lighting LED Vs Energy saving lights)

[TXCG]

Remember though Mike, a CFL is a relatively broad spectrum lamp extending to the IR and UV ends of the spectrum. As LEDs are monochromatic light sources, they will clearly appear brighter because the energy is concentrated into a narrow band of maybe 70nm, at your two discrete wavelengths. There is certainly some efficiency to be gained from omitting 'wasted' energy in the 530nm area, but the dominant wavelength of the LEDs may not correspond to the ideal wavelength for photosynthesis.



Comparing light sources in terms of Lumens per watt is like comparing apples with oranges. It's not a valid unit to use, as it is the perceived power of light rather than the radiant flux.

Welcome aboard mate you sound like you know what you're talkin about. Should be a useful addition to our rag-tag group of miscreants. Hope you stck around

 

[lee]

Translated: http://translate.google.com/transla...restaties-LED-lampen-vallen-tegen.htm&prev=_t

Thx for the link, but those translators s*ck. I can't even understand some parts of it

 

[SteveyG]

Welcome aboard mate you sound like you know what you're talkin about. Should be a useful addition to our rag-tag group of miscreants. Hope you stck around

Thanks for the welcome I'm an opto-electronics/analogue electronics engineer at work so enjoy joining in with these types of conversations

 

[lee]

Great, can't even get away from RoHS on my pepper forum anymore....


At my job we're in the middle of converting all our products to RoHS compliance. And my first "real" task is heading up one of the board conversions. Pretty much what I'll be doing until October or so.

And lead-free solder blows.

btw you noticed my comment, ok we can talk tech now

 

[TXCG]

Thanks for the welcome I'm an opto-electronics/analogue electronics engineer at work so enjoy joining in with these types of conversations

Nice. I work with a whole crapload of people just like you lol. Just a lowly technician myself

 

[willard3]

Comparing light sources in terms of Lumens per watt is like comparing apples with oranges. It's not a valid unit to use, as it is the perceived power of light rather than the radiant flux.

How is it, then that the IEEE, lamp manufacturers, and other major users list only lumens/watt for lighting efficacy?

 

[buggedcom]

How is it, then that the IEEE, lamp manufacturers, and other major users list only lumens/watt for lighting efficacy?

I imagine it's because they are quoting the visible spectrum which is what lighting is predominantly used for. Growing light isn't always visible.

 

[wordwiz]

Remember though Mike, a CFL is a relatively broad spectrum lamp extending to the IR and UV ends of the spectrum. As LEDs are monochromatic light sources, they will clearly appear brighter because the energy is concentrated into a narrow band of maybe 70nm, at your two discrete wavelengths. There is certainly some efficiency to be gained from omitting 'wasted' energy in the 530nm area, but the dominant wavelength of the LEDs may not correspond to the ideal wavelength for photosynthesis.

I meant to see what kind of lux reading I got at the bottom of the steps last night from the CFL and the LED panel but got busy watering and moving plants. Maybe tonight!

It's interesting to see more LED companies playing around with their designs. One company is using two red spectrums (420 and 460 I think) along with a blue one, plus adding in a couple of amber and white bulbs.

Mike

 

[SteveyG]

How is it, then that the IEEE, lamp manufacturers, and other major users list only lumens/watt for lighting efficacy?

Because these lamps are generally intended for illumination. Take for example a green LED and a deep red LED maybe at 670nm and set the radiant flux from both LEDs to be the same. To the human eye, the green LED will appear far brighter than the 670nm LED because the eye isn't as sensitive to this wavelength. If the manufacturers quoted the light output from these LEDs in lumens per Watt it would seem that the red LED had an awful efficiency, where in reality it just emits light that is less usable by the human eye.

With white light sources, lumens per Watt can be a useful guideline and is also an easy to measure the light output. However you will find that the same lamp offered in a variety of colour temperature options will each yield different figures for lumens per Watt due to the shift in their spectral peaks, despite it probably having the same radiant flux.

 

[wordwiz]

OK, I had a chance to check the lux (not lumens, per se, but the amount of lumens hitting a surface).

A 23 watt, 2700K CFL bulb with a reflector and a 14 watt LED blue/red panel were the contestants. The distance away from the light was about 209 feet. The CFL rated a 22 Lux and the LED a 13 on the meter (.9565 and .9285 lux per watt, respectively). But, and even though I don't have a meter to measure PAR wavelengths, I presume that the LED is putting out more useful lumens per watt than the CFL.

Just to add: An LED produces 683 lumens per watt at 555 nm (pure green).

Mike