The impending death of incandescent bulbs

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dacflyer
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Post by dacflyer » Wed Apr 11, 2007 7:30 am

What exactly is it that burns out in a fluorescent bulb?
the filiment (cathodes) as they age, the endsof the tube get black,, the cathode slowly burning off. lightbulbs and suck do not burn out,,they actually get full of darkness...the bulbs are dark suckers. when they are full..they fail to remove the darkness fromthe room,....lol

Also, what is the largest LED bulb available? biggest i know of are made by LUXION .... http://www.lumileds.com/products/luxeon/



How does the brightness/efficiency work out as LED's get larger or smaller? Does it make sense (or would it be possible) to make something like a 1 inch LED?

see the data pages...some leds are 5 watts + now days..

Craig
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Post by Craig » Wed Apr 11, 2007 10:07 am

actually get full of darkness...the bulbs are dark suckers. when they are full..they fail to remove the darkness fromthe room
Hmm, I always figured that the electrical company was teaming up with the light bulb manufactures. The electrically company will consume the darkness that the bulbs suck for a while, but eventually the bulb is triggered to not suck anymore.

Conspiracy!

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philba
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Post by philba » Wed Apr 11, 2007 1:03 pm

So, no one has used the so called dimable CFLs? They do seem to be a bit more available than I initially thought. I'll have to get one and give it a try. I'm not looking forward to the switch - CLFs just plain suck as light sources.

By the way, I have also seen ads for dimming converters - you screw them into a lamp socket and screw the CFL into that. I haven't figured out the economics of that, though. How long do CFLs really last?

And, about the legislation to ban incandescent bulbs. It's total grandstanding by the most loathfull elements of our society - politicians.

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Post by rshayes » Wed Apr 11, 2007 2:39 pm

Fluorescent lamps usually fail due to degradation of the cathodes. The cathodes have an emissive coating which can be stripped away by ion and electronic bombarcment. During normal operation this is a slow process and the lamps may have a lifetime of 5 or 10 years of continuous operation.

This process is much faster if the lamp is started when the cathodes are below normal operating temperature. A few hundred starts with inadequate preheating is enough to strip the cathode coating.

Most of the failures that I have had with CFLs appear to be abrupt failures of the electronic circuits used to drive the lamp rather than failures of the lamps themselves. The heatsinking of the power devices is marginal and appears to shorten the life of the ballast circuit to a few years.

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dacflyer
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Post by dacflyer » Wed Apr 11, 2007 3:49 pm

on a typical dimmable ballast.. am i right to assume that the filiment voltage remains constant as the HV is variable ?
HV is what causes the lamp to glow right ?

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Chris Smith
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Post by Chris Smith » Wed Apr 11, 2007 4:17 pm

Several separate ways to run a standard type of Fluro tube.

One is to run around 6 volts and ½ amp to the emitters which are pre-heaters for the tube, then the standard or raised voltage runs the tube gas when things are right going out of the heaters or emitters.


The next type runs HF voltages up to several hundred volts and varies the current for the variable by altering the wave dimentions.

Just Playing with the voltage makes them crash.

The standard HF types don’t need to pre heat the ends [emitters/heaters] either, with some exceptions.

With my 12 volt types the voltage was bumped upwards of 600 volts or more, and the wave front wasn’t the standard sine wave.

To make them variable the voltage and current did follow together so simply adjusting the input voltage lowered the over all voltage some what with a large current swing going to the tube.

Most modern systems keep the voltage high,... changing the wave timing to the tube,... thus adjusting the brightness.

The high voltage with lower amounts of on time dims the bulb but keeps the conduction always near the firing range, and when you increase the on time of the chopping circuit, your really increasing the current because the tube doesn’t have a large load dragging down the voltage in most situations any way.

Think of it like a strobe light, the longer the on time the brighter it seems over all because more current [not so much the voltage] is being deposited and used by the bulb.

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Post by perfectbite » Thu Apr 12, 2007 6:09 pm

I know this doesn't have much to do with dimming flourescents but I find that I like (perhaps even need) a nice balanced lamp light for reading.

I used to buy the incandescent Verilux bulbs that were made in France and that said on the box 'dyed blue glass, NOT painted blue glass like cheap imitations'.

Well, my local Ace Hardware still has Verilux incandescents but they are no longer made in France but are now made in China and the quality has suffered greatly. With the old bulbs the white plastic of my computer monitor was clear white. With these new bulbs that plastic appears greyish.

They had a closeout sale on ReaLite incandescents with frosted glass and Neodymium elements (again Made in China) and I used one and the monitor plastic is back to looking white again. Was it an oversight of quality control to provide a good product?

(Many years ago in Tokyo I could swear that some of the colours they used on the head height subway car advertising wasn't just neon but was a form of radioactive neon. (Positively glowing neon greens and oranges). Although the Chinese Imperial Red is a distinctive, and pleasing to me red, sometimes the lurid, lurid red that Mexicans use to paint their trucks and buses and icons with is not a pleasant shade of red to me perhaps because it doesn't exist anywhere in nature that I have ever seen but perhaps there is a cultural aspect to the pleasing quality of a light that would account for the difference in perception of the quality of light as in what I would find adequate and restful is what folks from other cultures could find dim or even dingy or it could just be that the Chinese Verilux bulb quality control is run by blind bean counters and the idea of different spectrums being a cultural artifact is a bunch of hooey BUT different regions of the world do have different qualities of sunlight and perhaps such cultural exposure determines one's perception of colour.

Personally I think that folks who are trying to corner the market and become the only game in town could come up with a slightly cheaper truly but shoddy product once any source of competition has been bought out and have done so. They aren't looking at quality for money they are just looking at the money.

Flourescent lighting is good for seeing triphazards and where the doors are and where one's sandwich is in relation to one's mouth etc. and I think they give a horrible quality of light but, within the next few years or so I may not even be be able to buy the inferior quality Chinese 'true colour' incandescendents and I wonder if any of you are aware of a commercially available LED or flourescent, spectrum adjusted for Northern European eyes decently illuminating (not just a spotlight) reading lamp that doesn't cost an arm and a leg and will last for some time. Can LED's be made to do this MrAl?

Does anyone know if such is being worked on?

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Chris Smith
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Post by Chris Smith » Thu Apr 12, 2007 7:26 pm

The Actual benefits behind the spectrum of light is a human response, showing that a cheap imitation doesn’t always work unless you aiming at something different.

The eye perceives much better using the brain because the total effect isn’t counterfeit.

Its mood altering.

Leds can be made to replicate ANY color if they take the time to chemically reproduce it.

However, as much as the led is totally flexible, the studies behind it a little lacking, not missing just a little slower than the general production needs. It is one aspect of the need for Leds, but it’s a cart and horse affair.

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Post by rshayes » Thu Apr 12, 2007 11:53 pm

Both LEDs and fluorescent lamps will be inferior to incandescent lamps for coler rendition. The light from an incandescent bulb is a continuous spectrum with some light at all wavelengths. Both LEDs and fluorescent bulbs use phosphors to convert short wavelenghts to longer wavelengths in the visible range. Phosphors emit light in a moderately narrow range of wavelengths, so a mixture of several phosphors are used to cover the visible spectrum. This coverage is not necessarily continuous, and colors between the phosphor emission bands will not be seen very well.

This really shows up when you try to read resistor color codes. The old American composition resistors were coded with very saturated color bands. The Asian resistors which have replaced them use less saturated colors. Some of these colors are very difficult to distinguish under fluorescent light. Brown, red, and orange are often difficult to distinguish and green, blue, and violet aren't much better.

The weak area with phosphors is probably in the red region. This was always a problem with color TV sets. Over the years, the red phosphor was improved, but it always seemed a little weaker than the green and blue phosphors, requiring more drive signal on the red gun of the CRT.

perfectbite
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Post by perfectbite » Fri Apr 13, 2007 12:30 am

I would like to know what commercial area (or name) such low energy decent lighting will appear from so that I can watch out for it.

Are any other countries focusing on this? The EU countries perhaps?

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MrAl
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Post by MrAl » Fri Apr 13, 2007 4:36 am

Hello again,

perfectbite:
Luxeon makes various LEDs that are really nice for reading.
The white 'star' is a good one. The pattern is a wide angle
where the light spreads out over an area, and the way it
lights a page of text is just great.
The LEDs are best set up like a reading light would be, where it
is not too far from the page. I have a set of two white 1 watt
LEDs run from a DC wall wart and series resistor (simple set up)
using an aluminum angle heat sink and i can read anything with
that as long as the page is placed under the LEDs.
They have various tints too. The cooler white is a more pure white
and the warm white is more like the color you get with an
incandescent bulb. They 'bin' the different color tints.
You'd have to check out their web site i guess to see just what they
have, and read up on the specs to understand the colors they offer.
They also have 3 watt and 5 watt models.
BTW with these LEDs you only get a tight narrow beam (like a spot light)
if you also purchase 'optics' with the LED. The optic is typically
a special lense that fits over the LED that focuses the beam into
a narrow beam maybe 10 degrees wide. This is mostly used for
flashlights where you want a longer beam 'throw'.
LEDs vs Bulbs, LEDs are winning.

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Chris Smith
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Post by Chris Smith » Fri Apr 13, 2007 7:53 am

For those who are picky about the light when reading, the low voltage Mercury lamps are the best for reading bar none.

A lot of people don’t have or lose the ability to see in certain frequencies of light [seems darker] and so things don’t appears to be as well lit as they should be which can be uncomfortable when reading especially over long periods of time.

Mercury provides a better spectrum for this malady combined with the paper reflection when reading.

Other colors of light can bounce off the pages and annoy the Reina after just a short period of time. Projection quantity or frequency is only one factor of human vision.

People all say that before where they had complaints about the light, now they are “comfortableâ€

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Post by rshayes » Fri Apr 13, 2007 7:25 pm

"on a typical dimmable ballast.. am i right to assume that the filiment voltage remains constant as the HV is variable ?
HV is what causes the lamp to glow right ?"

Dacflyer:

Ideally, the cathodes would be operated at a sufficient voltage to maintain their temperature at a level which will emit the desired current. A constant voltage, if adequate, will do this. If the cathode temperature is too low for the current being conducted then the cathode is increasingly bombarded by positive ions from the plasma surrounding it, resulting in faster erosion of the cathode coating and shorter life. Too high a cathode temperature results in evaporation of the cathode material, and also shorter life.

The light from the lamp is roughly proportional to the lamp current. In the region where fluorescent lamps operate, the current is carried by an arc discharge with a negative resistance region where increased current results in lower voltage drop across the tube. Operation with a constant voltage applied to the tube is not stable. The current tends to jump to a high level which will destroy the tube.

Operation can be made stable by adding a resistance or reactance called a ballast in series with the tube. The impedance of the ballast must be high enough that the voltage across the series combination increases as the current increases. Lamps operated on 60 Hz power usually use an inductive ballast. CCFLs used for backlighting LCDs usually use a capacitive ballast and electronic circuits operating the lamp at high frequencies may use either an inductance or capacitance as a ballast. Resistors can be used as ballasts, but this results in a substantial power loss.

Once a ballast element of some kind is added in series with the lamp, the voltage applied to the series combination can be varied to adjust the current through the lamp. This will change the light output in proportion to the current.

For a variable light output, the cathode voltages would remain constant and the current would be varied to control the light output. Some ballast impedance is necessary to insure that the current is a stable function of the applied voltage.

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dacflyer
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Post by dacflyer » Sat Apr 14, 2007 8:03 am

ok, thanks for the info.....

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Bob Scott
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Post by Bob Scott » Thu Jun 28, 2007 12:29 am

Hi Dean,
Dean Huster wrote: As a general rule, candlepower is directly proportional to the 3.5 power of the ratio of applied voltage versus rated voltage. So,

(applied voltage / rated voltage)3.5 x MSCP at design volts

Note: MSCP x 4p = lumens
Does the "(applied voltage / rated voltage)" part get multiplied by 3.5 or does it go to the 3.5th power? Did they forget to insert the "^"?

I realise that this is an old thread but lately, the characteristics of tungsten filaments has peaked my interest.

Thanks, Bob :cool:

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