KY-021 DC 3 V-5.5 V Mini Magnetic Reed Sensor Module  Reed module and the interface comes with digital 13 LED build a simple circuit to produce a Reed warning lamp 13 comes with digital interfaces of the LED， the Reed sensor access number 3 interface， when Reed sensors Sensed a key signal， LED lights， otherwise off. <br>  <br> Features:  <br> 1. Mini magnetic reed Sensor modules<br> 2. Fixing box hole<br> 3. Operating voltage: DC 3 V-5.5 V<br> 4. Size:18x14mm<br>  <br> Routines source code: <br>  <br> int Led = 13 ;\/\/ define LED Interface <br> int buttonpin = 3; \/\/ define the Reed sensor interfaces <br> int val;\/\/ define numeric variables val <br> void setup() <br> { <br> pinMode(Led， OUTPUT);\/\/ define LED as output interface <br> pinMode(buttonpin， INPUT);\/\/ output interface as defined Reed sensor <br> } <br> void loop() <br> { <br> val = digitalRead(buttonpin) ;\/\/ digital interface will be assigned a value of 3 to read val <br> if(val == HIGH) \/\/ When the Reed sensor detects a signal， LED flashes <br> { <br> digitalWrite(Led， HIGH); <br> } <br> else <br> { <br> digitalWrite(Led， LOW); <br> } <br> }<br>  <br> Package includes:  <br> 1 x KY-021 Mini Magnetic Reed Sensor Module