Hall sensor by Juan Guillermo (Coco) Gomez

A hall sensor is a magnetic field sensor, it can detect when a magnet is nearby. This example turns on a light (LED) connected to a digital pin when a magnet is near the Hall sensor

int ledPin = 48;  // onboard LED in the Wiring hardware (pin 48) 
int pinHall = 0;  // Pin for the Hall sensor
int pinLed = 1;   // LED that turns on if the magnet is near

void setup()
{
  pinMode(ledPin, OUTPUT);  // sets the digital pin as output
  pinMode(pinLed, OUTPUT);  // sets the digital pin as output
  pinMode(pinHall, INPUT);  // sets the digital pin as input
  digitalWrite(ledPin, HIGH);  //turn on onboard LED
}

void loop()
{
  if (digitalRead(pinHall) == HIGH)  // If a magnet is near the Hall sensor
  {
    digitalWrite(pinLed, HIGH);	 // turns ON the LED
  } else {
    digitalWrite(pinLed, LOW);   // if not turns OFF the LED
  }
}