Lightbulb police? (was RE: Anyone off to VCF-UK)

Tony Duell ard at
Sun Jun 6 13:15:18 CDT 2010

> 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 


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