Hello all. I'm building a rocket staging timer with an AVR (naturally) similar to the one at perfectflite.com/catalog/miniT3.html. The one on that page appears to have a PIC on the bottom, judging by the locations of the Vdd and Vss pins, but that's not very relevant here, now is it? :)
Mine will have most of the same specs and features as that timer, except it won't be as small, and it will use DIP switches instead of a button to set the timer duration. The DIP switches will limit the range and precision of the timers, but I can live with that. Maybe in a future version I will use a single push button to set the timer.
I'm currently using an N-channel MOSFET for supplying high currents to the launch fuse (upwards of 2 amps). If you look at the attached schematic, you'll see the load (ignition fuse) is connected to the source of the MOSFET. I arranged it this way so the fuse will act as a grounding switch to test for continuity (the continuity test takes only a tiny fraction of an amp which is not enough to light the fuse).
Is the MOSFET connected right? Most schematics that I've seen with a MOSFET have the load connected to the Drain, rather than the Source, so I'm not sure if this will work as I hope it will.
Also, does anyone see any other issues, big or small, with the circuit? Any feedback is appreciated.
EDIT: fixed the link