ECN Forum
Posted By: harold endean LED bulbs - 08/28/09 11:36 PM
Has anyone found LED bulbs that are good? Will fit a regular Par 40 recess down light fixture? That can be dimmed? Will fit in a sloped ceiling fixture (or eyeball trim)? Any websites out there to check out? Any thoughts?


Thanks
Posted By: twh Re: LED bulbs - 08/29/09 05:11 PM
I've installed a few and have a few in my own home. I don't think they have a lot of uses. They are best when they are lighting against total darkness. Outside is okay, night lights are okay, and I have a walkway between the house and garage with sky lights, so they are only on at night. I can't imagine wanting to dim them. They're already dim. I wonder how they hold up to vibration.
Posted By: Alan Belson Re: LED bulbs - 08/29/09 08:21 PM
Here's a good German site for browsing the latest technology on LEDs.

http://www.dotlight.de/products/en/...0-white-with-3-x-CREE-XR-E-GreenLED.html

Look at the prices though! These are never going to be more than novelty illumination at those costs. And the 40-50000 hour life is when they have dimmed to 50% of their 'new' brightness.
Posted By: renosteinke Re: LED bulbs - 08/29/09 09:56 PM
I've toyed around with a few varieties of LED bulbs. I suggest that you have a chat with a professional lighting supplier / contractor; chances are he has a few at home, or in the shop, that he's playing with.

The verdict? These bulbs are like politicians; they promise far more than they deliver.

The key, of all things, heat dissipation. Simply put, they get the brightness by forcing all manner of power through the diodes - meaning the electronics need truly massive heat sinks. Stick that PAR replacement in a recessed can, and you've just cut off air flow around the fins. That's how LED bulbs work: light out the front, heat out the back.

As for the light itself: LED bulbs cannot produce a 'spot' or 'beam' of light that is in any way comparable to the usual PAR bulb. Rather, it's a far less focused, "softer" spot. That may not be a bad thing; it all depends on what you're trying to do with the light.

Let's not forget that lighting is every bit as subject to the whims of fashion as are womens' skirt lengths. We have all seen passing fads for track lights, troffers, parabolic reflector grids, strip lights, indirect lighting, and -latest- recessed lighting. Who can say what the customer will want next year?
Posted By: Lostazhell Re: LED bulbs - 08/30/09 06:47 AM
Just driving around town and seeing the condition of many of the LED traffic lights makes me skeptical that all the kinks have been worked out when it comes to creating & manufacturing LED clusters viable for commercial & residential applications. At least 30-40% of the LED upgraded traffic lights around here are either partially flickering or partially out. Some are so dim I find it hard to imagine they meet FHTSA and DOT specs (Ironically it's the red that always has the dim issue as well, and over here, at some rather crazy intersections at that)
Posted By: Alan Belson Re: LED bulbs - 08/30/09 12:44 PM
And don't believe the "equivalent to" on manufacturers' packaging and ads. Look at these figures for CFLs- They are producing just over half of the claimed lumens output after 10 minutes warming up when new, making the much vaunted 'savings' a sick joke. I expect the claimed output from leds will be found lacking too.

http://www.telegraph.co.uk/news/wor...saving-light-bulbs-offer-dim-future.html



Posted By: Alan Belson Re: LED bulbs - 08/30/09 01:08 PM
...furthermore, to achieve the long life, a CFL should remain on for at least 15 minutes, otherwise its life will be no better than an incandescent. So the bathroom, garage, utility, pantry, cupboard and other short-visit rooms will eat bulbs.

And CFLs dim over their life. The 'standard' for the claimed 'life' is when the output reaches 50% of new. With tungsten bulbs you simply tossed them out when the bulb showed signs of darkening or it went phut. On that basis, the mean actual output over the life of a CFL will only be around 30% of an 'equivalent' tungsten bulb. At ten to twenty times the price, the low energy bulb is a scam. mad
The fact is, Joe Public doesn't want them, which is why so many Eu-Pocos are giving them away.
Posted By: twh Re: LED bulbs - 08/30/09 03:35 PM
If the lumen output isn't accurate, do they also misrepresent the wattage input?
Posted By: mbhydro Re: LED bulbs - 08/30/09 04:41 PM
Originally Posted by Lostazhell
Just driving around town and seeing the condition of many of the LED traffic lights makes me skeptical that all the kinks have been worked out when it comes to creating & manufacturing LED clusters viable for commercial & residential applications. At least 30-40% of the LED upgraded traffic lights around here are either partially flickering or partially out. Some are so dim I find it hard to imagine they meet FHTSA and DOT specs (Ironically it's the red that always has the dim issue as well, and over here, at some rather crazy intersections at that)


I wonder if there are different specs for LED traffic lights in Canada? Driving around my city I have not seen any flickering clusters and only a few with small missing LED segments. We range from -40 in the winter to the high 80's in the summer so I wonder if the lack of year round high heat gives us better results?

Red signals are the worse ones for bulb life because they are the ones that get the most use in a signal cycle from what I have been told.

Amber gets the least use so I have seen here that when a signal head gets upgraded the Red and Green will be LED and Amber remains a bulb. Only new signal heads are a new complete LED set.
Posted By: mbhydro Re: LED bulbs - 08/30/09 04:51 PM
Alan, its not only the EU-Powerco's giving bulbs away, at the start of this month I received a bag full from our powerco.

Manitoba Hydro is only pushing Power Smart devices to get people to conserve so they can sell more power at a higher price to the US power companies in North Dakota.
Posted By: renosteinke Re: LED bulbs - 08/30/09 06:14 PM
mbhydro, I beg to differ as to the motives behind the PoCo "giveaways."

First of all, they're not giving anything away. Look closely at your bill and you'll find some special fee or rate increase that's what is really funding these programs.

Secondly .... the PoCo is between a rock and a hard place. They have an absolue requirement to supply us with all the power we want - yet opponents have made it nearly impossible to increase generating capacity. So, in desperation, they need to find ways to put off Judgement Day.

No nukes, no oil, no coal .... sooner or later, despite the fantasies of the 'green' crowd, we WILL run out of power.
Posted By: Alan Belson Re: LED bulbs - 08/31/09 09:13 PM
Now it seems, due to the slipshod drafting of the regulations, that the UK has no power to entirely ban the sale of incandescent bulbs!

http://www.telegraph.co.uk/comment/.../Defra-lacks-power-to-ban-our-bulbs.html





Posted By: Alan Belson Re: LED bulbs - 08/31/09 11:31 PM
Reno, the lack of new power generation facilities will, as you say, hit us hard in the next few years, as the Greens learn the hard way than 'renewables' don't work yet. Anyone in the UK older than 50 will remember the early seventies, when we had daily rolling powercuts. Mrs B & I used to come home from work, light some candles and cook our dinner in the fireplace! Galling? I worked on an atomic reactor all day and went home to the Stone Age!

http://www.telegraph.co.uk/news/611...-Government-admits-power-shortfalls.html
Posted By: renosteinke Re: LED bulbs - 09/01/09 02:44 AM
Well, Alan ... that's another topic, for another time. Let's just say you're preaching to the choir!

I just brought it up to give some perspective as to where this problem originates. Just as mideaval rulers often stoked hatred of Jews to get their serfs to re-direct their resentments away from their lords, the "Greenies" are quite happy to have us mad at the power company - when they themselves created the problem!
Posted By: LarryC Re: LED bulbs - 09/01/09 03:58 AM
Alan,

So, aside from building staircases and asaulting innocent ablating individuals, what did you do, when you were slaving over those hot atomic reactors all day?

Larry C
Posted By: Up2code Re: LED bulbs - 09/02/09 04:11 AM
LED bulb equivalent to replace my 60w incandescent cost $40.00!! The locals would through sharp objects at me if I attempted to sell these bulbs right now. But the local POCO is offering big rebates to their non-residential customers for upgrading to LED Exit lights & T8 fluorescents, if installed by one of there "certified" electrical contractors, in which I happen to be. smile
Posted By: renosteinke Re: LED bulbs - 09/02/09 04:56 AM
I heartily endorse LED's for exit signs. Beyond that, I'll wait and see.

LED's are the "AFCI's of the lighting world"
Posted By: ghost307 Re: LED bulbs - 09/02/09 07:49 PM
Although I like the concept of LED exit signs, I have an issue with them being mostly red LEDs spelling out the word EXIT.

Being one of the many colorblind folks on the planet, I find it exceedingly difficult to see red letters in a darkened room.

Chicago is starting to allow LED exit signs but requires the same sign that has alwasy been used, only with white LEDs in place of the bulbs or CFLs as a light source. Those seem to me to be a great compromise between saving energy and keeping the appearance that people have been used to seeing for many years.
Posted By: Alan Belson Re: LED bulbs - 09/02/09 09:38 PM
Larry, I worked as a draftsman in the Pipe Office, [ducting air, water, elec-trickery and such-like], which was as boring as heck, since I had been working under one of the best machine-tool designers in the UK, but we got a free house and double the salary.... We had a reputation for procrastination in Pipes, and were known as the 'Paper Moderated Slow Reactor'....

Back to LEDS. This article looks interesting, at least someone is putting their money where their mouth is....

http://www.ledsmagazine.com/news/6/9/2

Posted By: LarryC Re: LED bulbs - 09/03/09 03:55 PM
Quote
Paper Moderated Slow Reactor



How very true. Even as an operator in the navy, I swore that we could burn the paperwork we generated and power the ship with just that.
Posted By: harold endean Re: LED bulbs - 09/03/09 08:45 PM
I thank each and everyone for the replies. I was just wondering if the LED lights were as good as "they" say they are. I was thinking that a LED light might not be damaged by high voltage problems like the regular incandescent bulb. I have the POCO transformer right outside my house, so the normal voltage here is between 125-130 volt. The normal 120 volt bulb doesn't last long at all. I went to the compact florescent bulbs and they last a lot longer. They are not able to be dimmed either, so I thought that may there is a LED type of bulb that could fill my need.
Posted By: mbhydro Re: LED bulbs - 09/03/09 11:30 PM
Harold are you sure you don't have dimmable CFL's available?

Up here in Canada they are on the store shelves at the big box stores. I think that Globe is one of the brands that makes them.

I don't have any but one of my friends put some in his basement rec room and was not impressed with the bulb life and he was not running them dimmed that often.
Posted By: Trumpy Re: LED bulbs - 09/04/09 07:28 AM
IMO,
Any attempts at trying to dim either a CFL or an LED lamp, would be pretty much fruit-less.

Reason I say that is because, look at the way that this technology works.

A Compact fluorescent lamp is just a smaller version of a 3-4-5-6ft linear tube.
If you reduce the voltage through that tube, the arc that keeps the lamp lit will fail, hence darkness.

On the same side of the coin, an LED is purely a P-N junction that requires a certain "bias" voltage to keep it lit, go under that, you get the same result as above.

The only way you are going to achieve actual "dimming", is to turn off individual LED's or parts of a CFL.
With current lamp-holder technology, that won't be happening any time soon.
Posted By: wewire2 Re: LED bulbs - 09/04/09 07:37 AM
Googled dimmable CFL and LED and found both are available. They have drawbacks though, like flicker and startup time.
Posted By: gfretwell Re: LED bulbs - 09/05/09 06:13 PM
LEDs might have early end of life problems but they should dim OK and there is no warm up time. The thing that burns your recordable CDs and DVDs is a LED and it goes from off to full on in a fraction of a microsecond.
Posted By: wewire2 Re: LED bulbs - 09/06/09 05:34 AM
Greg
I was thinking the thing that burns DVDs and CDs is a RLD.
(red laser diode). Are you sure an LED can also do that kind of work?
Just curious. smile
Posted By: gfretwell Re: LED bulbs - 09/06/09 06:02 PM
That is still a type of LED. The silicon junction emits light as soon as it is energized. There is no warm up time like you have in a filament or the slower CFL.
You also see the light output vary, based on the current going through the junction. It is probably not as linear as a filament but it is purer in color. ... at least that is what I see when I use LEDs in the things I build.
Posted By: Alan Belson Re: LED bulbs - 09/06/09 11:08 PM
There are many different types of LED based on the chemistry of the substrates in the device. There are several ways to make 'white' light: mainly, either run the photons emitted by the LED through a phosphor coating, [similar to fluorescent tubes or CFLs]. Or to mix the emissions from three or more diodes of primary light frequencies, [yellow/green, red and blue for light, as opposed to the paint primaries we learned when daubing at first grade], to create a 'white' light. The percieved 'temperature' can be adjusted by changing the frequency of the photons emitted, to give 'warm' or 'cold' white. The problem is balancing the emitting power against the temperature of the device when running, because the life deteriorates exponentially with temperature. Don't confuse working temperature with power-loss inefficiency. The working area in the LED is very small, say 1mm2, and it's hard to get the heat away from that small spot.

In practice, the outut from individual units is presently so small that they are most often fitted in multiples. Switching out some of the lamps is then probably the easiest way to create mood lighting effects. Colors are true, as Greg says, because the frequency of the actual light emitted can be controlled electronically.

The problem with all these 'high tech' light emitters is percieved color of the 'white', deterioration in brightness over the lifespan [L50] and cost effectiveness. Manufacturers 'get away' with low brightness, because humans compensate for low light levels so well. A 50% drop in output [ one 'stop' to camera buffs] can be compensated by the eyes and brain so well that we barely notice. Except when we need the brighness for fine work or reading, when the opening of the iris to let in more light interferes with focus and ability to see detail.
Here's a good article:
http://en.wikipedia.org/wiki/Light-emitting_diode
Posted By: n1ist Re: LED bulbs - 09/07/09 03:29 PM
LEDs are usually dimmed using PWM, not by reducing the current through them.
© ECN Electrical Forums