LEDs as lamp replacements

Most of the output of an incandescent is IR.

I was only mentioning figures of lumens per watt of visible light output to explain that an incandescent achieving 17.1 lumens per input watt is nearly 7% efficient.

Put 100 watts into an incandescent that chieves 17.1 lpw. You get 1710 lumens. Each lumen is about 1/250 watt of "white light", not the 1/683 watt assumed by those claiming incandescents are only 1-2% efficient.

- Don Klipstein ( snipped-for-privacy@misty.com)

snipped-for-privacy@manx.misty.com (Don Klipstein) wrote in news: snipped-for-privacy@manx.misty.com:

What I meant was, might more heat be carried away by the convection in the argon fill, and be either conducted or radiated away at far longer wavelengths? I mentioned convection specifically to be clear I'm not talking about directly radiated energy.

I've managed unintentionally to get you to say that three times now. :) I'm not always quick on the uptake, but I try... what I'm getting at, is can any other evaluation result in that lower figure? I'm not convinced that taking only the lumens at 555 nm accounts for this. Lumens seem slippery enough if they depend on spectra and photopic sensitivity anyway.

Wikipedia again: "In photometry, luminous flux or luminous power is the measure of the perceived power of light. It differs from radiant flux, the measure of the total power of light emitted, in that luminous flux is adjusted to reflect the varying sensitivity of the human eye to different wavelengths of light."

I guess that much can be relied on. So try it this way:

Take a 100W incandescent, and a large ellipsoidal mirror to gather as much of its radiant flux as you can, throwing it to the other focus of the ellipse where a black painted thermopile awaits. The incoming light is passed through a dichroic filter at 700 nm to send the IR elsewhere and pass only the visible light to the thermopile. Assuming you get close to ideal light gathering for the visible wavelengths (and IR rejection), how many watts will be read from the thermopile?

I understand that photometric measurements abount, and radiometric ones are rarer, but that's what I want to look at, as without that grounding the rest seems most insecure.

As far as I understand what goes on there, around 10-15 watts is convected from the filament in a 100 watt "USA-usual" "standard" A19.

I believe some who are not aware that the lumen is a unit of luminous and not radiant flux, or not aware of visible wavelengths other than 555 nm having less than 683 lumens per watt, divided a lumen/watt efficacy figure by 683 to come up with incandescents being only 1-2% or 2.6% efficient.

I expect about 6.7 watts in the case of a 1710 lumen 100W incandescent, if the ellipsoidal mirror is a whole ellipsoid and 100% reflective and the dichroic filter passes all 400-700 nm light.

As for the rest, approximately or "educated guesses":

UV passing through the glass: .12% UV absorbed by the glass: .02%

Heat conducted/convected from the filament: ~13%

IR passing through the glass: ~60% IR absorbed by the glass: ~20.16% ("rounded oddly" to make figures add to

100%)

- Don Klipstein ( snipped-for-privacy@misty.com)

snipped-for-privacy@manx.misty.com (Don Klipstein) wrote in news: snipped-for-privacy@manx.misty.com:

I was trying to keep the lumens out of this entirely, but I'll buy it. :) It makes me wonder what the fuss is about actually. While it's better to get more efficiency, it seems that incandescents aren't so bad we need to consider banning them, we just need to think more about what source we use for a given task. As for the case to ban all but halogen types, how much might be gained? With IR reflection to make them keep the tungsten hotter for a given input, we get more light, but even so, is there that much difference? Enough to say that they stay and standard incandescents go?

If LED's ever get a spectral match for a small efficient low-volt halogen, at least the choice will be easy.

Sunlight at high noon is considered "cold" lighting, even though the temperaure of the light is at its highest. It's just semantics.

I doubt anyone prefers indoor lighting at 6500 K during a summer night. It's stark lighting regardless.

Disagree. I think the bleakness Dickens refers to in this example is unrelated to color temperature.

Bert

I suspect that your liking of odd colour schemes, harps back to distant memories of your early life on Gallifrey, with its twin low luminosity suns, and before you became 'lost' ... ;~}

Arfa

"Arfa Daily" wrote in news:WSdli.34381$ snipped-for-privacy@newsfe1-win.ntli.net:

Yes, yes that would be it. >:) The high council didn't build the Panopticon for nothing, you know... All those lights in the dark, hypnotic.

"Albert Manfredi" wrote in news: snipped-for-privacy@news.boeing.com:

That was the point. Don't you see? That's exactly why it isn't the colour temperature that really defines our reactions at all, it's the context.

"Albert Manfredi" wrote in news: snipped-for-privacy@news.boeing.com:

Semantics? As in the usual current usage meaning 'empty meaning, splitting hairs'? That's only true if you ignore context. That's what gives it meaning. No-one in their right mind would consider high noon in the outback to be 'cold' either literally OR figuratively.

OK, I'm following all this - just about, I think. So let me now throw in a slightly new set of questions. Back to LED halogen substitutes. Some distance back up the thread, consideration was being given to losses in the control circuitry for the LEDs. So, the first question is, just exactly how are these things ballasted ? The reason that I ask this is that I was in an electrical cash and carry warehouse tonight, and I picked up a couple of LED-based GU10 replacements to have a look at. I didn't count the actual LEDs, but I'm guessing at about 15 or so - let's say 15. Let's also say that they are bluish types and let's guess at a forward drop of 4 volts. With them all in series, that's going to be around 60v DC that's needed to run them.

Now, these lamps were of exactly the same dimensions as a standard GU10 lamp, with the same 'nail head' pins, set in the identical ceramic base.

240v AC rating, stated on the packet. The glass 'cone' was exactly the same as on a standard GU10, and it appeared, as far as I could see, that for the most part, it was filled with the LEDs, which looked like 5mm types, and their support plate. So that leaves very little space for any drive electronics - certainly not a switch mode PSU, or even for a smoothing cap on the end of a simple reccy / resistor combination. Not that there would have been room even, for a resistor of a sufficient power rating to handle this kind of drop.

Next question. There were two types on offer, one rated at 1 watt, and one at 1.3 watts, both with a quoted lifetime of 50k hours. So what exactly is being said here ? Is that 1 watt input from the mains supply, or 1 watt used by the LEDs or 1 watt of visible luminous output power ? A website that I looked at quoted the output of a 0.62 watt one, at 20-30 l - I'm assuming that to be 'lumens'. If correct, and not a misprint, that seems to be a piddling amount compared to the 950 lumens quoted for an incandescent 240v

50 watt GU10, and yet the text suggests that they are only 'slightly dimmer'. It also says that these lamps give off almost no heat, and that they consume only around 10% of the energy of a conventional equivalent halogen GU10. So for a 50 watt type, that's about 5 watts, suggesting that around 4 watts is lost in ballasting ??

Setting aside the issues of colour temperature and CRI, which I am sure will shortly be overcome, it seems to me that these halogen replacement lamps are even now on their way to bettering CFLs in that they are already exactly the same pattern as the lamps that they are replacing, so must have sorted the ballasting problem. And yet there are no plans to phase out the incandescent version. This flies directly in the face of the proposals to ban standard incandescents, when the advocated replacement technology (CFLs) is far from being a satisfactory replacement, on several counts.

Arfa

You may well be right. But I wouldn't rely too heavily on the colour accuracy of a long exposure :-)

Laurence Payne wrote in news: snipped-for-privacy@4ax.com:

I guess not. Probably weighted by gamma correction or something. Worth trying a few different timings to see what happens though. Maybe with some small faint diffused blackbody source in frame as a reference.

Apart from correction added, there is no reason for colour to fail, because photons are quanta, each one will be treated the same by filters no matter how few or how many. The real danger is overexposure saturating any of the filtered sensors.

Lostgallifreyan wrote in news:Xns996B87D296F6Ezoodlewurdle@140.99.99.130:

Sorry, that's daft. It's modelled. :) But if you have enough the camera adds them up and the values can clip, which amounts to same thing.

"Arfa Daily" wrote in news:Fweli.25909$ snipped-for-privacy@newsfe5-win.ntli.net:

There might.. First, it needs to control a fixed current, and an efficient power converter can be tiny, flat, like this:

That's 95% efficient at converting voltage ranging from 5~32 VDC into a current source that can manage up to 7 LED's in series. A converter from

240 VAC to low volt DC can be had with similar efficiency (I hope), to feed what I already have. Ideally I can find a single module that does the entire power conversion at 95% or better.

That one sounds like a marketing hype. The first thing is that it has lots of standard 5mm LED's. Avoid like the PLAGUE, seriously. All that voltage drop, and no cooling to speak off, what kind of thermal coupling can be had for a 5mm LED?

The ones to look for are the Cree and Luxeon types. The easiest way to look for them is a single emitter, or at least very few of them, with high output claims. Look into one (unlit!, they WILL damage your eyes if you do that to lit ones at close range), amd you'll see a distinctive fluorecent dayglo green yellow cast to the phosphor unlike the chalky phosphors of weaker white LED's.

Re wattage claims, it's hard to say, without evaluating all the evidence you can find together. In short, a lamp that needs several emitters to manage 30 lumens is a joke, when you can cheaply get a single emitter that puts out >200 lumens with 1 amp pushed through a voltage drop of around 3 volts.

I think the ban is 'being seen to be done' kind of reaction. It's got more to do with trashing an icon known for inefficiency, but there are better ways to make people change than all-stick-no-carrot.

If governments really want to reduce power consumption I think they should be subsidising the public to buy computer mainboards based on Nehemiah CPU's and such. Turning a domestic computer into a fan heater just to run Windows Vista as a private office is a sick joke! Far more worrying than a few lightbulbs.

*Continuous spectrum* light is certainly an advantage for most work or hobbies. Which is where many so called high efficiency light sources fail.

--
*Marriage changes passion - suddenly you're in bed with a relative*

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

I don't have a problem with a switch mode converter being small - just with the front end to get from 240v AC down to some realistic DC level, also being small. I work with switch mode power supplies of every size on a daily basis, but I've yet to see the front-end electrolytic, which would fit in any space that was closed in so that you couldn't see it, on one of those GU10-s.

As far as 5mm LEDs needing a lot of cooling, I've played with all manner of superbright emitters from white thru' traffic light colours all the way to red, in 'standard' packages, and never found cooling to be especially a problem. Although these are not hyper bright Luxeon-style emitters that I'm talking here, which I know *do* require external cooling, They are never-the-less still bright enough to hurt your eyes, and light a dark room up quite well. Where I have found theremal issues, is in the current control circuitry, even if just a simple resistor.

I agree that the potential ban on incandescents is just a government knee-jerk reaction, brought on by hysterical claims from their 'scientific advisors' that these things are going to bring about the end of the world, but not if we use the marvelous direct replacement CFLs instead (ha!) ... I was just interested what others' opinions on this were.

So, I'm still no closer to knowing how the multi-LED GU10-s or even single LED types, are actually ballasted for 240v AC use, and whether the claim that "these lamps put out almost no heat at all" is at least basically true overall, in which case the ballasting arrangement must be *very* efficient, or refers specifically to forward IR radiation in the same direction as the light, which obviously will be minimal, or is a fundamental marketing hype lie. Maybe I'll just buy one, and see if I can figure out just what its guts are.

Arfa

"Dave Plowman (News)" wrote in news: snipped-for-privacy@davenoise.co.uk:

Well yes, but that's exactly why I'm advocating the new LED's Their spectra ARE continuous. They dip a bit in the breen, and the far red, but they're no-where near the gross discontinuity seen from a CFL.

"Arfa Daily" wrote in news:N3qli.26109$ snipped-for-privacy@newsfe3-win.ntli.net:

I'm not sure yet either, if it has to be really tiny. I'd allow for the mains to low-volt part to be done in something about matchbox size, not sure about smaller though.

The point with the 5mm LED's is that don't need much cooling, because they don't put out much heat. If they did they'd burn because they really ARE terrible for thermal coupling, thus proving that any claim to get high output from such isn't a good claim. Not even the best LED's are that efficient.

I agree that some strong output can be had but it's usually directional, and close to monochrmatic. As soon as that energy is spread in a broad spectrum by phosphor, you need a very strong source of shortwave light to pump the phosphors, and the clue is a heatsink, or a diode that is clearly made for mounting on one.

One thought, maybe not wildly helpful: I remember being suprised as a kid by a NiCd charger that was as small as the 4 x AA battery pack. It had no transformer. It had a rectifier and current limit resistor and did not run hot. I guess the unhelpful part of this observation is that it didn't have to provide one amp of current. On the other hand, power conversion needs to provide that amp at low volts, so as it's a lot less than an amp at 240V, the smoothing capacitor might not need to be large. There might be efficient circuits that don't even need one.

Points well taken, but I'm gonna reserve judgement at this time, until I can find out how it's done. If the whole string of LEDs is in series, and they are not super high power types requiring an amp continuous, then we could be talking just 150mA or so. Alternatively, we could be talking pulsing the whole string at an amp or so. I really think that I'm going to have to buy one, and attack it with the Dremmel ... I can't think that I have ever seen any kind of switching supply that works from low frequency AC input power, that doesn't have a smoothing cap. It's hard to see how it could be done without, unless you employ 'electronic' smoothing using a regulator with feedback, as I have sometimes seen done in 'professional' equipment, but even then, you're going to be talking circuitry that is as big as a smoothing cap of as little as 22uF at the required 400v working, would be.

Looking at the pictures of the Cree GU10 replacements, it's hard to say if the enclosure is a 100% ringer for the incandescent version, but even if it's not, it still looks pretty tight to get any kind of 'conventional' switcher squeezed into.

Arfa