i would like to outline worst events that could occur while experimenting..
even when unwatched

john has most experience and could give information
part, causation, resulting behaviour

- diode fails: will act like a disconnection ?
- transistor fails: heats up.. will act like one wire or will act like a disconnection ?
- resistor (tigger) fails: acts like a disconnection
- wheat bulb (trigger) fails: acts like a disconnection

worst case:
instead of triggering, a constant dc curren would flow,
overheat coil and other parts..
weakest parts will burn through, acting like a disconnection...
cable isolation braise?
parts could catch fire?
batteries could warm up? explode?
batteries could get shorted?

a idea:
if i let the wheel unwatched..
i will attach a RPM counter (reed-switch, computation via arduino) and
if RPM is going below or above my rated value range..
the primary battery will get disconnected..
so it should take care enough, not to get in trouble/fire

how should the room surroundings be "designed".. no wood? stone? not flammable dish/basin...?