Push Buttons — SIK Circuit 5

Use two push buttons for digital input. Learn about digitalRead(), pull-up resistors, and boolean logic (AND, OR, NOT) to control an LED.

Instructions

Parts & Introduction

Push buttons are the simplest digital input. This experiment uses two buttons with an XOR logic gate: the LED turns on if you press either button, but turns off if you press both. You'll learn about digitalRead(), pull-up resistors, and boolean logic.

Parts Needed

1x Arduino Uno + USB cable
1x Breadboard
2x Push Buttons
1x LED (any color)
1x 330Ω Resistor
2x 10KΩ Resistors (pull-ups)
7x Jumper Wires

Hardware Hookup

Wiring Instructions

Place both push buttons across the center canyon of the breadboard.
Button 1: Connect one pin to GND. Connect the opposite diagonal pin to Arduino Digital Pin 2. Add a 10K resistor between Pin 2 and 5V (pull-up).
Button 2: Connect one pin to GND. Connect the opposite diagonal pin to Arduino Digital Pin 3. Add a 10K resistor between Pin 3 and 5V (pull-up).
Connect LED positive leg to Digital Pin 13, negative leg through 330Ω resistor to GND.

Note: The pull-up resistors hold the input HIGH when the button is not pressed. Pressing the button connects the pin to GND (LOW).

Arduino Code

Open the Arduino IDE and upload the following sketch to your Arduino board.

push_buttons.inoarduino

/*
SparkFun Inventor's Kit
Example sketch 05 — PUSH BUTTONS

Use pushbuttons for digital input.
LED on if pressing button 1 OR button 2, but not both (XOR).

Hardware connections:
  Button 1: one pin to GND, diagonal pin to digital pin 2
            10K pullup resistor between pin 2 and 5V
  Button 2: one pin to GND, diagonal pin to digital pin 3
            10K pullup resistor between pin 3 and 5V
  LED: positive to pin 13, negative through 330 ohm to GND

This code is completely free for any use.
*/

const int button1Pin = 2;
const int button2Pin = 3;
const int ledPin = 13;

void setup()
{
  pinMode(button1Pin, INPUT);
  pinMode(button2Pin, INPUT);
  pinMode(ledPin, OUTPUT);
}

void loop()
{
  int button1State, button2State;

  button1State = digitalRead(button1Pin);
  button2State = digitalRead(button2Pin);

  // XOR logic: on if either pressed, off if both pressed
  if (((button1State == LOW) || (button2State == LOW))
      && !
      ((button1State == LOW) && (button2State == LOW)))
  {
    digitalWrite(ledPin, HIGH);
  }
  else
  {
    digitalWrite(ledPin, LOW);
  }
}

Test & Experiment

What You Should See

The LED turns on when you press either button individually. It turns off when you press both buttons simultaneously (XOR logic).

Troubleshooting

Not responding: Push buttons are square — it's easy to put them in the wrong orientation. Try rotating 90°.
LED always on or always off: Check the pull-up resistor connections. Without them, the input pin floats and reads random values.

Experiments to Try

Change the logic to AND (both buttons required) or simple OR.
Use the buttons to control an RGB LED — one button for color, one for brightness.
Try using INPUT_PULLUP mode to eliminate the external resistors.

Materials

•SparkFun Inventor's Kit - V3.2 - 1 kitNOK 999.20
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•Arduino Uno R3 - 1 piecePlaceholder
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•Breadboard - 1 piecePlaceholder
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•Push Button - 2 piecessNOK 11.20
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•5mm LED - 1 piecePlaceholder
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•330 Ohm Resistor - 1 pieceNOK 24.00
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•10K Ohm Resistor - 2 piecessNOK 24.00
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•Jumper Wires - 7 piecessNOK 39.20
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Tools Required

Computer with Arduino IDE

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