I am making an external power supply for a Arduino and xbee. Attached is the schematic. Can someone input on the goods, bads, or changes that need to be made. The plan is to minimize the Arduino by using just the Atmel chip and crystal after prototyping. For prototyping it will have 2 opto-isolators PS2501-4A-ND, Arduino UNO, Level Logic Converter BOB-08745, Xbee series 2. Among other resistors, capacitors, and diodes. The optos are probably not necessary but are cheaper/easier/neater than using transistors for 8 inputs from +12. The power (+12) is from 12v automotive so can swing 11v-16v maybe more. I am looking for a clean protected +5v and +3.3v with minimal heat sink. I’m hoping the 12v regulator will share some “heat” that the 5v and 3.3v would have had to do with out it. Overkill is not a bad thing in my mind, considering the input voltage.