Shield to control 6 relay, 6 digital input and 6 analog input with Arduino Duemilanove, Arduino UNO or Seeeduino. The digital inputs and relay outputs are equipped with an LED that indicates the status. The lines of I/O are connected to the Arduino through corresponding pin-strip pitch 2.54 mm. It gets its power directly from the Arduino module, which provides the 5 volt regulator derived from their contacts between the 5V and GND. The mini-relay Shield of work at 12 volts, so that the relays are working properly will have to connect the Arduino module with an external power supply can provide this voltage. The card can be used in many applications and in many ways. Find in this page a little sketch as to manage I/O via serial commands.
Input/Output Shield for Arduino – [Link]