Potentiometer/code error

Official Hardware Mega Mega 2560
1

Attempting to make a simple code that gives the Voltage(V) of leg3 on my potentiometer (POT) (just a beginner ). However, when the POT reads near its min (0.1 ohm), my serial monitor reads 522 and at its max (10k), 1023. But, moving the pot from 0% to 85% of its range, returns 522 - 585, then instantly starts climbing to 1023 (586 -1023) for the remainder of its %.
Nothing is wrong with the breadboard or POT. Even tried using diff gnd pins, and A# pins. I put in the the code I used but I've already recoded it a few times. Does anyone know how to fix this situation or possibly explain what I'm doing wrong, it'd be greatly appreciated!

int readPin=A3;
float leg1=0;

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

void loop() {
leg1=analogRead(readPin);
Serial.println(leg1);
delay(100);
}
2

Welcome to the forum

Seeing a schematic of your setup would help

Is it a linear pot or a logarithmic pot ?

3

Please explain why you say that. You said you are a beginner (or at least I think that's what you meant to say, because I have never heard of a beginner pot).

Have you tried a different pot? Or a different breadboard? Or at least a different part of the breadboard.

Even though you haven't shared details of your wiring, I can immediately imagine a likely cause. You are using a breadboard with a non-breadboard-compatlble Arduino, a Mega. That forces you use use Dupont cables, and these are notorious for their unreliability. Have you tried testing out at least replacing each one you are using?

4

Does the breadboard have continuous power strips along its edges or do they have gaps in the middle ? If the latter then have you got connections to each side of the break ?

5 
Serial.println(leg1);

but your code says leg1

6

What kind of pot, linear, log?

7

Sounds like you have a "volume control" pot with a logarithmic taper that more closely matches the non linear response curve of human hearing, a type "A" pot. Look at the back of the pot and post the lettering there (if any).

8

What are the characteristics of a linear pot versus log pot, that @anon789456 can observe on the DMM?

9

At one end of the track a small movement of the pot wiper will produce a small change in resistance whilst at the other end of the track the same size of movement will produce a much larger change in resistance

10

Screenshot 2026-11-01 at 10.15.14 AM
Screenshot 2026-11-01 at 10.15.14 AM1942×1370 170 KB

11

Is this observable with a DMM? (no graphic output)

12

Log or linear, it shouldn't start from 522..

13

Not nearly as easily.

14
  • Set the potentiometer to it's mid position.
  • Measure the resistance between the wiper and each end.
  • For a linear potentiometer the two values should be similar.
  • For a logarithmic potentiometer, one value should be about ten times the other.
15

Describing pot-turns-versus output might help @anon789456
Mark five spots along the pot dial and map them...

        1  2  3  4  5  6
Linpot  0  1  2  3  4  full
Logpot  0  1  1  3  5  full
16

Yeah, I counted that as graphic output, albeit paper and pencil.

17

I don't know how the pins of you potentiometer are numbered, but I would have thought that the wiper would normally be designated as pin2.

The wiper is the one that I would have connected to the Arduino analogue input.