6 Jun
2010
6 Jun
'10
11:15 a.m.
It's surprising how little voltage it takes to get
a glow out of a
lamp--a 120V incandescent will exhibit a visible glow on as little as
12V.
Yes, you're right.. I wasn't thinking too clearly last night, mainly
because my cat is very ill :-(
I have a set of copying lights (4 off 150W filament lamps) which I use to
illuminate PCBs, etc that I am going to photograph. First thing I did
when I got them was replace the switch so I could do series/parallel
switching. For focussing, eliminating shadows, etc, I have the lamps
running (2 in parallel) in series with (the other 2 in parallel), for
eactually takiung the photo, I have all 4 in parallel,
Anyway, in the first position, the lamps are quite bright, even though
they are running at half their rated voltage. Mind you, Since filament
lamps are a fair aproximation to a constant current load, in that state
each bulb would consume about 75W, so a total of 300W. And it's nowere
near as bright as a 300W mains bulb. Perhaps about the same as a 100W bulb.
As I said, an underrun bulb will probably last a long time, but it's not
efficient..
-tony