LED total photon output

[L.E.D.]

you know how they say halogens are more effiecient than LED's? is it true? wouldn't LED's put out more total photons seeing as how the halogen wastes a lot of the electricity as heat? OK, here's the question:
If you hooked up a halogen lamp to a 12v battery and a 5mm 8000 mcd white LED to another 12v battery(with resistors and voltage limiter of course), which one would put out more total photons during the whole runtime?

 

[Alaric Darconville]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by ColdLight:
you know how they say halogens are more effiecient than LED's? is it true? wouldn't LED's put out more total photons seeing as how the halogen wastes a lot of the electricity as heat? OK, here's the question:
If you hooked up a halogen lamp to a 12v battery and a 5mm 8000 mcd white LED to another 12v battery(with resistors and voltage limiter of course), which one would put out more total photons during the whole runtime?<HR></BLOCKQUOTE>

I think in some cases it could be said that LEDs are more efficient ONLY when they are single-color LEDs. In that case, a red LED would be much more efficient than a halogen shining through a filter. But white LEDs are going to suffer some loss in efficiency because in a way they work like a flourescent.

 

[Badbeams3]

Well, are you talking about a marine deep cycle batt of around 120 amps or a car batt. If you have a deep cycle 120 amp type in mind it would take three...maybe five years to complete and come up with the answer...Telephony is the man for this job.

Ok, all kidding aside the holagen would probably win...but ask the question next year and who knows. Also, during the winter, the holagen can contribute to heating you room-home and since you need light at night anyway...might as well have a bulb that helps in this respect. During the summer useing led or floresant would save$$$ by not adding unwanted heat to the room (air conditioning cost)

I know this did not help at all...sorry.

 

[Jonathan]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR> Halogen MUST have heat, LED its detrimental. <HR></BLOCKQUOTE>

Spot on!

LEDs are more efficient when they are cold. Halogens are only seriously efficient when the filament is about to melt.

Because of this, halogen filament lamps show economies of scale: they get more efficient as they get bigger; as the filament gets thicker, you can operate it at higher temperature, and you have fewer parasitic heat losses.

LEDs on the other hand have an inverse economy of scale. The bigger that they get, the harder it gets to carry heat away, and the less efficient they get.

If you need just 15 lumen of light, you can do it with a single Luxeon emitter operated at about 1 watt (this is for white light). If you tried to do this with halogen, it would probably take about 1.5 watt of electricity.

In the above example, in your proposed experiment, the LED would put out more total photons _and_ run for more time.

If you need 900 lumen of light, then you could do it with 60 Luxeons, consuming 60 watt of electricity, and needing quite a large heat sink to carry the heat away and keep the Luxeons cool. You could also get this same total light with a single, small Decostar IRC lamp, consuming 35 watt of electricity.

At this illumination level, the halogen would produce more total photons in your experiment.

Finally, if you needed _colored_ light, then the LEDs will beat the halogen at all illumination levels, at least for red, yellow, and green.

Regards,
Jon

 

[bikeNomad]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Jonathan:

If you need just 15 lumen of light, you can do it with a single Luxeon emitter operated at about 1 watt (this is for white light). If you tried to do this with halogen, it would probably take about 1.5 watt of electricity.<HR></BLOCKQUOTE>

True, but they're equal by about 3W.

In the 3W (bike light) sizes, halogens get about 15 lumens/W. And the Luxeon Star white gets 15 lumens/W when refrigerated to 5 deg. C (there's a 20 degree C gradient between the board and chip).

At room temp (i.e. with a really good heatsink) the LS light output is down by 10% or so, for an efficiency of about 13.5 lumens/W. And at 60 degrees C (like in an enclosed space), the efficiency is down to 12 lumens/W.

This is still close to the 2.4W-3W halogen efficiency.