Compact fluorescent light bulbs diagram link ?

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Externet
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Compact fluorescent light bulbs diagram link ?

Post by Externet » Tue Apr 24, 2007 10:02 pm

Hello all.
Anyone knows a link where to learn about the circuits built-into their bases ? Or schematic diagrams of the existing types?
Thanks,
Miguel
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Post by VIRAND » Tue Apr 24, 2007 11:41 pm

Some of the older compact fluorescents actually have a small ballast coil and starter tube
just like any other fluorescent. They're simpler and more reliable than what's in them now.
(Yuck board with weird power supply.)

I'm a fan of "cold cathodes", which to me seems to work more like neon signage,
and lasts 100,000 hours, so they say. No filaments to blacken the tubes.
I've never seen them flicker out either.

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Post by Externet » Wed Apr 25, 2007 11:56 am

Extending the question; I bought many years ago a plain (not really plain) fluorescent lamp for work bench use, -or under kitchen cabinet- from Sears, straight long tube with no ballast in it.

How does that one works ?
Miguel
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Post by haklesup » Wed Apr 25, 2007 12:33 pm

There must have been something. Newer lamps don't have the magnetic ballast (transformer) but use an electronic one but there still is a module that looks like a ballast. Even a cold cathode lamp has a HV supply module. The smaller electronic ballast is easier to hide in the fixture, maybe that's it.

I have a module for a cold cathode (12V input) and it consists of an LC oscillator circuit (2 transistors) which puts a waveform into the primary of a small transformer. THe secondary has only a couple caps on it. Without reverse engineering it, it looks just like a simple oscillator driving a step up transformer. Output V and I not marked on the module. It was the kind used in PCs to light those little neon like tubes.


Here are a few references easily found googling "CFL Schematic"

http://www.nxp.com/acrobat_download/app ... 0048_1.pdf
http://www.nxp.com/acrobat_download/app ... 8091_1.pdf
http://www.repairfaq.org/sam/samschem.htm#schcfl1 (scroll down to CFC ballast 1 &2 )
http://www.ece.vt.edu/ece3354/labs/ballast.pdf
http://www.irf.com/technical-info/refdesigns/cfl-2.pdf

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Chris Smith
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Post by Chris Smith » Wed Apr 25, 2007 1:18 pm

With some of the 18 inch or shorter types they fire up and stay running with out much help of the old balast.

The heater on both ends simply requires a lower value in the 6 volt range so dropping the 120 to this value is essential, also called a ballast.

Then some use a simple transistor to "spark" the tube into conduction after the ends are hot.

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Post by Edd » Wed Apr 25, 2007 1:33 pm

.

WOW..even the hosting site still had that schenatic archived that I had made from a reverse engineering teardown of a unit back in 2004.
Not so true.... for all of its accompanying explanatory text... in the impending changes that have been made in the forum since then !

The whole thread:
http://www.servomagazine.com/forum/view ... c&start=15


The schema:
Image


73's de Edd
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Post by Externet » Wed Apr 25, 2007 1:46 pm

Thanks, guys !

Finally found the "no ballast" animal from my second question.!

It's the "GE Bright stick". Since the eighties. Instant on, no flicker, no ballast, not bulky, no nothing in it, not even room for a fat wire in its capped ends, works great, but never found out how. Get the larger picture here:

http://cgi.ebay.com/New-ge-25-bright-st ... dZViewItem

Edited---> a better link:

http://genet.gelighting.com/LightProduc ... TEXT=12257

You would need to have it your hands to believe there is nothing to it. Another clever circuitry ??

Miguel
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Post by dacflyer » Wed Apr 25, 2007 2:22 pm

externet >>> the bright stik actually does have a hidden ballest, but you might never find it , and its not where you'd ever think to look

the bar that actually is the backbone of the fixture.its actually th ballast. super long and thin..if you look really close, you can actually see the copper wound around this,, the bar is either thin steel or something simmalar.
i took an old one apart long time ago. i had to see what made it tick,
actually tried to replace the lamp...lol
wasn't successful. :P

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Post by haklesup » Wed Apr 25, 2007 2:44 pm

I had some of those at one time, used them for a fish tank. They generate a fair amount of heat and when they finally failed (prematurely) they were dark at the ends like most stick fluros. I don't recall seeing components (though it is possible a few were molded into the endcaps). I think they just engineered the filiments to work at 120V as a basis.

With those specs that's an efficiency of 22 lumen/Watt which is pretty poor for fluorescent which generally exceed 40Lm/W (to qualify as high efficiency). Thats only slightly better than a 100W incandescent which gets 16 lm/W (down to 11 lm/W for a 40W bulb). With flourescent, the longer the tube the more efficient in general.

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Post by haklesup » Mon Apr 30, 2007 1:32 pm

I found one of those specific lamps this weekend (wile cleaning house) and tore it apart before trashing it. One end cap had a neon bulb in series with one of the pins and the other end had a component that I am not sure what it is yet. No transformer or PC board of any kind.

It's an axial leaded metal body with a glass cone shaped seal at one end. It may be a cap or it may be an inductor. I doubt its a diode even though thats what it most looks like. More later when I test it with a meter.

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Post by Chris Smith » Mon Apr 30, 2007 1:55 pm

A lot of old style tubes ran because of the reflector.

It was grounded and it acted as a base that caused a extension of conduction. [From the air]

Remove the metal reflector which had no electrical contact to the bulbs [but it went to ground] and the tubes would not run.

Small tubes don’t need a boost in voltage to run as that can run as low as 70 volts with a neon or other type igniter to fire them up.

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Post by Externet » Mon Apr 30, 2007 2:04 pm

Nice !!! Haklesup :grin:

The tube ends have two or one terminal coming out of the glass at each end ? Is there any connection of any kind from one end of the tube to the other? I suspect no.

What I would like to try is if a long plain type of fluorescent bulb could work using the same "no ballast" :shock: trick..., perhaps with beefier/suited components of the same sort, whatever they show up to be.
And perhaps try to substitute the circuitry from a compact fluorescent as inthe schematic above.

I was not that much crazy, this animal exists ! :grin: No coil, no transformer...

Miguel
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Post by haklesup » Mon Apr 30, 2007 3:14 pm

No reflector, the plastic span from end to end contained only 2 wires and no additional components. The bulb had two terminals at each end. Clearly from the darkening it has filiments but I suspect they are a different resistance than a typical 2 foot bulb.

The CFL schematic above is actually analogous to the traditional ballasted system if you look at it this way. First the AC is rectified and sent to supply the internal oscillator on the right. That in turn excites the primaries which develops the appropriate voltage at the tube. The higher frequency allows for a more efficient voltage step up through a smaller transformer

In a traditional system, it is excited at 50/60Hz naturally so not needing the rectifier or oscillator or primaries.

In a more efficient (newer design) the two transistor oscillator is replaced by an IC and a pair of MOSFETs which performs this function and has some adjustability to suit a wider range or inductors and bulbs. In fact the transformer is gone as this circuit develops the drive voltage directly. The designs do incorporate an inductor still. In the reference examples from my other links, it appears that a variety of other EMI supressing components are also added. One sheet mentioned that warm up time was programmable.

I expect that an Electronic Ballast for larger tubes is just a more robust version of what's used in CFL lamps, bigger inductor at least.

I'll look again, if I recall, in older lamps the starter was just a cap and a neon bulb but it still needed a ballast.

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Post by haklesup » Fri May 04, 2007 11:51 am

I took a closer look (this time I spent 10 whole minutes) at that lamp and found a few more things out.

The unknown component has 0 ohms in both directions, I think it is just a thermal fuse.

The plastic span connecting both ends is more complex than I thought. After snapping it in half I discovered that it has a strip of fine wire wound into a pattern along the whole length (24"). This strip goes along both long edges end to end and both are shorted together at the endcap. Additionally there is one insulated wire (normal conductor) going from end to end.

This wire's function is not yet clear and its pattern is hidden in the plastic, I would need an X ray to go much further in speculating but it could form an inductor, a virtual ground plane (reflector) or a resistor. It is a fine wire and looped so that it is effectively very long.

I'll try to work out a schematic later. I kept the bulb from the garbage truck today for that purpose.

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