[Al Skierkiewicz]

Jbot,
The 7805 series regulators have the center pin and the tab at the same potential, i.e. power supply common. It the Altoids can is going to be grounded, you can just bolt the tab directly to the can. A little heatsink goop will help in the tranfer. The way this works is a simple calculation on the drop and current for the regulator. If you are dropping 4 volts (9 volts in to 5 volts out) at 100 ma you are going to have .4 watts dissipated by the regulator. Not too bad. If you are dropping 7 volts (12 in and 5 out)at 1 amp then you have to get rid of 7 watts and that will cause you some problems with just the little can to get rid of the heat. You can always add a good heatsink to the bolt on the outside of the can to increase the amount of heat you can transfer to the air outside of the can. That way both the can and the heatsink will dissipate the heat. Remember that this family of regulators does have temperature compensation that will lower the output if they start to run hot.