Our 2 Channel 5V relay module comes with two on board 5V relays with all necessary pinouts. You can control two AC loads simultaneously using this module. Can be interfaced with Microcontroller and Arduino.
Note: Product color may vary as our stock rotates.
You should have used Opto-coupler and Metal Oxide Varistor on board !
Anyway, do you happen to have Shielded Ethernet Cable?
If anyone of you are having this kind of problems you may check the following sites, man !
http://arduino-info.wikispaces.com/RelayIsolation
http://arduino-info.wikispaces.com/ArduinoPower