Already have the hardware design and firmware done, just haven't built a prototype yet. It will run a landing and taxi lamp with the ability to turn on one or both steady, or wig-wag them. Dead simple design, all the smarts are in the (also dead simple) firmware. Switches can be individual SPST (landing, taxi, wig-wag) or a single center-off SPDT (off, both on, wig-wag) or a couple of other permutations. The output MOSFETs are some fairly robust P-channel devices rated for 8A each -- and I've got pairs in parallel -- so I would expect the load handling to be pretty good even if it were encapsulated without heatsinks. Have not done the math yet to figure out the exact heat dissipation, but I like running stuff as cool as possible.
100 watt landing lights in a 12 volt system draw a little over 8 amps, so if you load-share the P-channel devices that should be running at half-rating IF they are matched even remotely well. The IRF 5305 has a spec'd Rds of 0.06 ohms so at 8 amps that would be a little less than 4 watts, and that particular FET is good for 30 amps so I'll not worry about paralleling them. But the 0jc is about 45C per watt, so some heat sink is going to be necessary. I like to use an existing chassis/pc board copper where I can for heat sinking.
Device selection is pretty wide, once the PCB layout is done. I like my MOSFETs over-rated so I've got the option of using newer, better or just cheaper and more readily available parts. If I were to build one now, I'd probably go with the BMS3003. Reasonably priced for what they are, RDS(on) of .0065 Ohm. I like paralleling the outputs for a couple of reasons. It lessens the likelihood of one failed part taking out the light(s), for one thing. Overkill is still pretty cheap.
