Naked Science Forum
Non Life Sciences => Technology => Topic started by: DoctorBeaver on 04/04/2006 02:19:42
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Why do they initially light up very dim then, after half a second or so, shine at full power? Is it some kind of current regulation, the materials used, or what?
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its the materials used. they are a totally different kind of bulb than your normal incondesant light. more similar to the long tube flourescent lights that you see in most businesses. They have no filament.
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Thanks, Justin
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They are however quite a money saver over incandescent bulbs- you can buy a compact fluorescent with a higher lumens and it will still use less "juice". The added bonus is that they operate for thousands of hours without burning out, so you won't have to stand on a chair for a couple of years.
It's puzzling that after being available for years they still have not replaced incandescent bulbs, but that's because they cost more up front I suppose.
chris wiegard
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quote:
Originally posted by VAlibrarian
They are however quite a money saver over incandescent bulbs- you can buy a compact fluorescent with a higher lumens and it will still use less "juice". The added bonus is that they operate for thousands of hours without burning out, so you won't have to stand on a chair for a couple of years.
It's puzzling that after being available for years they still have not replaced incandescent bulbs, but that's because they cost more up front I suppose.
chris wiegard
There are several problems with compact fluorescent light bulbs, although some of these problems are rapidly improving.
Firstly, they should never be used in situations where one expects to regularly switch the lights off in less than 30 minutes after switching them on.
Secondly, until very recently, they were only available in very low colour temperatures. Modern devices now come in a wider range of colour temperatures, although they still don't have quite the same spectral purity as incandescent light bulbs.
Thirdly, only very recently have they been available in a sufficiently compact size to be easy replacements for most incandescent light bulbs (without having to change the fittings for the light bulb). Even now, there is one of my RO80 fittings that I cannot get the compact fluorescent bulb to fit into, and I still cannot get daylight balanced R80 fluorescents (although I can get daylight balanced incandescent R80s, and daylight balanced fluorescents in other shapes and sizes).
But, certainly, over the last year or two, the advances in commonly available compact fluorescent bulbs has been such that I have now changed most of my bulbs over to compact fluorescents.
George
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quote:
Firstly, they should never be used in situations where one expects to regularly switch the lights off in less than 30 minutes after switching them on.
Why's that?
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quote:
Originally posted by DoctorBeaver
quote:
Firstly, they should never be used in situations where one expects to regularly switch the lights off in less than 30 minutes after switching them on.
Why's that?
Because, as you have yourself noted, the slow warm up time, and the fact that any device that is regularly operated at below optimum conditions will have a foreshortened life span and excessive power consumption.
The 30 minute limit may be somewhat over generous, and it may be sufficient to allow for 5 to 15 minutes warm up – I really don't know. I have seen 30 minutes mentioned, but I suspect that this applies to older designs, but there is no doubt that warm up times are noticeable, and you should not be using the devices in situations where an appreciable amount of its life is spent warming up.
George
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I will admit that they do have their drawbacks (as someone mentioned they are a very rapidly improving technology). UNtil recently all the drawbacks were just small tings that i was picky about and ignored them. however, i recently noticed one difference thats pretty hard to get around. they don't work at all on a dimmer switch. this makes sense given their nature, but its something taht if you want you have to use the old bulbs.
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quote:
Originally posted by MayoFlyFarmer
I will admit that they do have their drawbacks (as someone mentioned they are a very rapidly improving technology). UNtil recently all the drawbacks were just small tings that i was picky about and ignored them. however, i recently noticed one difference thats pretty hard to get around. they don't work at all on a dimmer switch. this makes sense given their nature, but its something taht if you want you have to use the old bulbs.
Yes, I knew there was something I had forgotten off my list, and that was it.
I believe there are some specialist Compact Fluorescents that can deal with dimmer switches, but most cannot cope with operating below 80%-90% of rated power.
George
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quote:
Originally posted by VAlibrarian
They are however quite a money saver over incandescent bulbs- you can buy a compact fluorescent with a higher lumens and it will still use less "juice". The added bonus is that they operate for thousands of hours without burning out, so you won't have to stand on a chair for a couple of years.
It's puzzling that after being available for years they still have not replaced incandescent bulbs, but that's because they cost more up front I suppose.
chris wiegard
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You can get energy saving bulbs in various wattages for 47p at a well known store in Cambridge which I won't mention the name of. Don't all rush at once to get to Robert Sayles. Ooops! [8D]
Fuzzy
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quote:
Originally posted by VAlibrarian
It's puzzling that after being available for years they still have not replaced incandescent bulbs, but that's because they cost more up front I suppose.
This question shows the dilemma one always has with developing technology.
http://www.theregister.co.uk/2006/04/13/oled__white_light_invention/
quote:
Researchers working on organic light-emitting devices (OLEDs) have made a critical jump that could finally call lights out time for the humble bulb. Since OLEDs are transparent when switched off, the prospect is of whole surfaces like walls, windows, or even curtains flooding rooms with brilliant white light.
University of Southern California Professor Mark Thompson said: “This process will enable us to get 100 percent efficiency out of a single, broad spectrum light source.”
The American team's breakthrough was to make OLEDs able to emit the daylight-style white light needed in homes and offices. Previous efforts had had struggled to get the full spectrum of wavelengths required.
OLEDs are made of four ultrathin layers; one for each of the primary colours, and one that does the actual light emitting as excited electrons fall back to their original energy state.
The problem was with the blue phosphorescent layer, which wasn't as efficient as the other two and short-lived. Thompson's team switched the blue layer's phosphorescent chemical for a fluorescent one. The subtle difference in the speed of the electron's energy transitions between phosphorescence and fluorescence can be adjusted for, without losing energy.
OLEDs do not produce heat like a traditional incandescent filament bulb, and are even more efficient that current energy-saving fluorescent bulbs. In a current fluorescent bulb the colours are all produced in a single layer, which causes some of the light to be lost by electrons combining with each other rather than radiating light.
The only hurdle left for the technology, Thompson says is for the plastic coating to be improved so that water cannot degrade the OLED. They will only need replacing every five to ten years.
The invention has obvious tech applications. Companies are already looking into it for mobile screens, and flat panel displays.
The problem is that what is inevitable that the faster one moves to compact florescent light bulbs, particularly given their long life, the greater the delay to the next generation of light bulb beyond that. People are simply not going to want to invest heavily in the currently new generation of technology (and it would be environmentally harmful to do so), and the immediately throw is all away as the next generation of even better technology follows hard on its heals.
This applies not only to light bulbs, but on new generation cars, or any other fast moving technology. Each generation of technology may bring its advantages, but do you jump quickly to gain a small improvement in environmental (or other) benefit, if that only delays the an even greater jump in technology.
I am not saying that this means one should not seek to improve upon what we have, and it clearly is possible to always wait longer and longer, just in case an even better technology is just around the corner. All I am saying is that it has to be a very careful judgement as when one should jump, neither too early nor too late.
The reality, the best option is usually a gradual transition, where early adopters may jump on whatever is the newest and best (these people are inevitably wasteful, but they are useful in testing out the newest technologies, and if there are not too many of them, then the waste is slight); behind them will be people who will skip one technology or another, so some will jump straight from incandescent to LED's, while others who are earlier in adopting compact fluorescents may either delay adopting LED and may even skip the technology and move on to whatever follows.
This is why it is actually an advantage that people don't all jump on the latest technology as soon as it looks a little better than what went before, and why it has taken all this time for some people to adopt compact fluorescent light bulbs.
George