Do Halogen lamps need ballasts?
Randy Brumbaugh
Someone asked what the halogen gas did for these lamps.
Hope this helps . . .
(In this posting, "lamp" means light bulb, not a lighting
fixture).
A "halogen" lamp (also sometimes called a "quartz", "tunsten-
halogen", or a "Quartz-iodide" lamp) is basically the same
as a regular incandescent lamp -- it produces light by heating
a tungsten filament in a sealed envelope containing some gas.
It is still a form of incandescent lighting.
No ballast is needed for halogen lamps, although some small
fixtures use lower voltage lamps and need a step-down
transformer.
The difference is in the envelope, which is made of quartz
to handle the high temperature operation needed; and in the
gas which fills the envelope. The gas is a member of the
halogen family. Regular incandescent lamps use an inert gas.
In a regular incandescent lamp, the tungsten "boils" off the
filament during operation. It eventually contacts the cooler
glass envelope, where it deposits itself. This results in
darkening of the envelope as the lamp ages, and in weakening
of the filament.
A chemical process (the halogen cycle) is used to improve this
in these new fangled "halogen" lamps. The tungsten chemically
bonds with the halogen gas in the envelope. When the gas
contacts the hot filament, the chemical bond is broken, and
the tungsten is re-deposited in the filament. These lamps
won't last forever, because the tungsten isn't deposited
at the same spot it came off the filament.
This gives lamp designers 2 options:
- make the lamp produce brighter, higher color temperature
light at the same life expectancy.
-OR-
- make the lamp the same brightness with a longer life.
To maintain the halogen cycle, the lamp must run at fairly high
temperatures and pressures. Dimming may reduce this somewhat,
and cause the envelope to darken, but operating a while
at full brightness will reverse the process.
Also, the quartz envelope shouldn't be touched by bare
hands -- oils on the skin will weaken the structure and may
cause bubbles or lamp failure.
Tungsten-halogen (T-H) lamps are now used almost exclusively
for stage and television lighting applicatuions, where they
have been around for quite a while. This is due to thier
longer life/higher color temp and the fact that light output
does not decrease as the lamp ages, as it does with regular
incandescent lights.
Randy Brumbaugh
ra...@skipper.dfrf.nasa.gov
Blair P. Houghton
>A chemical process (the halogen cycle) is used to improve this
>in these new fangled "halogen" lamps. The tungsten chemically
>bonds with the halogen gas in the envelope. When the gas
>contacts the hot filament, the chemical bond is broken, and
>the tungsten is re-deposited in the filament. These lamps
>won't last forever, because the tungsten isn't deposited
>at the same spot it came off the filament.
If a region starts to thin-out its resistivity increases,
increasing its power dissipation, increasing its heat. The
rate of deposition is a monotonic function of the temperature,
so the hotter spots tend to _collect_ tungsten, fattening them.
The halogen cycle not only prevents rapid loss of filament
material, it repairs minor flaws in the filament and prevents
hot-spots due to these flaws.
Halogen lamps burn out (barring some extensive flaw) only
when one of the non-tungsten parts fails (the filament supports
weaken from temperature cycling, the way the filament would
if it weren't for the halogen cycle).
>Also, the quartz envelope shouldn't be touched by bare
>hands -- oils on the skin will weaken the structure and may
>cause bubbles or lamp failure.
The oil causes a region of different thermal conductivity;
when the heat is applied this will cause a region of
different temperature which will cause a difference in
expansion which will cause a stress that will rupture the
envelope. The oil doesn't "weaken the structure." You can
wipe it off.
>Tungsten-halogen (T-H) lamps are now used almost exclusively
>for stage and television lighting applicatuions, where they
--Blair
"Stage Nerds 'R' Us..."
Mark Fisher
and looked at some quartz-halogen replacement bulbs. They have what
appears to be a tungsten filament wire inside a quartz tube. Going
off the deep end, I would say that the resistance of the wire would
limit the current and no ballast is needed. I would also assume that
the dimmer circuit in halogen lamps is a regular high wattage dimmer.
I noticed on the demo lamp that dimming the light made the
quartz-halogen tube humm loud enough that I could hear it in a noisy
wharehouse type of store.
I looked up halogen in my dictionary. It said it was one of the very
active chemical elements, fluorine, chlorine, bromine, astatine, or
iodine. How does this apply to a light bulb?
--
// Mark M. Fisher
// fi...@gemed.ge.com
// uunet!crdgw1!gemed!fish
// sun!sunbrew!gemed!fish
Blair P. Houghton
>If a region starts to thin-out its resistivity increases,
Bubblehead. That's "resistance," not "resistivity."
It's the cross-sectional area that's changing, not
the mean free path...
--Blair
"What a maroon."
Bob Tidrick
>>contacts the hot filament, the chemical bond is broken, and
>>the tungsten is re-deposited in the filament. These lamps
>>won't last forever, because the tungsten isn't deposited
>>at the same spot it came off the filament.
One thing that has bothered me about these Halogen lamps with the
dimmer is, from my experiance if the bulb is not kept at least at
a certian high temperature they will fail faster. I have seen halogen
bulbs grow tungsten crystals on the ends of the filament when run at
a lower then rated voltage. Apparently this is because when the
filament is at a lower temperature the tungsten is not redeposited
on the filament while the bulb is operating. When it is turned off
and the gas cools it is deposited at the coolest point. In this case
the ends of the filament. The crystals grow depleating the material
on the rest of the filament. Hot spots do occur but there is always
some tungsten trapped in the gas when the bulb is turned off it cools
and again is deposited on the crystals. The bulbs we used where rated
at about 5000 Hrs. Most of them lasted about 2000. Some lasted as little
as 500 Hrs. These were bulbs rated at 12 Volts being run at 10V.
I wonder if the manufactures of these lamps know about this?
--
Bob Tidrick
GPID Engineering
Tektronix Inc.
Wilsonville OR.
Michael Alan Schuster
>material, it repairs minor flaws in the filament and prevents
>hot-spots due to these flaws.
>
>Halogen lamps burn out (barring some extensive flaw) only
>when one of the non-tungsten parts fails (the filament supports
>weaken from temperature cycling, the way the filament would
>if it weren't for the halogen cycle).
What's the principle behind the "krypton" flashlight bulbs being sold
now, and market as "70% brighter" than the standard type?
John Whitmore
>
>What's the principle behind the "krypton" flashlight bulbs being sold
>now, and market as "70% brighter" than the standard type?
There are three major different types of incandescant bulbs.
Vacuum, inert gas, and halogen. Vacuum bulbs are more energy-efficient,
and have a lifetime of circa 5-10 hours. Inert gas bulbs have some
gas-cooling of hot spots, so last longer (circa 750 hours), but still
blacken as they age. Halogen bulbs do not blacken, but must be run
hot.
Traditional flashlight bulbs have been vacuum types. For larger
power outputs (which modern batteries make feasible), one can use a
very dense gas (Krypton) which has lower thermal conductivity than
Nitrogen (which is the fill gas in most 100W household lamps).
The '70% brighter' effect is due to the filament running
hotter (and taking 50% more power).
I tested bulbs of all three types for my bicycle light;
the vacuum bulb spectrum was dreadfully red. The halogen and the
Krypton had the same color temperature, with the Krypton being
slightly higher power output. I ended up using the halogen
(and have had a hundred or so hours use so far) but the Krypton
bulb is what I'll be replacing it with (the cost is circa 8:1
in favor of Krypton).
John Whitmore
Simon Peter Gatrall
and no. Some halogen lamps are 12V (others are 6V or 24V or 120V) so
they need a power supply. Some manufacturers call this a ballast even
though it is not a ballast in the sense of a florescent light ballast.
Higher wattage halogen lamps are usually 120V ac. There are solid state
power supplies rated for use with 12V halogen lamps available.
-Simon Gatrall sg...@andrew.cmu.edu
Phil Ngai
|The bulbs we used where rated
|at about 5000 Hrs. Most of them lasted about 2000. Some lasted as little
|as 500 Hrs. These were bulbs rated at 12 Volts being run at 10V.
Is there any way you can avoid running them below their rated
voltage? Why are you doing this instead of getting bulbs rated
at less wattage? What do you think the manufacturers could do
about their products being used at a temperature too low for
the full halogen cycle to operate?
--
Compost: it's the right thing to do.
BACS Data Communications Group
arrays of lamps are sometimes connected in series with low-inductance,
high-current, air-core "inrush chokes" to protect switch contacts:
Resistance of metal increases with temperature; there is significant
difference between tungsten's cold resistance and its resistance at
halogen-lamp operating temperature.
--
Frank Reid re...@ucs.indiana.edu
jerome.t.abar..jr
as opposed to turning them on and off, cooling and heating them
(a previous poster mentioned crystals growing in cool spots)
Thanks.
--
*******************************************************************************
** Tom Abar My Company's Nifty, My Company's Fine, **
** mv...@mvgpn.att.com But These Opinions Are Strictly MINE!! **
*******************************************************************************
Phil R. Karn
Houghton) writes:
|> >Also, the quartz envelope shouldn't be touched by bare
|> >hands -- oils on the skin will weaken the structure and may
|> >cause bubbles or lamp failure.
|>
|> The oil causes a region of different thermal conductivity;
|> when the heat is applied this will cause a region of
|> different temperature which will cause a difference in
|> expansion which will cause a stress that will rupture the
|> envelope. The oil doesn't "weaken the structure." You can
|> wipe it off.
I don't think that's quite right. Quartz is used precisely because of
its
very low temperature expansion coefficient.
I think the problem is that the heat will decompose the oil, producing
elemental carbon which will then absorb the light hitting it from the
filament. This causes a hot spot on the surface of the envelope which
could well cause it to soften and fail.
Phil
Blair P. Houghton
>In article <11...@inews.intel.com>, bhou...@cmdnfs.intel.com (Blair P.
>Houghton) writes:
>|> The oil doesn't "weaken the structure." You can
>|> wipe it off.
>
>I don't think that's quite right. Quartz is used precisely
>because of its very low temperature expansion coefficient.
Very low != nonexistant. Also, quartz is very brittle.
Any deformation causes catastrophic displacement
(cleaving). When there's a uniformity of heat
distribution, things expand normally. When there isn't,
they don't.
>I think the problem is that the heat will decompose the oil, producing
>elemental carbon which will then absorb the light hitting it from the
>filament. This causes a hot spot on the surface of the envelope which
>could well cause it to soften and fail.
Take a halogen lamp. Turn it on. Allow a drop of water to
fall on it. Run like hell.
You don't need any chemistry. Temperature differences
are all you need to cause one of these to blow.
I don't think you can "soften" quartz without _extreme_
temperatures (thousands and thousands of K).
--Blair
"Billions and billions of Big Macs..."
Blair P. Houghton
>at less wattage? What do you think the manufacturers could do
>about their products being used at a temperature too low for
>the full halogen cycle to operate?
Sell more of them as replacements...
--Blair
"It's pretty obvious, really."
David G Metzger
>In article <1990Dec...@envy.bellcore.com> ka...@thumper.bellcore.com write
s
>:
>>In article <11...@inews.intel.com>, bhou...@cmdnfs.intel.com (Blair P.
>>Houghton) writes:
>[...deformation ==> rupture...]
>>|> The oil doesn't "weaken the structure." You can
>>|> wipe it off.
>>
>>I don't think that's quite right. Quartz is used precisely
>>because of its very low temperature expansion coefficient.
>
>Very low != nonexistant. Also, quartz is very brittle.
>Any deformation causes catastrophic displacement
>(cleaving). When there's a uniformity of heat
^^^^^^^^
>distribution, things expand normally. When there isn't,
>they don't.
Quartz does not have cleavage planes. When quartz breaks, it
is by conchoidal fracture.
David Metzger
met...@cup.portal.com
sun!portal!cup.portal.com!metzger
Alan Kilian
From the CRC handbook od chemistry and physics 63 edition 1982-1983
PP F65:
Coefficient of thermal expansion 5.5 X 10^-7 cm/cm/degree C From 20 to 320 C
(That's way low)
Tensile strength 7,000 PSI Compressive strength > 160,000 PSI
(That's very strong)
Softening point (Approx) 1665 Degrees C (1938 degrees K)
(That's way up there)
So, If I place some oil on the quartz with the lamp off and let the
temperatures equalize and then turn on the lamp WHY does the quartz
break (If it really does as so many have said).
I guess I'll have to buy some bulbs and try this at home because I don't
buy any of these theorys. (Except the carbon one maybe)
-Alan Kilian
Cray Research, Inc.
655 F Lone Oak Drive
Eagan, MN 55121 kil...@cray.com
Blair P. Houghton
>
>Coefficient of thermal expansion 5.5 X 10^-7 cm/cm/degree C From 20 to 320 C
> (That's way low)
Not low enough.
>Tensile strength 7,000 PSI Compressive strength > 160,000 PSI
> (That's very strong)
Not strong enough.
>Softening point (Approx) 1665 Degrees C (1938 degrees K)
> (That's way up there)
Lower than I thought, but higher than any spot of
carbonization will stick around to reach.
>So, If I place some oil on the quartz with the lamp off and let the
>temperatures equalize and then turn on the lamp WHY does the quartz
>break (If it really does as so many have said).
Halogen lamps in these pole-lamp assemblies come with
expensive-looking protective gear to keep the shards of
quartz envelope from splattering all over your living room.
They break.
The skin oil keeps heat in the quartz that is escaping
elsewhere on the envelope. The temperature difference
causes localized stresses. Poof.
--Blair
"Poof."
PARSONS, CHARLES
>In <36...@cup.portal.com> met...@cup.portal.com (David G Metzger) writes:
>
>>In article <11...@inews.intel.com>, bhou...@cmdnfs.intel.com
>> (Blair P. Houghton) writes:
>>>(cleaving). When there's a uniformity of heat
>> ^^^^^^^^
>
>> Quartz does not have cleavage planes. When quartz breaks, it
>>is by conchoidal fracture.
>
>Depends on how it grew doesn't it? Defects in the crystal can form very regular
>fracture planes that behave just like cleavage planes. This weak area is the one
>most likely to break if the deformation occurs nearby. But then again, there
>aren't supposed to be any defects are there?
>
"Quartz" halogen light tubes are not Crystals they are amorphous. The
quartz label just refers to the fact that the glass is almost pure SiO2
without the usual salts added to window glass to lower the melting point.
Adam David
Depends on how it grew doesn't it? Defects in the crystal can form very regular
fracture planes that behave just like cleavage planes. This weak area is the one
most likely to break if the deformation occurs nearby. But then again, there
aren't supposed to be any defects are there?
Adam David.
Stephen Tell
>In article <11...@inews.intel.com>, bhou...@cmdnfs.intel.com (Blair P. Houghton) writes:
>> In article <1990Dec...@envy.bellcore.com> ka...@thumper.bellcore.com writes:
>> >In article <11...@inews.intel.com>, bhou...@cmdnfs.intel.com (Blair P.
>> >Houghton) writes:
>> [...deformation ==> rupture...]
>> >|> The oil doesn't "weaken the structure." You can
>> >|> wipe it off.
You can certainly clean the oil off before turning the lamp on and get
near-normal bulb life. Instructions packed with lamps I've seen say to
clean them with alcohol if you accidently touch them during installation.
I've done this with no problems.
>> >I think the problem is that the heat will decompose the oil, producing
>> >elemental carbon which will then absorb the light hitting it from the
>> >filament. This causes a hot spot on the surface of the envelope which
>> >could well cause it to soften and fail.
>> I don't think you can "soften" quartz without _extreme_
>> temperatures (thousands and thousands of K).
I have personaly replaced a 750 Watt (or maybe it was 1KW) quartz/halogen lamp
that had a big blackened "tumor" of glass on the side where the envelope had
deformed. I was told that this happened because someone got a fingerprint on
the bulb when installing it. If this is not correct, what caused this? BTW,
this lamp was not the long thin kind found in $10 backyard lights, but one
with a two-pin base and the filament coiled into about a 1" x 1/4" dia spiral.
(Type FEL for 1K or the equivilent in 750).
Sometimes the envelope has broken; we attributed this to rough handling fo
the stage fixture, but it could be the
"different thermal expansion --> breakage" mechanism.
>I guess I'll have to buy some bulbs and try this at home because I don't
>buy any of these theorys. (Except the carbon one maybe)
I've noticed some computer-surplus places advertising 1KW quarts lamps for
very reasonable prices...
>[Alan Kilian Cray Research, Inc. kil...@cray.com]
Richard Snider
>I think I can answer my own question. I went to the hardware store
>and looked at some quartz-halogen replacement bulbs. They have what
>appears to be a tungsten filament wire inside a quartz tube. Going
>off the deep end, I would say that the resistance of the wire would
>limit the current and no ballast is needed.
A quartz-halogen bulb is no different from a regualar incandescent in as
much as how the power should be supplied to it. Most of the "Indoor"
type of fixtures use bulbs that run at 12V (For many reasons). This is
why in some fixtures there is a step-down transformer. It is not being
used for current limiting or starting as it would be in a flourescent.
Many "Outdoor" Halogens tend to use the line voltage directly.
>I looked up halogen in my dictionary. It said it was one of the very
>active chemical elements, fluorine, chlorine, bromine, astatine, or
>iodine. How does this apply to a light bulb?
When the bulb is run in the correct temperature range, the halogen
causes re-depositing of the tungsten that is boiled off the filament
at the elevated temperature. At lower temperatures (ie. light is
dimmed with a dimmer) the boiling of tungsten from the filament is
not a large effect so the scrubbing and re-deposition of the tungsten
is not so important.
Lastly, I am suspicious in general of many of the "indoor" halogen
types of lights. To get maximum "light for the buck" a halogen bulb
must be run a LOT hotter than the ones I see in stores are. Specifically
I have done quite a bit of theater lighting using lots of halogen
equipment, and usually when a light is on full, in order to get
proper re-deposition the quartz tube will glow bright red. It will
also keep glowing for several SECONDS after the light is shut down.
This is the temperature they must be run at to make the halogen inside
be reasonably useful. Otherwise you may as well have regular light
bulbs.
As far as getting oil on the bulbs (from skin or other things), if
the bulb is run in the correct temperature range (HOT) then getting
any kind of oil on the bulb will usually result in premature failure
due to a carbon hot spot, followed by deformation, followed by
(often spectacular) destruction. If anyone out there dosn't believe
that the quartz tube can deform, I have a few "neat looking" bulbs
that show quite nicely how well the quartz tube can deform.
...Rich
------------------------------------------------------------------------
Where: ..uunet!mnetor!yunexus!xrtll!rsnider Also: rsn...@xrtll.UUCP
An unbreakable tool is useful for breaking other tools.
Johnathan Vail
I posted a question about some halogen trak-lights. I have found a
few more things out (like the bulbs still work). To re-cap my earlier
post and pose the question differently:
* I bought a set of trak lights and some 110v halogen bulbs
* the bulbs didn't work in the fixture so I tested the bulbs with
a meter and they read open. it was easier than trying another
fixture. I assumed something killed them
* The bulbs are now known good and the original problem is solved
(the fixture contact needed adjusting)
MY QUESTION:
Why does the bulb read open on a 20 meg scale?
Theory: the rectifier circuit is causing this?
jv
``There's nothing remarkable about it. All one has to do is hit the right
keys at the right time and the instrument plays itself.'' -- J. S. Bach
_____
| | Johnathan Vail | n1...@tegra.com
|Tegra| (508) 663-7435 | N1...@448.625-(WorldNet)
----- j...@n1dxg.ampr.org {...sun!sunne ..uunet}!tegra!vail
Jeffrey Weiss
>Lastly, I am suspicious in general of many of the "indoor" halogen
>types of lights. To get maximum "light for the buck" a halogen bulb
>must be run a LOT hotter than the ones I see in stores are. Specifically
>I have done quite a bit of theater lighting using lots of halogen
>equipment, and usually when a light is on full, in order to get
>proper re-deposition the quartz tube will glow bright red. It will
>also keep glowing for several SECONDS after the light is shut down.
I'm trying to understand this. I have two different types of halogen
fixtures at home. One is by LSI (seen mostly in stores, malls, etc.) that
uses 12V 75 watt MR-16 lamps. The others use 12V 50 watt small bulbs. Both
of these glow for several SECONDS after the switch is thrown. This is the
reaction I have seen most often with all halogen fixtures I've had a chance
to turn on and off. I have a hard time figuring out what color the tubes
glow when at full power since (even at these modest wattages) I can't look
directly at them without going blind! For what reason would these lights
be run not hot enough?
--
j...@mckinsey.com (...mit-eddie!mck-csc!jw)
Jeffrey Weiss
richard b kronstad
to ride in) using a chainsaw engine for the motor.
He says that the gears will be direct drive. To me (little that I know) this
means that there won't be any belts from the engine to the wheels.
The only thing he doesn't have is a source for the gears. He would appreciate
any information on gear sources. Responses can be sent to me (or possibly
posted).
Richard Kronstad
Robert Wier
All of this talk about Halogen lights and possible destruction
thereof make me wonder if similar technology is being applied
to transmitting tubes (and maybe CRTs?). I know from talking
to broadcast engineers that you only have a matter of seconds
to shut off a 25,000 watt transmitting tube if the cooling
fans fail. In fact we have a very nice EMAC tube upstairs in
the electronics lab (4CX5000 I believe) that got destructed just
this way. The cooling fins (made of some type of metal) are
MELTED.
The tungston re-deposition properties of halogen lamps would seem
a natural for life extension on transmitting tubes (IF that is
a desired property - maybe not for the manufacturers :-) )
or would the presence of grids, plates, and other elements
negate the use of halogen?
- Bob Wier
-------------- insert favorite standard disclaimers here ----------
College of Engineering
Northern Arizona University / Flagstaff, Arizona
Internet: r...@naucse.cse.nau.edu | BITNET: WIER@NAUVAX | WB5KXH
or uucp: ...arizona!naucse!rrw
John Opalko, N7KBT
->
-> The tungston re-deposition properties of halogen lamps would seem
-> a natural for life extension on transmitting tubes (IF that is
-> a desired property - maybe not for the manufacturers :-) )
-> or would the presence of grids, plates, and other elements
-> negate the use of halogen?
Kind of contrary to the definition of a VACUUM tube, though, isn't it?
Robert Wier
Aha! VERY good point. My brain is scrambled from thinking about
silicon for too long (sigh...). I once had a QSL card which
had a cartoon about some guys using plumbing tools to try to
stop "grid leaks". If you remember this, you're as old as
I am!!!
Blair P. Houghton
newsletter) arrived today, and synchronicity of synchronicities,
there's a story on p. 6 (hidden as filler under the headline
"Intel's Newest Supercomputer" (no plug intended :)) about how
GE has just improved the electrical efficiency of halogen lamps.
They give the envelope an infrared-reflective coating. No details
on what it is, but it's probably just a half-wave-gel thing.
This reflects much of the heat back onto the filament, keeping
it incandescent-hot, saving the electrical energy that would
have been radiated. Since it works only on infrared radiation,
it doesn't affect the lumens in the visible spectrum. They claim
an energy savings of 60 percent.
--Blair
"I'm impressed."
Phil Ngai
|GE has just improved the electrical efficiency of halogen lamps.
|They give the envelope an infrared-reflective coating. No details
This is great. Any relationship to the shortage of MR-16 50 Watt bulbs?
You can't buy one for love or money here in the SF Bay area.
(no doubt thanks to the Taiwanese dumping those low cost low voltage
halogen track lights on the market without warning GE)
--
Charlie Ih
>GE has just improved the electrical efficiency of halogen lamps.
> .... This reflects much of the heat back onto the filament, keeping
>it incandescent-hot, saving the electrical energy ....
>....... Since it works only on infrared radiation,
>it doesn't affect the lumens in the visible spectrum.
I have been thinking about this for a long time. I am glad
somebody have made it. 60% energy saving (even more) is
possible. Actually the IR coating can improve the color
balance of the light. Can anybody tell me if this is already
a product on the market or where I can find more information.
Thanks in advance.
Charles S. Ih
Gordon LETWIN
Some folks have posted that they'd wondered why halogen bulbs weren't
coated with IR reflectors to improve efficiency before now. The problem
was finding a coating which could take the heat (and of course which was
also transparent to visable light). Natually, the technique only works
on bulbs with the proper shape, but most halogen bulbs are cylinderical.
The article that I saw showed a guy holding the bulb itself - a bit larger
than a peanut - in one hand, and an ordinary looking PAR reflector "bulb"
in the other. Presumably the halogen bulb mounts inside the PAR thing
(those cone-shaped bulbs you see in outdoor fixtures) for this application.
The blurb didn't say.
gordon letwin
Dan Dunphy
>>The halogen cycle not only prevents rapid loss of filament
>>material, it repairs minor flaws in the filament and prevents
>>hot-spots due to these flaws.
>>
>>Halogen lamps burn out (barring some extensive flaw) only
>>when one of the non-tungsten parts fails (the filament supports
>>weaken from temperature cycling, the way the filament would
>>if it weren't for the halogen cycle).
>
>
>What's the principle behind the "krypton" flashlight bulbs being sold
>now, and market as "70% brighter" than the standard type?
I suspect they use a principle similar to halogen. I just
tried my first. They are a lot brighter.
Dan Dunphy
time. The decrease in tempeature caused a significant
tungsten deposit to form on the inside of the quartz
envelope. There was a significant hole in the low beam pool of
light in front of the bike. I believe a dimmer defeats the
halogen cycle.
Charles R. Sullivan
>>/ col:sci.electronics / schu...@cup.portal.com (Michael Alan Schuster) / 4:41 pm Nov 29, 1990 /
>>
>>now, and market as "70% brighter" than the standard type?
>>----------
>I suspect they use a principle similar to halogen. I just
>tried my first. They are a lot brighter.
I don't know if Krypton bulbs use a halogen cycle too, but the idea of the
krypton is that it is a heavier gas than the usual fill gas, and so retards
the evaporation of tungsten more, and I think has lower thermal conductivity.
You can take the benifits of this as longer life or higher efficiency, depending
on what temperature you design the filament to operate at.
Charlie Sullivan char...@cory.berkeley.edu
Blair P. Houghton
>tungsten deposit to form on the inside of the quartz envelope.
>I believe a dimmer defeats the halogen cycle.
I would expect so, as the rate of deposition is proportional
to the fourth power of the temperature; so, where the vaporous
tungsten ends up would be very much affected by the power
dissipation.
--Blair
"This holds true for the
deposition of cats, too."
Blair P. Houghton
>[...]the rate of deposition is proportional
>to the fourth power of the temperature; so, where the vaporous
>tungsten ends up would be very much affected by the power
>dissipation.
I forgot to mention that I bought Mom one of these things
for Xmas, and the directions in hers (mine didn't have this)
mentioned that when the light appears less bright than usual
you should run it at full power for a couple of hours.
So, the manufacturers are aware of this phenomenon.
(Their English, however, could do with some brushing-up; as
I was assembling the thing Mom was reading the directions,
and she was thoroughly confused since the passage was written
"...if the lamp should never seem to lose brightness...")
--Blair
"Quoth the raven, 'Not for more!'"
leland.m.kornhaus
a room that had florescent lighting ith dimmer switches controlling the
florescent bulbs. How is this done? Would it be done before the ballasts?
Does it work by Pulse Width Modulation? There was absolutely NO flicker that
I could see. Any answers? Enquiring minds want to know.
Six o'clock News
>a room that had florescent lighting ith dimmer switches controlling the
>florescent bulbs. How is this done? Would it be done before the ballasts?
From: char...@cory.Berkeley.EDU (Charles R. Sullivan)
Path: cory.Berkeley.EDU!charless
I used to work for a company that makes these systems, so I could write
for days about this, but I will try to keep this relatively brief.
Method One: Put a phase control dimmer, in principle the same as a normal
incandescant dimmer, upstream of the ballasts. Unfortunately you need
special dimming ballasts. They have separate power inputs for the
arc power and filament power, because you need to leave the filament power at
full while dimming the arc.
Method Two: Use normal ballasts, but put some
kind of more complex dimmer upstream of the
ballasts. It isn't easy, but the company I worked for, Lutron Electronics,
has a couple of patented systems that put out waveforms set up to dim the
arc, and still keep the filaments heated. The system has to be set up
properly for the particular ballasts being used.
Method Three: Use a 'smart' ballast, which rectifies the AC input, and
then switches at high frequency (eg 30kHz), and runs the lamps on HF AC.
The control circuitry in the ballast can change the current drive to the
lamp s indicated by some external signal (eg from a knob on the wall).
Method One is reasonably inexpensive, but doesn't have great performance--
you can get some flicker, you can't reasonably expect to get good dimming
below about 10% of full light, etc. Method Two is particularly good
for retrofit applications, but because it can't dim to very low levels
(35% typical minimum), however, it is really only
suited for energy management applications
where you just want to throttle back energy use a bit, and maybe turn
the lights lower when there is lots of sun coming in the windows or whatever.
It doesn't dim low enough for aesthetic applications. Method Three is super
high performance (no flicker, 1/2% minimum light level, etc.) but expensive.
Charlie Sullivan char...@cory.berkeley.edu
Blair P. Houghton
>From the G.E. Lamp catalog:
[...halogens last longer at below-rated voltage if you use a variable
transformer but not if you use a semiconductor-switch dimmer...]
>
>I take this to mean: "Sure, they get dimmer but they don't last any longer."
What it seems more to mean is that you should
use a variac rather than a triac.
--Blair
"Ac, thphhth."
-Bill the cat
Norm Strong
Xenon is even heavier, and has the additional advantage of being a lot
cheaper. So where does that leave your argument?
--
Norm Strong (str...@tc.fluke.com)
2528 31st S. Seattle WA 98144