Arduino seems to pick up excessive noise

Other Hardware General Electronics
1

I wrote this simple program to diplay values through the serial connection when (and only when) the wiper of a potentiometer is rotated.

void setup(){
  Serial.begin(9600);
}

void loop(){
  int first = analogRead(3);
  delay(50);
  int second = analogRead(3);
  
  if (first != second){ //i.e if the value has changed
     int mapped = map(second,512,1024,3,250); 
    Serial.println(mapped);
  
  }
}

However, the arduino seems to be picking up a LOT of noise and therefore, continuously spits out values, even when the pot is not being rotated.
My circuit is as follows

Potentiometer terminal 1 --> arduino 5V supply.
Potentiometer wiper terminal --> Arduino analog in 3
Potentiometer terminal 3 --> Arduino ground

What's wrong? (If I remember correctly, I have used the same program before.. so that makes it even more puzzling. )
EDIT: The 3 to 250 in the map statement was just an arbitrary combination..

2

No pinMode() in setup?

3

I thought that pins were set to input by default. Anyway, I set A3 to INPUT but it didn't work..

4

Could it just be an imprecise pot? What's the variance between first and second? It may just be one, which is an error of less than 0.1%. I'm not certain the A/D circuit is that real-world accurate.

5

yes.. it's a difference of a about 1 to 5..

6

Hm.. Looks like a suitable fix would be to have a threshold for the difference between two adjacent readings. What kind of value should I have for the threshold?

7

What value of pot are you using? It should be no greater than 10K.
A 0.1uF capacitor from analogue input to ground also often helps.

8

No pinMode() in setup?

It's being used as an analogue input; there's no need for a pinMode.

9

Grumpy_Mike:
What value of pot are you using? It should be no greater than 10K.
A 0.1uF capacitor from analogue input to ground also often helps.

The pot is a 10K one.. I had the same problem with a 1k one as well. However, the difference of 1 unit is about 4.8 millivolts.. That shouldn't be too much of a problem. I'll try your capacitor solution too..