I have a push button wired to my Arduino but it seems to be triggering randomly.

I have one pin of the button connected to pin 2 on the arduino and the other connected to ground.

void setup() {

    pinMode(2, INPUT);

void loop() {

I expect it to print 1 continuously and go to 0 when I press the button down but sometimes it shows 0 even when I don't touch it.


When a button is connected in that configuration, the input is what's called floating, meaning it's not a 0 or a 1. When the button is pressed, it is connected to ground, so that's definitely a 0, but when it's not pressed down, we don't know the value of the pin.

Pull Up Resistor

We need to include what's called a "pull-up" resistor to pull the signal up to a logic 1 when the button is not pressed.

pull up resistor

Image from Sparkfun

What this means is when the button is not pressed, the Arduino reads a logic 1. When the button is pressed, the current flows through the resistor to ground and the Arduino reads a logic 0.

Internal Pull Up Resistor

The Arduino also has internal pull up resistors so you don't necessarily have to add an extra component to your circuit. There are a couple of ways to use this.

You used to have to do it like this:

pinMode(pin, INPUT);           // set pin to input
digitalWrite(pin, HIGH);       // turn on pullup resistors

Now we can do it simply in one line:

pinMode(pin, INPUT_PULLUP);

This enables the 20k pull up resistor on that pin. The input will no longer be floating when the button is not pressed.

Note: This only works when the other end is connected to ground.

  • 2
    It's worth noting that the same idea works for pull-down resistors too; i.e. the resistor normally pulls the pin low, but pressing the button brings it high. Obviously it has to be external though, as there's no internal pull-down on standard Arduinos. – Peter Bloomfield Feb 19 '14 at 23:16
  • I dunno if you evencheck arduino stack exchange now but I am unable to understand the pin diagram. I have push button, with one end having 5V, and the other end having my wire connected to arduino and a 20k Ohm resistor which is connected to ground. Still I am getting random value when the button is not pressed. When it is pressed, I always get 1 – Siddharth Agrawal Apr 16 at 17:35

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.