IntroductionRelay Shield employs high quality relay with four channels input and output. It can be connected to 250V/10A AC element or 24V/10A DC element to the maximum, therefore, it can be used to control lights, motors, etc. The modularized design makes it easy to connect to Arduino expansion board. The output state of the relay is shown by a LED for the convenience of actual application.SpecificationControl signal: TTL voltageActive at HIGH level Rated load:10A 250VAC10A 125VAC10A 30DC10A 28VDCRated Through-current: 10A(NO) 5A(NC)Max Switching Voltage: 250VAC 30VDCContact actuation time: ﹤10msDefinition of module pins:i) Pin 1- Pin 4----Controlling endii) Power supply (VCC)iii) Ground (GND)Connection Diagram Sample Codeint BASE = 2 ; // I/O pin connected to the first relay int NUM = 4; //total number of all relays void setup() { for (int i = BASE; i < BASE + NUM; i ++) { pinMode(i, OUTPUT); //set digital I/O pin as output } } void loop() { for (int i = BASE; i < BASE + NUM; i ++) { digitalWrite(i, LOW); //set digital I/O pin as ‘low’, i.e. turning off the relay gradually delay(200); //delay } for (int i = BASE; i < BASE + NUM; i ++) { digitalWrite(i, HIGH); // set digital I/O pin as ‘high’, i.e. turning on the relay gradually delay(200); //delay } }