Bulb Blow Out

considering a situation like for indicator lights in a car what special mechanism is there to protect the bulb from blowing out since they keep on flashing on and off?

The status of the bulb is confirmed at the vehicle's annual MoT test. A vehicle with a blown bulb will not pass the test.

Presumably the bulbs are designed to be more rugged than a domestic light bulb. Of course there is also the shock and vibration of the vehicle to consider. There are often fine wire supports to the fillament, maybe you should get one and take a look, you may find the answer.
Del

I believe they are operated at somewhat below their full power rating. It doesn't take a large drop in power/rated power to significantly extend the globe life.

Have a look at: (cut and paste to your browser)

http://www.controlbooth.com/forums/lighting-electrics/2912-relations-between-voltage-lamp-life.html

http://www.lumitroncorp.com/basics.html

I would concur with Del (#2) but it is interesting from the lumitron link given, the following is written: "Keep-alive current: Because the resistance of tungsten filaments is far greater when the filament is cold, supplying a small current (as little as one percent of operating voltage) to the lamp when switched off will keep the filament warm and buffer it against inrush current when switched on. This greatly extends lamp life."

Should someone tell them?

Steve.

I wasn't disagreeing with Del, simply adding that reducing the voltage and therefore both the operating and inrush currents greatly extends the life of the filament.

Are you sure about the 'resistance of tungsten filaments' ?

If you were correct, either

1. they would never heat up sufficiently to incandes, OR

2. they would experience catastrophic thermal runaway.

For them to stabilise and operate there must be negative feedback, ie the resistance must increase with temperature.

I refer you to:

http://hypertextbook.com/facts/2004/DeannaStewart.shtml

For a defined sample of any material (same length and cross section) the Resistance is proportional to the resistivity, and the reference shows that for tungsten the resistivity increases by a factor of more than 20 from 300deg K (27deg C) to 3000deg K (2727deg C). Therefore the resistance also increases by the same factor.

Hey Wauwaus - I was only trying to point out an error on the website! Of course the resistance is greater when hot, or lesser when cold.

I once found a middle Eastern website which proudly proclaimed (in English) their rough service equipments featured 'bu99erised' (spelling withheld) metal housings, when I belive they would have wanted to state they were 'ruggedised'. They were grateful when I pointed it out...

Steve.

'bu99erised' metal housings... LOL
Excellent, that will now feature heavilly in vocabulary alongside 'mended beyond repair'
Del

I think there are "rough service" incandescent bulbs.

As far as automotive bulbs, the stop/turn signal bulb filaments, their filaments are at least 2X's heavier than the tail/ running light filaments and as far as the effect of vibrations, the stop/ TS filaments do have more support, but the important point is all filaments while glowing, are more pliable, allowing them to better tolerate vibrations and shock. DJ

Well, they are supposed to be bulbs, not fuses.

You could use an electronic soft-start circuit which limits the inrush current when the filament bulb is first turned on. This type of circuit is relatively simple but the extra expense and low cost of most filament bulbs (such as vehicle indicator lights) is the main reason why you don't see these circuits being used in vehicles.

The circuit is good however for applications where filament bulb replacement is expensive and/or difficult (such as swimming pool lights).

Modern vehicles are starting to use more and more LED-based indicator, brake and headlights which eliminate the filament bulb failure mode, although they are more expensive and still suffer from electronic control board failure over time (depending on the quality of the components used). Still, this is the way the industries are going and I believe direct LED replacement indicator bulbs (that fit the same holders as the filament bulbs) are available for homes and vehicles in a store or garage near you.

1st recommendation is to fix the problem that is causing them to flash on and off.

2nd choice is an ICL for your instrument panel but you would have to put a separate ICL for each bulb. Probably better to just do #1.

If the indicator lights are incandescent, a bulb with a well-supported short, thick filament rated for a higher voltage than the electrical system supplies (and the reduction in luminous efficacy that goes with that) will resist the vibration and thermal stress from vibration and frequent cycling better than one with a lower voltage rating and a longer filament that burns brighter, at a higher temperature, and gives more light per watt consumed.

A similar stratagem has been used for many years to obtain a reasonable life span for incandescent bulbs used in traffic signals, which undergo thousands of off-on cycles every day. This is why LED vehicle indicators and traffic signals were widely adopted as soon as the price came down enough to justify their higher initial cost.

Switching off and on also shortens the life of fluorescent lights. I'm not sure about LEDs.

The thermal shock and electromagnet cycling induces fatigue stresses in the filaments. There was a story I read about a light bulb in a fire hall continuing functioning for at least one hundred and ten years plus. Here the link.

I was in a place that had a bulb burning for 100 years, it was really cool (at least that was their claim). They claimed it had never been turned off (intentionally), and it was their big main attraction... now if I could just remember where I was when I saw it.

_{<memory synapse failure imminent>}

Was it this one in a fire station in California?

Link

Yep, That's the place!

I have no idea why I was there, but I do remember the conversation about the bulb, and seeing it glow. Pretty cool. I didn't know it was the worlds longest burning bulb... That makes it way cooler.

Thanks!

There is something very suspicious about a claim for a lightbulb burning for 100 years in California...

The world's first public electricity supply was provided in late 1881, when the streets of the town of Godalming in the UK were lit with electric light. The first commercial AC distribution system in the US was inaugurated in 1891, in Ophir, Colorado, transmitting power about 2.6 miles. The Westinghouse Niagara Falls plant went on line in 1895...

Edison, with his bamboo filaments, was able to get 1200 hours out of his light bulbs in 1880 or so...

PG & E started playing around with electricity some time around 1906 or so...

So, it sounds like, if this light bulb in California has been burning for 100 years continuously, it must be one of the very, very first electric light bulbs ever illuminated in California(most likely with something other than Edison's bamboo filament), and it is unlikely that it was lit before 1906, which suggests that, if this claim was made prior to about 2006, someone is most likely really, really stretching the truth a bit...

Not to mention the uninterrupted supply of electricity. It must have stopped illuminating over that period?

How many generations of light bulb changers are in on this?

If I drive by I'll drop in any way

Here is the Information we are all speculating about:

Taken from http://www.centennialbulb.org/facts.htm#anchor1972

_{(I saw no copywright notice on the webpage)}

• Age: 110 years and counting (as of June 2011)
• Installed: First installed at the fire department hose cart house on L Street in 1901. Shortly after it moved to the main firehouse on Second. In 1903 it was moved to the new Station 1 on First and McLeod, and survived the renovation of the Firehouse in 1937, when it was off for about a week. During it's first 75 years it was connected directly to the 110 Volt city power, (subject to the power outages) , and not to the back-up generator for fear of a power surge. In 1976 it was moved with a full police and fire truck escort, under the watch of Captain Kirby Slate, to its present site in 1976 at Fire Station 6, 4550 East Ave., Livermore, California. It was then hooked to a seperate power source at 120V according to Frank Maul, Retired City Electrician, with no interuptions since.
• Proof of Longevity: From local newspaper records; also GE engineers researched it. Was donated to the Fire Department in 1901 by Dennis Bernal who owned the Livermore Power and Light Co.
• Vital Statistics: The improved incandescent lamp, invented by Adolphe A. Chaillet, was made by the Shelby Electric Company. It is a handblown bulb with carbon filament. Wattage- Began at 60 watts, currently shines at 4 watts. Left burning continuously in firehouse as a nightlight over the fire trucks. For some research test results on another Shelby bulb at Annapolis follow this link.
• Recognition: Declared the oldest known working lightbulb by Guinness Book of World Records. Ripley's Believe-It-or-Not in 1972 researched it and declared it the oldest.

So, it also survived the earthquake that devastated most of San Francisco in 1906...

Seems well-documented...

Funny, I had heard that it was an Edison lightbulb (dang that Edison). Glad to hear the true story behind this, thanks for the link.

Wattage- Began at 60 watts, currently shines at 4 watts.
How is that measured? Is the change because of increased resistance, or did they put in a series inductance or resistance to limit the current? It is not believable that they would have put in a wattmeter for one light bulb 110 years ago (or anytime since). Try reading your own tagline.

Hey, It's not my bulb... I just saw it once. The info is from their own webpage... But... It's not impossible in my mind.

Gueniss has verified it, whatever that's worth.

I saw it glow... very dimly, but you could see that it was on at least, put out less light than a LED.

harumph

• "How is that measured?"

I don't know about how they would have measured the original rating but at a guess like most globes I would say that it was probably written on the globe. As for now it's a simple case of measuring the voltage across the globe and the current going through it, probably with clamp on current metre so you don't have to interrupt the power going to the bulb.

• "Is the change because of increased resistance, or did they put in a series inductance or resistance to limit the current?"

The reduction in power is most probably due to an increase in the resistance of the filament. What could cause this could be anybody's guess but one possibility is erosion of the filament so that it's diameter has decreased. A decreased diameter means a higher resistance and lower current and therefore lower power consumption. However, that's just a guess and considering they aren't even sure what the filament was made from the reason for the output loss could be anything.

it's a simple case of measuring the voltage across the globe and the current going through it, probably with clamp on current metre

So you think they climbed the fire ladder, punched a hole in the ceiling, and used a clamp on current meter on the wires to the fixture?

..they aren't even sure what the filament was made from

In #30, he claims it is carbon. 110 years is a bit longer than the 1200 hours Edison got. All we really know is that they convinced Guinness. Guessing will get us nowhere.

Hey now... there is no need for any speculation. I'll tell you right now that the filament is made of LynDoor^tm Unobtanium. Unobtanium filament bulbs have a lifespan of at least 200 years... It's a well documented fact .

The closest alternative to the fairly overpriced LynDoor^tm Unobtanium bulbs, are the KrisDel^tm Inobtainium bulbs, but rumor has it they may be manufactured in China.

• "So you think they climbed the fire ladder, punched a hole in the ceiling, and used a clamp on current meter on the wires to the fixture?"

I quote from RVZ717 in post #30

• "In 1976 it was moved with a full police and fire truck escort, under the watch of Captain Kirby Slate, to its present site in 1976 at Fire Station 6, 4550 East Ave., Livermore, California. It was then hooked to a seperate power source at 120V according to Frank Maul, Retired City Electrician, with no interuptions since."

So considering it's on its own power supply I would hazard to say that gaining access to the line to read the current wouldn't be that much of a problem.

Something else that somebody may be able to confirm is whether or not it's now on an uninterruptable power supply. If I were moving something like that to a new power source and knowing that the failure time is nearly always shortly after the power is applied I would put in on an uninterruptable power supply. Then again, that does introduce the possibility of the uninterruptable power supply failing but in most places they are more reliable than mains power and on a bulb as old and fragile as this one limiting the number of times it's turned off and then on again is paramount to it continued longevity.

Forget the watt meter, I can't believe they gave it (a light bulb) a full police and fire truck escort. What next, a ten gun salute and a fly over by the Airforce for the light bulb holder!

Hey, its the US!

Why not a drone flyover in a swarm. Just think of the publicity. Drone swarm protects national heritage bulb so that all can see the light!

There is something very suspicious about a claim for a lightbulb burning for 100 years in California...
I have to agree. Your post prompted me to do some research, and things are not as I read many years ago. The first low cost tungsten filaments were made in 1910 as seen here, so it is possible. Bulbs that are very inefficient will last much longer, and they were probably made that way then.

i think it was at a fire station. an incandenent filament lasting that long is unlikely, but i've used 180v bulbs from a steel mill that seemed to last forever. they are dim of coarse.

Yes ! It may be true!

I have experinced like it [Not over a century but near a century] when in my home city Power supply company shifted to AC from DC in 1960s and my friend gained a contract to convert DC fans [Pakistan Railway]. I just as an electronic Trainee IN YMCA training institute helped him by telling him to use 4 x SD1 rectifier. [The only Si diode known to us].

He was also granted to replace Bulbs [25W] with 60Ws.

Railway authorities inform him that all the Electrical fittings are from the day Railway stations were electrified and from the Railway station's log not a single bulb, fan or swithes were replaced. Due to DC supply all the switches were Original Toggle design.

This all was in 1900s some 5=30 years before my birth.

I have in my life have replaced seldom a bulb in 1960s for years.

This was the quality of of product and the (+) limits on which the Tungston spiral / wire was used.

And the story is of a single bulb out of a big lot which is not astonishing.

Thanks for the reference to story.

Yes, but you have to take into account the duty cycle the bulb was designed for. Lights used in advertising, carnivals and such endure crazy power cycling. If you were to install a standard incandescent light bulb in that environment its life would be greatly shortened as compared to being used as a reading light in grandma's house.

Do you have something where the bulbs fail a lot? Designing something? Homework perhaps?

Yes.

In our Panasonic TV with a TY-LA1000 bulb it is estimated you lose about 4 hours of life with every turn on/off. So far every bulb has eventually failed with the high pressure envelope exploding. Thermal stress!

Yes. Just put a capacitor of the proper rating and it will act as the slow start for the bulb.

If you think about it carefully this won't actually work for a parallel-connected capacitor and a DC bulb.

The capacitor won't limit the inrush current connected in parallel, and the DC bulb wont work with the capacitor in series.

According to the video in this link, the 60 watt bulb is "only turned on to 4 watts". So apparently it does not have 120 volts applied to it. No wonder it has lasted a long time. You can see the bulb in the link.

Obviously

To me there would appear to be many variables in the equation. 1. How thick and what purity was the tungsten used in the filament? 2. What inert gas and what purity was the gas used in the envelope? 3. How stable was the power supply? It could be that manufacturers seeing a lamp last so long would not want lamps to last that long and may have "down sized" the parameters of the lamp so they would be repeatable purchases; the same as with Henry Ford; make a car that lasts too long and you don't have repeat business.