YOU TUBE: Voltage regulator tutorial & USB gadget charger circuit http://www.youtube.com/watch?v=GSzVs7_aW-Y
http://www.youtube.com/watch?v=IjJWWGPjc-w
LM317 Adjustable Voltage Regulator Tutorial
The output voltage of the LM317T is determined by ratio of the two feedback resistors R1 and R2 which form a potential divider network across the output terminal as shown below.
Adjustable Regulator