20W LED tube interchangeable with 20W fluorescent tube. 11

[grigson]

Hello,

We want to put a 20W LED tube into a socket for a fluorescent tube with a high frequency, switch mode fluorescent ballast driver.

...we dont want to remove the fluorescent ballast as it would be inconvenient.

Are there any standard solutions for this?

-we still want it to be quite efficient, so dont want a linear driver to be added in for the LED current control...we want efficient switch mode current control of the LED current.


...Ultimately, we would like to design a 20W LED tube (containing auxiliary circuitry and converter , etc) which could run off ANY fluorescent ballast.
..that is, it should be able to run off either a 50Hz magnetic ballast, or any high frequency switch mode fluorescent ballast.

....do you know if standard solutions exist for this?

 

[VEBill]

When buildings throughout North America switched from 4-foot 40w tubes with magnetic ballasts to the newer 34w tubes with electronic ballast, they (obviously) switched out the ballasts. It only required a few minutes each.

LED tubes are available and run off AC power directly. Just remove the ballast and twist a few wire nuts.

Leaving the ballast installed, where who knows how much variability exists between various ballasts and how they might react, is not likely to be practical as a general solution.

Watcha up to now?

 

[grigson]

Hi, Thanks, unfortunately i can't say too much as i signed a NDA.

I can say that ripping out the fluorescent ballast is not convenient in this situation......it would be too expensive in this particular application.......

-not only that...but the customer doesnt really know if they want LED.......they'd like to try it , and if they dont like it, they'll go back to their fluorescents....so another reason to leave the fluorescent ballast in.

 

[itsmoked]

There are OTS LED 'tubes' that directly replace fluorescent bulbs.

Google "fluorescent led replacement" and you will get over 8 million hits. Most of them plug right in and need no re-wiring. Have a ball.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[grigson]

Hi,
I have googled and found millions of LED tube lights.

...But all of these have their own specific LED Driver ballast.......

-none of the ones that i've found can run off any type of fluorescent ballast.

The manufacturers of fluorescent ballasts wont supply us with their fluorescent ballast circuit diagrams, because they dont want us to put LED tubes into these ballasts outputs....so theres another problem for this task.

 

[VEBill]

Then leave the ballast in place (physically) and wire around it. It's literally just a couple of minutes for the electrician and his trusty step ladder. They don't even bother killing the power as they shake ceiling tile dust all over your cubical.

You're looking for an extremely complicated and impractical solution to a non-problem.

On the other hand, if it's possible then it'll already have been done.

 

[DRWeig]

Hi Grigson,

Unless your new tube is like itsmoked advised, you may not get the results you want.

The purpose of the fluorescent ballast (in my learnings) is to provide a high voltage to strike the lamp, then to provide a reactance (or electronic modulation) to keep the current at the design level after the lamp is struck.

That initial voltage spike may damage LED lamps that are not designed to handle it.

Good on ya,

Goober Dave

 

[IRstuff]

I'm not sure what the difficulty is. Doesn't a ballast simply crank up the input voltage briefly during turn-on to get the fluorescent lamp's gas to ionize?

So, wouldn't you just have essentially and overvoltage clamp to limit the voltage into the LED circuit?

TTFN

FAQ731-376
Chinese prisoner wins Nobel Peace Prize

 

[grigson]

.........the thing is, before a fluorescent tube has struck, it looks like an open circuit....and thats how the voltage builds up across its terminals at start-up.

So any LED replacement is going to have to look like an open at start-up, or else the fluorescent ballast controller will think that it never struck, so to speak.

but since we dont have any of the datasheets for any of the fluorescent ballast controllers, its going to be difficult to sort out.

I have been asked to do this job, but i am not sure if its just a plain bad idea....and i should state that?

.....Surely , i keep thinking, it'd end up being cheaper to just rip out the fluorescnet ballast and put a LED driver in there?

...Though our sales people tell us the customer doesnt want this.

 

[Skogsgurra]

Making the thing look like an open is not a problem. There are able transistors that can easily take 300 - 400 V. Data sheets or measure the ballasts to see what they do can't be an issue either.

Still, if "sales" came up with this, I woudn't bother too much. Most likely a bad idea. Test the peddlers; ask them what the volume will be and how much money the company can make from this idea.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[OperaHouse]

Certainly a salesman's dream. Less light output for the same power because you now are doing two electrical conversions, but you can tell the customer he has high tech LED now. Maintenance might be less. Probably not if it ends up built a cheaply as the electronics in a compact fluorescent.

 

[jraef]

If this is intended as a universal field retrofit device, I don't see how it could be made practical. There are different types of fluorescent ballasts out there; instant start, rapid start, programmed start, as well as old magnetic ballasts and new electronic (SMPS) ballasts. Considering that most electronic ballasts ar firing at 20kHZ or higher vs older magnetic ballasts are at line frequency, do you think that will be a problem for your LED system?

"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
For the best use of Eng-Tips, please click here -> faq731-376

 

[grigson]

yes i do think the frequency differences will be a problem.

-but it is thought that we can put a frequency detector into the LED tube, so it sees what frequency the particular ballast is giving, and then the LED tube configures itself to be able to work with that frequency.

 

[MacGyverS2000]

With all of the checking you plan on doing, you're going to create an LED tube that costs $400 and no one will buy. In onesies, LED T8 tubes can be had for <$100. You're over-engineering for a market that is only in the mind of a salesman.

Dan - Owner

http://www.Hi-TecDesigns.com

 

[LionelHutz]

Why do you need to get schematics from a ballast company? IRF has all kinds of reference circuits and designs for electronic ballasts available on their website. I'm sure some Googling can yield you other designs too.

I suspect you'd have to somewhat match the ballast loading of the fluorescent bulb with the LED replacement, which would ruin your energy savings.

All-in-all, it sounds like a poor idea. The one time extra cost of re-wiring would more than offset the cost of the more expensive bulb and the extra energy used by the extra circuits required and conversions being done.

 

[VEBill]

...one time extra cost of re-wiring...

Bypassing the ballast would only require an additional 5 minutes maximum; that's worst case. Even at $100 per hour (also worst case), it's about $8. More realistically, it'd be about $2 labor per fixture. So if the fixture contains two bulbs, then your budget for this feature is about $1 per bulb (at retail). The manufacturing budget for this feature is perhaps $0.25 per bulb. Otherwise, it's not economical. A longer term analysis only makes the business case worse.

It'd be different if bypassing a ballast was difficult. But it's not. The wiring is RIGHT THERE. Pop off the ballast cover, relocate a few wire nuts, pop the cover back on, and slap on a warning sticker ("LED Bulbs ONLY").

 

[grigson]

VE1BLL: I am inclined to agree....bypassing would be a better idea than running led tube off a fluorescent ballast.

But i am now reckoning that its going to be best to just rip out the whole fluorescent ballast and put in a led driver.

There is an opinion that we can produce a LED tube which, in every way, electrically imitates a fluorescnet tube, and thus can be placed into any ballast that that fluorescent tube can be placed into.

Though i am inclined to agree with most of you that this is a non cost-effective solution.

By the way, out of interest, supposing the fluorescent ballasts were on several fleets of passenger aircraft.....i presume you would still say its not cost-effective.?

 

[VEBill]

Aircraft modifications carry so much overhead that the cost of the equipment itself is typically buried in the second digit.

 

[potteryshard]

As I recall, flourescent ballasts also include an autotransformer (or electronic conversion) to change line voltage to a voltage suitable for a particular lamp design. Voltage may be near line voltage, but likewise may not. Also; flourescents, especially the high-output versions, want to be kept up to a given temperature for proper operation. Fixtures designed for flourescents are not designed for the same heat transport and control needed for LEDs, which need to be kept as cool as possible.

 

[grigson]

VE1BLL:

i appreciate aircraft mods are going to be expensive....but the fluorescent luminaires are in the cabin, so surely this is a cheap modification.....not like replacing the cockpit controls or the engines.

....But by mentioning the high cost, are you now saying that its not going to be cost-effective to remove the fluorescent ballasts?, and that we really should try and find a way of interfacing the LED light tube to all the types of fluorescent ballast?