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Ultra low power / current (<250uA) LEDs

J

Jeepster

Jan 1, 1970
0
Does anyone know any LEDs that is rated for such a low current supply?
I'm unable to add extra components to make it work, so it would be
ideal to know if anything like that exists.

Thanks,
Jim
 
P

Phil Hobbs

Jan 1, 1970
0
Jeepster said:
Does anyone know any LEDs that is rated for such a low current supply?
I'm unable to add extra components to make it work, so it would be
ideal to know if anything like that exists.

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
 
S

Spehro Pefhany

Jan 1, 1970
0
Does anyone know any LEDs that is rated for such a low current supply?
I'm unable to add extra components to make it work, so it would be
ideal to know if anything like that exists.

Thanks,
Jim

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
 
J

Jeepster

Jan 1, 1970
0
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.
 
J

Jeepster

Jan 1, 1970
0
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?
 
Jeepster said:
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.

use an ultrabright

NT
 
I

Ian Stirling

Jan 1, 1970
0
Jeepster said:
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.
Could you live with a flash every second or two?
That could give you a full power flash every second.
 
R

Rich Grise, but drunk

Jan 1, 1970
0
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.

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
10 dB. what do I know?

Good Luck!
Rich
 
J

Jeepster

Jan 1, 1970
0
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
....
 
C

Chris Jones

Jan 1, 1970
0
Jeepster said:
Does anyone know any LEDs that is rated for such a low current supply?
I'm unable to add extra components to make it work, so it would be
ideal to know if anything like that exists.

Thanks,
Jim

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
 
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