Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!iuvax!cica!gatech!emory!stiatl!john
From: john@stiatl.UUCP (John DeArmond)
Newsgroups: sci.electronics
Subject: Re: How can I turn on this bulb with TTL?
Message-ID: <6010@stiatl.UUCP>
Date: 23 Jul 89 22:28:20 GMT
References: <4363@merlin.usc.edu> <5170048@hplsla.HP.COM>
Reply-To: john@stiatl.UUCP (John DeArmond)
Organization: Sales Technologies Inc., "The Procedure IS the product"
Lines: 21

In article <5170048@hplsla.HP.COM> tomb@hplsla.HP.COM (Tom Bruhns) writes:
>
>These two paragraphs, separated by several others in the original,
>seem to contradict eachother.  If "my" Simpson 260 will heat the
>filament enough to significantly change its resistance, then I'm
>quite sure the 2n2222 won't have much problem overcoming the cold-
>resistance effect.

Well try it and see.  I'm sure you'll see the light (or lack thereof).
The simpson WILL provide enough current to alter the "cold" reading.
Remember the objective was to obtain the cold resistance, right?
The ammount of current necessary to heat a filament a couple hundred
degrees and the ammount needed to reach incadescence (sp) is vastly
different.  When you are trying to mentally analyze this, remember
to account for radiative energy losses which go up exponentially with
temperature. (or is it geometrically?  anyway, a lot :-)

-- 
John De Armond, WD4OQC                     | Manual? ... What manual ?!? 
Sales Technologies, Inc.    Atlanta, GA    | This is Unix, My son, You 
...!gatech!stiatl!john    **I am the NRA** | just GOTTA Know!!!