From: jgd@dixie.com (John De Armond)
Subject: Re: Larry Lippman  [Actually a followup on the life extender project]
Date: Tue, 10 Nov 92 19:43:14 GMT
Organization: Dixie Communications Public Access.  The Mouth of the South.

lmh@iago.caltech.edu (Henling, Lawrence M.) writes:

>[This is a repost of Lippman article:]

>From: larry@kitty.UUCP (Larry Lippman)
>Newsgroups: sci.electronics
>Subject: Re: incandescent light bulb life extender (Bogus Advice Warning!)
>Summary: More on thermistors & Debunking Tall Tales from John DeArmond
>Date: 15 Dec 90 04:54:19 GMT

Now that everyone has seen Larry the Lid's rantings again, I thought
the net might be interested in a followup to my experiment.  (Wonder
if the Lid can figure out a way to rebut this one from his hole in
the ground.)

Background:  About two years ago I endeavored to find a method of extending
the life of lightbulbs in my home and lab.  My line voltage is an
average of 128 volts, averaged over a day as measured by a Tripplet
line voltage monitor.  GE says lamp life varies as the 13th power of
voltage deviation from the design point.  The effect in my place
was that bulb life was about 2 weeks or so.

It has been almost exactly two years since I installed the thermistors
in my den fixture and shortly thereafter, the fixture in the
stairwell to my lab.  The latter fixture is turned on and off dozens
of times a day.  During the two years since the start of the experience,
I experienced a fire in my lab caused by a video terminal.  Thus I've
had experience with all the different things the Lid wrung his hands 
about.

Here are the salient facts:

*	The original lamps are still in both fixtures.  I carefully removed
	and stored them during the reconstruction after the fire.  They have
	about a year and a half's actual use on them.  

*	The 125 deg C Templaq spots I placed on the termistors are still 
	intact.

*	I have since acquired a digital storage scope and hall effect
	current probe so I have been able to monitor the function
	of the thermistors in great detail.  The thermistor holds the 
	inrush current to about 125% of the normal operating current.
	That compares quite favorably to the estimated 6 times normal
	(my current converter is not fast enough to catch single cycles)
	without the thermistor.

*	There were a wide variety of "non-UL approved devices" in my lab,
	including several line-operated hardware prototypes.  At no point
	did neither the fire marshal nor the insurance adjustors show 
	any interest in these devices.  In the case of my commercial 
	policy, when the fire marshal certified the cause of the fire, 
	the adjustor wrote me a check on the spot.  Total elapsed time -
	about 3 days.  Though I had problems on my homeowner's policy
	regarding shoddy work during the repair, there was NO problem
	either with "non-UL approved devices" being in the premises or
	with there being a business in the basement.  At least here in
	Georgia, as long as arson is not involved, insurance has to pay.

*	The thermistors chosen were done so because the same series 
	was found in a switching power supply in my lab.  I like emulating
	success.  Were I to do it again, I'd probably use the Keystone
	thermistors mentioned by the Lid.  They were not, however, listed
	in my copy of the Digikey catalog at the time I started the experiment.

*	I have had Graybar and and Consolidated Electric look for the 
	thermistor-based bulb extenders that go in the socket under 
	the bulb.  Though the countermen at both places claim to have seen
	them, neither has been able to find them.  Any pointers would
	be appreciated.  Note that I am NOT talking about the diode-type
	lamp life extenders that work by half-wave rectifying the line
	voltage.  

Summary:  The experiment has been a success.  I converted most of the 
house over to either halogen or CF fixtures so I probably won't be converting
any more fixtures.  If you use a lot of incandescent lamps and your bulb
life is short, the thermistor modification is a very good thing to do.

John

-- 
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Newsgroups: sci.electronics