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LT SPICE transformer

Discussion in 'General Electronics Chat' started by MrDEB, Apr 29, 2010.

  1. MrDEB

    MrDEB Active Member

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    the transformer is each pri is 10 turns the sec is 30
    keep getting node error.
    it dosn't help when the help file is blank
    why ???
     

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  2. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi D,
    The secondary of the rightmost transformer is 'floating'.
    Either add a normal ground symbol or the F4 'COM' and link back to 0V, via say a 1meg, as shown here.
     

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    Last edited: Apr 29, 2010
  3. MrDEB

    MrDEB Active Member

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    Its not really a 8 ohm speaker but a piezo transducer. I was trying to simulate this circuit, just the amp output.
    http://googleads.sgdoubleclick.net/...superfindonline.com/index.php?search=ksn6001a

    400 watts!! yea right but I find it a learning experience to simulate different circuits.
    This particular circuit is for a deer chaser I am working on.
    See the post on ultrasonic or speaker?? something like that.
     
  4. dave

    Dave New Member

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  5. MrDEB

    MrDEB Active Member

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    I must not have the transformer command line right. I get nothing on the output??
    here is the link to other post http://www.electro-tech-online.com/threads/ultrasonic-speaker-or.106059/#post873270
     
  6. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Don't simulate it, what would be the point?, build it and see how it works.
     
  7. MrDEB

    MrDEB Active Member

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    Thinking about it but there has to be a better way to drive a piezo tweeter.
    Looking at using 1mh inductors as per EVIL GENIUS BOOK. see schematic in this thread and varying the output using taps (a 3 pos dip switch) to vary output frequency.
     
  8. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    It looks pretty simple and straightforward, using a transformer on the output allows reasonable power from a 12V supply.

    Trying to 'ring' a choke seems a very poor idea.
     
  9. MrDEB

    MrDEB Active Member

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    Trying to sim the schematic but the transformer I don't think is correct.
     
  10. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    What are you hoping to achieve from a simulation anyway?
     
  11. MrDEB

    MrDEB Active Member

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    Hopefully if it works in simulation it SHOULD hopefully work for real.
    Hopefully?
     
  12. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    I don't see as it has any bearing on it working?, you can't accurately simulate either the transformer, the piezo's, or the actual audible output. The circuit is simple enough, a crude push-pull transformer coupled ampliifer.
     
  13. audioguru

    audioguru Well-Known Member Most Helpful Member

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    The SIM program doesn't work probably because your coils are separate chokes instead of coupled together into a transformer.

    You bought "cheep, cheep, cheep cluck cluck" no-name-brand piezo tweeters that have no datasheet and no spec's. So you don't know how much of a load they are on the transformer.
     
  14. MrDEB

    MrDEB Active Member

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  15. audioguru

    audioguru Well-Known Member Most Helpful Member

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    Another cheap Chinese piezo tweeter without a manufacturer's name and without a detailed datasheet.
    Can you believe what they say?
     
  16. Sceadwian

    Sceadwian Banned

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    Absolutely not, transformers and compound devices like piezo transducers don't simulate accurately, there's too many things that are dependent on their physical structure and environment for the simulator the manage. Even professional engineers have difficulty modeling devices like that in a simulator, and they're never quiet right.
     
  17. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    This is WRONG, the coils are drawn as a transformer and defined with mutual coupling of 1 in the LTspice directive.

    EDIT:
    Added a cut down image of DEB's LTS file/image.
    He had mistakenly made the K1 L1 L2 L3 1 DIRECTIVE a COMMENT
     

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    Last edited: May 1, 2010
  18. Sceadwian

    Sceadwian Banned

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    Please note that inductor coupling in spice will not actually represent a real world transformer with any degree of accuracy. There are some transformer models on the Yahoo Groups LTSpice group, but not only are these models overly complicated for what you need they require a lot more information about the materials in the transformer than you probably have. There's really no point in simulating this in the first place as already mentioned. Simply use a dummy load resistor, tweak that resistors value until you get peak power output from your circuit, using that resistors value, and determining what the output impedance of your transducer is will give you the impedance you need to calculate the proper turns ratio and wire thickness of the primary and secondary of your transformer.

    If all you want to do is simulate the amp output, all you need to do is use a dummy resistor with a value that matches the impedance of your piezo transducer at the frequency you're producing. If you don't know what that impedance value is you have nothing to simulate.
     
  19. MrDEB

    MrDEB Active Member

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    I am finding out that simulating a transformer is almost impossiable. Keep getting different readings etc depending on which way I have the inductor pointing (the one I am using has a little dot for polarity.)
    going to build the push pull portion of schematic, connect to a 555 then use a d flipflop to alternate the two 3055 transistors for the push pull effect.
    As for transducers, hopefully the ones I have will work.
    Not sure what db sensitivity is. The tweeters are rated 94db sensitivity??
    the push pull section is in this document http://googleads.sgdoubleclick.net/...superfindonline.com/index.php?search=ksn6001a
    hopefully I can just connect the 555 and the D flip flop and get some output?
    reason for using the amp in the schematic = I have about 10 of each 2n3055 and 2n3054 power transistors.
     
  20. audioguru

    audioguru Well-Known Member Most Helpful Member

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    The link to your push-pull amplifier does not work. I get Google's home page.

    There is a small horn piezo tweeter with less sensitivity and there is a longer horn one with more sensistivity (narrower angle). The sensitivity at a 20kHz peak is 94dB at a distance of 1m with an input that would produce 1W into 8 ohms (2.83V RMS) and at 4V RMS. Sound level drops at -6dB each time the distance is doubled plus humidity, wind and grass on the ground reduces high audio frequencies further.
     
  21. MrDEB

    MrDEB Active Member

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    I just tried the link and it works?
    Is your computer on?? LOL
    no idea why it dosn't work.
     

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