Not being able to find a small internet radio to buy we liked, we got mobile phone with which we link with wi-fi to a modem router, and use it as an internet radio.
Keeping the phoned plugged into its charger all the time, we are using it to play *all-day* background classical music through an amplifier and speakers.
Since the phone has no 'moving parts' unlike a computer, we are wondering if this continuous playing all day of the phone is going to shorten its working life ?
Using anything shortens it's working life.
Not so. There aren't any obvious failure mechanisms in solid-state devices (other than dopant migration in high-power output transistors).
It's also true that most mechanical devices "like" moderate use. Letting anything mechanical "sit" most of the time will probably cause it fail sooner than if receives regular use.
It's now possible to build computers without moving parts (other than the optical drives). My new computer has a solid-state "hard disk", and you wouldn't believe how fast it boots up, or how fast programs start to run.
There are many factors that cause something to fail. I you don't use it, it has no working life. I don't wish to play semantics but if you use it you are using up it's working life.
Not so. With mechanical devices, regular moderate use provides a longer useful lifetime than using the device only rarely.
I don't agree but will say no more. Regards, Tom
Not sure if my News server supports x-posts to the entire Usenet, but I digress.
An incandescent light bulb is a good example, If it lasts 1000 hours when run continuously, its life will be considerably shorter if run (say) 4 hours a day and the time it is on added up. Equipment with lots of thermionic devices like very early computers were, as far as practical, never switched off because of the likelihood of failure.
-- Graham. %Profound_observation%
"Graham."
** Where ever did you get that nonsense from ??Some web forum ?
He is right, the stresses involved in the turn-on of the bulb each time is equal to several hours of continuous running. If you cycle a bulb on and off every few seconds, the total on time before the bulb fails will be only a few hundered hours for a 1000 hour rated bulb,
It would be a strange way to rate the life of a lamp - on constantly, since this pretty well never happens.
Do you find the 'flasher' lamps on your car failing more quickly than similar lamps which don't flash?
--
*A plateau is a high form of flattery*
Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.
I don't know of any data that supports this common idea, but I'd be interested in reading about it if anybody's actually done the experiment carefully. Electromigration is a smaller effect in an AC bulb, since the leading order effect cancels.
I suspect that the notion that cycling is hard on bulbs comes from the way that the bulb often fails at turn-on, when the thinnest hot spot vapourizes before the rest of the filament has a chance to come up to temperature and reduce the inrush current.
The tungsten in the lamp is run within a few hundred kelvins of its melting point, so it's always in the fully annealed state, which ought to mean that there are no metal fatigue mechanisms operating, just material migration due to sublimation.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
It's an accelerated life test. The deration curve of the incandescent light bulb is well known and assumed to be (Vapplied/Vdesign)^-12 to ^-16 * Life at design voltage See Fig 5 on Pg 5 for the graph. Nobody wants to wait 1000 hours for a bulb to blow. So, they increase the applied voltage, which dramatically decreases the lifetime down to reasonable test times. Using a rack of bulbs, they obtain an average (or median) lifetime at the higher voltage. Then, they work backwards on the curve to estimate what it would be at the design voltage.
When I was specifying lamps for a direction finder for the USCG, I had to deal with minimum lifetime specs. I asked the vendor (Dialight) how they tested their T-1 3/4 bulbs and was told that they did an accelerated lifetime test on a few bulbs from each lot to insure adequate lifetime along with the usual sampled 1.5% AQL failure test.
Yep. As I understand it (possible wrong), AC filaments break in the middle, mostly from vibration flexing.
Yep. See my comments on the relatively high failure rate on the
40watt theater marquee lamps due to cycling. The same lamps in the lobby and foyer were not cycled and seemed to last forever.Yep, but different failure mode. When the extremely thin layer of tungsten plating evaporates, the light becomes dimmer. Below some brightness level, it is considered to have failed. However, most such tungsten coated filaments fail due to corrosion of the base steel alloy wire which is exposed to the internal gases inside the bulb after the tungsten evaporates. The gases (mostly nitrogen and some argon) are inert, but there's a little water vapor outgassing from heating the glass envelope, which eventually corrodes the filament. Other failure modes are hot spots and notches caused by manufacturing variations and tungsten evaporation.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
You can't run an accelerated life test when the exponent isn't known more accurately than 12 to 16.
I don't think so, because there's no mechanism for that, as I said. The wire is fully annealed at all times, so there's no possibility of progressive fatigue failure.
I was actually disagreeing with you. There are lots of possible reasons for the marquee lights failing prematurely. I'm not a tungsten expert myself, so I'd be very interested in seeing actual data that shows a dramatic shortening of life due to cycling. I'm not saying it's impossible, just that I haven't seen any such data.
The filament isn't tungsten-plated, it's pure tungsten or a low alloy. The brightness drop comes from tungsten condensing on the envelope.
And the connecting wire isn't plain steel, it's generally Dumet,
which is a 42% Ni steel with OFHC copper or nickel plating.
You're making a lot of that up. I'd still like to see carefully-collected data.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
True, but I believe that's the range expected from different types of light bulbs (nitrogen filled, halogen, vaccuum), and not the range expected for a given device. I suspect that more accurate exponent value could be empirically determined for a given device, and later used only for that device.
One of the problems of the standard electric light bulb is evaporation of the filament. Small variations in resistivity along the filament cause "hot spots" to form at points of higher resistivity; a variation of diameter of only 1% will cause a 25% reduction in service life. The hot spots evaporate faster than the rest of the filament, increasing resistance at that point a positive feedback that ends in the familiar tiny gap in an otherwise healthy-looking filament.
Note the photo of the filament with a break in the middle. When I was quite young, I would break burnt out AC light bulbs to see what was inside. If the filament was intact, the break was always somewhere near the middle. If a piece broke off, one end of the broken piece was usually near the middle. In later years, I would look at the remains of DC panel lights (usually type 47 for old Motorola radios) and noted that the breaks were always near the supporting terminals, probably due to metal migration.
So much for my anecdotal data. My theater marquee experience was in about 1966. The theater actually did keep records so that they could stock enough replacement bulbs, but I don't have copies of any of that.
I tried Googling for similar repetative on-off tests and didn't find anything. If I have time, I'll try again. I must admit that the lack of test data does look suspicious. Perhaps sending the idea to Mythbusters and have them runs a test?
Oops. I thought it was plated.
No, not fabricated. It's my reliance on my memory in an area that I'm not familiar with. I tried Googling for the wire used, couldn't find much, and made a bad guess. The plating came from somehow getting thorium coated tungsten wire used in vacuum tubes mixed up with light bulbs. Sorry for the errors and muddle.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
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k -Hi Jeff, Phil. First I know nothing about incandescent bulbs. But how about this as a model of why turning bulbs on and off might cause them to fail sooner.
1.) I think we all observe that bulbs tend to blow when you turn them on. (unless you knock the lamp over or something.) 2.) I assume that the failure is mostly due to the thinner ?hot spots? on the filament. Thinner regions heat up faster (higher resistance with equal current). 3.) Now even if the thinner region doesn?t blow, it still gets hotter and loses a bit more tungsten than the rest of the filament. (For that small amount of time that it?s turning on.) But still this means that turning on the bulb causes the thin region to become a bit thinner.And that?s it. Repeated on and off means that the thin region has a higher average temperature than the thick part of the filament. It evaporates faster and fails sooner.
George H.
Won't a thin region of a lamp filament have a higher temperature than the rest of it all the time, not just when the lamp is turning on?
Rod.
It will, but due to the thermal coefficient of resistance of tungsten (most other metals are similar) the heating will be even greater when the filament heats from cold. The hot spot gains resistance faster, so it drops a greater voltage while the rest of the filament is still cold.
disclaimer: figures made up to illustrate the point
assume a constant-voltage supply compute the power disipated by he thin spot (middle resistor) in each case
cold ----[100]---[1]---[100]--- hot ----[1000]-[12]-[1000]---- during warm-up thin spot warms up fastest. start ---[200]---[3]---[200]---
yeah, it would be a good project for the mythbusters, I'd love to see a slow motion film of an incandescent lamp failing at turn-on. but could they affor do dedicate their fast camera for long enough.
-- ?? 100% natural --- news://freenews.netfront.net/ - complaints: news@netfront.net ---
Due to the apparently lack of data and my curiosity, I was thinking of throwing together a crude experiment. Two lamp bases, two 40 watt clear envelope incandescent lamps, two SSS (solid state switches), and some kind of pulse generator. 30 seconds on should be enough to get the filament hot enough for sublimation. 30 seconds off should be enough for it to cool down for a cold start (I need to check this with an IR thermometer).
However, I have no intention of running this test for 1000+ hours. Instead, an accelerated life test can be done with higher than normal voltages. For halogen bulbs, they use: Life = (Vdesign / Vapplied)^12.0 * Life at design voltage For a 1000 hr lamp running at 120% of the rated voltage, the life might be: life = (1/1.2)^12 * 1000 = 112 hrs which is more reasonable for my tinkering and for Mythbusters. With power cycling, the life will be even less. I should have a Variac somewhere in my junk pile.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Hi SEB. Well I sent an email to Don klipstein on this topic. And have permission to copy his reply.
My apologies - I have been off Usenet for a little over a year.
As for real data on effect of switching causing wear on incandescents:
I know some data.
1: It is true that incandescents often failon cold starts. However, I know a mechanism where an aging incandescent becomes unable to survive a cold start a little before it becomes unable to survive continuous operation.I explain this in:
However, traffic signal bulbs have a more vibration-resistant filament than standard incandescents.
3: Flashing and chasing marquee lights used to be incandescent until cold cathode CFLs became economically available. Cold cathode CFLs are special CFLs that are dimmable and blinkable, and flashing them does not detract from their life. However, their efficiency is less than that of hot cathode CFLs. Some marquees still use incandescents. 4: I did an experiment to check for voltage drop in one of those now-hard-to-get thermistor-type life-extending "buttons" to attach to the tip of the base of an incandescent. The device claimed to double the life of the bulb. I found enough voltage drop to account for 50-60% life extension. Light output was reduced 13%, and power consumption of the combo of the bulb and the thermistor was only 2.05% less than that of a bulb connected directly to the line. 5: In my experience, incandescent holiday lights that blink last longer than those that don't. However, most of my experience is with low voltage bulbs whose short filaments are probably sturdier. 6: Some incandescents make an audible "ping" when switched on. However, deflection of the filament does not necessarily strain the filament past its "endurance limit" - the threshold of causing metal fatigue. 7: Some railroad crossing signals have a set-up where bulbs have a resistor added in series with them for the first half second or so that they are on. However, this may be done because of how serious the problem is widely said to be, and how serious it actually is appears to me to be much less. 8: One of my friends had a bathroom fixture with a high wattage bulb that was constantly run dimmed by a dimmer. He experienced little gain in life extension. Since his bulbs significantly audibly buzzed, I suspect his filaments resonated at the power line frequency or one of the power line frequency's lower harmonics. 9: My mother had some incandescent nightlights that had diodes in them to significantly dim the bulbs - which should have made the bulbs last for decades. However, they did not. One thing I noticed: These 4-watt bulbs had extremely thin filaments, and with a diode and therefore being off half the time 60 times a second, their temperature varied greatly up and down 60 times a second. I could see that from rolling my eyes up-and-down while looking at them. Maybe the filaments at times resonated at the power line frequency or a lower harmonic thereof. That could easily produce sound too weak to hear from more than a couple inches away, because such low wattage 120V incandescents have a vacuum rather than a gas fill.Or, maybe those bulbs do not do well with DC due to high voltage, vacuum, and the ends of the filament being close to each other. Please see:
======================
Overall, I am seeing generally that cold starts are not nearly as bad as many say they are, but in a few bulbs they can be. The data appears to me to be majority in favor of "little to generally no problem from cold starts", but it is incomplete.
I would also suggest reading:
====================
Hope this helps!
- Don Klipstein ( snipped-for-privacy@donklipstein.com)
George Herold formulerede spørgsmålet:
I've been told traffic signals have resistors across the relays (or the semiconductor equivalent), so the bulbs are never turned completely off, eliminating the turn-on surge.
But it may be just rumours...
(Yes, I know its an old'ish message)
-- Husk kørelys bagpå, hvis din bilfabrikant har taget den idiotiske beslutning at undlade det.
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