Halogens and flashlights
Paul N. Nagata
I am just getting into into electronics/EE as a hobby and have some
questions. I would like to build an extremely bright flashlight
using a halogen bulb.
1. Is there any reason why this won't work? Is there any designs
that I should avoid? (Bulb explosion causing ones, esp)
2. Do halogen bulbs suck so much power that the practical life of
the flashlight will be short?
3. Has this been done before? Is there a better way to build a really
bright flashlight? (I already own a maglite, so "bright" would mean
that it is brighter than the maglite)
Thanks. Email or replies to the article would be appreciated.
Thanks,
Paul Nagata
Samuel M. Goldwasser
Halogen flashlight bulbs exist.
Halogen bulbs are more efficient than ordinary incandescents when run
at rated power.
Halogens should be run at their rated power for maximum life.
--- sam
Michael Starks
: Hello there,
: I am just getting into into electronics/EE as a hobby and have some
: questions. I would like to build an extremely bright flashlight
: using a halogen bulb.
: 1. Is there any reason why this won't work? Is there any designs
: that I should avoid? (Bulb explosion causing ones, esp)
Nope.
: 2. Do halogen bulbs suck so much power that the practical life of
: the flashlight will be short?
Nope. In fact, halogen is better than incandescent as far
as lumens per watt goes.
: 3. Has this been done before? Is there a better way to build a really
: bright flashlight? (I already own a maglite, so "bright" would mean
: that it is brighter than the maglite)
Yep. Your maglite is halogen, in fact. Perhaps you could seek out
a higher wattage bulb and rebuild the flashlight to use it.
I once had a spotlight that plugs into a car's cigarette lighter
that put out a quarter of a million candlepower or some such
ridiculous amount. Made things look like daytime.
Michael Starks
Boston University College of Engineering
john 015
said:
>I am just getting into electronics/EE as a hobby and have some
>questions. I would like to build an extremely bright flashlight
>using a halogen bulb.
>
>1. Is there any reason why this won't work? Is there any designs
>that I should avoid? (Bulb explosion causing ones, esp)
Halogen lamps *are* used in flash lights. They burn hotter,
which means a higher percentage of the power they consume is
turned into visible, useful light. I'd be a tad worried about
melting plastic when converting flashlights not equipped with
halogen lamps from the manufacturer but I have done it and still
do.
>2. Do halogen bulbs suck so much power that the practical life of
>the flashlight will be short?
That's the cost of making the light
>extremely bright.
By the time you extract 1 Amp from alkaline batteries their internal
resistance starts to eat significant amounts of power too.
Forget pulling 2 Amps from say 8 alkaline cells, you need to
get NiCds or lead-acids when you hit these currents.
>3. Has this been done before? Is there a better way to build a really
>bright flashlight? (I already own a maglite, so "bright" would mean
>that it is brighter than the maglite)
If you have a real need head to the nearest scuba store and look at
their 10 Volt (8 D-cell or bigger) rechargeable (flash) lights.
You'll find 5, 10, 15, 20, 30, watts etc. At 30 watts and up
there might be a clause about do not use above water.
The advantage of these impact resistant water proof scuba lights over
other flash-lights is that they will outlast just about anything.
Even Radio Shack I think has a good selection of halogen lamps.
To brew you own bright light I'd suggest you buy a 12V/5Ah or bigger
lead-acids and an MR11 halogen lamp/reflector assembly at your local
hardware store (or the MR16). The MRs come in different wattages and
beam-angles and should cost about $11. Two 35 W narrow beam MR16 on
the front of your bicycle f.ex will brighten any path considerably :-).
Ohh, when you drain batteries quickly you seldom get the rated Ah.
I haven't worked on my halogen faq in a while but here is a barebones
version:
A short note on halogen lamps.
Halogen lamps utilize tungsten filaments operating at a very high
temperature. A special glass envelope is needed as ordinary glass
cannot withstand this intense heat. Quartz glass is used.
To prolong the life of the filament the lamp envelope is filled with a
halogen gas: clorine sometimes but most often flouride.
Due to the high heat, the filament literally evaporates off albeit
at a slow rate. The tungsten that evaporates off the filament moves away
from the hot filament and bonds with the flouride into
tungsten-hexa-flouride. When the lamp cools the tungsten is redeposited
onto the filament.
In non-halogen lamps, the tungsten that evaporates
condences on the glass envelope. With time the filament gets thinner
and the glass envelope appears blackened. Halogen lamps in contrast
burn brighter and stay brighter even as they "age".
Generally, the hotter the filament and bulb, the more and better light.
Iron melts at 1800'K, Tungsten melts at 3655'K.
Halogen lamps operate at filament temperatures from 2700 to 3050'K.
Molybdenum seals are employed to keep the seals intact during the
thermal expansion/contractions.
The lifetime of an ordinary non-halogen lamp depends on the voltage:
expected_life_time = constant (nominal voltage/real voltage)^(13).
The light output of an ordinary lamp depends on the voltage:
lumine = constant (real voltage/nominal voltage)^(3.4).
The power consumed by bulbs depends on the voltage:
output in watts = constant (real voltage/nominal voltage)^(0.42).
The resistance of the hot filament, R_warm is generally 12 to 16 times
R_cold.
The expected life of halogen lamps are not as easily predicted.
It depends on a large number of factors.
A) The halogen "cycling" is expected to operate properly at +/-
15% of the rated voltage. Do not ecxceed 110% of the rated
voltage though.
B) Tungsten is deposited on the lamp wall (darkening) during
low-voltage operation (weak batteries). According to
Philips this deposit should "clear" when full voltage
is reapplied to the filament.
GE says the halogen will scrub tungsten off the bulb wall
as long as the glass envelope is above 250 degrees Centigrade.
Hot spots reaching 700'C is defined as normal.
C) Halogen lamps have less predictable life than standard
incandescent bulb. (Incandescent follow a voltage to the 17th
power law fairly well).
D) Inrush current limiters will help extend the life of the
halogen bulb. By how much ? I've been unable to get an answer.
E) DC operation is tougher on the lamp than AC apparently
because DC promotes filament notching.
Filament notching is an uneven evaporation of the filament.
It looks step-like or saw-tooth like.
Notching is especially likely in:
a) small wire filaments.
b) DC operation.
c) cold operation.
F) 90% of the light output is in the infrared.
G) Tungsten filaments are fragile below 250'C, the brittle-ductile
region. Be careful with lamps warming up or cooling down.
Protect them from mechanical impacts.
H) To help keep the lamp warm some bulbs use a multilayered film on
the quartz glass to reflect the infra red heat back into the bulb.
This can increase the efficiency by 30 to 50%.
.. more to come.
X) So, we see not all halogen bulbs are made equal.
========================================================================
Halogen Lamp Sources/Info:
Bulbman
Las Vegas
1-800-648-1163
(sells retail, $5s/h)
Bulbtronics
1054 N Cahuenga Boulevard
Hollywood, CA 90038
(45 Banfi Placa/Farmingdale, NY 11735, #516-249-2272)
800-654-8542 Office
213-461-6262 Office
213-461-7307 Fax
Bulbtronics
45 Banfi Placa
Farmingdale, NY 11735
516-249-2272
516-249-6066 Fax
1-800-634-2852
Carley Lamps
1502 W 228th Street
Torrance, CA 90501
310-534-3860 Office
310-325-8474 Office
310-534-2912 Fax
GE Lighting
Nela Park
Cleveland, OHIO 44112
1-800-435-2677
GE Lighting Infomation center at 216.266.3900
GE answer center 800.626.2000
Gilway Technical Lamp
800 W Cummings Park
Woburn, MA 01801-6355
617-935-4442 Office
617-938-5867 Fax
Philips Lighting
200 Franklin Drive
Somerset, NJ 08875-6800
Sunray
CA
800-854-4487 Office
Welch Allyn
4619 Jordan Road
Skaneateles Falls, NY 13153-0187
315-685-4344 Office
315-685-4392 Fax
The Thomas Register contains many more distributors/retailers.
john 015
Brian Edwards
You didn't mention that you shouldn't touch the quartz glass because the
uric acid from your skin (sweat) reacts with the glass at high
temperatures and can cause it to crack.
----------------------------------------------------------------
Brian Edwards "Still running against the wind"
10002...@CompuServe.Com -Bob Seger
be...@btmv56.se.bel.alcatel.be
Adam Felson
: You didn't mention that you shouldn't touch the quartz glass because the
: uric acid from your skin (sweat) reacts with the glass at high
: temperatures and can cause it to crack.
Flashlights don't run hot enough for this to matter. BTW: your headers
are bogus and prevent e-mail replies.
john 015
(Brian Edwards) said:
>You didn't mention that you shouldn't touch the quartz glass because
>the uric acid from your skin (sweat) reacts with the glass at high
>temperatures and can cause it to crack.
That's usually the only thing printed on the packaging !
Thanks, it slipped me.
I also wonder if not the stress is more due to the local heat
gradient caused by localized heat absorption in the organic material
that was added to the glass envelope.
While we are at it other worthy additions to the Halogen Lamp
FAQ would be:
i) The rated life of halogen lamps found under optimum laboratory
conditions. The lab controls the voltage, current (AC is best),
the current during turn-on, the *orientation* of the lamp,
the flow of air over the glass envelope etc. The orientation
of the lamp matters through heat considerations I guess.
ii) The higher the color temperature of the bulb, the shorter
the expected average life. A rough rule of thumb would be
that a 3300'K bulb measures in around 40 hours and that a
2800'K bulb will last of the order 2000 hours.
iii) Rule of thumb: At 110% of rated voltage you get 1/3 the
rated life. At 90% of rated voltage you get 3x the rated
life.
john
Collin Ong
CC01...@brownvm.brown.edu (john 015) writes:
>I haven't worked on my halogen faq in a while but here is a barebones
>version:
>A short note on halogen lamps.
>B) Tungsten is deposited on the lamp wall (darkening) during
> low-voltage operation (weak batteries). According to
> Philips this deposit should "clear" when full voltage
> is reapplied to the filament.
> GE says the halogen will scrub tungsten off the bulb wall
> as long as the glass envelope is above 250 degrees Centigrade.
> Hot spots reaching 700'C is defined as normal.
In your standard household "torchiere" halogen lamps, there is usually
a knob which controls the brightness of the lamp. Some friends who
leave the lamp on for extended periods turn the brightness down. Does
this actually save power? My thinking is that the knob controls some
variable resistor which changes the input voltage to the bulb. Thus,
more power is being used in the resistor when dimmed, thus the power
consumption is the same whether dimmed or at full blast. Can anybody
explain how this works?
Also, from the quote above, does running the lamp dimmed for extended
periods deposit tungsten on the bulb, thus decreasing filament life?
>F) 90% of the light output is in the infrared.
I also have a cousin who insists vehemently that halogen lamps are a
heath hazard, though she can not explain the mechanism. Is there any
theoretical or know danger through IR/UV emission, etc? Or is this
just an urban rumor?
Thanks for any help or discussion.
Collin Ong
col...@mcd.fm.intel.com
Not an Intel spokesman
Michael Starks
: A few questions I've been curious about, but never knew where to ask...
: In your standard household "torchiere" halogen lamps, there is usually
: a knob which controls the brightness of the lamp. Some friends who
: leave the lamp on for extended periods turn the brightness down. Does
: this actually save power? My thinking is that the knob controls some
: variable resistor which changes the input voltage to the bulb. Thus,
: more power is being used in the resistor when dimmed, thus the power
: consumption is the same whether dimmed or at full blast. Can anybody
: explain how this works?
The dimmer in those lamps is a typical triac-diac chopping dimmer
that works by allowing only part of the line-current sine-wave
through to the bulb. The threshold at which the triac turns
on is set via the variable resistor you control with the knob.
The chopping process creates all sorts of harmonics and is
responsible for the RFI and hum you hear when the lamp isn't at
full brightness. Power usage is generally less at lower bright-
ness since the triac isn't conducting part of the time.
: Also, from the quote above, does running the lamp dimmed for extended
: periods deposit tungsten on the bulb, thus decreasing filament life?
: >F) 90% of the light output is in the infrared.
I've heard that you should run the lamp at full brightness for
a few minutes if you've had it dimmed for a while in order to
clean up the bulb. I suspect this raises the bulb temperature
enough to redeposit tungsten back on the filament. Someone more
knowledgable can probably answer this definitively, though.
john 015
said:
>Collin Ong (col...@intel.com) wrote:
>: Also, from the quote above, does running the lamp dimmed for extended
>: periods deposit tungsten on the bulb, thus decreasing filament life?
Running the lamp dimmed too much will prevent the halogen cycle from
"trapping" the tungsten and the bulb will blacken.
But we have empirical evidence showing that the lower the filament
temperature, the longer the average life of the filament.
Then working against us is the filament notching at low temps.
I assume people must have studies the relative effect of these
mechanisms but I personally have no idea exactly which does what
and when. All Philips told me what that is was hard to predict
the life of halogen lamps but I assume a generic answer like
"the lamp will last longer [shorter?] can be made".
I have conflicting info. I have read but never confirmed that
the lamp will last shorter when dimmed. My own guess is that
it lasts longer (but the advantage of using a halogen lamp gets
a bit lost when you do).
The truth is I do not know why the filament fails.
Does it: become brittle, wear thin in spots, separate, change
crystalline structure, other ? Does the seal eventually leak air
(O2) in and things oxidize etc etc. All of the above ?
>I've heard that you should run the lamp at full brightness for
>a few minutes if you've had it dimmed for a while in order to
>clean up the bulb. I suspect this raises the bulb temperature
>enough to redeposit tungsten back on the filament. Someone more
>knowledgable can probably answer this definitively, though.
Run the lamp at full steam and hopefully most of the stray
tungsten gets trapped by the flouride. But it isn't until the
lamp is allowed to cool that the tungsten is redepostited.
All this to the best of my knowledge.
The heat from a halogen lamp shouldn't cause any harm.
The UV off a "white" hot-burning halogen lamp definitely could be
very bad for your skin and eyes. Most halogen lamps do their
job by gway of indirect lighting for this very reason.
I assume most surfaces found in a domestic setting absorbs
the harmful UV. Or maybe the UV is trapped by special glass
right at the source ?
Anyway I definitely wouldn't put AL foil f.ex right above
a halogen lamp to increase the amount of reflected light.
john
Arsenio Novo
Re: Halogens and flashlights (16 Jun 95 13:33:36)
CO> From: col...@intel.com (Collin Ong)
CO> Newsgroups: sci.electronics
CO> Subject: Re: Halogens and flashlights
CO> Organization: Intel Corporation, Folsom CA, USA
CO> A few questions I've been curious about, but never knew where to
CO> ask...
CO> CC01...@brownvm.brown.edu (john 015) writes:
CO> I also have a cousin who insists vehemently that halogen lamps
are a
CO> heath hazard, though she can not explain the mechanism. Is
there any
CO> theoretical or know danger through IR/UV emission, etc? Or is
this
CO> just an urban rumor?
CO> Thanks for any help or discussion.
CO> Collin Ong
CO> col...@mcd.fm.intel.com
Yes, UV is the danger. Even ordinary bulbs give off some UV. I know
for sure because I was experimenting with radiation measurement and
couldn't get the count down until I realized the table lamp was the
source.
The incadescent tungsten filament is the culprit since it emits some
electrons that in turn ionize gaz molecules which are in its
vicinity.
An ionized gas cloud carrying a current is in other words a plasma
and
the plasma will give off some UV.
Arsenio
... Anyone not wearing 2,000,000 sunblock is gonna have a REAL_ BAD_
DAY_7
~~~ ReneWave v1.00.wb2 (unregistered)
--
| InterNet: Arseni...@mba.org
| Standard disclaimer: The views of this user are strictly their own.
Robert Googe
>Hello there,
>I am just getting into into electronics/EE as a hobby and have some
>questions. I would like to build an extremely bright flashlight
>using a halogen bulb.
>1. Is there any reason why this won't work? Is there any designs
>that I should avoid? (Bulb explosion causing ones, esp)
>2. Do halogen bulbs suck so much power that the practical life of
>the flashlight will be short?
>3. Has this been done before? Is there a better way to build a really
>bright flashlight? (I already own a maglite, so "bright" would mean
>that it is brighter than the maglite)
>Thanks. Email or replies to the article would be appreciated.
>Thanks,
>Paul Nagata
Quartz Halogen bulbs are available (by Eveready here in Australia) for
general use in torches, they have a reasonably equivalent operating
criteria to standard torch bulbs but...
1. They are noticeably brighter (>%50)
2. They do run hotter (which probably implies higher current
consumption!), there are warnings not to use the bulbs in torches with
metalised plastic reflectors as they can melt.
Hope this helps.
Rob. G.
P.S. QH bulbs are a LOT more expensive than standard tungsten
equivalents.