Could you have a certain value equal a volume? Perhaps if you look at how the organ operated, you could see how it used the pedal, and give you an idea on how it used the pedal so you can create something based off of that.

The ancient wiring of the circuit is just a mess of huge resistors and strange capacitor-looking things. I can see that the wires from the photo-resistors go through resistors before going elsewhere, but when I put the analog input through a similar resistor before going into the Arduino it does change much.
There are too many fluctuating numbers to be able to set it to one volume, it would constantly be changing with little correspondance to where the pedal is.
I don't know, as long as the amount of light stays the same the value that you read should not change. Try adding a 330 ohm resister between the analog input and ground.
Don't know if it works the same for analog input, but if you want to have input from a switch, you need to connect the switch input pin to ground through a ~330 ohm resister, else when the switch is in 'off', the pin will 'float' between 'on' and 'off' randomly. However when the switch is 'on' it will always be 'on'. Something similar probably happened with analog input too.
How sensitive are the photo resistors? If they are especially sensitive, ambient light could be screwing you up, even in darkness.
You would most likely need to filter/dampen the input to account for the fluctuations in your analog input sample.
Off topic but look at the timestamps of the above 3 posts
c4ooo wrote:
Off topic but look at the timestamps of the above 3 posts

wow
Crazy!

(And also will need to rule out signal noise as well).
Two photoresistors controlled by an incandescent lightbulb going up and down, controlled by a piston, controlled by a pedal...? To be honest, I'd just find the high and low voltages produced by the ideal version of that setup, and then replace the pedal circuitry with a potentiometer. Much easier to manage.
oldmud0 wrote:
Two photoresistors controlled by an incandescent lightbulb going up and down, controlled by a piston, controlled by a pedal...? To be honest, I'd just find the high and low voltages produced by the ideal version of that setup, and then replace the pedal circuitry with a potentiometer. Much easier to manage.

^This. Sounds like a rough Rube Goldberg machine to be honest.

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