Can anybody point me to some information about how the light output of
incandescent and halogen lamps varies as they are dimmed? I'd like to
compare the efficiency of a high-wattage bulb when dimmed to lower
wattage bulbs operated full-on.

--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .

The only way I can think to really know is use a clamp on amp meter or
Kill-A -Watt since all bulbs are a bit different and need a minimum
starting voltage. A 100 watt bulb dimmed to 60 watts should put out less
light than a 60 watt will. A Kill-A -Watt meter is good to have around

"m Ransley" wrote in message
...
The only way I can think to really know is use a clamp on amp meter or
Kill-A -Watt since all bulbs are a bit different and need a minimum
starting voltage. A 100 watt bulb dimmed to 60 watts should put out less
light than a 60 watt will. A Kill-A -Watt meter is good to have around

There was also a thread recently about dimming halogen lights. they burn
out faster IIRC

More that you need to know about dimmers he
http://www.epanorama.net/documents/l...ghtdimmer.html

Good info he
http://www.clarkpublicutilities.com/...ves2001/6-01-4
You are correct that an old rheostat dimmer that uses a resistance coil to
divert some of the energy passing through it does not produce much energy
savings. The dimmers literally detour some of the light energy to a
component in the switch that converts the energy to heat. The lights are
dimmer, but the energy savings is minimal.

When shopping for a new dimmer to replace a rheostat model, make sure to
specify an electronic dimmer. Electronic dimmers use a circuitry called
TRIAC to control voltage to the light bulbs. TRIACs trim the voltage to the
bulb without creating heat, and effectively reduce the energy use while only
losing about one percent of the savings to operate the dimmer circuit. A
good TRIAC dimmer will reduce the light output over a broad range, and in
turn trim the energy use.

However, the ratio of light output to dimmer setting is not equal to an
overall reduction in wattage. In other words, a 100-watt bulb dimmed to the
equivalent light output of a 60-watt bulb actually draws 70 watts through
the electronic dimmer. If you always use the fixture in a dimmed position,
you'd be better off reducing the wattage with new bulbs instead of using a
dimmer.

In a related question----
If I leave the dimmer in the lowest position where the light is (looks)
turned off, is it still drawing power?

D.


"Edwin Pawlowski" wrote in message
t...

"m Ransley" wrote in message
...
The only way I can think to really know is use a clamp on amp meter or
Kill-A -Watt since all bulbs are a bit different and need a minimum
starting voltage. A 100 watt bulb dimmed to 60 watts should put out less
light than a 60 watt will. A Kill-A -Watt meter is good to have around

There was also a thread recently about dimming halogen lights. they burn
out faster IIRC

More that you need to know about dimmers he
http://www.epanorama.net/documents/l...ghtdimmer.html

Good info he
http://www.clarkpublicutilities.com/...ves2001/6-01-4
You are correct that an old rheostat dimmer that uses a resistance coil to
divert some of the energy passing through it does not produce much energy
savings. The dimmers literally detour some of the light energy to a
component in the switch that converts the energy to heat. The lights are
dimmer, but the energy savings is minimal.

When shopping for a new dimmer to replace a rheostat model, make sure to
specify an electronic dimmer. Electronic dimmers use a circuitry called
TRIAC to control voltage to the light bulbs. TRIACs trim the voltage to
the bulb without creating heat, and effectively reduce the energy use
while only losing about one percent of the savings to operate the dimmer
circuit. A good TRIAC dimmer will reduce the light output over a broad
range, and in turn trim the energy use.

However, the ratio of light output to dimmer setting is not equal to an
overall reduction in wattage. In other words, a 100-watt bulb dimmed to
the equivalent light output of a 60-watt bulb actually draws 70 watts
through the electronic dimmer. If you always use the fixture in a dimmed
position, you'd be better off reducing the wattage with new bulbs instead
of using a dimmer.

"Dave" wrote in message
news:G21rf.1153$OU5.630@clgrps13...
In a related question----
If I leave the dimmer in the lowest position where the light is (looks)
turned off, is it still drawing power?

D.

Mine has a "click" for the off position. Based on the following, I think it
still takes some power when turned down past visible light.

a 100-watt bulb dimmed to the equivalent light output of a 60-watt bulb
actually draws 70 watts through the electronic dimmer.

Perhaps someone knows for sure.

When shopping for a new dimmer to replace a rheostat model, make sure
to specify an electronic dimmer.

I would challenge you to find one (for residential use) that ISN'T an
electronic (triac) dimmer! They've been that way for decades.

The only dimmers that aren't are the variac (variable transformer) dimmers
which are very large affairs which I've never seen in residential use.
They are, BTW, superior in terms of putting out a normal AC waveform, not
the weird stuff a triac dimmer puts out. As for a rheostatic (resistance)
dimmer, I've never seen one outside of an old theatre stage lighting board.

(Technically the knob or slider you move on a triac dimmer is a variable
resistance but it's properly called a potentiometer as it is handling only
a control voltage not the actual power throughput which is what the term
rheostat implies.)

On Sat, 24 Dec 2005 01:13:52 GMT, "Edwin Pawlowski"
wrote:


"Dave" wrote in message
news:G21rf.1153$OU5.630@clgrps13...
In a related question----
If I leave the dimmer in the lowest position where the light is (looks)
turned off, is it still drawing power?

D.

Mine has a "click" for the off position. Based on the following, I think it
still takes some power when turned down past visible light.


A small enough amount of power won't be able to heat the filament to a
high enough temperature for it to emit visible light. It could still
be emitting some infrared.

a 100-watt bulb dimmed to the equivalent light output of a 60-watt bulb
actually draws 70 watts through the electronic dimmer.

Perhaps someone knows for sure.

--
2 days until the winter solstice celebration

Mark Lloyd
http://notstupid.laughingsquid.com

"Democracy is two wolves and a lamb voting on what
to have for lunch. Liberty is a well armed lamb
contesting the vote." - Benjamin Franklin

Steve Kraus wrote:
When shopping for a new dimmer to replace a rheostat model, make sure
to specify an electronic dimmer.


I would challenge you to find one (for residential use) that ISN'T an
electronic (triac) dimmer! They've been that way for decades.

The only dimmers that aren't are the variac (variable transformer) dimmers
which are very large affairs which I've never seen in residential use.

I did, once....But it was quite a residence, the home of John Hayes
Hammond, a prolific inventor obviously knowlegable in the electrical
technologies of his era.

They were in round housings designed for wall mounting, with a good
sized knob on the end to crank the sliding tap around with. IIRC they
were about 7 inches in diameter and stuck out from the wall about 5 or 6
inches.

A fun place to visit indeed:

http://www.hammondcastle.org/

Happy Holidays,

Jeff

--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"Truth exists; only falsehood has to be invented."

On Sat, 24 Dec 2005 02:20:09 GMT, Steve Kraus
wrote:

When shopping for a new dimmer to replace a rheostat model, make sure
to specify an electronic dimmer.

I would challenge you to find one (for residential use) that ISN'T an
electronic (triac) dimmer! They've been that way for decades.

The only dimmers that aren't are the variac (variable transformer) dimmers
which are very large affairs which I've never seen in residential use.
They are, BTW, superior in terms of putting out a normal AC waveform, not
the weird stuff a triac dimmer puts out. As for a rheostatic (resistance)
dimmer, I've never seen one outside of an old theatre stage lighting board.

You beat me to the punch. I was going to say the same. Except for
maybe wacko millionaires, I don't think anyone had dimmers in their
home until they had transistorized** dimmers. Others were too big to
fit in the regular box, and too expensive too.. **I count any
semiconductor as a transistor, including triacs and diodes



Remove NOPSAM to email me. Please let
me know if you have posted also.

m Ransley errs again:

... all bulbs are a bit different and need a minimum starting voltage.
A 100 watt bulb dimmed to 60 watts should put out less light than
a 60 watt will.

Incandescent bulbs have a minimum starting voltage? :-)

Nick

Edwin Pawlowski errs again:

There was also a thread recently about dimming halogen lights. they burn
out faster IIRC

Dimmed bulbs burn out faster? :-)

Nick

wrote:
Edwin Pawlowski errs again:

There was also a thread recently about dimming halogen lights. they
burn out faster IIRC

Dimmed bulbs burn out faster? :-)

Nick

Halogen lamps do. They require a certain internal temperature of the
inside glass envelope to start the halogen cycle.

http://www.goodmart.com/facts/light_...gen_cycle.aspx

--
Joseph Meehan

Dia duit

wrote:
m Ransley errs again:

... all bulbs are a bit different and need a minimum starting voltage.
A 100 watt bulb dimmed to 60 watts should put out less light than
a 60 watt will.

Incandescent bulbs have a minimum starting voltage? :-)

Nick

Well a minimum voltage at which they will emit visible light.

--
Joseph Meehan

Dia duit

m Ransley wrote:
The only way I can think to really know is use a clamp on amp meter or
Kill-A -Watt since all bulbs are a bit different and need a minimum
starting voltage. A 100 watt bulb dimmed to 60 watts should put out
less light than a 60 watt will. A Kill-A -Watt meter is good to have
around

That and measure the light output.

--
Joseph Meehan

Dia duit

"When shopping for a new dimmer to replace a rheostat model, make sure
to
specify an electronic dimmer. Electronic dimmers use a circuitry called

TRIAC to control voltage to the light bulbs. TRIACs trim the voltage to
the
bulb without creating heat, and effectively reduce the energy use while
only
losing about one percent of the savings to operate the dimmer circuit.
A
good TRIAC dimmer will reduce the light output over a broad range, and
in
turn trim the energy use. "

When was this advice written for, 1970? I don't think you could find a
rheostat type dimmer to use for home light control if you wanted one.
All the ones at any of the home center stores, etc have been electronic
for decades.

Yes incandesant have a minimum starting voltage as a dimmer reduces
voltage output. I just took my X10 dimmer and put a Kill-A Watt on it
with 100w incandesant. A 100 watt light bulb wont give visable light
till 5 watts are pulled . So at 4 watts you may think its off, but its
pulling 4 watts The Kill a watt in a different configuration to measure
V dimmed the display unreadably at 37v and the 100watt bulb using 16
watts, figuring reduction in steps of V it figures to 31V at 10 watts.

I always thought all filament bulbs lasted indefinatly dimmed as
incandesant do, I have several 240V incandesant bulbs that on average
burn 10-15 years 7 days x 12 hrs , but my dimmed kitchen halogens dont
last, as stated and now Ive learned, Halogen redeposit and need full
voltage to run right.

A triac wall dimmer on minimum setting I did not try, but X10 is
probably Triac and at its reading 4% would be waisted without being sure
the switch is off.

"CJT" wrote in message
...
Can anybody point me to some information about how the light output of
incandescent and halogen lamps varies as they are dimmed? I'd like to
compare the efficiency of a high-wattage bulb when dimmed to lower
wattage bulbs operated full-on.

Best place to find the information is the Illuminating Engineering Society
Handbook (any edition); but it's not on-line. You can usually find a copy
in a good reference library, however.

The light output and power of an incandescent or halogen incandescent bulb
are exponential functions of the applied voltage. One point on the curve
that I remember is the half-power point. Say you operate a 100 watt bulb on
a dimmer at 50 watts, the light output is about 1/3 of full rated. When you
operate a bulb on a rectifier (diode) such as a high-low switch in the low
position, it operates at 1/2 power. As I recall, the measured voltage is
about 85 volts.

Take a look at:
http://www.sylvaniaautocatalog.com/n...fila_lamps.htm to see
the curves. The values there apply to low voltage automotive, but the
numbers for 120 volt lamps aren't much different.

Since efficiency drops faster than light output when incandescent bulbs are
dimmed, dimming is not a good energy-saving strategy. At best, incandescent
bulbs only emit 10% of their power input as light anyway.

Variable autotransformer dimmers were never widely used for residential
lighting, but they were indeed used. Residential versions were made by the
Superior Electric Co. in the 1950s and 60s. If you happen to see some
reruns of the TV show "Frasier", you'll see several of them on the wall of
his radio studio. The have rather large control knobs -- about 4 in. in
diameter and required a wall box that is about 4 times the size of a
standard box.

TKM

Without a V meter test and from what the kill a watt read I guess 10-
22v is the point at which you will see illumination.

Without a V meter test and from what the kill a watt read I guess 10-
22v is the point at which you will see illumination.

"Edwin Pawlowski" wrote:


"m Ransley" wrote in message
...
The only way I can think to really know is use a clamp on amp meter or
Kill-A -Watt since all bulbs are a bit different and need a minimum
starting voltage. A 100 watt bulb dimmed to 60 watts should put out less
light than a 60 watt will. A Kill-A -Watt meter is good to have around

There was also a thread recently about dimming halogen lights. they burn
out faster IIRC

You do remember correctly. Running at full on, or more specifically
full temp, keeps the tungsten from depositing on the glass, and cycles
back to the filament.

In most cases, running for a while at full blast will re-activate the
halogen cycle in the bulb, and undo some of the damage done by dimming.

This high temp is also why it is important not to touch a halogen bulb,
since the oil from the fingerprint will cause the glass to bubble.

TKM wrote:

... When you operate a bulb on a rectifier (diode) such as a high-low switch
in the low position, it operates at 1/2 power.

Somehow that seems unlikely, since incandescents are so non-linear.

As I recall, the measured voltage is about 85 volts.

That looks like the rms value of the rectified sine wave. If 120 = sqr(2V^2),
V = 85.85 for half the waveform.

Nick

Joseph Meehan wrote:

Edwin Pawlowski errs again:

There was also a thread recently about dimming halogen lights. they
burn out faster IIRC

Dimmed bulbs burn out faster? :-)

Halogen lamps do. They require a certain internal temperature of the
inside glass envelope to start the halogen cycle.

http://www.goodmart.com/facts/light_...gen_cycle.aspx

I don't see that there. I can imagine it could go either way. A lower temp
filament will evaporate less, so the bulb might last longer. How long would
it last at 10% power? At 1%? At 0.0001%? :-)

Incandescent bulbs have a minimum starting voltage? :-)

Well a minimum voltage at which they will emit visible light.

Every black body above absolute zero emits some visible light.

m Ransley wrote:

A 100 watt bulb dimmed to 60 watts should put out less light than a 60 watt
will. A Kill-A -Watt meter is good to have around

That and measure the light output.

Easy, with a grease spot photometer. Move a 3x5 card with a grease spot
between dimmed and undimmed bulbs until the spot disappears, when it has
equal illumination on both sides and outputs are inversely proportional
to the square of the distance from each bulb.

Nick

wrote:
Joseph Meehan wrote:

Edwin Pawlowski errs again:

There was also a thread recently about dimming halogen lights. they
burn out faster IIRC

Dimmed bulbs burn out faster? :-)

Halogen lamps do. They require a certain internal temperature of
the inside glass envelope to start the halogen cycle.

http://www.goodmart.com/facts/light_...gen_cycle.aspx

I don't see that there. I can imagine it could go either way. A lower
temp filament will evaporate less, so the bulb might last longer. How
long would it last at 10% power? At 1%? At 0.0001%? :-)

Yes it evaporates less, but far more of it ends up on the glass while
when the cycle is working it just goes back to the filament. In real life
it does work in such a way that the lamps do not last as long.

That said, my experience with projector bulbs is that used at half power
they seem to last about the same time as full. While the older non-halogen
lamps lasted a lot longer at half power. My 60W lamps by my sofa don't seem
to be much effected, but the little peanut lamps under the counter last
longer at full power maybe 50% longer.


Incandescent bulbs have a minimum starting voltage? :-)

Well a minimum voltage at which they will emit visible light.

Every black body above absolute zero emits some visible light.

Difficult to measure if true. I fear my college physics is about 40
years old now and while I am sure the answers have not changed on that one,
my memory is a little weak.


m Ransley wrote:

A 100 watt bulb dimmed to 60 watts should put out less light than a
60 watt will. A Kill-A -Watt meter is good to have around

That and measure the light output.

Easy, with a grease spot photometer. Move a 3x5 card with a grease
spot between dimmed and undimmed bulbs until the spot disappears,
when it has equal illumination on both sides and outputs are
inversely proportional
to the square of the distance from each bulb.

That is what I would use, but there are other methods. I doubt if my
spot meter could measure the light from a filament cooled to 3º K. :-)


Nick

--
Joseph Meehan

Dia duit

TKM ) said...

The light output and power of an incandescent or halogen incandescent bulb
are exponential functions of the applied voltage. One point on the curve
that I remember is the half-power point. Say you operate a 100 watt bulb on
a dimmer at 50 watts, the light output is about 1/3 of full rated. When you
operate a bulb on a rectifier (diode) such as a high-low switch in the low
position, it operates at 1/2 power. As I recall, the measured voltage is
about 85 volts.

Another thing to consider when dimming an incandescent bulb (and I believe
halogens apply as well), is the spectral shift.

If you were to dim a 100 watt bulb so that it is only drawing 60 watts,
not only will its light output not be the same as the 60 watt bulb burning
fully, but the spectrum it puts out will be different.

What happens is that the lower temperature of the filament doesn't simply
lower the light output, but shifts some of it into the non-visible part of
the spectrum (the infra-red part: heat).

That 100 watt bulb that is dimmed so that it is only drawing 60 watts of
power will appear less bright and more red/orange in color than a 60 watt
bulb drawing its rated 60 watts.

--
Calvin Henry-Cotnam
"Never ascribe to malice what can equally be explained by incompetence."
- Napoleon
-------------------------------------------------------------------------
NOTE: if replying by email, remove "remove." and ".invalid"

Calvin Henry-Cotnam wrote:

TKM ) said...

The light output and power of an incandescent or halogen incandescent bulb
are exponential functions of the applied voltage. One point on the curve
that I remember is the half-power point. Say you operate a 100 watt bulb on
a dimmer at 50 watts, the light output is about 1/3 of full rated. When you
operate a bulb on a rectifier (diode) such as a high-low switch in the low
position, it operates at 1/2 power. As I recall, the measured voltage is
about 85 volts.


Another thing to consider when dimming an incandescent bulb (and I believe
halogens apply as well), is the spectral shift.

If you were to dim a 100 watt bulb so that it is only drawing 60 watts,
not only will its light output not be the same as the 60 watt bulb burning
fully, but the spectrum it puts out will be different.

What happens is that the lower temperature of the filament doesn't simply
lower the light output, but shifts some of it into the non-visible part of
the spectrum (the infra-red part: heat).

That 100 watt bulb that is dimmed so that it is only drawing 60 watts of
power will appear less bright and more red/orange in color than a 60 watt
bulb drawing its rated 60 watts.


Yep, and that's why I mounted a "hidden" dimmer with it's control shaft
(sans knob)sticking down through the top of the medicine cabinet in our
master bathroom. It's set a little bit down from full on and makes the
light from the bunch of 25 watt frosted globe bulbs around the mirror
redder than at full line voltage.

SWMBO likes it better for judging the appearance of the paint and stuff
the puts on her face, and I find it makes my own mug somewhat easier to
take on tough mornings.

As a plus, we've been here almost 20 years since I put that dimmer in
and I swear I haven't had to replace even one of the bulbs it's
controlling yet.

Happy Holidays!

Jeff

--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"Truth exists; only falsehood has to be invented."

On 24 Dec 2005 10:35:20 -0500, wrote:

Joseph Meehan wrote:

Edwin Pawlowski errs again:

There was also a thread recently about dimming halogen lights. they
burn out faster IIRC

Dimmed bulbs burn out faster? :-)

Halogen lamps do. They require a certain internal temperature of the
inside glass envelope to start the halogen cycle.

http://www.goodmart.com/facts/light_...gen_cycle.aspx

I don't see that there. I can imagine it could go either way. A lower temp
filament will evaporate less, so the bulb might last longer. How long would
it last at 10% power? At 1%? At 0.0001%? :-)

Incandescent bulbs have a minimum starting voltage? :-)

Well a minimum voltage at which they will emit visible light.

Every black body above absolute zero emits some visible light.

It would emit EM radiation (because of this, an electric heater is NOT
100% efficient). Would it always be in the limited frequency range
this is visible to humans?


m Ransley wrote:

A 100 watt bulb dimmed to 60 watts should put out less light than a 60 watt
will. A Kill-A -Watt meter is good to have around

That and measure the light output.

Easy, with a grease spot photometer. Move a 3x5 card with a grease spot
between dimmed and undimmed bulbs until the spot disappears, when it has
equal illumination on both sides and outputs are inversely proportional
to the square of the distance from each bulb.

Nick
--
1 days until the winter solstice celebration

Mark Lloyd
http://notstupid.laughingsquid.com

"Democracy is two wolves and a lamb voting on what
to have for lunch. Liberty is a well armed lamb
contesting the vote." - Benjamin Franklin

On Sat, 24 Dec 2005 08:53:09 -0600, (m Ransley)
wrote:

Without a V meter test and from what the kill a watt read I guess 10-
22v is the point at which you will see illumination.

You might be able to see something at a lower voltage, with a small
video camera that responds to infrared. Infrared is just below visible
light in frequency, and will be emitted by a filament that's not quite
hot enough to emit visible light.
--
1 days until the winter solstice celebration

Mark Lloyd
http://notstupid.laughingsquid.com

"Democracy is two wolves and a lamb voting on what
to have for lunch. Liberty is a well armed lamb
contesting the vote." - Benjamin Franklin

Alot of the radiation from incandesants is invisable to the eye, it is
in various areas of the spectrum and changes with voltage. Ever notice
how incandesants photograph orangeish, cameras have different
sensitivities to different wavelents of light. An incandesant outputs
only apx 10% of its energy as usefull light, hence it is actualy an
electric heater that emits light, where as a flourescent does better.
Incandesant output 17-19 LPW, lumen per watt, T8 flourescent up to 110
LPW with 45-60 for CFLs being average.

Mark Lloyd wrote:

You might be able to see something at a lower voltage, with a small
video camera that responds to infrared. Infrared is just below visible
light in frequency, and will be emitted by a filament that's not quite
hot enough to emit visible light.

Every black body above absolute zero emits visible light.

Nick

wrote in message

Every black body above absolute zero emits visible light.

Nick

Yeah, but you just can't see it.

On 2005-12-24, wrote:

Every black body above absolute zero emits visible light.

More precisely, every black body above absolute zero emits light in
the visible portion of the spectrum, often at an intensity too low for
the human eye to see.

Cheers, Wayne

Well nick I find lights kind of usless unless they illuminate things I
see.

Mark Lloyd wrote:

Every black body above absolute zero emits some visible light.

Would it always be in the limited frequency range this is visible to humans?

There would always be some visible light, but it's very faint at low temps :-)

20 PI=4*ATN(1)
30 LAMBDAU=7.8E-07'upper visible limit (meters)
40 LAMBDAL=3.8E-07'lower visible limit (meters)
50 FOR LT=2 TO 4'log F temp
60 TF=10^LT'temp (F)
70 TK=(TF+460)/1.8'temp (K)
80 GAM=.0143879/(LAMBDAU*TK)'Pivovonsky and Nagel (1961) polynomial term
90 CFRACU=0'initialize upper cumulative fraction
100 FOR M=1 TO 3
110 TERM=15/(PI^4)*(((M*GAM+3)*M*GAM+6)*M*GAM+6)
120 CFRACU=CFRACU+EXP(-M*GAM)/(M^4)*TERM
130 NEXT M
140 GAM=.0143879/(LAMBDAL*TK)
150 CFRACL=0
160 FOR M=1 TO 3
170 TERM=15/(PI^4)*(((M*GAM+3)*M*GAM+6)*M*GAM+6)
180 CFRACL=CFRACL+EXP(-M*GAM)/(M^4)*TERM
190 NEXT M
200 P=5.6697E-08*(TK^4)'total emissive power (W/m^2)
210 EFRAC=CFRACU-CFRACL'fraction of emissive power in visible spectrum
220 PRINT TF,EFRAC,P,EFRAC*P
230 NEXT

temp visible fraction total power visible power

100 F 6.010933E-22 531.1561 W/m^2 3.192744E-19 W/m^2
1000 2.753038E-07 24540.4 6.756065E-03
10000 .4668266 6.465423E+07 3.018231E+07

Nick

Joseph Meehan wrote:

wrote:

Edwin Pawlowski errs again:


There was also a thread recently about dimming halogen lights. they
burn out faster IIRC

Dimmed bulbs burn out faster? :-)

Nick


Halogen lamps do. They require a certain internal temperature of the
inside glass envelope to start the halogen cycle.

http://www.goodmart.com/facts/light_...gen_cycle.aspx


Wouldn't it be enough to periodically heat them up (i.e. isn't the
damage reversible to some extent, as long as the bulb isn't too badly
damaged)?

--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .

John Hines wrote:

"Edwin Pawlowski" wrote:


"m Ransley" wrote in message
...

The only way I can think to really know is use a clamp on amp meter or
Kill-A -Watt since all bulbs are a bit different and need a minimum
starting voltage. A 100 watt bulb dimmed to 60 watts should put out less
light than a 60 watt will. A Kill-A -Watt meter is good to have around

There was also a thread recently about dimming halogen lights. they burn
out faster IIRC


You do remember correctly. Running at full on, or more specifically
full temp, keeps the tungsten from depositing on the glass, and cycles
back to the filament.

In most cases, running for a while at full blast will re-activate the
halogen cycle in the bulb, and undo some of the damage done by dimming.

Ahh ... that's what I suspected.


This high temp is also why it is important not to touch a halogen bulb,
since the oil from the fingerprint will cause the glass to bubble.


--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .

In article , Edwin
Pawlowski wrote:

"Dave" wrote in message
news:G21rf.1153$OU5.630@clgrps13...
In a related question----
If I leave the dimmer in the lowest position where the light is (looks)
turned off, is it still drawing power?

D.

Mine has a "click" for the off position. Based on the following, I think it
still takes some power when turned down past visible light.

Perhaps someone knows for sure.

If turned down enough that when turning back up, the light suddenly
comes on, then no power was being sent to the light. If the light fades
on in a manner like it faded off (except reverse), then the light probably
was being sent power.

As for how much power a usual dimmer consumes when it is not sending
power to anything: Not zero, but generally a small fraction of a watt.

- Don Klipstein )

CJT wrote:

Joseph Meehan wrote:

wrote:

Edwin Pawlowski errs again:

There was also a thread recently about dimming halogen lights. they
burn out faster IIRC

Dimmed bulbs burn out faster? :-)

Halogen lamps do. They require a certain internal temperature of the
inside glass envelope to start the halogen cycle.

http://www.goodmart.com/facts/light_...gen_cycle.aspx

Wouldn't it be enough to periodically heat them up (i.e. isn't the
damage reversible to some extent...

So far, we seem to have no evidence of any damage.

Nick

In , Joseph Meehan wrote:
wrote:
Joseph Meehan wrote:

Edwin Pawlowski errs again:

There was also a thread recently about dimming halogen lights. they
burn out faster IIRC

Dimmed bulbs burn out faster? :-)

Halogen lamps do. They require a certain internal temperature of
the inside glass envelope to start the halogen cycle.

http://www.goodmart.com/facts/light_...gen_cycle.aspx

I don't see that there. I can imagine it could go either way. A lower
temp filament will evaporate less, so the bulb might last longer. How
long would it last at 10% power? At 1%? At 0.0001%? :-)

Yes it evaporates less, but far more of it ends up on the glass while
when the cycle is working it just goes back to the filament.

The way I saw it on a rather technical book (25 years ago) on this, the
halogen cycle slows down less than filament evaporation does when the bulb
is underpowered. This is, ideally!

However, the halogen cycle does attack the cooler ends of the filament.
You don't gain much when you dim below the point at which the ends of the
filament get eaten away faster than the filament gets damaged by
evaporation.
Yes, the halogen cycle is only a little good at protecting a filament
from evaporation - the evaporation is not perfectly even and the halogen
cycle is not that good at returning tungsten to the parts of the filament
that need it the most. Halogen lamps last longer despite higher filament
temperatures not as much from the halogen cycle but because the fill gas
is at a higher pressure and because the fill gas often has premium gases
such as krypton - whose larger atoms "bounce" evaporated tungsten atoms
back to the filament more than argon atoms do. The small size of halogen
bulbs/"capsules" makes premium fill gases more economical. Still another
advantage of halogen lamps is that the small capsule size slows convection
movement of the fill gas, and with the fill gas more stagnant the filament
evaporates more slowly.
These reasons rather than the halogen cycle are mostly why a halogen
lamp lasts longer than a non-halogen one of the same filament temperature.
Of course, an advantage of the halogen cycle is keepin the inside surface
of the bulb clean - which becomes more necessary when the bulb has a
smaller inside surface where tungsten deposit would be more concentrated
and more opaque.

Sometimes when a halogen bulb is dimmed severely, things go really awry
- depending on the quality of the bulb. Traces of water vapor or oxygen
could be doing the opposite of what the halogen cycle is trying to do, and
these bad effects do not slow down as much as the halogen cycle does when
the bulb is dimmed, and the bulb needs a certain filament and bulb
temperature in order for the halogen to outrun the negative effects of
contaminants.

In real life it does work in such a way that the lamps do not last as long.

That said, my experience with projector bulbs is that used at half power
they seem to last about the same time as full. While the older non-halogen
lamps lasted a lot longer at half power. My 60W lamps by my sofa don't seem
to be much effected, but the little peanut lamps under the counter last
longer at full power maybe 50% longer.

Incandescent bulbs have a minimum starting voltage? :-)

Well a minimum voltage at which they will emit visible light.

Every black body above absolute zero emits some visible light.

Difficult to measure if true. I fear my college physics is about 40
years old now and while I am sure the answers have not changed on that one,
my memory is a little weak.

Well, a blackbody does emit some visible light at any temperature, but
it appears to me that you need about 700 Kelvin to see it with a
dark-adapted eye.
In any case, I would think something would have to be far above body
temperature to squeeze more light from a filament through your pupil onto
any point of your retina than that point receives from the remainder of
your retina.

- Don Klipstein )

In article , CJT wrote:
Joseph Meehan wrote:

wrote:

Edwin Pawlowski errs again:


There was also a thread recently about dimming halogen lights. they
burn out faster IIRC

Dimmed bulbs burn out faster? :-)

Nick

Halogen lamps do. They require a certain internal temperature of the
inside glass envelope to start the halogen cycle.

http://www.goodmart.com/facts/light_...gen_cycle.aspx

Wouldn't it be enough to periodically heat them up (i.e. isn't the
damage reversible to some extent, as long as the bulb isn't too badly
damaged)?

I have heard - sometimes even in literature from halogen lamp
manufacturers - that that actually works.

If the bulb is badly damaged from the halogen cycle failing to outrun
effects of water vapor or oxygen, then I would say only maybe. And the
"repair" may not be good - the tungsten could have come mainly from one
region of the filament and it could go mainly to a different region, and
uneven filament thickness is bad since it tends to reinforce itself
(thinner parts get hotter and evaporate faster).
Also, the bulb material gets hotter than normal if the bulb is operated
full-blast while blackened. Some halogen bulbs operate under enough
stress as it is...

- Don Klipstein )

In article , m Ransley wrote:

Without a V meter test and from what the kill a watt read I guess 10-
22v is the point at which you will see illumination.

Most 120V incandescent lamps glow dimly visible to a dark-adapted eye in
a dark room at 6 volts. This varies from one lamp to another. For
example, the lowest wattages that get a gas fill have the heat
conductivity of the gas affecting things more, and need more voltage to
glow, and brightness varies a little more with voltage than with high
wattage lamps and vacuum ones.

With a tric type dimmer, you need a true RMS meter to get an accurate
meter reading of the voltage when dimmed.

- Don Klipstein )