White LEDs as Light Sources - Opinions?

[steve_hill4]

Candela can be a very misleading measure of light strength.

Total light emission of a light bulb is measured in Lumen. Candela is the light emission measured over some angle. If I have two flashlights, both emitting the same amount of light, but the first one concentrating the light on a quarter of the area, then the first one has the same Lumen, but four times the Candela of the second one. That's how people can build flashlights of a million candela, by concentrating all the light output into a tiny spot. It is just a big number, nothing useful.

Most LED lights just specify "equivalent to xxx watt light bulb".

Good point. I'm sure one of us will have the time later to look further into specific white LEDs and their equivalent Lumen. It would be interesting to see what wattage it would equate to, (along with other factors like cost and lifetime).

 

[~Shard~]

Good point. I'm sure one of us will have the time later to look further into specific white LEDs and their equivalent Lumen. It would be interesting to see what wattage it would equate to, (along with other factors like cost and lifetime).

Yep, I'm trying to look into all of that myself. Fascinating research, I love learning about things like this!

 

[mcmadhatter]

I get my white LED's of ebay
you can by them in bulk cheaply,

btw if you use a higher rated voltage on them you can get them brighter than 9000 mili whatits but the light goes slightly yellowish and they don't last as long

 

[steve_hill4]

I get my white LED's of ebay
you can by them in bulk cheaply,

btw if you use a higher rated voltage on them you can get them brighter than 9000 mili whatits but the light goes slightly yellowish and they don't last as long

As is always the case with these types of devices. The trade off between effeciency, power, voltage and application is always a tricky one. As time goes on though, these barriers are so often overcome by advancements.

 

[steve_hill4]

Decided to see what I could find and, as usual, stopped off at wikipedia first. They have a good efficiency table there, which states a 100W bulb having an efficiency of ~2.6% and 17.5 Lumen/Watt, compare that to low-power White LEDs and they have 2.2-6.2% and 15-42 Lumen/Watt. High power versions were 3.8-8.8% and 26-60 Lumen/Watt and developmental prototypes showed 8.8-14.7% 60-100 Lumen/Watt.

http://en.wikipedia.org/wiki/Incandescent_light_bulb
http://en.wikipedia.org/wiki/Light_emitting_diode

To me, once we can get over the costs associated with them at the moment, even getting down to similar prices of red, green and yellow/orange LEDs, and it will be a good, efficient light source. Revived memories of my Solid State Devices module too. Very interesting future indeed.

 

[~Shard~]

Decided to see what I could find and, as usual, stopped off at wikipedia first. They have a good efficiency table there, which states a 100W bulb having an efficiency of ~2.6% and 17.5 Lumen/Watt, compare that to low-power White LEDs and they have 2.2-6.2% and 15-42 Lumen/Watt. High power versions were 3.8-8.8% and 26-60 Lumen/Watt and developmental prototypes showed 8.8-14.7% 60-100 Lumen/Watt.

http://en.wikipedia.org/wiki/Incandescent_light_bulb
http://en.wikipedia.org/wiki/Light_emitting_diode

To me, once we can get over the costs associated with them at the moment, even getting down to similar prices of red, green and yellow/orange LEDs, and it will be a good, efficient light source. Revived memories of my Solid State Devices module too. Very interesting future indeed.

Agreed. And thanks for the links, I don't know why I didn't go there in the first place!

 

[adroit]

From personal experience, LEDs are much brighter than a light bulbs (if you group 9 of them together like I do), but I don't think they are much more efficient. Note that even with white LEDs I still find that the lights are still very blue and doesn't have the warm colour like the light bulb.

 

[~Shard~]

From personal experience, LEDs are much brighter than a light bulbs (if you group 9 of them together like I do), but I don't think they are much more efficient. Note that even with white LEDs I still find that the lights are still very blue and doesn't have the warm colour like the light bulb.

Thanks for the feedback, good to know. As I sated above, I think I'll just hold off making any significant investment in LED lighting for now. But it's a fun technology to keep track of and watch evolve! It'll be interesting to see where things are at in a couple years...

 

[iMeowbot]

Decided to see what I could find and, as usual, stopped off at wikipedia first. They have a good efficiency table there, which states a 100W bulb having an efficiency of ~2.6% and 17.5 Lumen/Watt, compare that to low-power White LEDs and they have 2.2-6.2% and 15-42 Lumen/Watt. High power versions were 3.8-8.8% and 26-60 Lumen/Watt and developmental prototypes showed 8.8-14.7% 60-100 Lumen/Watt.

Careful with those numbers. Those efficiencies are for individual LEDs and leave out power supply losses and cooling requirements (clustered enough to be useful as room lights you often need a fan).

 

[~Shard~]

Careful with those numbers. Those efficiencies are for individual LEDs and leave out power supply losses and cooling requirements (clustered enough to be useful as room lights you often need a fan).

Good point - I guess that's why you'd want the more in a desk lamp situation, or something like that, as opposed to a huge array of them heating - er, lighting a room.

 

[Lord Blackadder]

LEDs offer more precise wavelength control, draw less power and (as a result) produce less heat than other more conventional sources. They also have pretty long lives. The two larges downsides I can think of are high cost and the lack of large, very powerful LEDs to directly replace incandescent and fluorscent lights in larger applications.

An engineer friend of mine with a green thumb built an array of some 300 red and blue LEDs that he uses as a grow light for some of his exotic plants (and no, he doesn't have any of those plants ). apparently it works pretty well.

BTW, I can't comment on the numbers but my friend's array does use a fan as a precaution, though he said that so far he thinks passive cooling would have been sufficient. The heat they generate feels less than that of a small fluorescent bulb, though it is present.

 

[ftaok]

Find me one that can be dimmed and I'll happily fill up my shopping basket.

*dims lights, puts on soft music, slips into something comfortable, fixes drink*

The one on the bottom is dimmable. GE Lightbulbs