# How to compare brightness: equivalent LED with halogen?



## Mdemon

Is there any way of working out the LED equivalent of a halogen bulb please?

For example:

35w halogen = ...w LED.
50w halogen = ...w LED.

The reason I ask is that the bigger LEDs seem to be rated in luminous flux (lumens) and finding equivalent lumen ratings for halogen seems impossible.

Can anyone help please?


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## Gomer

> *Household Halogen Reflector Flood Incandescent *
> (figures published on lamp cartons and wrappers)
> 
> watts lumens hours
> 40 410 4000 * Philips
> 45 530 2000 ** Philips
> 50 530 2000 Philips
> 50 590 2000 GE
> 60 880 2500 Philips
> 75 940 2000 Philips
> 90 1280 2000 Philips
> 100 1400 2000 GE



Cree P4's (budget priced in comparison to the new R2's) put out around 230 lumens at 1000 mA, about 175 at 700mA and about 90 at 350mA.


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## tonycollinet

You definatley can't compare power with power, cos later led generations put out more light at the same power. This tends not to be true for halogens, due to the mature technology.

Based on the info from Gomer, the P4 is equivalent to between a 20 to 25W halogen.

This matches my esperience. My 3 luxeon III stars put out a total of about 180 lumens, and are not quite as bright as my halogen lights at 20W


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## jirik_cz

For common bulbs i have seen numbers around 10lm/W and for halogen bulbs 15 - 23 lm/W. So new high power leds are 4 - 6 times more efficient than halogen bulbs.


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## Mdemon

Thanks for the figures - that's great!

So if I use one of the single 20w LED packages, I will be getting something as efficient as a 60w+ halogen?

Looks good to me!


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## aljsk8

single 20w led? (does one exist)

your would be better off with a few of the cree / seoul / rebel leds rather than some 20w led with worse efficiency


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## tonycollinet

Mdemon said:


> Thanks for the figures - that's great!
> 
> So if I use one of the single 20w LED packages, I will be getting something as efficient as a 60w+ halogen?
> 
> Looks good to me!


 
Depends on the LED. As stated above - dont' look at the power (W) rating of LED's, look at the lumen output.

You cannot say that just because 1 LED puts out 50lm/W that they all do.


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## Mdemon

The one I'm looking at is rated at 700 lumen. The Deal Express one is 800!


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## tonycollinet

then yes - that is going to be around the brightness of a 60W halogen.


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## LukeA

That should be fine. Do you have something lined up to drive it?


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## tonycollinet

Read the comment here:
http://www.dealextreme.com/details.dx/sku.5848

You should be aware that cooling a 20W led will be a serious challenge.


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## Mdemon

Not at the moment - any suggestions? A friend and I were looking to build something bespoke but if there is a recommended package...

Heat shouldn't be a problem. The bulb housing is metal, as is the torch body. It won't be used out of water. The plan is to fix the emitter using thermal epoxy to the metal bulb housing. The bulb is in good contact with the torch body (thermal goop?) and the plan is heat to be conducted through the body and glass front into the water.

The light head usually takes a 35w halogen so should be fine. It's just a matter of how well the LED is cooled by conduction...


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## tonycollinet

If you've got good solid conduction to water cooling, you should be OK. Be carefull of metal to metal interfaces - even with thermal compound in the joint, they can have quite high thermal resistance.

Comparing with a 35W halogen bulb isn't really vallid - the fillament of the bulb could be as high as 2000C. The junction of your led probably shouldn't run much hotter than 130C. This is why cooling for LEDS is much more critical than for filament bulbs.


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## Mdemon

Thanks Tony.

The bulb turned up today, which was amazingly quick! The bit where the two pins stick out is a separate non-metal section. Since the light head inside is bulb-shaped at the front then just a cylinder, I was thinking that I could fit the front section (with LED) direct to some form of metal (copper?) bar to act as a massive sink/conductor. 

Now, I have no lathe, so trying to think of a good way (copper springs?) to ensure good contact to the inner light walls.

Any thoughts? I know this isn't strictly relevant to LEDs, but I'm sure I'm not the first person trying to make a heatsink!


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