theotherjonv – Member

stoatsbrother +1

I guess the two areas I'd like to see improvements in are price, and battery technology (the output to weight ratio)

TBH I don't think we need further advances in actual light power. At the Gorrick last weekend the power output on the majority of rider's bikes was astounding compared to a few years back. I just don't see that we need more light.
+1 on that. Make them cheaper and last longer on the battery but no more light output required for MTB use.

I read this thread with interest last night – I am a lighting designer/engineer and I work for a company that sells the most advance LED technology on the market – this is far more advanced than stuff your seeing in bike lights or automotive uses etc.

It is interesting to read the opinions on here – obviously bike lights are a niche market, but in general the public opinion of LED technology is very skewed – how many of you have bought LED GU10 'replacements' from B&Q for your kitchen or Bathroom? And I bet your now rightly very sceptical of anything claiming to be 'good' LED technology! There is an awful lot of junk and misinformation out there.

As I dont actually do much night riding I don't have a lot of experience of LED bike lights but certainly some of the stuff out there is impressive. Its still far from the forefront of technology though.

Just have to say I've yet to see an LED that produces the same quality of light as the first Halogen VistaLites I owned. If the technology advances to produce quality rather than quantity, then great.

DEzB sounds like one of the people I described! DezB trust me there is LED technology that blasts Halogen out the field, but you wont see it in the cycling industry.

Colour rendition is the thing for me.

JonEdwards you have the right idea. A very important factor is what we call "Colour rendering index". You have also noted the very important difference between 'bright' light, and actuall good quality light.

The reason your Halogen/HID was better than your P7 was the colour rendering was higher – your P7 I am guessing has a colour rendering of around 70, which is pretty poor.

(Remember what its like walking down a street with Sodium (Orange) street lamps – where its quite 'bright' but all the colours look wrong, all the cars look black, etc etc? Thats because of the poor CRI of the Sodium street lamp. )

Something you wont have seen in the cycle industry is remote phosphor. (just like a flourescent lamp) This is one of the technologies that is improving LED lighting – it enables control of many factors such as colour temperature, colour point consistency, CRI, etc etc.

I'm pleased to see that there are some really nice LED stuff out there being used as bike lights – but there not quite at the forefront of technology!

Described where? In your bit about B&Q LEDs? I don't get you I'm afraid.

As in – you seem to be disillusioned with the LEDs you've tried!

My point is theres a lot of rubbish out there (whether that by cyle lights or things to fit in your kitched) that people have been sold on the basis of 'its as good as the halogen your replacing' when it clearly isnt!

There are LEDs out there that can genuinely match Halogen for light quality, but you wont have seen them on bicycles yet.

Ultra LED have stuff that will not be in main stream production for a few years yet.

We use this MR11 led lamp for interior lift lighting.

It is true 18w compatible and runs cold as ice.

I'm pleased to see that there are some really nice LED stuff out there being used as bike lights – but there not quite at the forefront of technology!

You might consider what is commercially available and applicable to the bespoke requirements of off road cycling.

Constraints are aplenty.
😉

As for cheaper lights. Not sure thats my field, quality will always come at a premium over absolute basics.
I prefer quality components that I'm confident will do the job very well, and having those components included into a good design solution.

The good thing is, there seems to be a light to fit most budgets now, which gets people out on the bike, when otherwise they might just stay home.
😉

@snotrag – fair enough. Not really though – for the size and weight they are fantastic, but 30W of Halogen for £80 was better light than £200 of LEDs.

Luminous your quite right – and as I said, as I dont actually do much night riding, then I'm not to experienced with the various systems available – certainly itsn ot bad thing with all this development going on and more people riding bikes can only be a good thing!

I really should get round to having a mess with one of our units and trying to fab a bike light – my problem is I know Zilch about battery technology, and everything I deal with runs off mains!

I work for a company that sells the most advance LED technology on the market – this is far more advanced than stuff your seeing in bike lights or automotive uses etc.

Given bike lights are using the most up to date LEDs produced by Cree/SSC how exactly is what you do more advanced? I'm fairly sure there aren't more advanced versions of these LEDs available to other companies which we haven't heard of. Or is there some other way by which you mean "more advanced"? I suspect from what you say that you're simply not aware of how bike lights are at the cutting edge regarding use of LEDs.

LED's are still only 10% efficient which means 90% percent of the power you put in is turned into heat and not light.

You're either vastly out of date, or don't understand the numbers. Given 100% efficiency producing white light is only ~250lm/W, and current LEDs manage well over 100lm/W, they're doing far better than that.

Yeah, LEDs are moving on, I'd still like to see more light and less heat, but wouldn't we all.

And when I'm saying "more light", thats only cos then we might run the LEDs at lower currents and stretch-out battery runtime
😉

Things probably will get much better in the future, but the nights are getting longer now, and as an earlier post pointed out, at this time of year, we're still benefiting from relatively mild nights and dry trails.

🙂

Given bike lights are using the most up to date LEDs produced by Cree/SSC how exactly is what you do more advanced? I'm fairly sure there aren't more advanced versions of these LEDs available to other companies which we haven't heard of. Or is there some other way by which you mean "more advanced"? I suspect from what you say that you're simply not aware of how bike lights are at the cutting edge regarding use of LEDs.

Apologies if I've come across in any way forceful, it wasnt meant that way! I am quite impressed with what seems to be out there in terms of bike lights, I havent really been following it much but this thread prompted me to do a bit more research and digging
Its hard to compare though as the stuff I deal with is for very different purposes/markets where there are very different aims aswell, obviously.

Part of the improvements that are coming with LED is not the actual LED units themselves (where CREE etc are obviously the leaders in this field) but in control and selection of them, and how they are manufactured into a light source…

I'm far from bad mouthing the bike light scene – Solid state lighting is something I've been learning about a lot recently through work and I've just been applying knowledge learned at work to my hobbie, and as you've said its really interesting that the bike industry is right up there.

All I'm saying is that there are other developments in other fields aswell that could become relevant to bike lights – 'Brightness' is already well covered, its Colour rendering, efficacy etc that matters now, and thats where these other developments such as remote phosphors will come in to play.

Given 100% efficiency producing white light is only ~250lm/W, and current LEDs manage well over 100lm/W, they're doing far better than that.

100% efficiency would be 680 lm/W if all the electrical energy were turned into light. If they can do better than that then they have a perpetual motion machine and free energy 🙂

100% efficiency would be 680 lm/W if all the electrical energy were turned into light.

Ooh, that's twice this week Simon has got the science wrong.

Only for a 555nm (greeny blue) monochromatic source. Given the lumen factors in the sensitivity of the human eye, and that the eye is less sensitive to other frequencies, then a 100% efficiency ideal white light source is what I said before (admittedly a white LED is far from a pure white source, with significant amounts of energy in the higher sensitivity part of the spectra, so the theoretical 100% efficiency for that is probably a little higher).

Part of the improvements that are coming with LED is not the actual LED units themselves (where CREE etc are obviously the leaders in this field) but in control and selection of them, and how they are manufactured into a light source…

I'm still not sure what you're getting at here – how other than using an optic can you improve the way you direct light out of them? I suppose you could use liquid cooling to keep the temperature down and so improve the efficiency, but that hardly makes a major difference.

I agree there are issues with colour rendering, but if you wanted to you could improve that with warmer coloured LEDs (which are readily available). I'm assuming your remote phosphors effectively do something similar but better by broadening and flattening the spectra? The trouble is that such things decrease the brightness, and whilst I'm sure for fixed applications you just throw more power at it, with bike lights you don't have that option – personally I'll take poor CRI and bright every time (it's not like I'm wanting to admire fine art using my bike light).

I don't disagree that there are developments which could be incorporated into bike lights – it's just your "far more advanced" I have an issue with, when bike lights still appear to be fairly near the cutting edge (personally I got some of the first ever batch of Cree XR-E LEDs, and had a working bike light using them within a couple of weeks of their commercial release).

aracer,

I guess the idea snotrag is on about is to produce a high brightness blue LED, and use remote phosphors to downconvert and tune the colour output.
A good way of choosing the exact colour rendition you want.
New "phospor like" materials (OLED's for instance) can have very high conversion efficiency and this may be higher than trying to do the converison within the LED itself. Only a guess as I don't know anyting about the manufacturing process of these LED's.

As for who will drive the development. I suspect it will be a variety of nich markets (like bike lights, "designer lighting", etc) along with the automotive industry.
I know the Merc, BMW, Audi, etc that make big heavy cars are looking into any way of reducing emissions in the fear that tough new euro legislation will hammer then for tax. LED's are more efficient, an so ultimately less fuel, and light units can be made lighter too. As an example I used to work for a company that was close to a big deal with merc to replace about 10 of their dahboard switches for a single "smart switch". They said the main driver efficiency (electrical) and weight.

I've got 2x 240lumen (well, a claimed 240) Q5 head torches.

Brightness is excessive, everything appears white in the center of the spot. You end up pointing the spot past what your looking at so the trails lit by the dimmer bit and can retain some contrast between mud/water/rocks/roots etc

aracer

I think you're the one who doesn't get the numbers. Lumens per watt is a measure of efficacy – the amount of light that an LED emits for a watt of input power. Efficiency relates to how much of the input power is turned into light, which for current LED's is about 10%.

Check out some datasheets.

So has the lumems per watt and general efficiency flattened out a bit in the last year or so? I know that Fenix still havn't got a 2xAA torch better than the one I bought 2 years ago (Q5 or something), I accept that batteries and optics are being optimised, but are we anywhere near 500 lumens from a pair of double AA cells with a few hours run time??

I think you're the one who doesn't get the numbers. Lumens per watt is a measure of efficacy – the amount of light that an LED emits for a watt of input power. Efficiency relates to how much of the input power is turned into light, which for current LED's is about 10%.

When you're in a hole stop digging.

You should also try reading what I wrote: "Given 100% efficiency producing white light is only ~250lm/W". I could have said "Given 100% efficiency producing white light is only ~250lm/W efficacy", but I didn't really think that would add much in the way of illumination (see what I did there?) You see you can convert between efficacy and efficiency quite easily by using the theoretical maximum efficacy as a divisor. ie if 100% of the input power is turned into light then you'll get ~250lm for every Watt of input power for a white light source if you need it clarifying further.

Where exactly does your 10% figure come from? As I said before, current white LEDs are better than 100lm/W efficacy, or to do the conversion, better than 40% efficient. Maybe you should check out the datasheets!

I'll dig a bit more if I may?

Where does your theoretical maximum figure of 250lm/W come from?

Well it's mentioned here (see "ideal white source") – any number is only ever an approximation, as it depends what you call "white light". Some more numbers here – I note the figure there of 331lm/W for white LED light, which is about what I'd expect for the reasons I gave before, though whilst I was GTFY I also found mention of Cree being through the 200lm/W barrier in the lab, so over 60% efficiency at turning electrical power into light. Also http://www.candlepowerforums.com/vb/showthread.php?t=250994 which has some discussion about this issue.

are we anywhere near 500 lumens from a pair of double AA cells with a few hours run time??

Depends on your definition of "a few hours". If 2 is enough, then not that far away at all – a pair of AAs has ~7Whr of energy, so you'd need 500lm at 3.5W. Cree is due to release an LED very soon which does 160lm at 1W and 500lm at 7W, so probably about 400lm at 3.5W. Given the 160lm/W in the lab press release was about 2 years ago, and recently there's been a press release about a 200lm/W LED (what you'd probably need to scale to 500lm at 3.5W) in the lab, then we're probably only a couple of years away. The only question then is how happy you are with a floody beam, given the die sizes are getting bigger and bigger on these more efficient LEDs.

Thanks for the info. Having, ahem, checked the datasheets of some now obsolete Luxeon K2 green, amber and red devices which I used previously against the white Luminus SST90 that I have just used to replace a Welch Allyn Solarc HID, I see things have improved dramatically, particularly for the white devices.

How illuminating…. 😳

2 questions… How does an LED actually work and why does it stop my Cateye computer from working when i turn my Hope Visions on?

aracer

Hmmm……I do see where you are going with your effciency argument but it doesn't feel quite right. Below is extracted from a Luminus thermal application note. Apologies for poor formatting!

Consideration of Optical Power
In the previous examples, for simplification purposes, it was
assumed that all electrical power was converted to heat. Obviously,
this is not the case and a portion of the input electrical
power is converted to light. The amount that is converted into
optical power depends on the color of the LED and the drive
conditions of the LED. Since different color LEDs have different
efficiencies and the efficiency of LEDs degrades as a function
of input power, each use case will be different. For the most
up to date information on the optical power emitted from
PhlatLight devices, please consult the latest product data
sheets.
Once the optical power emitted from the LED is known, it can
be factored into the calculation of junction temperature. The
thermal resistance equation (2) can be modified as follows:
(4)
Thus when optical power is taken into account, the demands
on the heat sink are reduced.

Variable Red Green Blue Unit
Current 8.1 8.1 8.1 A
Voltage 2.3 4.3 4.1 V
Optical Power 2.3 1.8 3.5 W
Power Dissipated 16.3 33.0 29.7 W
Tamb 30 30 30 ºC
Tjmax 80 120 120 ºC
R? j-hs 1.32 1.32 1.32 ºC/W
?Tj-hs 21.6 43.6 39.2 ºC

So, in terms of efficiency when comparing input electrical power to output optical power using Watts, the above efficiencies range from about 5 to 15%. Now I know these figures are for colours but I believe a white LED is based on a blue device with a phosphor doping so its probably fairly representative?

What do you think?

2 questions… How does an LED actually work and why does it stop my Cateye computer from working when i turn my Hope Visions on?

In response to the second question… I imagine that your Cateye computer is wireless? If so, your Hope lights are likely creating sufficient EMI (Electromagnetic Interfearence) to jam the comms to the computer. The most likely cause is the switch mode driver that is used to supply the LED with the correct current. The noise created is likely overloading the front end of the computer receiver.