This Relay Shield for Arduino acts like a switch. It is commonly used to control anything over 5V such as lamps, water pumps and garage doors. 

One of the most interesting projects for your boards is perhaps being able to control High power devices like Lamps, water pumps, garage doors and so on. But interfacing with high power and AC is quite a dangerous task when building the circuitry. Relays allow for interfacing an external electrical circuit like a switch. With relays you can now connect external circuit or devices directly to your Arduino.

This Arduino Shield is a completely newly designed that is able to control 4 relays at a time. The max switching power DC 90W or AC 360VA gives direct control by Arduino Uno/DFRduino controllers through digital I/Os with external 9V supply. With built-in Xbee socket, it can be wireless remote controlled via Xbee/bluetooth/WPM.

This arduino relay shield is an ideal solution for home automation and robotics applications.

NOTE:The Arduino board requires an external power supply to drive the xbee module and relays.

Warning:Pay special attention to the voltage that is over 38 volts. 

Project 1: IR Home Automation based on DFRobot's Relay Shield

Materials:

• Arduino UNO Rev 3

• 4 Channel Relay shield

• IR Kit for Arduino

• Compatible with Arduino UNO Rev3
• Each Relay has its own test button to test the connection
• Standard DFRobot 3 Pin out
• XBee I/O direct control

• Compatible with Arduino Rev3
• 4 buttons to test module
• LED status indicator of relay
• Support Xbee IO directly control
• Xbee socket for wireless communication
• Selectable digital IO pin for control(Default digital 2,7,8,10) 
• 6 channels Analog IO & 13 channels Digital IO 
• Up to 4 Relay with photo-coupled circuit
• Contact Rating  3A AC 120V / DC 24V
• Max Switching Voltage  AC 240V / DC 60V (Less than 38V is recommended)
• Max Switching Current  5A
• Max Switching Power  AC 360VA / DC 90W
• Electrical Life (Min)  100,000 Operations
• Mechanical Life (Min)  10,000,000 Operations
• Safety Standard(relay)  UL cUL TUV CQC
• Coil Working Voltage  9VDC
• Working temperature  -30℃ to +85℃
• Working Humidity  40% - 85%
• Size:95x65mm

• Wiki (Relay Shield for Arduino V2.1)
• Schematics
• Board Layout
• Sample code
• HJR4102 datasheet

Package Includes:

• 1 x Relay Shield for Arduino V2.1   
• 2 x Nylon stand-off with screw