Make a Pushbutton Without a Resistor

Intro: Make a Pushbutton Without a Resistor

Need a pushbutton but don't have any resistors?

Using Arduino, 2 wires, one pushbutton, and one led, and Arduino, turn on and off an LED (or anything else you decide to turn on and off).

Instead of using the typical button schematic using a pullup or pushdown resistor, like the Fritzing image, here's a way to get around that, using Arduino, and declaring the button pin as a digital input, but then writing HIGH to that digital input pin. 

In the setup function:
pinMode(buttonPin, INPUT); 
digitalWrite(buttonPin, HIGH);
LED from pin 13 to ground

Wire it like the schematic in the photograph: 
Arduino pin 2 to the button pin. 
the other side of the button is wired directly to ground. 

Upload the following code:

//button wired pin 2 to ground directly

// constants used here to set pin numbers:
const int buttonPin = 2;     // the number of the pushbutton pin
const int ledPin =  13;      // the number of the LED pin

// variables will change:
int buttonState = 0;         // variable for reading the pushbutton status

void setup() {
  //initialize the serial port
  Serial.begin(9600);
  // initialize the LED pin as an output:
  pinMode(ledPin, OUTPUT);      
  // initialize the pushbutton pin as an input:
  pinMode(buttonPin, INPUT);  
  //initialize the buttonPin as output
digitalWrite(buttonPin, HIGH);  
}

void loop(){
  // read the state of the pushbutton value:
  buttonState = digitalRead(buttonPin);

  // check if the pushbutton is pressed.
  // if it is, the buttonState is HIGH:
  if (buttonState == HIGH) {     
    // since we're writing HIGH to the pin when, if it's HIGH , the button isn't pressed, as in there is no connectivity between ground and pin 2:
//so do whatever here that you want when the button is not pushed    
    digitalWrite(ledPin, LOW);  
    Serial.println("button not pushed ");
  } 
  else {
    // turn LED on, or do whatever else you want when your button is pushed
    digitalWrite(ledPin, HIGH); 
    Serial.println("button pushed");
  }
}

Comments

[cmahler1]

Thank you for the code that you wrote, it was very helpful to get us started on a school project. We are looking for a way to change the code to allow multiple independent push buttons and lights without resistors, would you be able to help us?

[rameshsheran2]

Thank you very much.This was helped me for my non-arduino simple project. :-)

[Radioactive_Legos]

A simpler way of enabling the internal pull-up resistor is to replace this: pinMode(buttonPin, INPUT);
digitalWrite(buttonPin, HIGH);

with this:
pinMode(buttonPin, INPUT_PULLUP);

[frank26080115]

your code comment "initialize the buttonPin as output" is wrong, you are actually enabling the internal pull-up resistor for that pin.

[frank26080115]

your code comment "initialize the buttonPin as output" is wrong, you are actually enabling the internal pull-up resistor for that pin.