Arduino UNO Tutorial 11 - Hall Effect Switch

Arduino UNO Tutorial 11 - Hall Effect Switch

Ok, this is an easy one to make. We are going to use a hall effect switch to turn the Arduino UNO's built-in led on and off with a magnet.

We will be using the Allegro Microsystems A1120EUA Hall Effect Switch

  • Connect pin 1 of the switch to the Arduino +5V supply (red wire)
  • Connect pin 2 to 0V (black wire)
  • Connect pin 3 to Arduino input pin 12 (orange wire)

A pull-up resistor is required between pin 1 and pin 3 to pull-up the switch's output to +5V.

When the switch detects a magnet, it will pull it's output pin low, which we can easily detect on the Arduino board.


Arduino UNO and Hall Effect Switch

Here is the Arduino sketch

 Hall Effect Switch
 Turns on and off a light emitting diode(LED) connected to digital  
 pin 13, when Hall Effect Sensor attached to pin 2 is triggered by a magnet
 Hall effect sensor used is the A1120EUA from Allegro Microsystems
 This example code is in the public domain.

// constants won't change. They're used here to set pin numbers:
const int hallPin = 12;     // the number of the hall effect sensor pin
const int ledPin =  13;     // the number of the LED pin
// variables will change:
int hallState = 0;          // variable for reading the hall sensor status

void setup() {
  // initialize the LED pin as an output:
  pinMode(ledPin, OUTPUT);      
  // initialize the hall effect sensor pin as an input:
  pinMode(hallPin, INPUT);     

void loop(){
  // read the state of the hall effect sensor:
  hallState = digitalRead(hallPin);

  if (hallState == LOW) {     
    // turn LED on:    
    digitalWrite(ledPin, HIGH);  
  else {
    // turn LED off:
    digitalWrite(ledPin, LOW); 

Here is a video of it in action

Tutorial 10 - LCD

Tutorial 12 -

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