Author Topic: anyone else with an interest in LED lighting?  (Read 16734 times)

0 Members and 1 Guest are viewing this topic.

Offline slburrisTopic starter

  • Frequent Contributor
  • **
  • Posts: 542
  • Country: us
Re: anyone else with an interest in LED lighting?
« Reply #25 on: September 22, 2010, 02:30:17 pm »
I did purchase the larger of the two new landscape lighting fixtures
I mentioned a few posts ago in this thread.  I like it!  It's significantly
brighter than my previous lighting and seems to be holding up well.

Inside the house, I'm struggling to find lights for two applications.
The first is a nightlight which is a ball with a rice paper shade.
It came with a 7w CFL, which is OK, but too bright for my
intended use.  I've been looking for an LED replacement with
a candelabra base (E12 in the US).

The best I've been able to come up with so far is this
50 lumen 2 watt bulb from Osram Sylvania:



I've also been searching for lights for a bathroom fixture that looks
kinda like this:



I've tried my favorite Home Depot 40w LED replacement bulb, but it's too
directional for this fixture.  I've also found that it has a different dimming curve
than the incandescent bulbs.  So if you mix the bulb types then dim them,
you'll have one kind of bulb going out far before the other.  Should have been
obvious in retrospect, but I didn't think of it.

Scott
 

Offline Simon

  • Global Moderator
  • *****
  • Posts: 17720
  • Country: gb
  • Did that just blow up? No? might work after all !!
    • Simon's Electronics
Re: anyone else with an interest in LED lighting?
« Reply #26 on: September 22, 2010, 04:37:45 pm »
I think bulb wattages should be abolished as the main characteristic as today it is totally meaningless. Lumens should take the place of watts (which can still be mentioned) and the colour temperature should be on the packaging and bulb by law. I get the impression that higher temp bulbs do not appear to make as much light which may be why 2700K (yellow) is preferred by manufacturers as it dupes the users into thinking more useful light is being made than there really is. I had to use a 20W 5000K CFL in my 4 sq metre bedroom to be happy with the amount of light !
 

Offline slburrisTopic starter

  • Frequent Contributor
  • **
  • Posts: 542
  • Country: us
Re: anyone else with an interest in LED lighting?
« Reply #27 on: September 22, 2010, 04:48:21 pm »
http://en.wikipedia.org/wiki/Incandescent_light_bulb

has a table with incandescent light bulb wattages and lumen output.
I refer to it frequently when trying to estimate what kind of LED bulb
could replace something.  This is for 120v systems -- I don't know how
this should be adjusted for 240v areas.

The table is about 2/3rd's down the article.

There's also a claim made that incandescent bulbs are *less* efficient
(in terms of lumens/watt) at higher voltages.

Scott
 

Offline Simon

  • Global Moderator
  • *****
  • Posts: 17720
  • Country: gb
  • Did that just blow up? No? might work after all !!
    • Simon's Electronics
Re: anyone else with an interest in LED lighting?
« Reply #28 on: September 22, 2010, 05:17:56 pm »


There's also a claim made that incandescent bulbs are *less* efficient
(in terms of lumens/watt) at higher voltages.

Scott


well from why I've seen it's actually a case of "x" volts per watt of light, the more watts you want the longer the tube and the higher the voltage needed to get it going. of course the table still ignores colour temperature which is important as while we can ajust to a certain range of light colours (our brain will do an automatic white balance - literally) we see colours differently and will be more sensitive to a certain colour (green I believe)
 

Offline PetrosA

  • Frequent Contributor
  • **
  • Posts: 625
  • Country: us
Re: anyone else with an interest in LED lighting?
« Reply #29 on: September 23, 2010, 03:23:21 am »
The 2700 Kelvin goal is more to make the color attractive to consumers who are used to incandescent bulbs. There's also something to be said for matching the color of all the bulbs in a house.

While there are fluorescent bulbs capable of a high CRI that match 5000K and 6500K (they are available for graphic's purposes) they cost a lot more because of the gases that have to be mixed to provide a fuller spectrum. Many CFL and LED lights have too little spectrum to have a decent CRI and while you might think that your eyes balance the color out, they really don't, because they can't - there's just too little information to see all the colors. There are LEDs designed for use in gallery lighting, but you won't touch them for $100 ;).

A few of you have mentioned difficulty trying to find LEDs with the right throw of light - this is one of the biggest challenges for LED designers. There is a huge difference in the spread between incandescent, CFL and FL, but LEDs are another beast altogether. They have a hugely directional beam spread which works great for flashlights and headlamps and somewhat ok in dense lighting strips designed to bounce light off of reflective surfaces, but they don't work so well for replacing room lighting. They also have different cutoff characteristics from either CFL, FL or incandescent (the lumens drop off much faster with LED than other types of light). There are still lots of hurdles to get over with LED.

Efficiency of incandescent bulbs drops non-linearly when voltage drops which is one of the common arguments against dimmer switches and lifespan of bulbs is reduced drastically at higher than nominal voltages. At half the rated voltage of a given bulb, you may actually only be getting 25% of the light output. On the other hand, at 95% of nominal voltage, you may get better than 50X the expected life out of the bulb, which again changes the equation. So while it may be a more power efficient plan to swap the bulbs out each time you want less light, the dimmer may be reducing your consumption of bulbs to such a large extent that it offsets the losses in power efficiency.

The bottom line is that incandescent is the one type of light source that doesn't violate the KISS principle and price reflects that. LED has a good chance to compete, but it needs a lot of work yet.
I miss my home I miss my porch, porch
 

Offline NiHaoMike

  • Super Contributor
  • ***
  • Posts: 8951
  • Country: us
  • "Don't turn it on - Take it apart!"
    • Facebook Page
Re: anyone else with an interest in LED lighting?
« Reply #30 on: September 23, 2010, 04:55:47 am »
There's halogen (technically just another kind of incandescent) which offers an even better spectrum and slightly higher efficiency, but can't be dimmed very much.

And yes, incandescent lights (regular or halogen) are generally less efficient at higher voltage ratings, particularly at low wattages. It has to do with the thickness of the filament and the operating temperatures. There used to be a "high efficiency" incandescent bulb that had a series diode as a cheap way to reduce voltage (thereby allowing the filament to be thicker and hotter), but it has since disappeared due to CFLs.

"Broadband white" LEDs (UV LED with RGB phosphors or blue LED with RG phosphors) exist, but I do not know of a source for them. They are used mostly in high quality LCD displays.

One application where incandescent will always be the clear winner is infrared heat. (I have used reflector incandescents to stay warm during the winter.) They use much less power than any space heater and even heat pumps have difficulty matching the efficiency if all that's needed is a spot of heat.
Cryptocurrency has taught me to love math and at the same time be baffled by it.

Cryptocurrency lesson 0: Altcoins and Bitcoin are not the same thing.
 

Offline Simon

  • Global Moderator
  • *****
  • Posts: 17720
  • Country: gb
  • Did that just blow up? No? might work after all !!
    • Simon's Electronics
Re: anyone else with an interest in LED lighting?
« Reply #31 on: September 23, 2010, 06:44:18 am »
2700K is far too low, it is essentially yellow but you eye adjusts, try playing with colour temperature in photography to see what I mean, when we used to use film you just could not use outdoor film under CFL's without filters or specific film. 3500K is getting closer, but I can assure you that incandescents DO NOT put out 2700K, infact no end of people complain that they cannot see well under CFL's and I heard of someone looking for an incandescent bulb for some elderly people because they could not see to read under the CFL lighting, I explained about colour temperature and suggested she find a CFL of more "normal" colour temp. I do now seriously doubt the efficiency of CFL's ok they are better than incandescents but no where near as good as the manufacturers claim, again going back to my experience in photography, do you realize just how sensitive our eyes are and what a huge range (dynamic range) of brightnesses it can handle, the ratio is well over 1:1000 I believe (try using an SLR camera indoors and then going out into a sunny day and see the settings change required), so it's easy to say that a 20W CFL is equivalent to a 100W incandescent, it's not ! I think the problem with my 5000K bulb is that it puts out pretty much 5000K only so does not as you say cover the full spectrum, but 2700K is just as bad on that band, really it's a case of what colour (literally) do you want your lighting. When I do need more bulbs I'll go for 3500K, 2700K ones just send me to sleep particularly in the winter and yes it's medically proven and some people really have an issue with it, that's how bad those damn things are.

on the original topic though I would like to get into led lighting and may well convert my whole house some day, it also makes it very easy to power from a 12/24V battery that was charged by a solar panel
 

Offline Zero999

  • Super Contributor
  • ***
  • Posts: 19284
  • Country: gb
  • 0999
Re: anyone else with an interest in LED lighting?
« Reply #32 on: September 23, 2010, 07:36:33 am »
I dislike 5000K for room lighting, it just looks bluish grey and the light isn't full spectrum or anywhere near bright enough to simulate daylight.

Incandescent is better, halogen probably the best. I don't really like 2700K CFLs but it's acceptable. I've never tried 3500k in my house but I know it's what's used in offices and I'm not sure if I'd like it.

By the way, I noticed at your dad's house that the 5000k bulb was dimmer than the 2700k: is it because it's a lower wattage? I would generally expect a 2700K lamp to be brighter than a 5000K lamp of the same power level because the eyes are less sensitive to blue, there again blue phosphors will be more efficient because there's less of change in wavelength from the UV emitted by the mercury arc.
 

Offline Simon

  • Global Moderator
  • *****
  • Posts: 17720
  • Country: gb
  • Did that just blow up? No? might work after all !!
    • Simon's Electronics
Re: anyone else with an interest in LED lighting?
« Reply #33 on: September 23, 2010, 11:40:46 am »
the 5000K light is 20W the 2700k is 18W and is in a smaller area. like you say the 5000k looks not so bright and bodied as it's not emitting a full spectrum but then neither is the 2700K as it doesn't go much above. like I said I think some of it is physiological you don't expect the 5000 light. I was using one of those 5000K lights in my 4 sq metre room and that looked ok but that say's alot about the real efficiency of CFL's as in that room 40-60W incandescent will do the same job. I had some 3500K strip lights and they were good.

the cfl in the bathroom is 4200K not so stark but yea I'd stick to 3500 as a general recomendation
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf