# what makes one lamp assembly brighter than another



## bigmikey (Feb 24, 2004)

I was curious about lamp assemblies. I dont know what they are except that it contains a bulb?, anyway, I notice surefire makes different lamp assemblies, where one might give the light 100 lumens, and say you stick another assembly on that light, and it will double that. I dont understand how thats possible. What makes one assembly different from another?..


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## jayflash (Feb 24, 2004)

The filament in the bulb determines the lamp's output. Provided that the batteries can handle the increased load, a filament that consumes more current will, generally, output more lumens. A lamp with double the output will drain the batteries approximately twice as fast.

The reflector determines the nature of the beam and whether the light is concentrated into a spot or a diffused flood.


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## JerryM (Feb 24, 2004)

*Re: what makes one lamp assembly brighter than ano*

In that light, I notice that there is a great difference in 1W LS lights. For instance, the CMG Reactor, and the TL-2LED and the PM6 LED. 

Why is there so much difference in the output of those lights?

Jerry


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## JohnK (Feb 24, 2004)

*Re: what makes one lamp assembly brighter than ano*

The filament in the bulb determines the lamp's output.>>>>>>>>>>

/ubbthreads/images/graemlins/confused.gif

I really don't know this either. Is the filament in a "brighter" bulb (same batteries/current/etc. thinner, thicker, longer, different material, than a lower brightness bulb ? Is there more/less resistance due to which factors previously mentioned ? In other words, what factors influence brightness , assuming the same battery input.

A for instance is the SL TT 2L with a lower wattage (?) bulb than might have been used, compared to a Scorpion bulb.

I've asked several others this question, and no one REALLY knew the answer. 

I hate not knowing.


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## jayflash (Feb 24, 2004)

*Re: what makes one lamp assembly brighter than ano*

A HOLA for use in the same flashlight will generally have a thicker filament which will draw more current and have less resistance and less runtime than a LOLA.


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## phyhsuts (Feb 24, 2004)

*Re: what makes one lamp assembly brighter than ano*

Let me try. The output of a lamp depends on several factors. The main ones are: the size (surface area really); its temperature (thus life); the emmisivity of the material (how well the material emmits light energy) and the physical structure (how much of the light given off by the inner surfaces can get out before being absorbed). Thus for the same energy input (same battery and current) the hotter the filament, the brighter the lamp. Lamp life suffers as a result. Almost all filaments are made of Tungsten as it has the second highest melting point of all metals ( so it can operate at high temperatures) and has a very good emmisivity in the visible spectrum. Thus projector lamps have high output and short life (50-100 hours) and a household lamp have much lower output but longer life (200-4000 hours). The size of wire and length of wire depends on the operating voltage and current. they have an effect on the output via the "physical structure" and "size" factors above. But theirs is a smaller effect than the "temperature" factor. Clear as mud, eh? /ubbthreads/images/graemlins/grin.gif At least I tried!


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## JerryM (Feb 24, 2004)

*Re: what makes one lamp assembly brighter than ano*

It is clear, and I guess that all Lux or any LED is not the same as some other of the same size or wattage.

Jerry

Jerry


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## JohnK (Feb 24, 2004)

*Re: what makes one lamp assembly brighter than ano*

/ubbthreads/images/graemlins/help.gif

Thanks phy, I still want clarification if I can. OK, if you have a larger copper wire (or tungsten filament), you have LESS resistance, more current, but, it seems less heat, and therefore less light emmited ?

Smaller wire (filament) hotter/more light ?

Heat = more emmisive properties ? Shorter lamp life ?

I've re-wired large boats , maybe my anology is poor.

Again clear as mud......

I majored in physics when there were a lot fewer elements on the periodic table. I NEVER had a mental picture of electrons flowing down a wire. If you can't "see" it in your mind, you don't understand it. Duh !!


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## jayflash (Feb 24, 2004)

*Re: what makes one lamp assembly brighter than ano*

Wrong about less heat and, therefore, less light. If the power source is "stiff" and can increase its current to meet the demand, a thicker, lower resistance lamp filament will draw more current and be brighter - albeit with less runtime with the same batteries. Lamp life is dependant upon other factors and, therefore, a brighter lamp may have equal life.

LED's have different characteristics than incandescent filaments and should not be confused.


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## CM (Feb 24, 2004)

*Re: what makes one lamp assembly brighter than ano*

Power = (I^2)*R so halving resistance (thereby doubling the current) results in twice the power (heat).


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## phyhsuts (Feb 25, 2004)

*Re: what makes one lamp assembly brighter than ano*

How hot a filament gets depends on two things mainly: the power being fed to the filament and the rate of energy loss to the surrounding. If the later is less than the former, the temperature will rise. As it rises, the rate of energy loss increases. Loss by conduction increases linearly as the temperature difference. Convection loss is not very predictable and radiation increases as the *fourth* power of the temperature. Thus at high temperature, the main mechanism for loss is radiation - both IR and visible. The ultimate temperature will be the one at which the rate of energy loss equals that of the energy supplied. Note that the "loss" includes the visible radiation we are trying to produce. Thus we can have many combinations of wire size and length for the same power rating and luminous output. The voltage (and thus current) ratings can be variedas much as we wish within the manufacturing limitations (wires cannot be made smaller than a certain diameter! Thus a 10,000 V 0.001A lamp is not practical). /ubbthreads/images/graemlins/grin.gif


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## cheesehead (Feb 25, 2004)

*Re: what makes one lamp assembly brighter than ano*

phyhsuts, 

Excellent posts, as usual.

Like phyhsuts said, the whole thing is interesting, in that there is a max temp for tungsten and the closer you get to that temperature, the more efficient your light, but the shorter its life. If you give up some efficiency, you can get longer life (thus, you can have a brighter light (albeit more yellow) with longer life, but you "pay" with using a lot more power). Also, the longer life light will radiate a lot more heat for the same useful lumens.

Also, the filaments don't behave strictly according to E=IR, rather they like to increase some resistance with increasing temperature. Thus a wire half as long won't have half the resistance, but a little more (as it will get hotter for the same voltage and resistance will go up). And conversely, a wire twice as long will have a little less than twice the resistance (again, keeping voltage constant, the temperature will be lower). 

Er, I don't know if that helps,
cheese


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