Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!dali.cs.montana.edu!milton!whit
From: whit@milton.u.washington.edu (John Whitmore)
Newsgroups: sci.electronics
Subject: Re: krypton .vs. halogen, which is better?
Message-ID: <1991Apr25.024044.5654@milton.u.washington.edu>
Date: 25 Apr 91 02:40:44 GMT
References: <38610009@col.hp.com>
Organization: University of Washington, Seattle
Lines: 27

In article <38610009@col.hp.com> billp@col.hp.com (Bill Pherigo) writes:

>     What is the performance difference between halogen "flash light type"
>bulbs and krypton bulbs.  They both seem to use the same amount of power, but
>the halogen cost about 5 times as much as the krypton. 

	Standard flashlight bulbs are vacuum type, and are VERY efficient.
Their average lifetime is 9 hours.  Halogen bulbs last longer (2000 hours
is typical in home use), but run hotter (lose energy by heat conduction),
so could be presumed to be less efficient.  That presumption would be
incorrect, however, since there's a second difference: the halogen
bulbs run a higher filament temperature, and give off much whiter
light than vacuum bulbs.  Krypton bulbs similarly run a higher
filament temperature, but will not last as long (perhaps 100 hours,
however, a LOT longer than the vacuum bulbs).

	For my bike light, I purchased all three types of bulbs,
and tested them for light output and color.  The Krypton and halogen
bulbs both had much bluer output (vital for night vision; your eye's
rods are insensitive to red light) than the vacuum bulb.  The Krypton
bulb used more power than the halogen I used, and was accordingly
brighter (as well as more energy-efficient) than the halogen.

	And I ended up using the halogen, because it is probably more
reliable.

	John Whitmore