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Cost of electricity for light dimmer

D

Don Klipstein

Jan 1, 1970
0
Relatively small. I would expect it would be something like a normal NP
junction where the voltage drop is about 0.6 volts. Assume a 50 watt load
using about a half ampere current. = about 0.3 watts. Other components in
the circuit may have more disappation than that.

I believe there are two diode drops in a triac, resulting in a 1.2 volt
drop.

- Don Klipstein ([email protected])
 
D

Don Klipstein

Jan 1, 1970
0
Sylvia Else wrote said:
I use flourescent substitutes in some places, but they're not exactly a
perfect solution either. The ones I use take a significant time
(minutes, I think) to reach their peak brightness, an effect that seems
to get worse as they age. However I've yet to have to replace one.

I don't know that you can use a dimmer with them, though. I rather
suspect they wouldn't like that.

A few are, such as the dimmable version of the Philips 23 watt SLS -
available at Home Depot.

- Don Klipstein ([email protected])
 
S

someone

Jan 1, 1970
0
Don Klipstein said:
I believe there are two diode drops in a triac, resulting in a 1.2 volt
drop.
Isn't only one diode conducting at a time? Regardless, the power
dissipation is small and would be at maximum disappation when the lamps are
at full brightness. But it would need a heat sink. Suppose there were 8
100 watt bulbs. Say 10 amperes. The power disappated by the Truac could
be 12 or 6 watts.
 
S

Sylvia Else

Jan 1, 1970
0
R.Lewis said:
Not for the past 40 years they have not - they would be too expensive to
produce.


Ever notice some of commercial dimmers and the huge heat sinks on



I am sure that there will be plenty of respondents explaining the purpose of
these (relatively small) heatsinks.
Have you no idea of the size of heatsink required to 'burn off', say, 100
watts in air and keep the surface temperature of the heatsink below the
hundreds of degrees!!

I have a 3 kW heat sink cooled by a fan.

No - wait, I think that's my room heater.

Sylvia.
 
W

Watson A.Name - \Watt Sun, the Dark Remover\

Jan 1, 1970
0
Don Klipstein said:
Now for the bonus extra trickery: Using fewer lightbulbs is better than
using lower wattage ones, as long as you get adequate light distribution.
Higher wattage lightbulbs are slightly more efficient. There is more than
one reason, but one is that thicker filaments can be operated at a higher
temperature (better for radiating visible light as opposed to infrared)
for a given life expectancy.

I wanted to ask about this. Does that mean that a 220VAC lamp is less
efficient than a 120VAC lamp, because the filament has to be much
thinner, and so must be operated at lower temperature?
True, but for among different ways of achieving a given light output
lower wattage (or better still fewer) undimmed bulbs will cost less than
dimmed ones. In most of the USA, the cost of the electricity is so much
more than the cost of buying replacement bulbs that it pays to consider
energy efficiency.


A few bulbs benefit from "soft starting", many and probably most do
not.

I know that I find that the dimmers that have to be turned are *much*
more inconvenient, because instead of just poking it with your hand as
you go by, you have to stop and twist it. When you're just passing thru
a room, it's wasteful of time and patience. And it wears the pot out
faster, because the whole carbon element gets wiped by the wiper each
time it's turned full on. So it will fail sooner, and my guess is the
cost of replacement is much more than the savings of light bulbs you get
from using this instead of push-on type.

There are also dimmers that use a touch plate, and they have a memory
that turns them on at the same setting every time, without any fiddling.
But these are more expensive than the usual cheap dimmer.

And there is the dimmer that's just like a switch, it has the toggle
that can be moved thru its range with the same effect as a regular
switch. Just push up on it quick and it's full on. This would solve
the problem of twisting a regular 'volume control' pot.

[lots of good info snipped - thanks, Don.]
 
W

Watson A.Name - \Watt Sun, the Dark Remover\

Jan 1, 1970
0
Dave Platt said:
One figure I've seen (in a manufacturer's ad) cited an 80% reduction
in electricity use in stoplight applications.

I've seen as much (or as little) as 1/10 the power of an incandescent.
But that may be some sales hype.
The power saving seems to be one big motivation for switching
stoplights over to LEDs. Reduction in the number of person-hours to
do bulb replacement seems to be the other.

One other motivation that was used a few years ago (here in Calif) was
that the power companies were giving grants to cities to switch over to
LEDs to reduce the electrical load and save having to build another
power plant.
Here in the Silicon Valley, almost all of the stoplights seem to have
been completely converted over... all three colors are now LED-based.

'Cause if so, it seems like

Some are bluer, some are more white... depends on the manufacturer,
phosphor, etc. The better ones seem to be roughly comparable to a
"cool white" fluorescent tube.

Also, some cheap LED flashlights use three cells, and the current
limiting resistor is very low resistance. So when the batteries are
fresh, the curent thru the LEDs is 2 or 3 times the max rated current,
and the LEDs are pushed past their limit, and the light turns bluish or
even purplish. This shortens their life if the flashlight is used for
more than a short period, and the LEDs get real hot.
I'd be tempted to see how well one might do, in terms of color
temperature, with a set of "white" LEDs, plus a few ultrabright red or
red/orange to warm up the spectrum.

Actually there is one project on the web that uses one yellow LED for
every four white LEDs, and the author says that it makes the spectrum
much more normal and less bluish, compared to all white.
I believe so. Most high-brightness LEDs seem to be spec'ed in terms
of candellas of brightness, over a specific angular range, at a given
current, with a specified forward voltage.
AE6EO
 
D

Don Klipstein

Jan 1, 1970
0
Watson A.Name - \"Watt said:
I wanted to ask about this. Does that mean that a 220VAC lamp is less
efficient than a 120VAC lamp, because the filament has to be much
thinner, and so must be operated at lower temperature?

This is indeed true. And 12V ones are more efficient than 120V ones.

There is another reason that applies with gas-filled bulbs: Making the
filament thicker makes the "boundary layer" of gas around the filament
thicker, and reduces the temperature gradient in this "boundary layer" of
gas. That reduces the amount of heat conduction loss by the gas per unit
area of the filament.
In fact, if the filament has much less than somewhere around 10 watts
per centimeter of visibly-apparent length, they usually put a vacuum in
the bulb instead of the usual argon-nitrogen mixture. With really thin
filaments, the heat conduction disadvantage of the gas outweighs its
advantage of enabling higher filament temperature by slowing filament
evaporation.

Now for what happens with really low design voltages: With a high
temperature gradient along the ends of the filament, heat conduction
through the ends of the filament becomes a more significant loss.

For wattages around 20-100 watts, if design voltage is variable, to
maximize efficiency with a given life expectancy in mind the optimum
design voltage is not far from 12 volts. For just a few watts it's closer
to 6 volts. For around a watt or a fraction of a watt it's closer to 5
volts.

Here's an example: The 1156 automotive backup light bulb typically
produces 400 lumens from 26.9 watts at 12.8 volts with a life expectancy
of 1200 hours. That's 14.9 lumens/watt. A 120V 40 watt lamp designed to
last 1000 hours gets about 12.6 lumens/watt.

- Don Klipstein ([email protected])
 
D

Don Klipstein

Jan 1, 1970
0
Watson A.Name - \"Watt said:
I've seen as much (or as little) as 1/10 the power of an incandescent.
But that may be some sales hype.

They do indeed make LED traffic signal units that consume about 11
watts, and I believe they replace incandescents of 92 or 116 watts. (It
is common for incandescent traffic signal lamps to have oddball wattages.)

Not only are really good red and green LEDs nowadays at least 5-6 times
as effcient as red-filtered or green-filtered 8,000 hour incandescents,
but also I suspect the light distribution pattern is tailored a little
better with LEDs.

- Don Klipstein ([email protected])
 
W

Watson A.Name - \Watt Sun, the Dark Remover\

Jan 1, 1970
0
| And, as an additional issue, it's generally a bad idea to use a dimmer
| with quartz-halogen lamps. When dimmed, the bulbs run a good deal
| cooler, the halogen-sequestering-and-redeposition of the tungsten
| doesn't work as well, the tungsten tends to plate out on the inside of
| the tube and dim the bulb, and the bulb lifetime is greatly decreased.

And this is a frequent problem with those torchiere floor lamps which
usually have a dimmer and a 300 (more than you need most of the time)
watt QH bulb. So people dim them, usually. Unfortunately, getting a
lower wattage bulb is more expensive, if they can even be found in the
same size.


| All in all, as others have said, it makes more economic sense to use
| smaller bulbs at full power rather than dimming a high-wattage bulb.

Agreed. Getting variability should be done in the form of turning more
or fewer bulbs on. A lamp with 8 small 40 watt QH bulbs and a switch
to control how many are on would be nice ... and expensive.

And one oher problem is they're fire starters, but that's a subject for
another discussion. My thought would be to replace a larger
incandescent blub with a few fluorescents, switched to give a dimming
effect. But another possible method, which I see used on the modular
furniture 'cubicle' lights, is to use a sleeve over the fluo tube, to
dim it by turning the tube. THe tube is partially transparent on one
half, so turning it varies the light.

BTW, why would you need eight 30W blubs? You would need a 150W for half
as much light, an 80W for quarter, a 30W for 1/10, and some boolean
logic in the switching to give other in-between settings. Maybe two
30W, or maybe a 30W and an even lower wattage lamp. But you get the
idea. You would only need 3 or 4 lamps, which is much simpler and
cheaper than 8 smaller lamps. But I digress from the fluorescent lamps.
Just use fluos instead.
 
W

Watson A.Name - \Watt Sun, the Dark Remover\

Jan 1, 1970
0
In alt.engineering.electrical "Watson A.Name - \"Watt Sun, the Dark
Remover\" said:
| Say for instance you had four 25 watt bulbs and you needed only 25 watts
| of light. Well, you switch on only one. and you get 25 watts of light
| and pay for 25 watts of power. But if you dim your 100W lamp to get 25
| watts of light, then you might be paying for 50 watts of power. You get
| less light per watt when it is dimmed.

The 100 watt bulb in this condition has a lower color temperature. This
results in far more infrared output relative to light output compared to
normal operation. It's that "orange look".

Exactly. And that's a big advantage of white LEDs, they don't get
orangish as they're dimmed.

What would be nice for incandescents is a way to dim them without
turning orangish. The only way seems to be by pulsing them on and off.
But that causes really noticeable flicker. Probably too obnoxious.
 
W

Watson A.Name - \Watt Sun, the Dark Remover\

Jan 1, 1970
0
Don Klipstein said:
This is indeed true. And 12V ones are more efficient than 120V ones.

There is another reason that applies with gas-filled bulbs: Making the
filament thicker makes the "boundary layer" of gas around the filament
thicker, and reduces the temperature gradient in this "boundary layer" of
gas. That reduces the amount of heat conduction loss by the gas per unit
area of the filament.
In fact, if the filament has much less than somewhere around 10 watts
per centimeter of visibly-apparent length, they usually put a vacuum in
the bulb instead of the usual argon-nitrogen mixture. With really thin
filaments, the heat conduction disadvantage of the gas outweighs its
advantage of enabling higher filament temperature by slowing filament
evaporation.

Now for what happens with really low design voltages: With a high
temperature gradient along the ends of the filament, heat conduction
through the ends of the filament becomes a more significant loss.

For wattages around 20-100 watts, if design voltage is variable, to
maximize efficiency with a given life expectancy in mind the optimum
design voltage is not far from 12 volts. For just a few watts it's closer
to 6 volts. For around a watt or a fraction of a watt it's closer to 5
volts.

Here's an example: The 1156 automotive backup light bulb typically
produces 400 lumens from 26.9 watts at 12.8 volts with a life expectancy
of 1200 hours. That's 14.9 lumens/watt. A 120V 40 watt lamp designed to
last 1000 hours gets about 12.6 lumens/watt.

I always liked my Tensor lamp with the 91 blub in it. It seemed
brighter than a regular lamp. THen I got a 6V tractor lamp and mounted
it on a post with a filament transformer as the base. It was really
great for those fine soldering jobs. But I had a hard time finding
lamps for those old timers.
 
S

Spehro Pefhany

Jan 1, 1970
0
Exactly. And that's a big advantage of white LEDs, they don't get
orangish as they're dimmed.

What would be nice for incandescents is a way to dim them without
turning orangish. The only way seems to be by pulsing them on and off.
But that causes really noticeable flicker. Probably too obnoxious.

An iris-type variable aperture will work, but it's a bit wasteful.


Best regards,
Spehro Pefhany
 
W

Watson A.Name - \Watt Sun, the Dark Remover\

Jan 1, 1970
0
Don Klipstein said:
They do indeed make LED traffic signal units that consume about 11
watts, and I believe they replace incandescents of 92 or 116 watts. (It
is common for incandescent traffic signal lamps to have oddball wattages.)

Not only are really good red and green LEDs nowadays at least 5-6 times
as effcient as red-filtered or green-filtered 8,000 hour incandescents,
but also I suspect the light distribution pattern is tailored a little
better with LEDs.

It rained here last week, and I was kind of surprised at how much light
those LED stop signals put out. The reflection off wet pavement was
really noticeable. They must use narrow beam LEDs in those, maybe the
30 or 20 degree ones. So far, I think I've only seen one signal with a
few bad LEDs in it, they must be running them very conservatively, to
handle the conditions as well as they do.

http://auto.howstuffworks.com/framed.htm?parent=question178.htm&url=http
://www.lrc.rpi.edu/programs/lightingTransformation/led/bibliography.asp
I think I found out what CIE means.
 
A

ABC

Jan 1, 1970
0
Watson A.Name - "Watt Sun said:
It rained here last week, and I was kind of surprised at how much light
those LED stop signals put out. The reflection off wet pavement was
really noticeable. They must use narrow beam LEDs in those, maybe the
30 or 20 degree ones. So far, I think I've only seen one signal with a
few bad LEDs in it, they must be running them very conservatively, to
handle the conditions as well as they do.

Don't all LED's have a narrow beam? That is the problem of using them for
genearl lighting.
 
R

Rich Grise

Jan 1, 1970
0
On Sun, 31 Oct 2004 07:38:13 -0800, the renowned "Watson A.Name - \"Watt


An iris-type variable aperture will work, but it's a bit wasteful.
I wonder if maintaining color balance through dimming would actually
seem "unnatural" in some way. When the sun goes down, it gets orangey
for awhile, and you don't really _expect_ to see vivid colors when
it's not very light out. Or maybe we're just used to the look of dimmed
incandescents.

Thanks,
Rich
 
R

Rich Grise

Jan 1, 1970
0
I always liked my Tensor lamp with the 91 blub in it. It seemed brighter
than a regular lamp. THen I got a 6V tractor lamp and mounted it on a
post with a filament transformer as the base. It was really great for
those fine soldering jobs. But I had a hard time finding lamps for those
old timers.
Has any electronics guy _not_ built one of these? ;-)

Cheers!
Rich
 
D

Don Klipstein

Jan 1, 1970
0
Don't all LED's have a narrow beam? That is the problem of using them for
genearl lighting.

Popular beam widths for transparent "bullet" style LEDs are 15, 30 and
45 degrees. Some come in other angles in this range. A few have even
narrower beams.

Diffused "bullet" style LEDs are available with 60 degree nominal beam
width ("viewing angle").

There are wider angle LED lamps:

1. Many LEDs of shape other than "bullet" have nominal beam widths of
100-120 degrees, often 120 or not much less. Many of these have a
"lambertian" radiation pattern and are 3 dB below axial brightness at 60
degrees off axis (120 degree FWHM beamwidth) but have light throughout 180
degrees or almost 180 degrees.

This includes many Lumileds "Luxeon" models and some similar Osram ones.
Cree makes some similar ones with a radiation pattern that I would call
"slightly narrowed lambertian". There are also surface mount LEDs and
flat-top rectangular LEDs that have such wide radiation patterns, although
maybe a little less wide than "lambertian".

2. There are LED cluster lamps with several directional LEDs aimed into
different directions.

3. You can always add a diffuser.

- Don Klipstein ([email protected])
 
W

Watson A.Name - \Watt Sun, the Dark Remover\

Jan 1, 1970
0
Don Klipstein said:
Popular beam widths for transparent "bullet" style LEDs are 15, 30 and
45 degrees. Some come in other angles in this range. A few have even
narrower beams.

Diffused "bullet" style LEDs are available with 60 degree nominal beam
width ("viewing angle").

There are wider angle LED lamps:

1. Many LEDs of shape other than "bullet" have nominal beam widths of
100-120 degrees, often 120 or not much less. Many of these have a
"lambertian" radiation pattern and are 3 dB below axial brightness at 60
degrees off axis (120 degree FWHM beamwidth) but have light throughout 180
degrees or almost 180 degrees.

This includes many Lumileds "Luxeon" models and some similar Osram ones.
Cree makes some similar ones with a radiation pattern that I would call
"slightly narrowed lambertian". There are also surface mount LEDs and
flat-top rectangular LEDs that have such wide radiation patterns, although
maybe a little less wide than "lambertian".

2. There are LED cluster lamps with several directional LEDs aimed into
different directions.

3. You can always add a diffuser.

Excellent info - thanks.

It looks like the cars of the last few years have designed their stop
and signal light reflectors to resemble LEDs, by breaking up the
silvered reflector into multiple 'dimples' which look like individual
LEDs. Kind of a shame that they don't use the Real Thing.
 
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