how many forum members does it take to change a light bulb?

[ATrebeau]

Just goes to show that it really is true that the funniest things do actually come from real life and can't be made up. lol

[Karlsweldt]

Do I need to shutdown the power to change the light bulb in the water of my swimming pool? If I shutdown the other lights, the water will be dark, I can't see anything. What would be the best way to proceed? I mean any inconvenient to dim the other lights by using a big resistor before my electric meter? I'll use a diving suit indeed.

Those lights submerged in swimming pools should be accessed from the outside, never the inside. Otherwise, a leak may exist that can cause injury or rapid failure of the lamp. Those lamps typically have a 12 or 24 volt supply circuit for safety, some do have a line-voltage supply, but through an isolation transformer. The bulb would likely be the quartz-halogen type, and should not be handled with bare fingers. Skin oil can penetrate the quartz shell, and may cause it to shatter when hot! Same applies to automotive headlamp bulbs.
It would be advisable to turn off the power to those lamps, and use a flashlight to change any non-functioning lamp. Safety first!!

[MrG]

How much will the lightbulb cost? They can get bloody pricey:
http://www.google.com/hostednews/afp/ar ... e88739.1b1

[Karlsweldt]

(Quote from link by MrG)

The Ministry of Defence pays 22 pounds each for lightbulbs worth just 65p, according to The Sun newspaper.

Sounds typical of government spending, anywhere!! Many obnoxious reports of American military payouts at 10x or higher for the same item that is available in almost any home center!!

Those new super-bright LED lamps for home use may be expensive at first glance, but for the life-span of one, you may need more than 200 standard incandescent bulbs.. and pay perhaps 5x the cost to power them! Just think.. if this technology had been available several years back, the thread for this poor light bulb that burned out may never have started!

[Mark H]

(Quote from link by MrG)

The Ministry of Defence pays 22 pounds each for lightbulbs worth just 65p, according to The Sun newspaper.

Sounds typical of government spending, anywhere!! Many obnoxious reports of American military payouts at 10x or higher for the same item that is available in almost any home center!!

Those new super-bright LED lamps for home use may be expensive at first glance, but for the life-span of one, you may need more than 200 standard incandescent bulbs.. and pay perhaps 5x the cost to power them! Just think.. if this technology had been available several years back, the thread for this poor light bulb that burned out may never have started!

Nah, the thread would have been "How may forum members does it take to change a light bulb when it burns out?"

[ataboy]

Those new super-bright LED lamps for home use may be expensive at first glance, but for the life-span of one, you may need more than 200 standard incandescent bulbs.. and pay perhaps 5x the cost to power them!

In theory yes, and that's what marketing will say anyway. In France we've been forced by law to change all incandescent lamps by new "low energy" fluos that cost 10 or 20 times more and are so "environment friendly" because they will last at least 10 years, maybe 20. Worth the spending? Nope, we all now see our fluo having delay at power on, that starts with .5 seconds, then 1s, then a bit more, after only 1 year, not talking about the colors problems... Because indeed fluo last longer than filament, but to ignite a fluo you need a starter device, which is the element introducing the delay. An I'm sure this is done on purpose. The lighing industry has been known to have agreements between competitors to have lights that doesn't exceed 1.000 hours before failing. The members of this cartel were fined (yes fined) when their lamps were lasting more than 1.000. They called that the "built-in obsolescence". So look at it twice for LED. Led may last long, but what about the 1.5V power supply that is required to feed the LED? Or other elements... The industry will not favor a solution that decrease their profits. Then how is that compatible with their devices lasting a very long time, at a ratio than makes them interesting for buyers? That's simply impossible, so...

[Karlsweldt]

The first LED lamps had a minimal light output, mainly intended for "marker" lamps on control panels. Most would work at 1.5 to 5 volts, but required a resistor to limit the current or they would burn out quickly. Modern LED lamps work with 3 volts or so, but still require a resistor to limit the current. But the light output is many times higher. LED lamps do illuminate almost immediately, just a bit faster than a filament lamp. But they are very efficient, giving about 6 x the light output for current input. Incandescent lamps are very inefficient, producing only about 30% light output for the current input. The rest of the energy is wasted as heat. And they (incandescent lamps) generally give only about 2,000 hours of use maximum. LED lamps can last more than 50,000 hours!
Those compact fluorescent lamps are efficient, giving about 4x the light output for input power. They do produce some heat, but very little. Their life is about 10,000 hours maximum. They are affected by temperature changes, taking longer to full-brightness as temperature drops.
There are two basic types of fluorescent lamp designs. One is the older pre-heater type, with a glowing filament at each end that caused the mercury vapor inside to become an active plasma. They relied on the 120 volts or so line voltage to then keep the plasma glowing. They used a ballast that kept the input current down, as well as voltage across the lamp to about 55 volts. Once the plasma was active, the "starter" was deactivated. The "starter" was a bimetallic switch inside a small glass tube filled with neon gas. Heat from the neon gas igniting caused the switch to momentarily close the filament circuit.. causing the lamp to light. Later designs used a ballast transformer with a low-voltage winding that caused the filaments to glow, and they glowed less when the lamp was activated. Another type is the "rapid-start" which uses a high-voltage (around 350 volts) to ignite the mercury vapor, then the ballast transformer drops the source voltage to about 60 volts, keeping the lamp lit.
LED lamps can be operated only on DC current, where fluorescent lamps are not fussy.. AC or DC voltage works equally well. An incandescent lamp can be wired in series with other lamps, as long as the filament current is identical in all bulbs. An example is those strings of Christmas tree lamps. They can be 6 volts or 12 volts, in series.. one burns out, they all go dark! Same is true of LED lamps. Fluorescent lamps cannot be used in series. Special ballast designs allow two lamps on one ballast transformer, but both lamps will go dark if only one does.
Modern incandescent lamps usually contain an inert gas, which gives the filament longer life. Earlier lamps were in an evacuated bulb only.
Photography work requires a specific light intensity and color level for best results. It is known as the Kelvin temperature. Incandescent lamps give off a different Kelvin level than fluorescent lights, LED lamps or "outdoor" sunlight. Older film cameras and vidicon TV cameras had special settings for each light type.. or flesh tones became blue or green alien colors!

Sorry, long posting. Hope it was interesting.

Reference: Kelvin chart..
Reference: incandescent lamp history..
Reference: fluorescent lamp history..
Reference: LED lamps..

[ataboy]

And they (incandescent lamps) generally give only about 2,000 hours of use maximum. LED lamps can last more than 50,000 hours!"

I'll not argue on each statement, just this one that is typically a marketing statement, not link to actual life.

Lifetime are measured using some protocol, for instance I think the "low energy" are so wonderful in marketing documentation because the protocol to measure the time to die is to switch the lamp on and off only once per day and to keep it on during let's say 4 or 6 hours. That means the starter cycle will be once a day, and maybe the fluo will last 10 years, that is 3650 days. Now you put this lamp in toilets or in a corridor, the lamp will be switched on 5 times or 20 times a day, but very shortly. The fluo device will never reach the 2.000 hours or any other limit, because the starter mechanism will die after 3650 cycles, and that will be as short as 2 years, maybe. Do be fooled by marketing without looking at the details of what they are talking about.

Same for LEDs. First there is a big difference between old and new LEDs. Both are diodes. While old diodes were monochromatic and the color was there monochromatic light, the new white ones are a combination of a blue or UV LED (there is no white LED) and a phosphor that produce yellow light when hit by this radiation, the result (blue + yellow) is seen by human eye more or less white. This principle is exactly the same than the phosphor on fluo. There is also a possibility to mix three LEDs (red, blue, green) in a single device, that produce a trichromatic spectrum, but that is more for LEDs that change color on demand, not for ambient lighting.

Now we are back to the fluo problem: this is not the bulb that died first, but the starter, and here this is not the LED (blue or UV) that stops emitting, but the phosphor that will degrade. So read again what marketing says about LEDs and their 50.000 hours of lifetime. Look at the details of the protocol.

It is somehow wrong to talk about color temperature for LEDs. There is no continuous spectrum in LEDs, so you cannot compare a LED spectrum with the spectrum of a pure black object heated at some temperature. The eye maybe fooled (metamerim effect), but not the spectrometer.

[Karlsweldt]

Worth a read: Incandescent Lamps:
The filament in an incandescent lamp typically runs higher than 2,000° C, at which point most metals would liquefy. But due to the formula for the filament, and enclosed in a near-total vacuum, it remains in a semi-solid state. The harshest part of its life is when current inrush to the cold metal filament is highest.. causing stress. Some lamp filaments burn or glow at a higher temperature than 2,000°C. Incandescent filament temperatures:
While true that older type fluorescent lamps may endure harsh starting cycles, the newer series use an electronic ballast that does not impress the same stress on filaments. The "firing off" of the mercury vapor to a glowing plasma is almost instantaneous, and within smaller confines than a standard tube.

[AmEv]

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