What current is drawn by LED mains night light?

What is the point of using blue in night lights ?

Blue light will inhibit the melatonin production, so it may help wake early in the morning.

However, if the intention is to continue sleeping, after being awake for while in the middle of the night, blue is a bad idea.

OTOH, if the intention is to maintain night vision (scotopic vision), red light is used e.g. for reading maps while navigating, since rods do not respond to red and hence does not destroy the dark adaptation.

For best subjective effectiveness, the spectral peak (683 lm/W) at moderate to high intensity levels is at 555 nm (yellowish green), but for a dark adapted eye, the sensitivity peak (1700 lm/W) is around 507 nm (bluish green). In fact, the scotopic sensitivity is over 685 nm for 445 .. 555 nm.

Paul

crap.

The other side of that coin is that if it doesn't interfere (as much as one that doesn't) because it's dithering, who cares?

e is

Also, after a decade of non-use. Neon lamps are actually filed with Ne-He mixture, a lot like laser tubes used to be. That gas mix has the advantage of low breakdown (high ON time in the AC duty cycle), but the He will diffuse out in time.

Big highvoltage neon installations will light even without the helium in the mix.

It is possible in the high wattage LEDs that the active die temperature is relevant to denaturing the phosphor and/or the clear plastic. It is hard to deny that that pictures at the URL cited elsewhere in the thread do show a phosphor with a dark shadow over the square die area when illuminated with a secondary source. It seemed like the exerimenter had driven them for many hours at constant voltage which is to say the least more than a bit unkind.

I suspect as someone pointed out a combination of inrush current, mains transients and high frequency noise is killing them. I too find it hard to believe that they would degrade so quickly in a nightlite application unless something was seriously wrong with the design.

Regards, Martin Brown

On a sunny day (Thu, 24 Sep 2009 22:59:02 +0000 (UTC)) it happened snipped-for-privacy@manx.misty.com (Don Klipstein) wrote in :

I accidently shorted the series resistor of a white LED, It must have gotten some amps... The phosfor became a darkish mold. Accelerated life time test :-) And of course no light from it. But did not measure short or open! Did I take a pic of it? Maybe, but where is it?

Easy for somebody ELSE to repeat the experiment though.

Hmm. I suppose I missed looking at that link. Different situation, though. Most of the phosphors I've worked with are formed from about

Indeed.

Oh, well. I don't think anyone here knows much more. I am curious and I suppose I'll just try and keep aware if something else crops up about this.

Jon

I should have added, though, that I've made a couple at around 900C and 1000C. But in general, they are made at temperatures from that range to well above it.

Jon

I'd be surprised if they do by much unless the intensity is getting to the point where two photon processes can be significant.

I was surprised how much abuse an LED can stand. The old red ones are fun to dunk in LN2 if you have some around. QE improves remarkably at low temperatures and they usually survive the thermal shock.

Regards, Martin Brown

Both fluorescent lamp and LED phosphors do degrade with use. As was pointed out by John Waymouth way back at LS:5 in York in 1989, effects we do not observe during normal "laboratory" time scales, can still have a big impact on the performance of lamps, that last from 10,000 to 50,000 hours.

Yes, local heating because of inconsistencies. Ok after turn-on, then gets hotter and hotter in that spot while the rest remains ok.

LEDs need to cost must less than a penny a pop ;-)

Also, greed can set in. I remember guys from the Belgian Ford factory griping over a switcheroo that management (they really meant engineering I guess) pulled on them. A new water pump was prescribed because it saved half a buck or so. After that, problems galore. To the point where if someone wanted to buy a Ford some of his friends would say "Look underneath the engine and make sure it doesn't pee."

It is, but there's always penny-pinchers at work. Folks who want to get the cost just a smidgen below the competition.

I don't know either why (technically) deterioration happens but have seen LEDs dim over time. There has to be a reason why major manufacturers such as Philips educate the public about lifetime limits and degradation of their LED products:

Back in my university days we could bicycle over to the Philips lighting research center and watch rocks falling upward :-)

It was right in town.

BB seemed to have had some massive foundry problems after being integrated into TI. To the point where they simply could not ship product and guys like me had to blacklist them for new designs for a little while. But they fixed it.

Maybe Philips (not NXP) would be a good source to probe further. If they are still like they used to in the 80's they research every technological effect to death, until they really know what's happening. Not sure if they'll publish everything through. And they have success on their side. For example I have never seen such fast-starting and long-lasting CFL as their Marathon series. So, we bought the almost exclusively.

P.S.: This story ran today in our local paper. Verbatim, they seem to all copy from each other ...

Interesting that they already use past tense when discussing the CFL.

Okay. I'll take your word on that. Still, I cannot imagine any of reaching temperatures where the phosphor would sustain damage. These things are, for the most part, high temperature ceramics. And in three months time? No, I need to see the mechanism.

Well, no one can take away from you these facts. But as far as I know, it's easier to let the major producers produce the stuff and get it from them. Shop around for discounts, yes. But set up your own combustion process? I'd have imagined it would be cheaper to just find a discounted source. Maybe what you mean, here, is that they are buying up flawed materials that didn't turn out right in the first place. But even then, they are likely to be ceramic flawed materials and just as stable, even if they don't perform right at the outset. I think they'd maintain their lousy performance for more than 3 months. They are ceramics, basically. Even when they are garbage.

Phosphors will decline in performance over time, no doubt. If exposed continuously, without stop, they will decline to something like one half their early performance in a few years. Years. And continuous. This 3 months of occasional LED light is... well, crazy-minded. I'm struggling here.

But we are just pushing back and forth about stuff neither of us knows the truth about. I have made some of this stuff in the modest means available to me (tubular furnace.) And I've been using such materials for a long time, with xenon flash lamps. Their response does degrade and it can be quenched by other materials, but I've never seen anything go to a flat zero and even when I've seen less degradation (which happens, of course), it's never been like 3 months unless there was something else happening to the material (some known quenching process.)

Well, they certainly exist. It's just not a mechanism I know about, here. Which is why I was asking if anyone knew what exact phosphor was involved. As I think I said already, I gather no one here knows. I'll keep my eyes peeled, though. Interesting to consider, because if such phosphors are intruding into the marketplace on a large scale then I probably need to know about it so that I can devise a way to defend against the possibility.

Did you read that? I didn't even find the word "phosphor" in there and couldn't find a discussion about it as a failure mechanism. Did I miss it?

:)

Do you know what the mechanism might have been, though? I've found a few papers describing the same behavior, but none of them providing a mechanism by which it could occur. They were as mystified as I was. I'm trying to understand how it occurs -- what interactions take place with the 3D geometry and space charge distributions to explain it. I'm still in the dark.

Philips has a serious attitude problem about "Americans," which is consistent with some nothern German attitudes, broadly. They don't really see us as well educated, meticulous, able to follow or develop scientific processes, or worth much of any effort there. It will be like pulling teeth, I imagine. But I can try.

Their Marathon is well-designed, it seems. Like I said, I've only had two failures so far and they both appear to be failures from the loss of the emission mix that vaporized onto the glass tube. In taking them apart, their parts were high quality and still working so far as I could tell. And construction looked good, as well. The only comparison, design wise, was a note that there were numerically more expensive parts in it, which meant to me they were pinching pennies less than the Costco brand (ConservEnergy, memory serving) that I had used and from which I'd had so many dangerous failure modes illustrated.

Jon

I need to keep a focus on what was said on that web site. We are talking here about night lights and three months and going from "useful" to "dead." No one (not me, anyway) has argued that phosphors don't degrade over time and exposure. But not like that for any I've been exposed to. Like Martin mentioned, organic/laser dyes may be an issue here. But rare earth phosphors? Nah.

Jon

As I understand the issue, the epoxy package clouds up and the phosphor deteriorates, the latter issue being the same as in a fluorescent lamp.

Note that Philips did not give a price, and the L Prize is only for 60-watt equivalent lamps. 900 lumens for 10 watts is quite an achievement, but if the price is not less than $5 consumers will not buy it. And, as opposed to other types of lamps, the cost of an LED-based lamp will rise significantly with light output. A 100-watt equivalent, producing say 1700 lumens, will cost 50% to 75% more than the 60-watt equivalent. (This does not mean that the selling price will reflect the same cost difference.)

Fluorescent lamps sans the electronics, so far as my experience goes, usually degrade due to a loss of the emission enhancing materials (thermionic) which wind up plating on the glass surface and removing themselves from where they do some good -- at the point of thermionic emission. I have yet to see a fluorescent lamp go bad because of the phosphor dust simply stopped working (unless there was some sudden shock which removed large amounts of it from some part of the interior surface.) [I imagine it would be kind of dangerous to keep them running in that case, too.]

I have no idea what near molten LED-epoxies (if things were to get that hot) might do to rare earth phosphors. Because I've not experimented with those epoxies, so far as I'm aware. So it might have a quenching effect. But it might not.

The reason I say "might not" is that I regularly mix phosphors with epoxies in order to bind the phosphors and they work fine (with suitable epoxies, of course) in target-use temperatures sometimes exceeding 450C on a regular basis. There are many other and well known reasons why LEDs fail and which I think explain almost every case, not to go grasping at this one as a significant source without even knowing a mechanism.

Jon

Fluorescent lamps certainly do not suddenly stop working because of their phosphors. However, the phosphor in all fluorescent lamps slowly degrades with use.

The published lumen depreciation curves for fluorescent lamps are not the result of evaporation from the electrodes, because the results are the same for lamps is independent of lamp length for lamps using the same technology, operating at the same current and that have the same diameter.

When the phosphor is removed from old fluorescent lamps, the depreciation in performance of the phosphor powder can be measured - and the glass of most modern fluorescent lamps is clear once the phosphor has been removed.

I haven't heard about three months either, but over a year of constant use, yes. There were some that degraded to the point where they weren't all that useful anymore.

No, but they talk about degradation, lifetime etc. To me as an end-user or a guy who designs this stuff in it doesn't really matter what causes degradation. I only want to know how bad it is for a particular product.

No idea. All I was told in the BB case was that some sort of "transfer" had gone wrong. Which can mean all sorts of things, including some guys leaving who knew the intricacies of certain recipes. Like the butcher in town who had to discontinue a few sausage products when my great-grandma passed away at age 98. He just couldn't get the spices right like she could.

Now, now ... I am one of those Teutons :-)

Actually I had some really good exchanges with NXP and that's almost all former Philips guys. I told them their web site is stinko and they fixed it. Despite the fact that I live in America.

They have another advantage in that their former colleagues at NXP make ligting control chips. And from Aachen (lighting center) to Eindhoven (semiconductor R&D) it's only two hours by car, probably even less by train.

Yeah, and after some serious disappointments with CFL even the willingness to pay five bucks may not be there, at least not with the masses. Not if you can get a decent 60W replacement bulb for 69c.