The control of all the channels of this shield have to be done through the digital I/O pins 5, 6, 7 and 8 of the Arduino board where this shield is mounted on, anyway it is necessary an external 12VDC power source to correctly supply the relay coils. The 12VDC power presence is pointed out by the switching on of the red led PWR placed next to the corresponding teminal block.
An important characteristic of this shield is the presence of the XBee interface connectors that allow, through the use of the wireless XBee modules, a remote communication with the Arduino board where the Relay Shield is mounted on, making more easy the use of the shield in robotic applications, in industrial controls and in home automation projects.
During the programming of the Arduino board, the presence of the XBee module could interfere with the serial port signals; for this reason it has been implemented a switch (see Fig.1) to interrupt the connection between the Arduino board and the XBee module mounted on the shield. In normal mode the switch has to be moved into the RUN position, while during the programming of the Arduino board, it has to be moved into the PROG position. Because of the presence of this switch it won't be necessary to remove and insert constantly the XBee module at every changing operation of the Arduino sketch.