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 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 here:
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.
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.
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.)
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.
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:
Jeff
-- Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
"Truth exists; only falsehood has to be invented."
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:
Incandescent bulbs have a minimum starting voltage? :-)
Nick
Edwin Pawlowski errs again:
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.
Well a minimum voltage at which they will emit visible light.
That and measure the light output.
"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.
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:
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.
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.
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.