I am familiar with this diagram:But I can't seem to quite figure it out...
I googled it: http://translate.google.com/translate?sl=zh-CN&tl=en&js=n&prev=_t&layout=2&eotf=1&u=http%3A%2F%2Fhq-chn.cn%2FProductView.asp%3FID%3D186%26SortID%3D2&act=urlOn the photo you see that it is for 14V. The number "-112DM" seems to indicate that it is for 12V.This is a typical relay for in a car.Can you measure the current through the coil at 12V? I doubt that a 2N2222 can handle this heavy relay.
What's the trouble?[I thought you were getting some relay board for this deal.] http://arduino.cc/forum/index.php/topic,103055.0.html
That simple circuit will work for your application. An Arduino cannot supply the current needed to energize this relay. The transistor can. It acts like a switch to complete the circuit to energize the relay. What switches the transistor off or on is the signal from the Arduino pin.Relay power + would be power from the positive battery terminal and Relay power GND would be from your battery's negative terminal. This doesn't mean you have to run wires to the battery; it's just to say that the battery is the source of those two connections. K1 (written horizontally) is the coil of your relay (pins 85 & 86). S1 & 01 of the K1 written vertically are the 'switch' that turn your lights on or off. S1 & 01 are connections 86a & 30 of your relay. Diode D1 is necessary to prevent damage to the transistor when the relay goes from on to off. The resistor in the circuit limits the current coming from the Arduino so as to not damage it. The lower part of the diagram with all the GND connections is showing that the ground of the Arduino must be attached to the ground you are using to power the relay coil. Basically this circuit is a s follows: The output from the Arduino turns on the transistor, the transistor turns on the relay, the relay turns on your lights. By the way, I believe this relay can be considered a 'small' relay since a similar relay's data sheet indicates it consumes 1.6 watts which would be around 130ma @ 12V which the 2N2222 can handle.. - Scotty