Gentlemen - thank you for your help. I have one additional question I am having trouble with. I purchased a transistor kit and even had a PCB board fabbed based on the suggestion to use a 2N3906 transistor, so I'm pretty committed to this design.
Here is my issue. The transistor is (as I understand it) in a high-side configuration relative to the load, with the atmega output feeding the base through a 330Ohm resistor. What I'm finding is that when the ATMEGA output goes HIGH, the transistor does not allow current to flow. When I ground the base (or have the ATMEGA pin go LOW), current flows fine! This is the opposite of what I was expecting.
The good news is that using a 2N3904 in the same configuration seems to work fine, with output HIGH on the ATMEGA toggling my load on very nicely. I'm just flummoxed because this was not what I was expecting. Can anyone comment on this?
