Ive recently completed a project in microcontrollers (my first project with uc's actually) and I built a power supply which gives me 12v and 5v dc. I use a transformer to step the voltage down to 12v AC from mains and then the 12v AC is converted to 12v dc using a bridge rectifier with a capacitor filter. From this point I take two outputs, one goes to a voltage regulator IC (LT7805) which gives me pure 5v dc. I still get 12v dc from the other output, but I also end up getting about 17v AC. Why is that? Is there anyway I can block the AC component and route it to ground?