Naked Science Forum
General Science => General Science => Topic started by: bkelly on 17/07/2007 02:43:37
-
I am looking for some LED bulbs to replace incandescents. I have found a number of places to buy them, but they are almost all units with about 35 LEDs. The stated equivalence is a 15 watt bulb with only 3 watts of power.
A 15 watt bulb is a rather puny. I want a 60 watt equivalent to put in a floor standing light that shines over my shoulder for reading. I have yet to find anything of that size.
But maybe I judge to hastily. Does anyone have any of these 15 watt equivalents. How is their brightness for reading?
I expect to pay about $100. The power savings should be around 48 watts per bulb. I will have to calculate the savings in air conditioning cost. But the long term advantage of getting the market going and getting lower price bulbs might be worth it.
Any suggestions as to where to look?
Thanks for your time,
Bkelly
-
I have never used LED bulbs, but talking to my local electrical retailer recently, he did suggest that LED bulbs were underpowered.
Any reason you are choosing LEDs over the more established compact fluorescent bulbs?
-
i have three lamps in my living room. one has a three way bulb, one has a sixty watt and the other has a forty watt light bulb. the only one i ever use is the forty watt unless i'm doing a big project on the other side of the room. i think thirty watts may be brighter than you're thinking it is.
-
...except you said fifteen not thirty. lol. i don't know how i made that mistake... sorry!
-
As you have previousy mentioned the wattage of an LED lightbulb is increased by a factor of 5, to represent the wattage of a standard incandescent light bulb.
so you are looking for a 12 watt, LED bulb. Curiously, i have found referance that you can increase the wattage by a factor of 10, but i don't know how accurate that is.
i will PM you with a link to an online store.
-
First, Paul, why PM me rather than put the link Right up here?
But I will summarize: A 60 watt incandescent generates about 900 lumens. At the unmentioned site, the big one is 150 lumens. I would need six of them to get to 900. And at $54.95 each, that is $329.70. I don't think I want to go that far. However, that one is really focused and standard light bulbs are not.
I would really like to hear from someone that has purchased and used some of these lights.
Thanks for taking the time to respond.
bkelly
-
First, Paul, why PM me rather than put the link Right up here?
Because the link i PM'd you is to a commercial website. The advertising of which is against forum rules.
-
Problem is atmosphere; the nicest lights to work under are definitely high temperature, conventional, filament lamps.
I guess we all like real sunlight and that is broad spectrum 'black body' radiation.
I have a brilliant 'head light' with 4 leds and it works fine for reading in a tent or messing around under the car.
It's still a disgusting colour and I wouldn't like to have every room in the house lit this way.
One day they will find a led which gives a broad range of spectral colours which approximate to sunlight but, even the discharge tube high efficiency lamps they make now are pretty naff, imho.
I am on the horns of a dilemma; can I be green enough to put up with the vile colours? Perhaps the secret is to use motion sensors everywhere which only turn lights on when you are actually in a room. That would reduce the consumption to less than 25%, I'm sure, so I can have my light and save energy.
-
Problem is atmosphere; the nicest lights to work under are definitely high temperature, conventional, filament lamps.
I guess we all like real sunlight and that is broad spectrum 'black body' radiation.
I have a brilliant 'head light' with 4 leds and it works fine for reading in a tent or messing around under the car.
It's still a disgusting colour and I wouldn't like to have every room in the house lit this way.
One day they will find a led which gives a broad range of spectral colours which approximate to sunlight but, even the discharge tube high efficiency lamps they make now are pretty naff, imho.
I am on the horns of a dilemma; can I be green enough to put up with the vile colours? Perhaps the secret is to use motion sensors everywhere which only turn lights on when you are actually in a room. That would reduce the consumption to less than 25%, I'm sure, so I can have my light and save energy.
But is that not where CRI comes in - and increasingly it is possible to have high CRI lamps that are not incandescent.
-
If you take a colour picture indoors by tungsten light using film balanced for daylight you will find just how poorly normal artificial light imitates sunlight. The pictures come out looking orange. Our eyes (and brains) can compensate for markedly different lighting conditions. Unless we really need good colour rendering (like matching socks when they come out of the wash), it doesn't matter. Interestingly I still like candlelight even though I know it leaves me with very poor perception of blue colours and I know that after a few seconds my vision adjusts so I hardly notice the colour cast.
BTW, if you really want something that is a fair match for the spectrum of sunlight then incandescent lamps aren't up to it. You need things like high pressure xenon arc lamps. I don't know anyone who uses those domestically
-
I reckon your brain / vision is a lot too smart not to notice the difference between a black body source and a crude set of line spectra.
This is probably because of the confusion with colour matching familiar groups of objects in natural and artificial light. There is very little confusion in colour matching under tungsten, compared with gas discharge.
High pressure in a gas will spread out the lines nicely . Does this mean that a suitable LED could have broad spectrum too, it's in a condensed medium - Pauli Exclusion principle and all that?
The nicest time of day for lighting is late afternoon, when the colour temp is quite a bit lower than an arc lamp - in my opinion.
Candles are a pretty good black body source.
-
"I reckon your brain / vision is a lot too smart not to notice the difference between a black body source and a crude set of line spectra. "
I don't and I'm looking at this image on an RGB monitor on which I often watch perfectly convincing television pictures.
Since my eyes only have 3 colour receptors (and their responses overlap massively) I think it's pretty easy to fake colour temperature quite well. In my experience, matching dark blue socks under tungsten light is a problem. The socks only reflect blue light and there simply isn't much of it to reflect. They all look more or less black.
Most of the "white" LEDs I have seen have used a blue led to drive a "white" emitting phosphor. In principle you could get pretty much any spectrum you wanted but most people are after the highest perceived brightness.
-
How long does An LED light against it's fluorescent counterpart ?
-
How long does An LED light against it's fluorescent counterpart ?
LED lights can last for 100,000 hours which makes them extremely attractive even though they have a high cost at pesent. There are some led facts (http://www.ledbulbs.co.uk/) listed on my LED page.
-
I think i can help you ,Our led lights can provide enough Lum to you and the price is competitive
<mod edit - link removed. We don't allow advertising on the forum, but if you feel you can help, please feel free to send the instigator of the tread a private message with a link to your company>
-
I don't and I'm looking at this image on an RGB monitor on which I often watch perfectly convincing television pictures.
Yes, a TV picture can be a very good metemeric match but the colour it is referenced to is white. When you are looking at other familiar coloured objects, illuminated by the fabricated white there is more brain processing involved.
Furthermore, unlike LED lamps,the phosphors of a TV display are not fabricated to be as efficient as possible and are designed with colourimetry specifically in mind. TV phosphors are much broader band (see Wikkers, for some graphs of each). Certainly, the specrum from the Single white diode , using Stokes shifting is pretty ghastly
-
are LED and maxlee spammers then? If so, 'may the devil walk amongst their children'.
-
Yes.
Furthermore - as for the colourimetry of viewing objects in LED lighting compared with colour TV. The essence of colour TV is the ANALYSIS of the original scene. that analysis is done with a broadband (dichroic filters, it used to be) analysis. Light of any wavelength is detected by two or more of the analysis curves and the colour will be reconstructed with the phosphors.
Viewing a colour under narrow band LEDs could make the colour look black due to the analysis of your eyes in conjunction with the LED light, if its reflected wavelengths don't correspond with the LED spectrum.
Horses for courses.