Mini Reed Switch Module (KY-021)

The following sketch will turn on the pin 13 LED on the Arduino when the module detects a magnetic field. Place a magnet near the KY-021 to activate the reel switch.

int led = 13; // LED pin
int reelSwitch = 2; // magnetic sensor pin
int switchState; // variable to store reel switch value

void setup()
{
pinMode (led, OUTPUT);
pinMode (reelSwitch, INPUT);
}

void loop()
{
switchState = digitalRead(reelSwitch); // read the value of digital interface 2 and assign it to switchState

if (switchState == HIGH) // when the magnetic sensor detect a signal, LED is flashing
 {
digitalWrite(led, HIGH);
}
else
{
digitalWrite(led, LOW);
}
}