commgrp@silver.bacs.indiana.edu (01/03/90)
I am looking for references and formulae for light output and color temperature vs. filament life for tungsten-halogen lamps, in terms of percent of rated voltage and lifetime. I want to use (relatively inexpensive) 12-volt automotive quartz- halogen bulbs in portable (dc) configuration where I need maximum illumination. Automotive bulbs are designed for long life in a high- vibration environment, leading me to believe that I can increase the voltage substantially and trade-off bulb life for extra light. (I can minimize thermal shock by increasing the voltage above rated value after the filaments are already hot.) Is it desirable to heat-sink the bulb base or to protect the lamp from wind? Thanks in advance-- e-mail replies don't always go. -- Frank Reid W9MKV NSS 9086 reid@gold.bacs.indiana.edu P.O. Box 5283 Bloomington, Indiana 47407 USA
jgd@rsiatl.UUCP (John G. De Armond) (01/03/90)
In article <7200047@silver> commgrp@silver.bacs.indiana.edu writes: > > > >I am looking for references and formulae for light output and color >temperature vs. filament life for tungsten-halogen lamps, in terms of >percent of rated voltage and lifetime. > >I want to use (relatively inexpensive) 12-volt automotive quartz- >halogen bulbs in portable (dc) configuration where I need maximum >illumination. Automotive bulbs are designed for long life in a high- >vibration environment, leading me to believe that I can increase the >voltage substantially and trade-off bulb life for extra light. (I can >minimize thermal shock by increasing the voltage above rated value >after the filaments are already hot.) I have a study around here somewhere published by Westinghouse about 20 years ago that developed a formula for relating operating voltage to life. I don't remember the exact details but I DO remember that there was a 13th power term in the voltage equation. In other words, life declines FAST with increasing voltage. Automotive bulbs acheive a good life by running at a much lower temperature than, say, a photographic lamp. If you goose one of these bulbs up to get the color temperature up to photographic values, the life will become similiar to the photographic lamps. Which begs the question. If you need bright, white light, why not use 12 volt nominal halogen photographic lamps instead of mucking around trying to figure out what voltage is necessary to make an automotive lamp run at the proper color temperature? These bulbs are quite similiar to the H-x automotive bulbs and not much more expensive. The ones with integral reflectors are very nice in that the coating on the reflector is IR-transparent which means the light is very cool. > >Is it desirable to heat-sink the bulb base or to protect the lamp from >wind? > It will depend on the bulb. In general, you want to avoid thermal transients and excessive heating of the glass/metal transitions of the terminals. BTW, I've been using souped-up halogen lamps for photographic purposes for years. I'm using the 500 watt tubular reflector type lamps commonly used to illuminate buildings or yards. You can buy them at the hardware store for a few bucks. I use a boosting transformer to boost the voltage to about 160 volts. Fine tuning is done with a variac. This produces GOBS of very white light with reasonable lamp life (~ 100 hours or so). Kinda tangent to your question but somewhat similiar. John -- John De Armond, WD4OQC | The Fano Factor - Radiation Systems, Inc. Atlanta, GA | Where Theory meets Reality. emory!rsiatl!jgd **I am the NRA** |
frankb@hpsad.HP.COM (Frank Ball) (01/04/90)
*From: commgrp@silver.bacs.indiana.edu *Subject: Need quartz-halogen lamp info * *I want to use (relatively inexpensive) 12-volt automotive quartz- *halogen bulbs in portable (dc) configuration where I need maximum *illumination. Automotive bulbs are designed for long life in a high- *vibration environment, leading me to believe that I can increase the *voltage substantially and trade-off bulb life for extra light. (I can *minimize thermal shock by increasing the voltage above rated value *after the filaments are already hot.) GE and Sylvania publish info on their halogen lights. I have some very old copies. They don't have all the info you want, but some. I saw a graph that showed bulb life cut in half for a 10% voltage increase. Even halogen lights have most of their output (about 90%) in the infared range, so more voltage would help the light output by shifting some of this into the visable region, as well as increasing the total output. Automotive bulbs are not rated at 12 volts. Cars can run up around 14 - 14.5 volts when running. The GE headlamps are rated to last 200 hours at 14 volts. Frank Ball frankb@hpsad.HP.COM