Ultra low power / current (<250uA) LEDs

LEDs work fine at low currents--one of my gizmos used them at about 5 pA. They aren't very bright at low currents, though. You'll be able to see a high-efficiency LED run at 250 uA, if you're looking right at it, and if it's being used indoors. You won't be running any LCD backlights, that's for sure.

Cheers,

Phil Hobbs

You want an LED that is "rated" for min/max output at 250uA or do you just want one that will work?

Many, if not most, narrow angle super-bright LEDs will give sufficient light output for decent indoor visibility, especially behind a filter, at that current. Of course they cost a bit more, and you're not getting the blinding light you'd get at 20mA.

Best regards, Spehro Pefhany

Yes, they're for indoor use and for displaying an 8x8 graphic to be viewed from about 2 - 3 meters away.

So they don't have to be super bright or anything.

But it would be nice to have a wider viewing angle (angle of half intensity?) than having to look right at it.

Yes, I just want one that will work at 250uA.

They're for a indoor use to display an 8x8 graphic to be viewed from 2

- 3 meters away. So they don't have to be super bright.

But it would be nice to have a wider viewing angle than having to look right at it.

So you'd recommend me trying a super bright LED?

use an ultrabright

NT

Not necessarily. Check the data sheet current versus light output curve. Ultrabrights may suck at low current levels.

Could you live with a flash every second or two? That could give you a full power flash every second.

This doesn't compute. "Wider viewing angle" doesn't mean you don't have to "look right at it". In any case, you're going to have to look right at it, unless you mean having it show up in your customer's peripheral vision. The "Viewing angle" is the angle from 90° to the LED that its brightness (while "looking right at it") is 3 dB down, or maybe 6 dB down. Or maybe

Good Luck! Rich

Yea, I just meant that it can be seen when you at it. But not necessarily from right in front of it.

I could do flashing techniques, but I can't really add more components, so I'd leave that as a last resort.

I'm looking at super bright LED datasheets to see brightness vs current ...

What voltage do you have available? Could you put your 8x8 array of LEDs in series and short the ones you aren't wanting to illuminate, or even use some kind of DC-DC converter to get more current by using more voltage?

Chris

Hundreds of LED datasheets here.