Are LEDs a big con?

[ericmark]

I remember the discussion on fitting head lights or not, clearly not an option with a road vehicle, but is an option with trains, and in the UK we did not fit head lights, as it takes miles to stop a train further than the head light could illuminate, but without lights the driver even at night could see for miles, and actually see more of value than with a head light, the problem was every time the train went through a lit area it took time after for drivers eyes to readjust to low light levels.

I had said the hired engine with the head lights working looked photogenic, why not get all the head lights working, but the feeling was if they got them all working then if the head light was not on then it would be used as an excuse for not seeing the train.

Also the steam turbines do need maintenance, and the maintenance department was hard pushed enough as it was. Main line trains never had steam turbines they powered carriage lights with dynamos driven by the wheels, but many of the narrow gauge are limited to 15 MPH flat out so lights powered from the wheels is not really an option, so lights were all powered where required from the engine steam turbine generator.

 

[SimonH2]

Typical white light leds actually emit 3 distinct colours.

NO - that is not correct.
One way, and just one of several, is to mix Red Green, and Blue - such an option giving you (with decent LEDs and drivers) the appearance of creating most of the visible colour gamut.
For white LEDs, the LED itself is usually blue (as that's a colour that's easily produce AND which can be used to excite phosphors) or it may be UV which is better for exciting phosphors. Each phosphor will emit a distinct set of spectrum lines - with a mix producing what would appear to be a continuous spectrum of some sort. The blend of different phosphors will determine the emitted spectrum - with a larger variation in phosphors producing a smoother spectrum. This graph from CREE shows the spectra for two variants of one of their LEDS :

Source: CREE XLamp XD16 Data Sheet
Note how the cool white emits a lot of a particular shade of blue and relatively little of any other colour, while the warm white (with a higher CRI) has converted more of the blue into other colours - though still with far from a continuous spectrum (hence only 80 CRI).
The higher the CRI, the flatter and more uniform the emitted spectrum - but there are two costs to that ...

• Firstly, if you compare spec sheets, the cool white LEDs typically have a higher lumen output than warm white. If you look at the tables in that data sheet, the lower the colour temperature and the higher the CRI - the lower the lumen output for a given drive current and operating temperature.
• Secondly, the better the spectrum, the more complex the phosphor mix needed - and hence higher costs in manufacture.

Both these factors drive the cheaper end of the market to cool white and low CRI - hence the number of cheap LED bulbs that just look 'orrible.

I remember the discussion on fitting head lights or not, clearly not an option with a road vehicle, but is an option with trains, and in the UK we did not fit head lights, as it takes miles to stop a train further than the head light could illuminate, but without lights the driver even at night could see for miles, and actually see more of value than with a head light, the problem was every time the train went through a lit area it took time after for drivers eyes to readjust to low light levels.

Yes, I've observed something similar over the years. A lot fo the time, the roads would be safer (from one PoV) if no cars had lights on them. Without lights, visibility can be for miles - but then some b***ard comes along with their anti-aircraft searchlights shining in your face and you can see absolutely nothing with or without lights for a bit. And of cours,e car manufacturers are engaged in an arms arace to see who can create the brightest headlights which exacerbates the problem. Just don't get me started on the road safety issues caused by these stupid daylight running lights which are often brighter than headlights

 

[ericmark]

Years ago I had a Lucas book on lighting regulations, it was a surprise as there was a range of wattage permitted for each light, seem to remember brake lights were 15 to 36 watt, but there was a limit to how many and what size a head light could be, seem to remember 3 dip beams and 5 main beams, so on my mini as a young lad I had the max, it looked good, don't think I really needed them, so dip switch turned off two lamps, centre one set low, but seemed the police did not know the rules, and I was stopped for having one spot light on with the head lights not two, they were telling me what I needed to do, and I did not want to upset them so it was yes sir, yes sir, until he decided to book me, then I recited the actually regulations, to which they said that's not quite correct but they would let me off this time.

In hind sight I was asking for problems making the mini look like a rally car. But many of the laws stated wattage, both road traffic act and building regulations and they have not really caught up, so garden flood light was 150 watt max, so with LED that is around 35 watt, but there are loads of 50 watt flood lights for sale, I have some where a 70 watt metal halide lamp, which makes a 300 watt halogen look dim. I am sure the laws will catch up, but 75 watt head light bulbs had a limited life, so when the limit was placed on them I think 65 watt was the limit it was not long before you needed a replacement and 75 watt bulbs were clearly marked not for use on public roads, so we all dropped back to 65 watt. But LED lamps last a long time, so better even if law is still in watts to consider 35 watt is outside limit without planning permission.

Daylight running lights, rear guard fog lights were illegal now car fails MOT without a rear guard fog light, I remember having to disconnect Volvo daylight running lights as not permitted in this country at that time. I also remember Honda motor cycles had illegal indicator lamps 8 watt where minimum was 15 watt, and too small, but police seemed to turn a blind eye. I look as some modern cars and question if the lights are big enough? orthographic projected. Didn't know what the word meant until I had read the regulations.

 

[SimonH2]

A useful reference is The Road Vehicles Lighting Regulations 1989
At least for those of use running older vehicles - my old Land Rover could legally have more than 2 headlights, and any extras don't have to be e-marked

 

[SUNRAY]

So having had energiser G9's recommended earlier on I purchesed 12 of them at £4.07 each from CPC and eagerly cut the package open then popped the bulb in a fitting, turned on the light and was greeted by a marvelous display of nothing. not even the faint glimmer of the failed device.

Assuming this was a fitting failure I swapped 2 bulbs and the darknes followed the new Energiser. I then tried it in 3 other fittings all different makes etc and still nothing.

At this point I'll comment that all of the previous bulbs I've used have decent metal tabs as the connexions, the expensive Energisers only have bits of flimsy wire.

Assuming the wire was the problem as it appeared to form a smaller contact than another Energiser I opened a second pack and tried that in several fittings and still nothing.

Right time for proper testing, 2 croc clips direct onto the first bulb and nothing, second bulb worked. Comparing the Energiser wires with the other bulbs its very obvious the loops are not as far apart as the metal tabs and by careful bending have been made to work in the fittings.

Modifying 8 bulbs finds us with 3 fully working fittings again, well as long as the following day when I turned the lights on again and a bulb has failed. Modifying another has worked now for nearly a week.

So to the person who reckons I won't regret buying Energiser... Guess what?

Yep at this point in time they are the only G9's I've purchased with one DOA and one failed on the following day.

So far they are the most expensive
So far they are the most complicated
So far they are the most unreliable


So sadly I currently feel I do regret buying them. I'll try to report back when they fail.

 

[chris1roll]

Re the G9's.
We put a new fitting in our kitchen with 7 G9's in it back in September.
I should explain now that I am very intolerant of LED flicker.

First up were the ones we bought at the same time the fitting, moderately priced.
Unbearable flickering, thought I was going to puke after about 5 minutes.

Ok, so lets try some slightly more expensive ones - think they were Energizer.
More bearable, but definitely couldn't live with them.

Thirdly, the most expensive I could find, I don't remember the make. Almost as bad as the first ones.

In desperation I got some extremely cheap 'Ascher' brand ones from amazon after googling 'non flicker G9'
(they seem to have gone up in price at the moment, but amazon varies stuff all the time)


And they are perfect for me, No flicker that I can see, and I figured at the price they were, it doesn't really matter if I have to replace them more often.
So far they are all still going.

Worth a try?

 

[d000hg]

I must admit I'm pretty disappointed the technology is still so bad when it's now the norm.

And yeah I hate any discernable flicker or sound.

 

[SimonH2]

The technology isn't bad - bad implementations of the technology are bad.

 

[aptsys]

LED's are typically 40 to 50% efficient. Incandescent, depending on the type of lamp and their intended life, are typically 10 to 20% efficient. The inefficiency proportion of both types, being dissipated as unwanted heat.

Sorry but you're way out. High power LEDs used for lighting are nowhere near that kind of efficiency, even less so given the dies operate way over 20 or 25C which is the optimal temperature for both the LED die and the phosphor.