Buy this sensor on Amazon with the 37 in 1 kit

When the key is pressed the build in LED on pin 13 will be turned off.

Connecting to the Arduino

• Pin – = GND, connect to GND of the Arduino
• Pin (middle pin) +5 v, connect to Arduino +5
• Pin S signal, connect to Arduino pin 10

Example code

int Led = 13 ; // define LED Interface
int buttonpin = 10; // define the key switch sensor interface
int val ; // define numeric variables val
void setup ()
{
  pinMode (Led, OUTPUT); // define LED as output interface
  pinMode (buttonpin, INPUT); // define the key switch sensor output interface
}
void loop ()
{
  val = digitalRead (buttonpin); // digital interface will be assigned a value of 3 to read val
    if (val == HIGH) // When the key switch when the sensor detects a signal, LED flashes
  {
    digitalWrite (Led, HIGH);
  }
  else
  {
    digitalWrite (Led, LOW);
  }
}