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Transformer for a stun gun circuit.

Discussion in 'High Voltage' started by zoom, Feb 1, 2012.

  1. zoom

    zoom New Member

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    I found a stun gun circuit on the web, everything is ready but transformer.
    Couldn't find any transformer to reach at least 150.000 volts
    There are stun guns reaching around 500.000 volts and they are not huge, as big as a mobile-phone. So, what kind of a transformer am I supposed to use ? Everyone I asked told me it's not possible to reach that voltage with a transformer.
     
  2. canadaelk

    canadaelk Active Member

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    You will be stunned at what the courts will do to you after the cops find out you have a stun gun! E
     
    • Like Like x 1
  3. zoom

    zoom New Member

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    Well, thanks but that's not the subject :)
     
  4. dave

    Dave New Member

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  5. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    Its possible but it would be big.
    TVs us fly back transformers to make a few tens of thousands of volts.
    Look in to SMPS.
     
  6. JimB

    JimB Super Moderator Most Helpful Member

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    Just advertising bull shine!

    Consider that 25000 volts will spark across a gap of 1 inch in dry air.
    So 500,000 volts will jump across 20 inches, does that seem sensible, a useful practical tool?

    If a stun gun can be considered a useful practical tool in the first place.

    JimB
     
  7. zoom

    zoom New Member

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  8. shortbus=

    shortbus= Well-Known Member

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    Last edited: Feb 2, 2012
  9. 4pyros

    4pyros Well-Known Member Most Helpful Member

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  10. zoom

    zoom New Member

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    Thanks for the answer.
    Found another one;
    http://www.ebay.com/itm/EI-14-Audio...381?pt=LH_DefaultDomain_0&hash=item23193143cd
    This one is magnifying about 266 times.
    However another point is still ambiguous; How can I determine the maximum voltage I can apply to primary coil (the coil with less turn) in order not to burn the transformer ?

     
  11. zoom

    zoom New Member

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    Determining the max voltage for Transformer

    I'm planning to buy a radio transformer which is 150:40K 40K:150 ohm FS

    http://www.ebay.com/itm/EI-14-Audio...ltDomain_0&hash=item23193143cd#ht_1205wt_1187

    I'm planning to magnify the DC voltage. However don't know what the maximum voltage the coil with less turns can handle. Is there a way to calculate that ? Looks like it's not stated in the description part of the product. I'm not familiar with transformers so I appreciate if you show me a way to calculate that for any transformer. Thank in advance.
     
  12. alec_t

    alec_t Well-Known Member Most Helpful Member

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    Not understood. Transformers only handle AC.
     
  13. zoom

    zoom New Member

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    Well, The circuit I've been building has a 555 timer, so it's kinda AC voltage. Suppose that explains the case.
     
    Last edited: Feb 3, 2012
  14. audioguru

    audioguru Well-Known Member Most Helpful Member

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    The size of the transformer depends on its power rating. The AC voltage rating of each winding are determined by the power rating.
    What is the power rating of the transformer?

    Maybe the transformer is designed to boost the very small voltage from a dynamic microphone then it might break down if you feed its 150 ohm winding from your 555 oscillator.

    To make a high voltage you should use the transformer used in a disposeable camera's flash circuit. Be careful with the high voltage.
     
    Last edited: Feb 3, 2012
  15. JimB

    JimB Super Moderator Most Helpful Member

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    He is trying to build one of those "stun guns" a kiddies electric shock toy.

    A transformer will transform the voltage in the same ratio as the ratio of the turns on the windings.
    For example, 90 turns on the primary, and 900 turns on the secondary will give a voltage ratio of 10 to 1.
    ie 10 volts on the primary gives 100 volts on the secondary.

    The transformer in the link is badly specified.
    For each winding, the DC resistance is given, as is the "AC impedance" whatever that means, maybe the impedance measured at 1khz with an impedance meter.

    What is not explicitly stated is the turns ratio.
    My best guess at the turns ratio is that it will be close to the square root of the ratio of the primary and secondary "AC Impedances", I calculate (guess) the turns ratio as 16:1.

    The maximum voltage that the transformer can handle will depend on the insulation on the wires and the way they are wound.
    The transformer in the link is made as a small signal transformer and would normally only handle a few 10s of volts.
    Hundreds of volts will breakdown the insulation.

    JimB
     
    Last edited: Feb 3, 2012
  16. audioguru

    audioguru Well-Known Member Most Helpful Member

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    NO!
    The voltage ratio is determined by the turns ratio which is the square root of the impedance ratio.
    The square root of 3000 is 55 times.
    A 555 powered by a 15V supply has an output of about 13.5V p-p. The output of the 555 should be capacitor-coupled into the transformer to avoid saturating its core. Then the output from the transformer is 743V if it doesn't break down.
     
  17. audioguru

    audioguru Well-Known Member Most Helpful Member

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    Why are there two threads about this?

    In the other thread another little transformer produces 743V if it doesn't break down.
    This transformer produces 217V if it doesn't break down.

    The voltage is much too low to stun a person but it might tickle a little.
     
  18. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    Threads Merged.
    Moderation.E
     
  19. ronsimpson

    ronsimpson Well-Known Member Most Helpful Member

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    These little transformers are designed for 1000 volts 14 watts. It will work to 3,000 volts. I have used then many times. Your little audio transformers are designed for 20 volts and will work to maybe 400 volts.

    If 1 watt is enough for you, look at a photo flash transformer.

    Mega voltage is not needed.

    I have some 10kv transformers used in 5" CRT monitors.
     
  20. zoom

    zoom New Member

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    Handling 9Volts is what I'm looking for, so it's enough for me.

    In the description of retail stun guns like taser gun, they state that it reaches more than 100K volts even 500K volts and yet their size is not huge at all. So what kind of transformer do they use to obtain such a high voltage difference ?
     
  21. ronsimpson

    ronsimpson Well-Known Member Most Helpful Member

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    I do not know. I have experience with 30kv transformers. The back light transformers in post 18 have briers between sections of the transformers. When we are dealing with voltages that want to jump inches you can't have inches of air in the transformer. We can not have PCB material open to air. The transformers I use are potted! There can not be a bubble of air in the transformer. The windings are split like the transformer above. Some have 20 sections. Each section is wound in layers so no two wires with more than 500 volts difference will get near each other. At about 1kv to 2kv the core material starts to conduct. The wires can not get close to the core. The bobbin design is key. Magnet wire is not a good insulator. It will hold 500 volts. I have seen it hold off 1kv for a day before it broke down. The transformer must be made right. Some of the methods use a layer of tape between each layer. These transformers usually are not small because of the internal spacings.
     

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