Cost of electricity for light dimmer

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

- Don Klipstein ( snipped-for-privacy@misty.com)

Reply to
Don Klipstein
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fed into it. (Roughly, only roughly that is.)

Why would that be? With cooler operation, the bulb would last indefinitely. The iodine lets it operate really HOT without suffering the

25 hour lifetime that such operation usually brings.

If there is any darkening with lower power operation, it can be burned off with operation at full power.

Reply to
John Gilmer

In , Sylvia Else wrote in part:

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

- Don Klipstein ( snipped-for-privacy@misty.com)

Reply to
Don Klipstein

potentiometer,

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.
Reply to
someone

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

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

Sylvia.

Reply to
Sylvia Else

[snip]

distribution.

infrared)

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?

consider

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.]
Reply to
Watson A.Name - "Watt Sun, the Dark Remover"

incandescent

I've seen as much (or as little) as 1/10 the power of an incandescent. But that may be some sales hype.

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.

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.

reading

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.

AE6EO

Reply to
Watson A.Name - "Watt Sun, the Dark Remover"

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 ( snipped-for-privacy@misty.com)

Reply to
Don Klipstein

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 ( snipped-for-privacy@misty.com)

Reply to
Don Klipstein

decreased.

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.
Reply to
Watson A.Name - "Watt Sun, the Dark Remover"

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.

Reply to
Watson A.Name - "Watt Sun, the Dark Remover"

expectancy

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.

Reply to
Watson A.Name - "Watt Sun, the Dark Remover"

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

Best regards, Spehro Pefhany

Reply to
Spehro Pefhany

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

Reply to
ABC

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".

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

  1. You can always add a diffuser.

- Don Klipstein ( snipped-for-privacy@misty.com)

Reply to
Don Klipstein

,

wrote

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.

Reply to
Watson A.Name - "Watt Sun, the Dark Remover"

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