Help: need to run 2.8v led using 2.4v

Discussion in 'General Electronics Chat' started by Louie101086, Sep 4, 2008.

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  1. Louie101086

    Thread Starter Member

    Feb 17, 2008
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    i am trying to run 4x 2.8v 3mm white led lights using only 2.4v(2x 1.2v rechargeable batteries) is it possible and if so what do i need i have already goolged and havent come up with much
     
  2. SgtWookie

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    Jul 17, 2007
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  3. Louie101086

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    Feb 17, 2008
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    is that the only way because i see that the project was old and made in 1999 its 2008 maybe there is a new technique you might know of
     
  4. Louie101086

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    Feb 17, 2008
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  5. Audioguru

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    Dec 20, 2007
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    Garden solar lights use a voltage stepup circuit. some use the Joule Thief circuit and others use only an inductor and a couple of transistors.
    There are many garden solar lights circuits on the internet.
     
  6. beenthere

    Retired Moderator

    Apr 20, 2004
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    Simply a neater (and more expensive) form of the joule thief SgtWookie linked you to.
     
  7. Louie101086

    Thread Starter Member

    Feb 17, 2008
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    i rather build the one that cost more because its smaller and space is limited in my setup please help
     
  8. thingmaker3

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    May 16, 2005
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    The newer & more expensive version is larger, not smaller. "New" does not mean "better."
     
  9. Louie101086

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    Feb 17, 2008
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  10. thingmaker3

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    It's the same circuit as Sgt Wookie's link. Uses a different BJT and fatter insulation on the wire.
     
  11. hgmjr

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    Jan 28, 2005
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    The one you have linked to appear to be identical to the one that sgtwookie cited.

    hgmjr
     
  12. Louie101086

    Thread Starter Member

    Feb 17, 2008
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    so could i do the project wookie showed me using the different parts
     
  13. thingmaker3

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    May 16, 2005
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    Yes. Or the original ones. Or a third set with similar parameters.
     
  14. SgtWookie

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    Jul 17, 2007
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    Gee, I can hardly believe you're knocking the circuit I sent you to.

    Sure, it might be a few years old. No, it's not the most efficient design on the planet. But if you had looked at the entire page, you would have seen that one can indeed be built very, very small, and very, very inexpensively.

    Go ahead and buy that fellow's kit for $10 if you like. But if you shop around, you can buy enough materials to build dozens of Joule Thieves for that much money.

    It looks like the kit the fellow's selling is a spin-off of a circuit that was published in Electronic Design Ideas awhile back. That one consisted of two 2N3904 transistors, five resistors, a capacitor and a 1N4148 diode plus the LED. This fellow eliminated the diode and a resistor somewhere.

    You're free to use any design you like. If you're looking for small, cheap and easy to build, the Joule Thief is hard to beat.
    [eta]
    The BC549 transistor in Big Clive's Joule Thief can be replaced by a 2N3904; they're really quite similar.
    You could use a great big toroid like they used on the Evil Mad Scientist if you want, but that's really overkill, and will make your project much larger than it needs to be. The small ferrite beads work just fine; they simply cause the circuit to oscillate at a much higher frequency than the large toroids would.

    I bought a bag of ferrite beads from a local surplus shop for a quarter. I had a spool of 34 gauge wire on hand, along with an assortment of resistors and transistors. I built several of them, and I needed to keep them quite small and lightweight. They're used to align the rotor blades on a helicopter.
     
    Last edited: Sep 4, 2008
  15. Louie101086

    Thread Starter Member

    Feb 17, 2008
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    i dont wanna buy his i like the one you showed me but i need one that will last long because i will be installing this on a xbox 360 controller so i want it to last awhile and not suck all energy in an hour will the one you showed me last or is the other guys better
     
  16. thingmaker3

    Retired Moderator

    May 16, 2005
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    Louie, your question has already been answered. Twice.

    Just build your circuit.
     
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