Saves those bulbs too!
I think you'll find that switching a bulb on and off contributes to shortening its life. Or did the exclamation mark mean that you knew this already?
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L'escargot by name, but not by nature.
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I think the newer BMWs have a system whereby as the light is switched on, the voltage is ramped up over a few milliseconds, rather than 12v being applied all at once. I have been told this is to prolong the life of the bulbs, but I don't know how effective it is.
I suppose that bulbs in the house tend to go as they are switched on, rather than at some random time while they are already on. Thermal stress?
number_cruncher
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"Saves those bulbs too! "
Unlikely. The wear and tear on bulbs happens when you turn a light on or off, at which point the filament either expands or contracts as it heats up/cools down, which after a while causes fatigue in the filament and eventually will make them go. That's why bulbs at home almost always go when you switch them on.
It's also why manufacturers can state huge lifetimes for their bulbs. Never swiched off, they take a long time to fail.
V
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Back in the pre motorway 60's it used to be part of the lorry drivers code to switch off headlamps when following another lorry at night. When a following lorry decided to overtake, on would go the headlamps and as the overtaking lorry drew clear of the slower one, the overtaken lorry would switch off his headlamps, indicating that it was safe for the faster lorry to pull back into lane. Headlamps would stay off until the faster lorry was some distance away. Very helpful in the days of single lane main roads, less traffic and slower speeds. I'm not to sure about the need for of all the headlamp and hazard light flashing that goes on today though - especially on motorways in daylight.
As for the longevity of bulbs. At work ( Truck rental mechanic) I'm forever replacing blown stoplight bulbs, at least a couple a day, very rarely have to replace a blown indicator bulb though - and they switch on and off thousands of times a day.
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...very rarely have to replace a blown indicator bulb though - and they switch on and off thousands of times a day.
I'd have thought they never work, or is it just the one's I'm behind!
(lol)
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Davy S.
Oops, where did that screw go!!
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...very rarely have to replace a blown indicator bulb though - and they switch on and off thousands of times a day.
It has been some (considerable!) time since I changed any bulbs on trucks, but are the brake light and indicator bulbs the same type?
If they are the same type of bulb, then any difference in life must be caused by another factor in the circuit. The most obvious being the difference in how indicators and brake lights are switched.
number_cruncher
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NC,
We use the same aftermarket 12v and 24v bulbs all the time. VW LT's eat brake light bulbs. The local dealer blames the high failure rate on the constant slamming of the back doors, but indicator bulbs seem to be immune to the slamming. Transits aren't quite as bad but if I have to replace a rear bulb in one, it's almost always the brake light bulb. We sometimes have a van returned from long term hire with both brake light bulbs blown. We used to have problems with premature failure of aftermarket headlamp bulbs (where the headlamp is located in the vibrating front bumper). Using Hella bulbs has reduced the problem to occasional replacement. But as for indicator bulbs - 12v or 24v - no problems.
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Every time the bulb is switched on it suffers a shock. It would last much longer if it is left on. Automobile bulbs are a different animal from household bulbs. The filaments are strongly supported and made for use in conditions of shock and vibration. The equivalent bulb for household use is the 'Rough Service' bulb. They are available from wholesalers, but you generally have to ask for them. They give a little less light, but last for years. I use them in my handymans lamp.
I drove Volvos for 15 years. The sidelights and dim-dipped headlights come on with the ignition, hence they get a lot of use. The first time I changed bulbs for the rear lights I bought them from local accessories shop. The bulbs life was very short, weeks or even days. I found that the only way is to buy the bulbs from the main dealers, in the car manufacturer's packaging. It costs more initially, but is balanced when you compare the cost with the alternative of multiple bulbs.
I now have a Subaru, and leave the sidelight switch permanently ON. Hence I don't forget to switch on the lights at dusk. The lights are switched via the ignition, pretty much in the same way as the Volvo. It ensures, too, that I can't accidently leave the sidelights or headlights on and flat the battery.
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Why haven't LEDs caught on? They last longer, are brighter, and illuminate more quickly than filament bulbs. Returning to the original point of the topic, they also use less power. They're still a rarity on cars.
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Wasn't this covered a while back in that they have only recently become legal? (i.e. Con&Use regs I believe specified filament only? Or something like that)
Only slight disadvantage of LEDs over bulbs is that, for the high intensity ones anyway, the output angle is a lot smaller so they can only be seen from infront, usually +/- 30 deg. from head on, while a filament has much wider visibility. However, as you tend to use loads of them, you can arrange them to be move visible.
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"Saves those bulbs too! " Unlikely. The wear and tear on bulbs happens when you turn a light on or off, at which point the filament either expands or contracts as it heats up/cools down, which after a while causes fatigue in the filament and eventually will make them go. That's why bulbs at home almost always go when you switch them on. It's also why manufacturers can state huge lifetimes for their bulbs. Never swiched off, they take a long time to fail. V
Now here's a funny thing. I just finished reading this thread, went into the kitchen, turned on the light, and the bulb went.
Spooky.
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If the current is ramped up gradually into a light bulb the electrical and mecanical stresses will be lower, and the ramp up will also suit it from a heat point of view. The electrons being excited quiclky will do nothing for the condition of the material. Gradual increase to the desired current will allow the material to become more uniformally excited so that stresses are much reduced.
It is the same engineering reasoning that suggest you don't fill an overheated rad with cold coolent or poor boiling water on a windscreen in the winter (or anytime of the year for that matter).
You don't want to create a sharp energy or temperature gradiant, otherwise the differential stresses in a material, whether it be a filament, a cast iron engine block or a piece of glass.
We used to apply a ramp up when testing electo magnetic components in the aerospace industry.
Why do I get the feeling people are getting up and leaving?
H
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Likewise, in the theatre, most dimmers will pre-heat the lamp (which can be often be as much as 2500W in our installation), partly to reduce the shock of bringing it up to full power in a hurry. The other reason is to reduce the time lag when it powers up - keeping the filament just glowing means the light will come up a lot quicker than from cold.
However, in my experience, a lamp has nearly always gone when it's brought to full intensity from a cold start, rather than when it's been switched on continuously for ages.
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If Hugo thinks that's a dull post, he's not trying hard enough.
In a previous life I briefly worked in the accounts department of a very large light bulb (lamp to those in the trade) manufacturer.
My immediate boss had worked his way up from the factory floor. He told me that he had saved the company a fortune by hitting on the idea of gently warming the filament wire when working with it as this made it much less susceptible to breaking. Prior to that, the company had wasted a very high proportion of the wire through breakages.
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One day I was accosted by a very angry cyclist who accused me of ignoring his very bright multiple LED front lamp and nearly putting him off. (He was comming down a very steep hill, frighteningly fast for a bike, and behind a row of parked cars.) Although the lamp was very bright when viewed front on, the power was very low, from a 3 volt torch battery, and focus was very narrow. It couldn't be seen behind the cars when viewed side on. There was no spill spread of light that you get from the 100 watts or so car headlamps. That cyclist was riding under a misconception that his bright light made him easier to see.
I hope that he rides more cautiously now. I no longer use that road in case I meet him again.
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and focus was very narrow.
That's the problem with using LEDs in a headlight unit as mentioned earlier. The narrow beam means that getting the light reflecting and refracting, and so creating the right kind of pattern, would require a lot of LEDs all pointing in different directions.
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A few years ago I was discussing lamps and bulbs with an old gent (Well into his 70\'s) and the subject went to his wartime experiences and carbon arc searchlights. \" dangerous things they were\" says he. I asked why, expecting a few technical details. \" One fell on my mates foot while we were loading it on the back of a lorry, put him in hospital for a week\"
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>> and focus was very narrow. That's the problem with using LEDs in a headlight unit as mentioned earlier. The narrow beam means that getting the light reflecting and refracting, and so creating the right kind of pattern, would require a lot of LEDs all pointing in different directions.
LEDs probably aren't really suitable as headlamps but I still think they're ideal for rear lamps and indicators: after all, most central brake lights are LEDs now.
I have a decent quality LED rear lamp for my bike. Although it doesn't conform to the letter of the law (which I believe still insists on a filament bulb) it's far brighter than a traditional cycle lamp, and the fact that it's made up of a number of LEDs with reflectors means it can be seen from the side as well as any other cycle lamp. The much lower power consumption of LEDs also means that there's less chance of their being dimmed by batteries that are on their last legs.
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What about a Renault Scenic? In the rain the windscreen wipers turn off when you come to a stop to save battery power, amazing! What will they think of next.
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What about a Renault Scenic? In the rain the windscreen wipers turn off when you come to a stop to save battery power, amazing!
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It helps you to stay relaxed when someone hits you head on as you did not see them?
>>What will they think of next.
Maybe Ford will allow YOU to select wipers when you have wetted the screen rather than smear crud around. Progress?
Is automatically switching off dipped beams when the ignition is switched off a good idea. Having this feature on my old Sierra, without a lights left on warning buzzer, has saved me having a flat battery in the past when I have left lights on from 0900 to 1730.
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