Controlling AC/DC lamps using channel relay modules
A channel relay is a large mechanical switch. This switch is toggled on or off by energizing a coil. Wiring between the I/O control and the relay output does not connect with each other, so the MCU, which controls the I/O relay, is safe. For further information about how to use a relay, read the article available at http://www.circuitstoday.com/working-of-relays.
You can buy a channel relay module from your local electronics or online stores. The following are the online stores to get this stuff:
Sainsmart, http://www.sainsmart.com/arduino/arduino-components/relays.html
Sparkfun, https://www.sparkfun.com/products/11042
DFRobot, http://www.dfrobot.com/index.php?route=product/product&product_id=992
Amazon, http://www.amazon.com/
SunFounder, http://www.sunfounder.com/
LinkSprite, http://store.linksprite.com/
If you note a channel relay module, you should see some of the output pins, such as COM, N/A, NO, and NC, on the relay module body...