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240v Flyback

Discussion in 'General Electronics Discussion' started by Phil2002, Aug 27, 2012.

  1. Phil2002

    Phil2002

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    Aug 27, 2012
    Hi Guys,

    I'm trying to build a flyback driver that i can run on mains voltage inorder to build an electrostatic flocking machine. I have been given a schematic diagram from a guy who built one in Germany but cannot seem to get hold of him to help me with a few questions i have.

    on the diagram below should pins G and K of the transistor be joined together?

    [​IMG]

    Has anyone built a flyback driver like this before(running on mains voltage)

    here's a pic of the one he made

    [​IMG]

    will keep this updated as i progress.

    Thanks for any help in advance

    Phil
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    If his construction is anything like yours he has probably expired after electrocuting himself.
     
  3. john monks

    john monks

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    1
    Mar 9, 2012
    No. G stands for "gate" and K stands for "cathode"
    The gate is used to turn on the trac at the best time.
    The diagram is drawn this way out of convention.
     
  4. Phil2002

    Phil2002

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    Aug 27, 2012
    Thanks for the reply steve that picture is of the one that he built not mine. It does look extremly dangerous i must admit.

    I will build mine on a bread board.

    thanks,
    Phil
     
  5. Phil2002

    Phil2002

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    Aug 27, 2012

    ok, thats great thanks very much.

    Does the diagram look right in your opinion?

    thanks for you time,

    Phil
     
  6. john monks

    john monks

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    1
    Mar 9, 2012
    The diagram looks correct although I don't see the value of the capacitor in series with the transformer.
     
    Last edited: Aug 27, 2012
  7. Phil2002

    Phil2002

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    Aug 27, 2012

    Finding out what the value was was a question i wanted to ask him. Now i may be very wrong here but from looking at the picture both the caps look the same so i have ordered 2 of the same value.

    thanks,

    Phil
     
  8. Electrobrains

    Electrobrains

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    5
    Jan 2, 2012
    The 47nF cap is no big deal. A diac use to switch on at about 30V, so that cap could for instance be specified at 47nF/100V

    The cap without information is something totally different!
    I guess it is specified for several kV, if it's used in a high voltage flyback circuit like that. The triac must also be a high voltage type.

    EDIT: After looking again at that circuit, I realize this is NOT a flyback circuit at all!
    It gives a surge pulse through the capacitor at the moment the diac triggers, which is adapted by the potentiometer and will have maximum when the diac triggers at the peak of the sine wave.
    The unknown capacitor must not be rated for kV, but would need to be able to handle the surge current (transformer too). I suggest using an X2 AC-capacitor. The size of it should also be adapted to the transformer.
     
    Last edited: Aug 27, 2012
  9. Phil2002

    Phil2002

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    Aug 27, 2012
    The triac i have bought is this one BT-138 - 800v

    http://www.ebay.co.uk/itm/160692591237?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

    and the caps i have bought are these 47nf 1000v

    http://www.ebay.co.uk/itm/251002900...NX:IT&_trksid=p3984.m1439.l2649#ht_702wt_1271

    could i use the same value cap in both points of the circuit?

    thank you for you help,

    Phil
     
  10. Electrobrains

    Electrobrains

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    5
    Jan 2, 2012
    See my edit comments above!
    I think your circuit could work with those values. You can probably use the same type of capacitors.
     
  11. Phil2002

    Phil2002

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    Aug 27, 2012

    so should i just build it with what i have bought and see if it works?

    thanks,
    Phil
     
  12. Electrobrains

    Electrobrains

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    Jan 2, 2012
    Let's say like this: If you are not a professional in this area and you are here playing around with lethal voltage, even producing high voltage (that I have no idea about how powerful it is), I cannot recommend that you build anything!

    If I would happen to have those components lying around on my work bench, I don't think I could resist putting them together for a test (with protective goggles, rubber gloves, rubber boots, my left hand bound to my back, installed RCCB/GFI and my wife with first aid equipment in the background)
    ;)
     
    Last edited: Aug 27, 2012
  13. BobK

    BobK

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    1,662
    Jan 5, 2010
    What, no insulating shoes. You really are quite the dare-devil.

    Bob
     
  14. Phil2002

    Phil2002

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    Aug 27, 2012
    I'm gonna give it a go, your only your young once. If this works i'm definatly going to build a flux capacitor

    rubber gloves - CHECK
    goggles - CHECK
    House RCD's - CHECK
    wife - first aid trained

    need both hands so will miss that step.

    Thanks for all your help,

    Hopefully i'll let you know how i got on.

    Phil
     
  15. Electrobrains

    Electrobrains

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    Jan 2, 2012
    Oh Bob! I missed that one! Now corrected!

    Phil, you scare me...
    [​IMG]
     
  16. Phil2002

    Phil2002

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    Aug 27, 2012
    Thanks,

    I've been a auto electrician fro about 11 years so i'm quite confident with electrics it's just the science involved with circuits and electronics i'm unsure of.

    As long as i know the above circuit has the potential to do what i want it to do i'm more that confident i know who to be safe.

    Thanks again for all your help.

    Phil
     
  17. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,214
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    Jan 21, 2010
    And there you go, ignoring one of the techniques used down the ages to keep technicians working on high voltage equipment alive.

    It doesn't stop you from receiving a nasty shock, but it helps mitigate somewhat the risk of it stopping your heart.

    Whilst that list of things may have seemed funny, it is based in fairly normal practice.
     
  18. Phil2002

    Phil2002

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    0
    Aug 27, 2012
    Hi everyone,

    well i'm still alive and have built the circuit which did work but not to my expectations.

    The output from the HV side of the coil is not larger enough, any ideas how i could increase the output.

    I did originally build this with a variable rate 470k resisitor but it didn't seem to make any difference.

    if i lower the value of the resistors with that increase the input to the coil?

    here is a pic of my build.

    All comments welcome

    [​IMG]

    Thanks,
    Phil
     
  19. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,214
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    Jan 21, 2010
    Please explain what your results were (preferably quantitatively).

    Details like the actual inductance of the primary of your flyback transformer and the value of the series capacitance would also be useful.
     
  20. Phil2002

    Phil2002

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    0
    Aug 27, 2012
    Thanks for the reply Steve my knowledge on how to measure inductance is zero. My results are more practical than theory. The resistors in series values are 220k and 470k the resistance of the primary coil is 1.0 ohm


    Basically the electrostatic attraction between the HV + and HV - is too low.

    My hopper(HV+) that contains the nylon fibers has to be really close to the item that has the HV- connected to it before the fibres are a statically attracted to the HV-.

    If the HV+ terminal and HV- terminal are as close as 10mm then and arc will jump between the two. (I have read some where that they should arc at a distance of about 25mm)

    I do have access to a scope but have no idea what i'm looking for or how to use it. If anyone could let me know what to look for and how to use the scope to find it that would be great.

    thanks in advance for any further help,

    Phil
     
    Last edited: Oct 6, 2012
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