Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!cs.utexas.edu!uunet!portal!cup.portal.com!Sullivan
From: Sullivan@cup.portal.com (sullivan - segall)
Newsgroups: comp.sys.amiga
Subject: Re: Leaving Computer On
Message-ID: <17193@cup.portal.com>
Date: 15 Apr 89 04:38:07 GMT
References: <7684@phoenix.Princeton.EDU> <5500027@hpfcdc.HP.COM>
Distribution: usa
Organization: The Portal System (TM)
Lines: 20

With all of this diatribe about leaving computers and other equipment on
permanently, I'd like to settle it down with a little real information.

After working in the R&D division of North American Phillips Lighting
for half a year, and burning out more than a thousand bulbs  (we were 
working with quartz halogen, but the principle still applies) I can make
the following generalization.

Bulbs which are turned on for 45 minutes and then off for fifteen in
a constantly repeating cycle last about 75% as long as bulbs which are
left on constantly.  This is called a 75% duty cycle.  At a 25% duty 
cycle bulbs last about 130% as long as bulbs left constantly on.  AT
a 10% duty cycle they last about three times as long.

What all of this research goes to show is that what burns out a light
bulb is how long it is left on, with some attention paid to how many
times it is power cycled.  But what this means for the world of electronics
I couldn't say.

                           -Sullivan Segall