3.3v to a small transistor to switch 12v to a mosfet to switch the lights.
except I'll have to hold the output pins high to have the lights off.
This circuit should accomplish what I want, except I'll have to hold the output pins high to have the lights off. I imagine this is fine, except in my head it "feels" wrong. Like I'm wasting power or wearing out outputs since these lights will be off 99% of the time.
If you only want the LED to be on when the arduino output pin is high,
then try a modification on the first circuit.
The IRF510 may only be rated low on current depending on how much the LEDs draw.
Absolutely no point, you are not wasting electricity it is the way it works.
No matter what you do with the first circuit you will never be able to switch 12V with it because it is an emitter follower and so the voltage on the emitter can never be greater than 3V3 - 0.7 = 2.6V. This is not enough to turn a FET on.
That sentence makes no sense at all.
When the NPN is turned on, it should provide a flow path for the 12v to the gate, possibly charging it to ~11v.
As to your not understanding the statement, well you met my expectations on that point.
could I connect each gate, drain, and source, or is this bad?
Can I just replace my N-channel mosfet with a P-channel and move the light assembly to between the drain and ground