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Homemade Capacitors ~50kV

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

  1. Krumlink

    Krumlink New Member

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    mickey mouse capacitors?!?

    I just want to know how to test my 500pf caps in somthing that I can verify easily. I need to test 20 of them...
     
  2. Sceadwian

    Sceadwian Banned

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    You really should try glass bottles. Go buy a six pack of beer (or soda) and clean them out real good afterwards. Never done it myself but I see people using those kinds of capacitors on the net frequently. Glass is a significantly better dielectric than plastic.
     
  3. kchriste

    kchriste New Member Forum Supporter

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  4. dave

    Dave New Member

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  5. Krumlink

    Krumlink New Member

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    Thats where I got the schematic from! Ive searched that site through and through!

    Im underage! I cant buy beer! I Cant drive either!!!
     
  6. Krumlink

    Krumlink New Member

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    Also, I have decoded my Transformer's coils. It says I need a 18kHZ signal for my xformer. Do I have to have this? I dont want to build all that, I just want to hook my xformer up to some Voltage and at least get that firing...

    As a last ditch effort to get 10kV, what kind of transformer is this?
    http://www.uoguelph.ca/~antoon/circ/hv/hvdcgen/hvdcgen.html
    Its labeled as T1. What pinout/what can I get that from or one like it? I have a monitor circuit board, so I should have somthing like that in there.
     
  7. Oznog

    Oznog Active Member

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    No kidding. The cap's only rated for a few hundred volts at most. I wouldn't be surprised at less than 100V.

    More of a point, a cap with air in it will break down quickly. Air breaks down into a corona at high voltage or high dV/dT rates. That corona will chemically and or thermally destroy the saran wrap. You try to generate a pulse with a Marx generator and you can expect it to break down on the first shot... well it's not going to make it to 50KV in the first place.
     
  8. Oznog

    Oznog Active Member

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    That transformer is used all the time in zenon camera flashes.
    Can put out like 300V at very low current.

    Are you seriously trying to get 10KV out of plastic party cups? I haven't seen your cups but I doubt they'll hold that.
     
  9. Krumlink

    Krumlink New Member

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    I redesigned the capacitor to use polystyrene after I looked at its breakdown voltage. Go to Homemade caps not working. I wana only have to look at one thread :D
     
  10. Krumlink

    Krumlink New Member

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    The site I got the idea off of said that he got them up to 33kV before they broke down. I still cant get it working. Any more tips?
     
  11. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Should have keep your CRT and used that!, they make a nice high voltage capacitor between the aquadag and final anode - I've known them hold their charge for over five years!.
     
  12. JimB

    JimB Super Moderator Most Helpful Member

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    The same idea occured to me. They would make excellent capacitors.

    JimB
     
  13. Krumlink

    Krumlink New Member

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    I cant figure out how to hook up my flyback transformer. Any help and tips?
     
  14. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    You need to essentially duplicate the drive circuit in the TV, a high frequency (15,625Hz for 625 lines), high voltage, switching circuit - with the transformer (and load) tuned correctly.

    How are you trying to connect it?.
     
  15. Hero999

    Hero999 Banned

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    Perhaps it's sparking through?

    That would make sense, we did try to tell you that this isn't a good idea.

    You could try immersing the whole thing in transformer oil.
     
    Last edited: Aug 31, 2007
  16. Krumlink

    Krumlink New Member

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    I went to my local TV repair guy and he helped me find the HV coils and HVGND and stuff. We also found a driver circuit that will run the transformer.

    They arent holding charge, because they are discharging into the air, so I have to either create a vacuum or fill it with a dielectric fluid (any suggestions as to what fluid? I was going to use Mineral oil)
     
    Last edited: Aug 31, 2007
  17. Krumlink

    Krumlink New Member

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    Attached Files:

    Last edited: Aug 31, 2007
  18. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    They aren't holding charge because they are totally useless capacitors! :p

    They are also too small to hold much charge anyway.

    What voltage are you hoping for from your LOPTX?, the circuit is fed from too small a voltage to give much. In a TV/Monitor it probably provides 25KV or so, but you're only feeding it a fraction of it's normal input voltage, so you 'might' get 2.5KV to 5KV?.

    BTW - thread moved to Chit Chat, as it doesn't meet the criteria for the Electronic Projects forum

    Moderator.
     
    Last edited: Sep 1, 2007
  19. Hero999

    Hero999 Banned

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    That would make sense but have you checked the cups for any signs of electrical damage?

    Please re-read my previous post.

    Also, your schematic looks wrong.
    [​IMG]
    Why is the LM7808 connected incorrectly?

    There is nothing on the input and the power is applied to the output, did you check the datasheet?

    Even if you used the LM7808 correctly, the chances are it will current limit when the transistor turns on, you don't really need a regulated supply for something like this. I'd go for a 9V 2A transformer with a large 4700:mu:F capacitor on the output.
     
    Last edited: Sep 1, 2007
  20. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    You need to look again! :D

    The input is clearly shown, and it's connected the correct way round!.
     
  21. Hero999

    Hero999 Banned

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    You're right, it's drawn backwards!

    The 555 is powered from 8V and the flyback driver is powered from an unregulated 10V to 25V. Please disregard my comments relating to the regulator and current limiting.
     

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