3 Sep
2006
3 Sep
'06
3:58 p.m.
My father built himself a board which was similar but
more elaborate:
he could select among (1) a small (7.5W?) light bulb, (2) a large
(100W?) light bulb, (3) a high-wattage heating element that was still
under the breaker trip current for that mains circuit (an iron, I
think), or (4) no limiter at all.
Another useful limiter (to repleace (3) in your setup is a 1000W tungsten
halogen bulb (e.g. one of those 'security lamps'. They're pretty cheap
now).
The advantage of light bulbs is the postive temperature coefficient of
the filament. THey have a low resistance when cold (and thus drop almost
no voltage, often a small device will happily run with a bulb in series),
but limit the current if there's a dead short.
-tony