Joule Theives

Discussion in 'The Projects Forum' started by takao21203, Sep 8, 2015.

  1. takao21203

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    Apr 28, 2012
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    Last edited by a moderator: Sep 11, 2015
  2. DerStrom8

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  3. takao21203

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    No but the circuit has things in common with a Tesla coil, particulary the secondary is open on one end.
    And the circuit is increasing voltage many times, far beyond the transistors breakthrough voltage.

    Ive got large inductor and different transistors want to see if it can be improved.

    What stops the voltage from rising to infinte when the ground is floating? Things like small capacitance between the windings.

    Specific to a Tesla coil is just the spark gap, but I was wondering how I could produce high voltages without a spark gap or large complicate circuits or special parts.

    2n3906 used has max voltage of 30V but I can reach about 100 with 2x AA batteries.

    In a joule thief the ground isnt floating so the voltage you can get out is much lower, and its accross the primary or the transistor.
    So its not a Joule Thief either.
     
  4. DerStrom8

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    While that may be true, it is not a Tesla coil. A TC is an air-cored resonant transformer. A Joule Thief is not. And for the record, a spark gap is not required or used in a solid state Tesla coil. There are quite a few differences between TCs and JTs, and their theory of operations are fairly different as well.
     
  5. Art

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    Sep 10, 2007
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    Obvoiusly, for the particular design, you can burn yourself.
    MrCF pulls away each time it arcs to his finger,
    and just as obvious, you can touch it without burning yourself.
    MrCF comes back for more.

    A real one is as simple as it gets. An oscillator achieved with a spark gap and capacitor, and a tuned coupling. Funny how they have become complicated so the spark gap doesn't run away.

    It must have been nice to vitrtually own the entire spectrum. I gather you get harmonic noise all the way into VHF?
     
  6. Art

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    Takao, to get more action out of a joule theif cycle current in both directions behind the transformer with a H bridge or single chip Texas Instruments SN754410 instead of pulsing in one direction with a transistor.
    So something like a 555 for an oscillator, a flip-flop to toggle the TI chip direction pins, and out put to the transformer primary. Then you might light a pigtail neon with it or zap your fingers.
     
  7. takao21203

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    Apr 28, 2012
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    I want to light a 110v green neon bayonet lamp.

    Ive got a much larger coil now.
     
  8. Art

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    Sep 10, 2007
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    You can light a pigtail neon with a small audio transformer with a centre tap on one of it’s windings,
    and pulsing a 9-12 Volt signal with a heavier transistor.
    If the neon has a pair of of visible electrodes inside it, only one side is lit until you can swap
    directions of the current on the transformer primary with something like the chip I mentioned earlier,
    but it’s enough to light it convincingly, and you can also zap your fingers with it.
    I imagine the neon you describe would be ok.. pigtails are supposed to be 90 Volts.

    All I’m doing differently here is constantly changing the frequency to make the dimming effect.
    The flickering is the camera, I can’t see that here.
     
    Last edited: Sep 10, 2015
  9. DerStrom8

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    We're getting a bit off topic here guys. This is not a solid state Tesla coil, which is what the OP started this thread to discuss.

    Could a moderator move this to its own thread please?

    Thanks,
    Matt
     
  10. takao21203

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    Apr 28, 2012
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    but ive got the idea from tesla papers
     
  11. Art

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    Sep 10, 2007
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    Well now it’s off topic of joule thieves :D but it’s now your own thread so.....

    I wouldn’t necessarily call this a joule their anymore since that’s designed to squeeze every drop from a battery
    with particular regard to running LEDs. It’s also not the size of a coil that will make any difference lighting a neon.

    For any small neon around thee 90V range, and I suspect the 110V one you’re talking about:
    You will notice inside you should see two electrodes. If you want to light one of them, you just have to pulse a DC current through it.
    That can be done with a 555 timer and a small speaker transformer. There are circuits on the net for that.
    If you look close you’ll see only one side lit, but this is ok for most uses if you wanted it behind a panel,
    and you also won’t notice if it’s a blue or green neon with frosted glass.

    To light both sides you need a H-bridge to switch positive and negative signal continuously.
    OR you can use a centre tapped transformer, supply the centre, and use transistors to alternately
    send both sides to ground. This can also be done with a 555.

    The second way is a bit more interesting because you can do different things with the neon,
    and other things with the same circuit like ring an old telephone or make a solenoid go batty.

    Ideally you want a transformer with an uneven turns ratio, so the secondary has many more turns than the primary.
     
  12. takao21203

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    Apr 28, 2012
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    Well my circuit lights both sides. And requirement is 2 batteries maximum, no more than 3v.

    The schematic is incorrect but you can find out yourself.

    Capacitance between the primary and secondary isn't very high.

    Its not a joulethief since you need more than almost empty batteries to light a neon bulb.

    The circuit at first had a tinfoil electrode for starting. Layout of the connections is quite important. As well the white led just turns on with 7 windings so the design isn't optimal.
     
  13. GS3

    Senior Member

    Sep 21, 2007
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    Typo in thread title hurts my eyes and brain.
    Please correct if possible.
     
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