#include <SoftwareSerial.h>

/*
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.

http://www.hobbytronics.co.uk/arduino-tutorial8-hall-effect
*/

// constants won't change. They're used here to set pin numbers:
const int hallPin = 4; // the number of the hall effect sensor pin
const int ledPin = 3; // 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);
}
}