Datasheet

So, let's start with power. We're using a barrel jack (http://adafru.it/373) that matches the

plug on our power brick (http://adafru.it/658). These jacks have three pins. The one on the

side isn't used here, it's just for detecting when a plug has been inserted. The other two pins

connect to the outside casing of the barrel plug, and the center pin. In the most common

arrangement, this outside shell is negative (ground) and the inner pin is positive.

It's really important to make sure your power supply voltage and polarity are correct. If

either is incorrect, you can damage your LEDs. If you have a digital multimeter handy, use

its DC Volts setting to test the voltage on the barrel jack before you start soldering.