Not the brightest LED but "low low low low low low"

[jan.]

Hi there:

I'm just be curious about the possibility to make a small keyring pendant with a glowing or flashing LED in it.
I have seen a lot with tritium or gitd, but tritium is not bright and GITD needs charging up.
This would be an exelent keyring locator in the dark.
This glowring must have an very long runtime on an battery smaller than AA with no on/of switch on it.
The LED must be seen from every angle. But glow or flash must be a little brigter than tritium.
Flashing every one or two second saves batteries and gives a longer runtime, but howlong can an small led runs on one AAA battery?
Battery change or charge to frequently would be an problem I think.
I never seen one at internet and I can not make one by myself I think.

Thanks...Jan.

 

[bstrickler]

Driving an XP-G @ 1 miliamp can get you 10 days constant with a single AA. To add on battery life, one could always add a photovoltaic switch (I don't know the proper term, but it's a switch that opens/closes based on how much light it recieves), like the ones on night lights. That should increase battery life a good amount, depending on where you leave your keys. Mine are usually left in the open, so the life would actually be longer than someone who keeps theirs in a drawer.

To make it visible from almost any angle, you could get a bit of plexiglas bar stock, and etch it, before you mount it on the LED.

~Brian

 

[paulr]

There is or was a circuit called LM3909 that would blink a red led at 1 hz for 3 months or so on an AA. If you're using one of those tiny tritium markers, you could move up to a tritium glowring. Those are a lot brighter than the little marker vials.

 

[jan.]

I think the easyest way would be modding an AA or AAA flashlight with an low current blinking LED.
Howlong would be the runtime? Minimum 3 months or longer?
I don't know nothing about electronics.

--Jan.

 

[TorchBoy]

To add on battery life, one could always add a photovoltaic switch (I don't know the proper term, but it's a switch that opens/closes based on how much light it recieves), like the ones on night lights.

The opposite of a light dependent resistor. I've got a feeling I should know what it is but it's too late for me to think of it. The normal arrangement to reverse an LDR's action results in a transistor conducting the whole time.

 

[JohnR66]

Use a CR2032 coin cell and indium gallium nitride LED (blue, true green or white) in series with a 1K ohm resistor.

At such low currents using any LED would be below its peak efficiency. Using a power LED makes no sense. Use a high brightness 20ma LED.

 

[2009Prius]

Buy this
http://www.dealextreme.com/details.dx/sku.824

and then do a mod maybe? Good luck!

 

[Lumenz]

I disagree about tritium not being bright enough to be a keyring locator. I have some of the Merkava I and II tritium glowrings and they work great for finding my keys in the dark.

I have had people comment on the glow from my keychain before the sun is below the horizon. I think that if you purchase one of the Merkava glowrings, you will be pleasantly surprised at how bright they are at night.

 

[TorchBoy]

Buy this
...
and then do a mod maybe? Good luck!

Please don't hotlink images. See rule 3.

People have mentioned it's possible to use those things with just one of the coin cells to get a very dim light that lasts ages, and of course you'd still have the second cell to use.

 

[2009Prius]

Please don't hotlink images. See rule 3.
....

Oops! Thanks! I have removed it.