# LED Fluorescent "tubes"



## PhotonWrangler (Aug 5, 2007)

Only 70 times more expensive than a fluorescent bulb! Swiiiiinnng and a miss...


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## evan9162 (Aug 5, 2007)

That's a hard sell. Only slightly longer lifetime, only slightly more efficient, and the "environmentally friendly" aspect vis-a-vis the construction of the tube is questionable, since manufacturing LEDs isn't exactly a squeaky clean process. The mercury in fluorescent tubes can be easily recycled, and not released into the environment. 

These would be nice as more durable fluorescent tube replacements, and also where the tubes get powered on and off many many times per day, but the cost is still a bit too prohibitive.


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## James S (Aug 5, 2007)

it's a great idea. No replacing or working in the fixtures, just pop it in. But... So you've potentially got those huge hot inefficient ballasts boosting the voltage up and current regulating for a hot gas arc... and then you put another power supply at the other end of that to get down to LED voltages... 

It's a great idea! And there are certainly places where converting the fixtures would be expensive if not completely impractical, but at that price you can hire an electrician for a long time to work at your place...


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## PhotonWrangler (Aug 5, 2007)

It seems like a workable idea for places where it's really difficult and expensive to reach a lighted area, such as backlit signs mounted atop buildings or high poles, where the cost of mobilizing a crew with a bucket truck is far more than the cost of the lamp.


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## AJ_Dual (Aug 6, 2007)

Sigh…

I had come up with almost the exact same idea on my own a few weeks ago. I don't know exactly how these are constructed, but my thought was to put two Cree, or other high efficency emitters on the end caps, and have the tube in between be made of diffraction plastic or "light pipe" etc. to send the light out and down.

The other idea was to use the phosphor coating like that of a flourescent tube, but have UV LED's excite it instead of the mercury vapor discharge.
Oh well.


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## jtr1962 (Aug 6, 2007)

Unless the LED drivers are very efficient, in a system like this you end up with losses in both the fluorescent ballast and the LED driver. I can't see something like this making much sense except in situations where tube replacement is difficult, or where a tube is cycled frequently. Long term purpose-built LED fixtures make a lot more sense.


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## Oznog (Aug 7, 2007)

Doesn't that tube fit directly in a std fluorescent socket?

If so then the starter and ballast are still being used- not only completely unnecessary, they must have had to give some thought to how to drive it with those present.


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## winny (Aug 7, 2007)

Replacing flurecent tubes with LEDs sounds very stupid to me. With LED's dropping efficiency with increasing temperature and they will for sure get hot if you install the power needed, they will not be as efficient as fluorescents tubes. Increased lifetime? Hardly, with 100 000 hours to 50 % light for LEDs vs. 60 000 hours to 80-90 % light for florescent tubes. Increased efficiency? No, unless they use top of the line LEDs and underdrive them, they will have a hard time beating 100+ lm/W for T5 HE tubes.



James S said:


> So you've potentially got those huge hot inefficient ballasts boosting the voltage up and current regulating for a hot gas arc...



Are you saying that you use the ballast to boost the voltage after the tubes have been started?


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## Kinnza (Aug 7, 2007)

Ive seen LED replacementent for fluorescent tubes both working from the fluo ballast and working directly from mains.

The fluo ballast already limit the current. If i remember well, 40w tubes (4ft) drive very near 300mA. Very good range to get the max duration and good efficiency from 1w LEDs. But i dont know how close are the standards, meaning the expected differences in current from one generic ballast to another. The specs of LED replacements tubes shows a difference on power noticiable (50% more), from 12 to 18w same tube depending on ballast. Anyway, keeping drive current at about 300mA seems very safe in order to get max LED's duration.

Those tubes working from mains should include its own driver. If differences between generic fluo ballast are huge, i would choose tubes with its own driver.

*Winny, *you must think in terms of fixture efficacy, not only the bulbs. You must expect losses in the fluo fixture of 20%. Avalaible lm from the fixture always is lower than the bare bulbs. In fluo fixtures, you need a reflector wich drive light donwards, and you dont need it with LEDs. Actual T5HE fixture efficiency is below 80lm/w, and probably below 70 lm/w. 

Anyway, i agree with you in LED fluorescent tubes offer too little improvement currently for the high price difference. But with the fast improvement of LEDs, they are going to be a very good alternative in two years.


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## starlinklighting (Aug 7, 2007)

*LED Fluorescent "tubes*
We can produce it .


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## Oznog (Aug 7, 2007)

Actually considering the losses where 50% of the tube's light has to reflect off the white fixture to make it into the room, LEDs can probably compete but not in any wide-margin victory. Fluorescent lights don't exactly take a lot of $$ to run so what does a few % of efficiency matter one way or another?

Not having to replace them has real benefits. They can also be dimmed, except I doubt you can dim them in this configuration with that ballast in the way. You're not even supposed to install a dimmer going to any fluorescent fixture at all. Still, these are going to have to be way cheaper to be of any practical value.


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## lyyyghtmaster (Aug 8, 2007)

Well, I had a very nice reply ready, but CPF logged me off, and in logging back on the reply was lost, and I'M NOT RE-DOING IT. NICE GOING, CPF!!:thumbsdow


Edit: Well, OK, I _may_ re-do it sometime this weekend IF I get time. :sigh:


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## 2xTrinity (Aug 9, 2007)

Oznog said:


> Actually considering the losses where 50% of the tube's light has to reflect off the white fixture to make it into the room, LEDs can probably compete but not in any wide-margin victory. Fluorescent lights don't exactly take a lot of $$ to run so what does a few % of efficiency matter one way or another?
> 
> 
> 
> ...


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## yuandrew (Aug 23, 2007)

Hmm, the company name looks familiar.

http://www.everled.com/everled-tr/


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## The_LED_Museum (Aug 23, 2007)

As far as I'm aware, LED lighting products powered by mains (110 to 240 volts AC 50 to 60Hz) are as-of-yet undimmable, unless a special dimming circuit made for that specific lamp is used.

The reason is that common "household" dimmers alter the AC waveform in a manner that LED bulbs do not like.
If the lamp is dimmed in this fashion, it will overheat, and maybe even start an unwanted fire. You don't want rats or rattlesnake eggs...I mean...you don't want *an unwanted fire.*


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## SemiMan (Aug 24, 2007)

Realistically, that is just a matter of making ballasts for LEDS that can be dimmed via a traditional dimmer similar to what has been done for compact flourescent lamps with some of them working off a traditional dimmer. It is something impossible, and probably not even difficult, it just needs to be done.

However, in the interest of noise, I would rather see a dimmer system that does not involve noisy triacs cutting up the AC line. There are a lot of other alterative technologies such as very low cost RF that could be used. When you look at the reduced wiring costs of not having to directly hook the light switch to the lamp, I would guess the overall installation would end up being cheaper.

Semiman


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## Canuke (Aug 25, 2007)

The_LED_Museum said:


> As far as I'm aware, LED lighting products powered by mains (110 to 240 volts AC 50 to 60Hz) are as-of-yet undimmable, unless a special dimming circuit made for that specific lamp is used.
> 
> The reason is that common "household" dimmers alter the AC waveform in a manner that LED bulbs do not like.[/i][/b]



As I understand it, it's the triacs that don't like the nonlinear load of LED's. I was advised here on CPF somewhere that I could dim LED's with a triac dimmer, but not only would I have to rectify and filter the chopped-up AC, but the triac needed to see sufficient resistive load in parallel with the LED's to switch properly -- about 5W worth of incandescent bulb, to be exact.


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## 2xTrinity (Aug 25, 2007)

> Realistically, that is just a matter of making ballasts for LEDS that can be dimmed via a traditional dimmer similar to what has been done for compact flourescent lamps with some of them working off a traditional dimmer. It is something impossible, and probably not even difficult, it just needs to be done.


I have tried some of those CFLs, and the only problem there is that the entire interface is very kludgy feeling -- for example, different fluoresecnt bulbs would "sense" the setting in the dimmer setting at different rates, and you would get funky effects where some bulbs would dim more than others, and where there would actually be observable lag in the process of diming as well, one would actually cycle off and on intermittently. The other problem was that unlike the T8 dimming ballasts I have seen, which go extremely low, the screw-in dimmable CFLs did not dim low enough. I believe this is due to the limited ability for the ballast to "cope" with the noisy output of stadard dimmers.

The way that LED dimming needs to be done is with a fully electronic ballast that acts as a constant-current power supply, whereby the current sense can be changed remotely. Such a system would be complteley free of RFI problems caused by "noisy" sine-waves, that plagues standard dimmers (and the CFL alternatives are much worse for RFI)

One thing that I have oftened wondered about is this -- why is it, especially considering the poor reflector efficiency of most standard fluorescent fixtures, that there are not tubes for sale that have a reflector coating on one side, and the phosphor coating on another side -- so that they would emit light in a 180 degreen pattern (or less) as opposed to a 360? Certainly a tube like that would have the same nominal advantage as the LED product in the original post.


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