the everlasting LED

Thread Starter

The Ignorant Artist

Joined Jul 31, 2012
5
Hello all,

I'm new here and new to electronics in general. I am an artist and architect very humbly asking for your advice. If this type of inquiry is not welcome on your forum, I apologize.

I want to create a completely sealed block of resin internally lit by a battery powered LED circuit that lasts as long as is currently possible. I'm shooting for years. It should be about the size of a beer can and provide enough light to read by if held very close to the page. Is this possible? I have found examples of this being done in the past but with no stated life expectancy. How could I roughly calculate this? How long do you think an optimally designed circuit might last?

potential problems:
-I understand the heat damages LEDs over time. Encasing the circuit in resin may accelerate this as the plastic will inevitably retain the heat generated by the light. Is this actually a problem? How might I mitigate it?
-From what I have read, LEDs never truly burn out but rather slowly dim. For my purposes, it would be best if the bulb died fairly suddenly. Could I create a circuit that switches off or self destructs when a specified low level of power consumption is reached?

Any comments would be greatly appreciated. Thanks!
 

Markd77

Joined Sep 7, 2009
2,806
I wouldn't worry about heat or the LED fading over time, if you all you have is a beer can with batteries in, it will have to run at very low power levels.
Just as an example, you need 3 AA cells to give enough voltage for a white LED.
Lithium cells are around 3000mAh so with 3 cells and the LED at 1mA (fairly dim) it will run out after 3000 hours which is about 4 months.
Put 12 cells in there and it will last 9000 hours (about a year) at the same current.
 

tracecom

Joined Apr 16, 2010
3,944
You could add an inertial switch that turns the LEDs on when the "can" is shaken, and a timer that keeps them on for a few minutes, and they turn off until the can is shaken again. This would prolong the life of the batteries. In addition, you might embed a small solar cell inside the acrylic to recharge the batteries.
 

KJ6EAD

Joined Apr 30, 2011
1,573
Four 19Ah lithium D cells would give you 8mA for more than a year (24 hrs day) and that's enough current to provide ~5 lumens (enough to comfortably read) using the best available LEDs.

Is a non-contact rechargeable system an option?
 
Last edited:

Wendy

Joined Mar 24, 2008
22,239
Four 19Ah lithium D cells would give you 8mA for more than a year (24 hrs day) and that's enough current to provide ~5 lumens (enough to comfortably read) using the best available LEDs.

Is a non-contact rechargeable system an option?
I like that, basically a hidden coil that recharges the batteries with no electrical contact.

There is an old concept call throwies where you light up LEDs with no battery included. They couple into a pulsating magnetic field from a coil hidden under a blotter. Just put the LEDs on the surface of the blotter and they glow, with no apparent power source. A common theme is to make them in the shape of bugs.

http://www.instructables.com/id/LED-Throwies/

Another different kind of throwie is a LED with a watch cell battery and a magnet, you can stick them to vehicles and other metal surfaces. It is a form of art unto itself.
 

BMorse

Joined Sep 26, 2009
2,675
A "joule thief" circuit to drive the LED (I have successfully driven 9 white LED's off of 1 AAA battery with a joule thief circuit) and an inductive charging unit to charge an internal battery/capacitor bank might make this a pretty interesting project......
 

KJ6EAD

Joined Apr 30, 2011
1,573
Pretty expensive...$20 each...
That's right, it would be a $100 light. This is the "is it possible?" stage of development, not the "how cheap can we make it?" phase. The OP specified only self-contained longevity, size and luminosity.
 
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