the everlasting LED

Discussion in 'The Projects Forum' started by The Ignorant Artist, Aug 18, 2012.

  1. The Ignorant Artist

    Thread Starter New Member

    Jul 31, 2012
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    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!
     
  2. cork_ie

    Member

    Oct 8, 2011
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    Last edited: Aug 18, 2012
  3. Markd77

    Senior Member

    Sep 7, 2009
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    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.
     
  4. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    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.
     
  5. KJ6EAD

    Senior Member

    Apr 30, 2011
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    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: Aug 18, 2012
  6. Wendy

    Moderator

    Mar 24, 2008
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    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.
     
  7. Markd77

    Senior Member

    Sep 7, 2009
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  8. BMorse

    Senior Member

    Sep 26, 2009
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    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......
     
  9. KJ6EAD

    Senior Member

    Apr 30, 2011
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    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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