I have a potentiometer of 10k and I connected it this way:

When I turn the potentiometer I change the resistance of the circuit but in the Arduino documentation they say that an analog pin in INPUT mode will have 1 megaohm resistance. So, for example, if I turn the potentiometer to the middle it will generate 5k of resistance + 1 megaohm of the analog pin it will result in a tiny, very tiny current. If I use U = R x I across the potentiometer it will be:

U = 5000 x 0.0000001

U ~ 0 across the potentiometer. So U will be 5 V at the analog input because there was no drop of voltage in the circuit. If turn the potentiometer all way up to 10k resistance the voltage in the analog input will also be 5 V because the voltage drop across the potentiometer is still really small.

I know that an analog pin in INPUT mode will read 0 V as 0 and 5 V as 1023. But as I showed you it should always read 5 V even when I turn the potentiometer all way up because the voltage is not being changed. I know I am wrong cause when I log the input pin it shows different values as I turn the potentiometer. So how does this work?

• Potentiometers have 3 pins. One for 5v, one for ground, and one that outputs the voltage in between (depending on the orientation of the knob). Nov 23, 2014 at 19:48

• This is incorrect. A `potentiometer` is by defintion a three terminal device. It forms its own voltage divider. The input impedance of the ADC, if substantially higher, has minimal loading effect. Your answer would be correct if the poster had a simple two terminal `variable resistor` rather than a potentiometer. Nov 23, 2014 at 3:18