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I was thinking in terms of calculations based on absolute temperatures.

temperatures when dealing with everyday temperatures, including in engineering.

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Update: the 800lm 8.5W 2700K non-dimmable LED bulbs are now down to ~$4.6

I cut the diffuser top off one and the basic engineering is impressive. 12 LEDs in series on an aluminum-core PCB. Could be used as mountable lamp assembl ies on home-made lighting projects, since they solve the problem of heat-sinkin g and connecting the LEDs, for $2.30.

Can't tell if they're being nice to the LEDs. 9W / 12 LEDs may be aggressi ve.

(view in Courier)

_ .-. _ .-. _ .-. _ #######################

The "corn lamps" are dirt cheap and obviously dangerous. But a nice source for LED panels.

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I like the aluminum-core boards. Wide availability of those would be a nic e tool in the high-power toolkit.

I don't think you can beat the Walmart bulbs for spare LED parts though. This darn 2700K bulb array without the diffuser has got to be >100lm/watt, nice color temp, soldered on an insulated aluminum core board, for $2.30.

The stuff of nerd-dreams.

Cheers, James Arthur

Main scale, yes. Fusion reactor engineering uses keV, because the Kelvin numbers have too many digits... they got this habit from astronomers, I suppose, because the astronomers have a long history of fusion studies...

I see no problem. 1 keV corresponds to about 12 MK. Multiplier prefixes apply to any unit. It's just a matter of habits.

Jeroen Belleman

What's wrong with kK, MK, GK, TK etc.?

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Oh you got them from Walmart? These "Great value" leds?

George H.

Using energy units instead of temperature works fine as long as your system is in local thermodynamic equilibrium (LTE). You have to be much more careful if that isn't so, e.g. in a plasma, the electron temperature and ion temperature can be pretty different, and in low density plasmas such as interstellar giant molecular clouds, you can be very far from LTE even inside strong absorption lines.

Cheers

Phil Hobbs

You could also use a logarithmic scale as in audio or RF such as decibels relative to 1 mW.

Define the baseline as 1 at 273K (0 C) or at 1000 K (727 C).

I bought a dozen of these...

Three for $10.97.

I replaced CFL ceiling floods and the results are impressive... almost twice the LUX at 2/3 the power (10W for 60W incandescent equivalent).

...Jim Thompson

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Yes, you nailed it. Slightly cheaper in two-packs.

The 5000K versions are rated 950 lumens and cost a little more, but the color temperature is icy blue--good for a shop, but too harsh for indoors.

Cheers, James Arthur

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Not very. Haven't actually measured any temperatures... just by feel ;-)

My ceiling "cans" are white and cone shaped so the light output, measured at floor level (with the meter Spehro sent me :-), is decidedly better (~2X) than the CFL's they replaced (same incandescent equivalent). ...Jim Thompson

}snip{

Yes, amazing. Now get a permanent marker and on each LED write the date of purchase. You'll be disappointed once they start breaking down. Gone investment...

joe

Sure, we'll all use dBmK.

Cheers

Phil Hobbs

One nice thing about consulting is that you can do client work in the hammock once in awhile--it's sunny and +54.70 dBmK at the moment

My RF clients used to drive me bonkers with their dBm and dBthat, when I need to know Vp-p when I'm designing a circuit.

So my son Aaron wrote this little program for me...

on the Simulation Tools & Macros Page of my website. ...Jim Thompson

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I stopped and had a look. They are awfully cute, but they simply have to b e really hot inside. The can has half or one-third of the surface area of th e Walmart bulbs, plus it's dissipating 10W instead of 8.5W.

Heat is the only drawback I see. ISTM the mfrs are okay with a shorter lif e, but I'm just not.

Home Depot had a Philips LED bulb that looks awfully like the Walmart Great Value bulbs I've been writing about, but rated at 10,000 hours instead of the GV's 25KH. That seems more realistic, since they run close to 80C.

Of course hotrodding a $2.44 LED bulb is silly, but mine run ~34C cooler wi th two beer-can heat sinks. That just plain feels better, and it'll save me a n early shopping trip.

I was noticing that yesterday. One of these 8.5W/800 lm bulbs lights the r oom much brighter than the 13W CFL it's replacing, tested side-by-side.

Cheers, James Arthur

I will check out the heat. Wonder how much heat is passed thru the ground side of the threaded portion? For ceiling applications where there is no chance of "fingers" maybe solder "wings" onto the socket?

Side-by-side... Yes I did a careful A-B test, so I'm going to replace all the CFL's not in an enclosed fixture. I only have four... bathroom/shower-in-the-ceiling types. ...Jim Thompson