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Topic: Need help with these potentiometers (Read 797 times)previous topic - next topic

mzzrrt

Mar 27, 2013, 06:48 pm
Hey guys, I have found several components inside an old Numark mixer, and I'd like to use them with Arduino.

I have a potentiometer, i measured the resistance and found out it gives minimum 16.6?, maximum 40.8K?. (between first and last pin).
How can I use it with arduino?
I'd like it to give me a value that goes from 0 to 1023.

I also have this other component, it's a slide potentiometer (NUMARK QC-45E).
it has 5 pins. i found out that the resistance changes between pin 1 and pin 3, and goes from 33? to 0.45M?.

do you think i can use it with arduino?

thanks!
i also attached pics

oric_dan

#1
Mar 27, 2013, 06:53 pm
Simple, just be darn sure the wiper does NOT go to ground!

http://www.arduino.cc/en/Tutorial/Potentiometer

majenko

#2
Mar 28, 2013, 10:11 am
Those 5-pin potentiometers are stereo audio volume control potentiometers.

They are typically a logarithmic taper, so you won't get straight readings from them, but the values will be more sensitive towards one end.

They contain two potentiometers in one casing, and one end of both potentiometer tracks are joined together to a "common" pin.

Once you have identified the common pin (on one I have it's at one end), and which pins are the two wipers, you can use it on the Arduino.

Identifying the pins is a little tricky.  You will find that

1. The resistance between two pins and a third pin will be static and the same (often between 1/5 and 2/5)
2. The resistance between two of the pins in 1 will be double the static resistance from 1 (that would be between 1/2)
3. The resistance between the third pin from 1 and the other two pins will vary between 0 and what was measured in 1.
4. The two pins from 3 will show variable resistance between one pin each from pin 1.

The arrangement on mine is:

1. Input A
2. Input B
3. Wiper B
4. Wiper A
5. Common

If that proves to be the same on your pot, then you can connect the two inputs (input A and input B) to +5V, and the common to ground.  The two Wipers can then connect to two analog inputs, and you will be able to read the values between 0 and 1023 - both inputs should read about the same.  Of course, you can connect just one Input and Wiper up if you just want one reading...

mzzrrt

#3
Mar 29, 2013, 10:19 am
Thank you majenko!
It works exactly as you told me.

I only connect:
pin 1 - 5v
pin 3 - analog in
pin 5 - GND

and it works like a charm.

What's the point of having 2 pots inside one, if they both provide the exact same output value?

thanks

majenko

#4
Mar 29, 2013, 12:11 pm

What's the point of having 2 pots inside one, if they both provide the exact same output value?

They are for stereo audio.  The two audio signals go in to one end of the pair of pots (where your 5V is), and they come out of the wipers attenuated by the same amount.

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