I don't remember if the P5 has a chuff input or not... if it does, do your reed switch and magnet thing, trigger the P5 and you will probably need a small transistor circuit to drive the fan on a smoke unit, you could use an MTH, Aristo, or TAS unit.
The TAS unit already has a low current switching circuit, so you reed switch could directly drive the P5 and the TAS unit.
Regards, Greg
The TAS unit already has a low current switching circuit, so you reed switch could directly drive the P5 and the TAS unit.
Regards, Greg