“What do you do with the third pin?”, he asked.
“You can connect it to the middle pin if you want — or just leave it unconnected”, I replied.
“Huh?”
A potentiometer has three legs.
When you’re used to resistors with two legs, it might seem strange.
So, take a look at the following images:
Photo of a potentiometer
Potentiometer symbol
The two pins at the sides work as a normal, fixed-size resistor. If you have a 100k Ohm resistor, this value will be 100k Ohm.
Then you have the middle pin.
The middle pin is connected somewhere in between the two end points.
When you rotate the shaft of the potentiometer, the resistance between the middle pin and each of the end pins change.
Often, you only use two pins: The middle pin and one of the others.
That leaves you with an unconnected pin.
Often, the unconnected pin is connected to the middle pin.
But this doesn’t affect the circuit. It’s like connecting a resistor in parallel with a wire. Like I’ve done in this light-detecting circuit:
https://www.build-electronic-circuits.com/ldr-circuit-diagram/
The potentiometer is just one of the basic electronic components I explain in my eBook “Getting Started with Electronic”:
https://www.build-electronic-circuits.com/products/ebook-2nd-edition
Keep on Soldering!
Oyvind
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