I'm designing and building a breadboard power supply for myself, which draws power from an ATX-like SMPS (Mains in, single Molex plug out) via a 4-pin Molex connector. The design includes a switch to select either 12V or 5V output, but the only appropriate switch I can source is rated for a paltry 30mA!
Obviously I can't switch up to 2A with a 30mA-rated switch, but what can I do (that's cheaper than the ~$5-10 local vendors want for 2A-rated switches)? I thought of using an NPN transistor (see diagram, below), but in simulations that resulted in an unwanted voltage drop, and having the load connected to both emitters seemed to do weird things to the voltage.
(Note: Q1 & Q2 are generic NPN transistors, I've not considered part specifics yet.)
I thought of perhaps using a MOSFET, but decided that since I really don't know what I'm doing, asking for help was perhaps an even better idea.