I'm working on my first Arduino project and learning quite a bit as I'm going. I would like to control a few CPU fans from the Arduino using an external power supply. I'm hoping that I can use a transistor or small relay that can be controlled by a digital output pin on the Arduino. It wouldn't have to be a variable control, just on and off. I already have the external power supply of 12V and 1A to power 5-6 fans. What would be the best transistor or relay to use?