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Homemade Capacitors ~50kV

Discussion in 'Members Lounge' started by Krumlink, Aug 30, 2007.

  1. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    'Backwards'? - you mean it's not drawn the way you would like it to be! :p
     
  2. Hero999

    Hero999 Banned

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    It's not drawn in a conventional manner which is with the input on the left and the output on the right.
     
  3. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    You have a much too narrow view of what 'conventional' might be! :D

    In the not so distant past convention was for the power input of a circuit to always be on the right, but really it makes no difference whatsoever.
     
  4. dave

    Dave New Member

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  5. audioguru

    audioguru Well-Known Member Most Helpful Member

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    He replaced the Mosfet with an NPN transistor. The circuit has nothing to limit the base current so the 555 tries to feed hundreds of mA to the base.
    In the datasheet the NPN transistor has a base current of 1.25A which the 555 certainly cannot provide.
    Maybe now the 555 is fried.
     
  6. Krumlink

    Krumlink New Member

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    so how should I get 1.25A into the transistor? Should I hook up a bunch (of 2907A/2222A, I dont care if they fry, im just that mean) to increase gain?

    Or should I get the IRF830?
     
  7. kchriste

    kchriste New Member Forum Supporter

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    As Audio points out you need a resistor in the base lead. A 33:eek:hm: 2 watt resistor will limit the current to just under the 200ma max output of the 555. The problem is that your transistor has a really low beta so the max you'll be able to switch is apx 2Amps. Go with the FET, it'll work way better.
     
  8. Krumlink

    Krumlink New Member

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    OK I will order one of them. I was hoping to use the 5296. Can I still use it? I dont need 2 amps. I was going to use this as much as possible. So do I still need a 1.25 amp input? I was going to use a IRF630 to get some more amps into it.

    I was also going to replace the 7808 with a 7805, since the 7808 only supplies the 555 timer.
     
    Last edited: Sep 1, 2007
  9. Krumlink

    Krumlink New Member

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    Also, the IRF630 can switch up to 9 amps. Problem solved :)

    Ill put a 100ohm 2watt resistor on the gate
     
  10. Hero999

    Hero999 Banned

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    Use an IRF540, especially if you plan to go down to 5V, it can switch lots of current at low gate voltages.

    The resistor doesn't need such a high power rating for a MOSFET, a 1/4W resistor will do fine.
     
  11. Krumlink

    Krumlink New Member

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    Lol good because I have a 540 too and only one :)

    What is teh pinout?
     
  12. Hero999

    Hero999 Banned

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    Look at the datasheet which can be found using Google.

    Come on you should know that by now.
     
  13. Krumlink

    Krumlink New Member

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    I do know this! The one that I looked at just gave them numbers, but never defined them!
     
  14. Krumlink

    Krumlink New Member

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    Ok I figured it out:D

    I was going to use AC mains current for the circuit. I would Run one end through a 12V 3.5amp transformer, than take that into a rectifier and run that through a 5v regulator with bunch of smoothing caps. I would then take the output of the 555 that then would run through a IRF540N, and the output of that would run through the C5296. The C5296 would then run on rectified and smoothed (somewhat) DC voltage of 120. That would power the transformer. Bingo I got high voltage! This should work right?

    Just imagine the 10-25volt input of the schematic is changed with regulated 120VDC and 12VDC. the 12VDC goes to the 555 (through the 7805) and the 120VDC would then run through the C5296. :D
     
  15. Bob Scott

    Bob Scott New Member

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    I bet this was a datasheet was from International Rectifier. They said that the sheets would be corrected 3 years ago!
     
  16. things

    things New Member

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    is this to power the flyback? if so there is a much simpler way out there, just google "single transistor flyback driver". i know it's crap, but it gets the job done, and it already drives the flyback at it's resonant frequency. i have tried it and got about 50kv output, but i think i have fried the flyback now as the utput has dropped significantly. actually there was a capacitor built into my flyback, and i could get huge loud sparks:D :D i have a vid of them here :http://youtube.com/FOURTYTOTHEFLOOR:D :D :D :D
     
  17. Hero999

    Hero999 Banned

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    That's true, it's easy to fry the flyback, even at 12V.

    I would never allow the output of the flyback to go open circuit and use a variable voltage supply.
     
  18. Krumlink

    Krumlink New Member

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    Should I just have a 12VDC as the positive power bus?
     
  19. Hero999

    Hero999 Banned

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    Like I said, use a variable supply, if at all possible. Start with a low voltage and ramp it up untill it works.

    One thing you could do is build a 555 timer circuit with a variable duty cycle (see the 555's datasheet). Start out with a low duty cycle and increase it until the output voltage doesn't get any higher when the duty increases further.
     
  20. Krumlink

    Krumlink New Member

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    Ok, Ill try that out.
     
  21. Krumlink

    Krumlink New Member

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    I found some LM317s laying around, so that might suit me better. How do I hook those up?
     

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