ho@s10.csrd.uiuc.edu (Samuel W Ho) (03/21/91)
If the goal is to minimize cold inrush current, I'd suggest putting a small thermisistor on the bulb. Something that dropped from a few hundred ohms down to zero at operating temperature. I seem to recall that a few of the stick-ons actually worked this way. Most are diodes, which work by reducing the average voltage on the bulb. Typically, you get a 20% reduction in power consumption, a 40% reduction in light output, and a 20% increase in bulb life. You can get the same effect by using 130V bulbs. For the ultimate, use a traffic light bulb. Traffic lights are inconvenient to replace, and a dead bulb is a safety hazard, so the tradeoff is weighted heavily to long life at the expense of efficiency. Traffic lights are usually rated 5000 hours life or so. Sam Ho
bender@oobleck.Eng.Sun.COM (I want to be eating rich soup in another town) (03/21/91)
In article <1991Mar20.193344.25597@csrd.uiuc.edu> ho@s10.csrd.uiuc.edu (Samuel W Ho) writes: >If the goal is to minimize cold inrush current, I'd suggest >putting a small thermisistor on the bulb. Yeah, I think Digi-Key sells them. But don't bother spending your money on the expensive kind, just get the cheapest one that will work. And you don't need to heat-sink the thermistor - the base of the bulb and the socket can take PLENTY of heat. How do I know all this you may ask? Why, I've been reading sci.electronics for quite a while now... :-) mike -- Won't look like rain, Won't look like snow, | DOD #000007 Won't look like fog, That's all we know! | AMA #511250 We just can't tell you anymore, We've never made oobleck before! | MSC #298726
bc338569@longs.LANCE.ColoState.Edu (Brian Catlin) (03/21/91)
In article <1991Mar20.193344.25597@csrd.uiuc.edu> ho@s10.csrd.uiuc.edu (Samuel W Ho) writes: > >You can get the same effect by using 130V bulbs. For the ultimate, >use a traffic light bulb. Traffic lights are inconvenient to replace, >and a dead bulb is a safety hazard, so the tradeoff is weighted >heavily to long life at the expense of efficiency. Traffic lights >are usually rated 5000 hours life or so. I just pulled a light bulb out of a stoplight and found that it is a 69 watt bulb rated at 130V and is made by Westinghouse USA. I have had these stoplights for several years and have never had one go out. Anybody know where to get these bulbs or the cost? I noticed that the bulbs are not real bright when they aren't in the reflectors, but once you put them in you better cover your eyes when it switches to yellow or you'll be blind for quite some time! (Hey, that rhymes!) Just another stupid observation and question :-) B. J. Catlin * Brian J. Catlin Electrical Engineering * e-mail : bc338569@longs.lance.colostate.edu * Compuserve : 73540,17
bill@thd.tv.tek.com (William K. McFadden) (03/23/91)
In article <14740@mcdphx.phx.mcd.mot.com> hbg6@citek.mcdphx.mot.com writes:
->I gather the general opinion of the net is that bulb life is diminished
->by repetative thermal shock. Presuming that's true, wouldn't you increase
->bulb life by installing a high value resistor across the switch which
->controls the bulb? This would turn 'OFF' into a sort of 'STANDBY - KEEP WARM'
->mode.
Another way to reduce thermal shock, which was discussed a while ago,
is to ramp up the voltage gradually when turning on the bulb. This has
the advantage of not wasting energy when the power is off. Some
dimmers already do this.
--
Bill McFadden Tektronix, Inc. P.O. Box 500 MS 58-639 Beaverton, OR 97077
bill@videovax.tv.tek.com, {hplabs,uw-beaver,decvax}!tektronix!videovax!bill
Phone: (503) 627-6920 "SCUD: Shoots Crooked, Usually Destroyed"rpw3@rigden.wpd.sgi.com (Rob Warnock) (03/26/91)
My understanding from something I read a few years back was that the lifetime of an ordinary incandescent bulb was inversely proportional to the 12th (!) power of the voltage. So that if you run a 130v bulb at 117 volts, you get 3.5 times the life expectancy. (This applies to continuous operation, only.) -Rob ----- Rob Warnock, MS-1L/515 rpw3@sgi.com rpw3@pei.com Silicon Graphics, Inc. (415)335-1673 Protocol Engines, Inc. 2011 N. Shoreline Blvd. Mountain View, CA 94039-7311