Is it possible to calculate an incandescent bulb's temperature from V?

[Eric Bretschneider]

I seem to be having some trouble making my primary point.
My "model"(your word) can be written down in three lines if you know the physics. It requires no spreadsheet or even knowing the numerical constants.
So with one pencil and a small scrap of paper the original questioncan be answered simply with an emphatic "yes, if you know a little physics"....

The answer is also an emphatic "yes, if you do a little research"

You can always try first principles calculations, but Mother Nature makes no assumptions.

And the tristimulus response curves can't be derived from first principles . . .

 

[hutchphd]

The tristimulus response curves have nothing to do with the Planck temperature.
They do tell us what the surface temperature of the sun is (and has likely been for some time!)
But the sun would shine the same whether we can name its colors or not (falling tree in the forest notwithstanding!)

 

[Eric Bretschneider]

The tristimulus response curves have nothing to do with the Planck temperature.
They do tell us what the surface temperature of the sun is (and has likely been for some time!)
But the sun would shine the same whether we can name its colors or not (falling tree in the forest notwithstanding!)

"Planck temperature" is a very different concept - it is the highest possible temperature (about 1.4e+32 K). I think you were referring to the temperature of a Planckian source which is different.

Tristimulus response curves are used to calculate chromaticity. Without those you can't calculate color temperature. The concept of color temperature includes the human visual system which in turn brings in the tristimulus response curves.

They have nothing to do with the surface temperature of the sun. They allow us to calculate the chromaticity coordinates of sunlight (which does not lie on the Planckian locus).

 

[hutchphd]

Yes the term "Planck Temperature" was absolutely incorrect. I was unaware of that definition and was using it as a shorthand for the temperature of the blackbody radiator. My bad.

Tristimulus response curves are used to calculate chromaticity. Without those you can't calculate color temperature. The concept of color temperature includes the human visual system which in turn brings in the tristimulus response curves.

They have nothing to do with the surface temperature of the sun. They allow us to calculate the chromaticity coordinates of sunlight (which does not lie on the Planckian locus).

The entire response of the human eye has evolved to maximize the use of solar radiation. Compare the response curve of the eye to a 6000K blackbody. Serendipity? Do you really think that if we lived near a red dwarf we would have the same color response?

No Mas...

 

[weirdoguy]

"Planck temperature" is a very different concept - it is the highest possible temperature (about 1.4e+32 K).

No it is not. The same goes with Plancks lenght, time and other units. They don't have any physical meaning, except that they can define some sort of usable scale. But not always, e.g. Plancks resistivity is about 30 ohms and it's not the highest nor the lowest resistivity possible.

 

[pinball1970]

I did some similar work on this with LEDs What changed increasing wattage on measurement was the intensity not the SPD or CCT. More photons but at the same wavelengths.

 

[Baluncore]

I did some similar work on this with LEDs
What changed increasing wattage on measurement was the intensity not the SPD or CCT.
More photons but at the same wavelengths.

Unlike a filament lamp, LEDs are fixed voltage devices, with light output dependent on forward current, and forward voltage dependent on material = fixed colour.
The blank lines in your post make it look like you used an MS windows based editor, then pasted your text ?

 

[pinball1970]

Unlike a filament lamp, LEDs are fixed voltage devices, with light output dependent on forward current, and forward voltage dependent on material = fixed colour.
The blank lines in your post make it look like you used an MS windows based editor, then pasted your text ?

Yes I am lazy, I am always missing words out or something then noticing after,so I type in a blank email then paste. I am usually on pf at lunch at work while I am answering mails.
You can get dimmable LEDs, does the SPD change on those?

 

[Baluncore]

You can get dimmable LEDs, does the SPD change on those?

We see Spectral Power Distribution as colour, which is set by quantum chemistry of LED materials.
A dimmable LED will probably be a violet LED, with three or more fluorescent chemicals to change the colour balance. It should not change colour with power.

 

[martin314159]

Regarding the 220 volt incandescent 2800 cct running at 110 volts. Omcheeto had It correct. The cct goes to the 0.38 power of voltage. The new cct is 2125 K. The power drops from 100 watts to 33.3 ; the lumen output from 1550 to 95; the operating resistance from 482 ohms to 363.
best regards,
Martin314159

 

[martin314159]

I would also like to say Eric Bretschneider reply below in his August 19, 2019 #31 is correct too. The power of the voltage can vary from .38 to .42 depending on the temperature of the filament whether and whether the filament is in a vacuum or inert gas.

The following is from "Lighting Handbook: Reference and Application" (8th ed.) from the IES (Illuminating Engineering Society) p.186

Life1/Life0 = (Volt0/Volt1)^13
Lumen1/Lumen0 = (Volt0/Volt1)^1.9
Efficacy0/Efficacy1 = (Volt0/Volt1)^3.4
Watt1/Watt0 = (Volt1/Volt0)^1.6
CCT1/CCT0 = (Volt1/Volt0)^0.42