Potentiometers - Basic info for DIY synthesizers

"A potentiometer is a three-terminal resistor with a sliding or rotating contact
 that forms an adjustable voltage divider. 

 1 = input

 

2 = wiper

 

3 = Gnd 

 

Total Resistance = R1 + R2

If only two terminals are used, one end and the wiper, it acts as a variable resistor or rheostat."
(wikipedia)

 In synths, usually terminal 3 is connected to ground.

They come in lots of shapes and sizes.
 Eg Slider, thumb, trim pots. 

Sliders are often called faders.

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 Trimpots come in lots of shapes too.
They are meant for fine tuning, and to be adjusted infrequently.

Trimmer Marking  Value

PR1        102         1K

PR2         503        50K

PR4         203        20K 

PR140     104       100K

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 There are two main types of pots:
1. Logarithmic  or audio (A)
2. Linear (B) 

Linear
The resistance between the contact (wiper) and one end terminal is proportional to the distance between them. ... ie the angle of shaft rotation is proportional to the resistance.
Used mainly for CV (control voltage) pots

Logarithmic 
The resistive element follows a logarithmic taper.
Used alot in audio pots.

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This is how you could set up an arduio Uno to measure the voltages from the wiper.

I'm using TinkerCad here for the simulation.

// set up variables
int myVoltPin=A2;
int readVal;
float V2;
 int delayT=250;


void setup()
{
  Serial.begin(9600);
}

void loop()
{
  readVal=analogRead(myVoltPin);
  V2=(5./1023.)*readVal;
  // converts to a voltage -- remember to place the decimal
  // points after the 5 & 1023 ... these may be floating points
  Serial.println(V2);
  delay(delayT);
}

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