led at low current

PS - Thanks for the LED's, James.

John

Sure. Surprised you could still find 'em after all this time!

I've been working some time on commercializing exactly this, the main problems being how to make zillions of something, and sell it with no margin.

It's a marketing / manufacturing thing.

(Once I had the idea the technical part was easy. The logistics aren't.)

Cheers, James

That is impressive and about an order of magnitude less current than the best ones available 5 years ago when I made my always slightly on night light torch.

What is it's quantum efficiency or lumens/W ? It may be getting close to the 200 L/W figure if that photo is in daylight.

Some batteries seem to have slightly better lifetimes with a tiny current draw than when left on the shelf.

There is a correlation between early failure and fingerprints left on the battery sometimes.

As stocking fillers at Xmas? I really don't understand why there are not more clear acrylic LED torches with an always on weak ambient find in the total darkness functionality. I guess powercuts are not that common.

The ones that glow in the dark using passive phosphor luminescent material are becoming more common.

Regards, Martin Brown

"James Arthur" skrev i meddelelsen news:vQwQk.3225$ snipped-for-privacy@nwrddc01.gnilink.net...

How about Not making millions of them? Find people who will pay more.

Maybe sell them at USD 200 a pop to the millitary as wayfinding ligthts and such - they will be very visible on the night-vision goggles. The people who camp are willing to pay a big margin too for something practical to mark the toilet-hole with f.ex. or light up the map/tent/compass with.

On a sunny day (Wed, 05 Nov 2008 20:56:04 -0800) it happened John Larkin wrote in :

That is very impressive at that current.

Becaue it sells? And those high efficiency LEDs are sort of a new thing, they may not know about it. Hey, I used the viewfinder of my digital camera to find my way in the dark.. LEDs are great.

On a sunny day (Thu, 6 Nov 2008 02:18:56 -0800 (PST)) it happened Martin Brown wrote in :

Why us a battery? A small supercap, with a small photocell in that clear acrylic housing would pick up enough energy to last forever.

1.5uA in 1 Farad say at 4V dropping to 2.5 V means 1.5V at 1.5uA. Q = C.U = i.t, so t = 1.5 / 1.5.10^-6 = 1000000 seconds, or 11.57 days. Once in 10 days the sun *ought* to shine a bit. Even a very small solar cell would deliver more then 1.5 uA to the battery.

Math right?

Perhaps the emergency flashlights are made the way they are because if you wind the current up by 1000 in your lamp you will still have a torch that is useless for anyone who actually needs a torch to see something. A single digit mcd source like this may seem impressive if viewed/ photographed in very dark surroundings but as your picture shows it doesn't even illuminate the book onto which it rests - all we see is a specular reflection of the source.

To add insult to injury running leds at such low current (densities) invites problems of current channeling with the possibilty that the leds will sporadically not illuminate at all.

I put all small parts in brown paper coin envelopes, and festoon same with notes. Works great.

That can be a problem. My strategy is far more intelligent: price things at huge margins, and sell none of them.

John

A less tiring strategy, for sure. ;-)

Best regards, Spehro Pefhany

--
"it\'s the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

The Brat taught me to use my cell phone!

John

At 1.5 mA it would be... calculates furiously... 1000x as bright! And battery life would go down to... ditto... 1700 hours! Few emergencies last that long.

Excuse me, but that observation makes absolutely, positively, no sense at all.

Explain?

John

Hey, this is cool:

As-is, the led, at 1.5 uA, is bright enough to find in the dark, and might barely save your life if you were lost in a cave.

But lick your fingers and hold it across the resistor, and it gets a lot brighter.

Then, stick it in your mouth and bridge the resistor with your tongue. You now have a very bright, hands-off, headlight sort of illuminator of variable intensity (well, if you have a versatile tongue[1]).

I realize that this is a brilliant patentable concept, but I hereby donate it to the public domain, for the illumination of mankind.

John

[1] Roughly half of the population can do tube-tongue, and the rest can't. Spare us the obvious tasteless follow-ons.

On a sunny day (Thu, 06 Nov 2008 08:59:33 -0800) it happened John Larkin wrote in :

Well, if it has to be mouth related:

On Wed, 05 Nov 2008 20:56:04 -0800, John Larkin wrote: ...

Because every time you need it in a real emergency situation, the batteries always pick that moment to die. ;-)

Cheers! Rich

I once had an idea to make the on/off button on Mag-Lites out of luminous plastic, so you could find it in the dark. Nothing ever came of it, though. )-;

Cheers! Rich

Some of the Avago HLMP-Cxxx green parts claim 520 l/w, which I think is about 70% efficiency, which I find hard to believe.

Imagine a *really* efficient light storage phosphor. That could change a lot of things. The strontium aluminate stuff is already good enough that people in villages, without power, could charge sheets of it during the day and get useful inside immumination at night.

John

I love that strategy--it's much more practical, business-wise. And you get to have a gang of great folks, and make cool stuff you can all be proud of.

I'd like something similar, with the added wrinkle of making things that save energy and other resources, that are affordable and fun, and making them widely available, so they can do the most good.

That's been my aim, anyway.

Cheers, James Arthur

Amen!

Regards, James Arthur

In fact, they die in betwwen emergency events - it just seems like they die at the latter time.

Larkin iss illustrating a multi-year app life of a coin cell.

RL