Will this lamp life increasing scheme work?

I believe it does make a difference. Mosr incandescent bulbs blow on switching on IME.

You don't need a circuit - just a Surge-Gard.

Graham

I am aware of a mechanism where the unrush current kills a filament when its hours are numbered, and can do even zero damage if short of a kill even if the filament is jolted badly enough to produce an audible "ping" sound.

Now for a bit of data: I did an actual test of one of those "soft start" "stick-on" "buttons" of negative temperature coefficient (NTC) thermistor type. When fully warmed up, they dropped enough voltage in my test to increase lightbulb life by about 50%, and they only claimed to double lightbulb life.

There is another kind of "button" (diode) that makesd much taller claims, probably largely achievable in truth, but power consumption is reduced to about 58-59% of "full" while light output is reduced to about

26-30% of "full". Even if the lightbulbs last until after your children die of old age, there is probably something else much more economical - compact fluorescents, commercial service incandescents, or maybe even incandescents of a lower wattage! Usually, most of the cost of lighting with incandescents is electricity cost rather than lightbulb replacement cost. This means that usually energy efficiency is more important than anything else. Even where lightbulb replacement has a high labor cost or high labor value and where incandescents are favored, the usual solution is "traffic signal lamps" - which are incandescents rated to last 8,000 hours, even when turned on and off close to half a million times! There are even 130V versions of these! Highly liklely you will maximize your value with something that values energy efficiency more or at least no less than something that is the most economical for traffic lights in union-city Philadelphia!

- Don Klipstein ( snipped-for-privacy@misty.com)

I have a bit of data on use of NTC thermistor lightbulb-life-extension "stick-on buttons":

One experiment that I did and published has them when fully warmed up dropping enough voltage to increase life by 50% in continuous operation, and they only claim to double life.

Meanwhile, when fully warmed up they result in a decrease in power consumption of only 2% but light output is decreased by 11%.

Also, I don't see any surge protectors (that absorb transient surges in the power line voltage) doing much to save lightbulbs since over 95% of lightbulb failures appear to me to be unrelated to such surges.

I am aware that lightbulbs like to burn out during a cold start. However, it truly appears to me that the main reason is that an aging lightbulb becomes unable to survive a cold start only several to a few dozen operating hours before it becomes unable to survive continuous operation. The usual burnout mechanism is from melting of a "thin spot" in the filament that a cold start can kill. Meanwhile, in continuous operation such "thin spots" normally have their negative condition accelerating worse than exponentially as operating time goes on!

- Don Klipstein ( snipped-for-privacy@misty.com)

Yes, but most solutions are not cost effective. Look for cheap dimmers if you must - but the lamps'll still burn out one day!

That's effective. If it can't start at full brightness then the inrush won't happen.

Graham

What voltage was that across the Surge-gard ?

That sounds very believeable.

I know of applications such as theatre lighting where the bulbs were very costly and they used a 'keep alive' current that extended bulb life.

Graham

I used to have a 3-way light for reading next to my easy chair. It seemed like that damned thing was going out everytime you turned it on. I put a dimmer switch on it a couple of years ago and the bulb hasn't went out since. I'm wondering if maybe it will last forever.

The dimmer switch is in a plastic electrical box on the floor on the side of my chair and has the switch and two outlets in it.

Your answers don't include numbers. Numbers from simple equations were developed generations ago - are that well known. For example, increase 120 volts to 126 volt and the bulb burns out twice as fast. Lower that voltage to 113 and the bulb lasts twice as long. Meanwhile bulb efficiency drops significantly and light output drops by maybe

20%. You would only be consuming more electricity.

Myth is that power cycling causes bulb failiure. That thermal resistor causes less voltage to a bulb - therefore bulb lasts much longer.

Those thermal resistors were once sold in 1950s as a miracle (scam). But as apparent in above numbers, those thermal resistors only meant less light from more electricity. If power on surges were so destructive, then such devices - even in the 1950s - would have been in all lamps. Further science was posted in "Never turn off the computer???" in 24hoursupport.helpdesk on 4 Sept 2006 at:

Manufacters provide numbers for bulb life expectancy complete with equati> A long subject line, I know. Anyway, after having another light bulb

You may have some exacerbating circumstances?

I had a situation where I had to turn an alarm lamp on outside in an area with a lot of vibration and bitter cold temperatures. Rough Service Bulbs would last 2 months tops.

Wouldn't have been too bad but the bulb filaments ionize the gas inside the envelope when they open and that ionization is a short circuit to the solid state relays we used.

We added an inrush current limiter thermistor and the bulb/relay life was extended to 5+ years.

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Re; The tungsten filament doesn't fail because of the current inrush; it fails due to the combination of thermo/mechanical fatigue (cooling and heating cycles) and the evaporation of tungsten from the filament. At the high temperatures of the filament, about 2800 C, the equilibrium vapor pressure of the tungsten is in the range of 8 torr. This tungsten vapor "condenses" on cooler parts of the interior of the bulb; like the glass envelope and the filament supporting stem assembly. This situation can be further exaxcerbated by mechanical shock and vibration to further shorten the life of the filament.

When the filament is energized there is a power surge. However, the negative temperature coefficient reacts instantaneously to limit the filament temperature such that the temperature of the filament never exceeds it's steady state incandescent temperature. It is the rapid heatup of the filament that causes the typical failure upon energization, but generally speaking, that is because the filament has been so weakened that the failure was immenent anyway.

Reducing the power dissipated in the filament just a little has a dramatic effect on the filament temperature, thus it's equilibrium vapor pressure at that temperature, and thus it's evaporation rate. Reducing the power dissipated in the filament is the key to longer filament life. Try a dimmer or other such voltage technique.

Dan Akers

Greetings Everybody, This question of mine generated way more answers than I thought it would. After reading all the responses it really does make sense, considering how the bulbs work, to just use the bulbs as is. Lowering the voltage, while extending life, also lowers the light output dramatically and so from an economic standpoint it jest don't pay to build a soft start light switch. Thanks again for all the thoughtful answers. Cheers, Eric R Snow

In my experiment published in:

(I am forced by my newsreader to split into 2 lines:)

The voltage drop across the thermistor-type "stick-on button" was 4.2 volts in this particular experiment after being allowed to warm up.

I am aware that this is done. However, I have yet to see data from rigorous controlled experiments to show whether this is truly effective or merely done because lightbulbs are known to like to blow during cold starts.

- Don Klipstein ( snipped-for-privacy@misty.com)

When my grandmother bought her first all tube TV I rewired it so the filaments always stayed on. It ran about 15 years with no repairs whatsoever.

I have fixed a couple all-tube TV sets, a few other all-tube items, and helped a friend fix a lot more. Broken heaters and filaments of vacuum tubes do not rank high on the list of problems - in fact, I have trouble remembering if I have seen this happen at all.

- Don Klipstein ( snipped-for-privacy@misty.com)

I've replaced my share of tubes in TVs.