rockiron101:
Should I get a heat sink for the 12V->5V regulator only powering the Ardunio and it's few sensors? Right now it only has a real time clock, few temperature/atmosphere sensors, and powers a couple relays.
It's the drop of 7V in the regulator that makes heat proportional to the current drawn. It won't kill the board, just waste power.
wolframore:
there are losses on the transformer too but it’s a good solution. Buck is not bad either and simplifies the conversion. Either way spec everything for full current and put in a safety factor.
A linear PS (has a transformer aka boat anchor) can be about 70% efficient while a switching power supply can be about 95% efficicent. Switching PS's have been used in PC's since the 80's if not before. It can pay to switch to a switcher even for small things, they're even cheaper to ship!
Besides the excess mass, one way to tell if the supply has a transformer is if it's warm even when it's not supplying power for days, linears really do suck and no, that's not counted in the efficiency of the supply but does count on the electric bill.
A 12V 1A wall wart runs maybe $3 or $4 (shop around) and a 3A output max (so use half or less) buck converter is < $3 or you could build a linear PS around a transformer at higher cost and weight.