Piezo transformer help

Discussion in 'The Projects Forum' started by airplane100000, Aug 2, 2016.

  1. airplane100000

    Thread Starter Member

    Aug 2, 2016
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    I am working on a project which requires a high voltage, to be achieved by a step-up transformer. The project space is physically limited in size, so I am in need of utilizing small/thin components. I found and ordered a thin piezo transformer with a 1:80 step up ratio, seen here.
    The transformer's working frequency is 55.5khz +- 3%, which I accomplish by using a 555 IC.
    Due to the physical constraints I use four 2032 3V button cells in parallel, giving me 12V.


    The circuit requires a relatively high current, so I placed a capacitor following the 12V, with the intention of having the capacitor charge when the 555 output is high, and discharge while it is low. I did this using a push pull transistor example I found online.
    In the simulator the circuit seems to function correctly, with a constant 12 V output from the capacitor. It looks as follows:
    [​IMG]
    I built a breadboard prototype, and in actuality it does not function, the problem being unclear.
    My goal is to use this piezo transformer to deliver a constant high voltage using 4 button cells.
    Am I going at it correctly? What changes need to be made?
    Any help is greatly appreciated.
     
  2. ericgibbs

    Senior Member

    Jan 29, 2010
    2,499
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    hi air,
    Your simulation circuit is showing capacitor C2 as 100 FARAD's!
    E
     
  3. airplane100000

    Thread Starter Member

    Aug 2, 2016
    59
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    100uF that is supposed to be,
    Thanks for spotting that, I had it correct when I was testing it.
    Not exactly a constant 12V from the capacitor, it starts at 12 and slowly falls until it stabilizes.
    Anyway, if anybody could inform me whether or not I'm on the right path, or if this is not the way to go about,
    It would be greatly appreciated.
     
  4. AlbertHall

    Well-Known Member

    Jun 4, 2014
    1,886
    375
    The piezo link you give is a 1:50 device not a 1:80 device.
    The calculated '555 frequency is 57.6kHz but the spec of the device is 55kHz +/- 3% which gives a maximum of 56.65kHz, about 4.7% error.

    You say it does not function, but you need to more specific - output voltage only 100V?, no output?, '555 doesn't oscillate?...
     
  5. airplane100000

    Thread Starter Member

    Aug 2, 2016
    59
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    I realized the link error immediately after posting, though I could not a way to edit the thread.
    The correct link is HERE.
    I do realize that the current 555 resistor/capacitor combination gives a higher frequency.according to most calcuators.
    For some reason in Multisim, the 555 calculator values are different (maybe someone knows why).
    Anyway, I went with the multi sim values.

    Unfortunately I am not currently in possession of an oscilloscope, so determining the exact error in RL is difficult.
    It appears as if the chip is oscillating, as there is voltage amplification at the transformer output. The value is inconsistent, but it see to be around several hundred V. The high voltage output is not consistent, at times there is no output at all, and then suddenly it spikes.
    I will be obtaining a scope in the coming days, and that will surely assist troubleshooting if the problem a solution is not found by then.
     
  6. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,771
    1,103
    Post deleted
     
  7. AlbertHall

    Well-Known Member

    Jun 4, 2014
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    Did you remove C1, C0, R0, L0 from the actual circuit, and include a load resistor for the transformer?
     
  8. airplane100000

    Thread Starter Member

    Aug 2, 2016
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    C1 C0 R0 L0 were never in the actual circuit, that is an equivalent diagram (perhaps i should have specified).
    And yes I did include a load resistor.
     
  9. bertus

    Administrator

    Apr 5, 2008
    15,641
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    Hello,

    Do you have an output signal in the transistors without the transformer?
    It could well be that the coin cells do not have enough power.
    Also the 20 Ohms resistor in the powerline might stop the circuit.

    Bertus
     
  10. AlbertHall

    Well-Known Member

    Jun 4, 2014
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    I thought that was the case, but it was worth checking.
     
  11. airplane100000

    Thread Starter Member

    Aug 2, 2016
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    The 20 ohms is to simulate internal resistance, its not actually there (again I should have specified, I wish I could edit the thread)
    I have actually been testing it with a large 12V battery so far, so the current issue is not associated with the coin cells.
    My intention here to draw current from the 100uF capacitor and not directly from the coin cells.
     
  12. bertus

    Administrator

    Apr 5, 2008
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  13. AlbertHall

    Well-Known Member

    Jun 4, 2014
    1,886
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    There may be problems when you try powering this from 4x2032. Doing some back of the envelope calculations, a 500k load will be transformed to 78 Ohms (ratio squared). 12V across 78 Ohms gives about 150mA which will only be drawn for half the time giving an average current of 75mA. Looking at the spec for the 2032, the lowest load resistance it shows is 1k and at that load the voltage will be only 2.6V - output current 2.6mA.
    upload_2016-8-2_11-38-6.png
     
  14. airplane100000

    Thread Starter Member

    Aug 2, 2016
    59
    0
    My idea was to use a capacitor in parallel with the power source to bypass the button cell's limitations. The capacitor is to charge/discharge in sync with the 555. Is that realistic?
     
  15. AlbertHall

    Well-Known Member

    Jun 4, 2014
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    The required current is some thirty times the current that the 2032 can supply, so the transformer would have to be off for 29 times as long as it was on. During the on time the current would be supplied by the capacitor - 1000uF would run it for about 25mS, and then it would have to be switched off for 750mS. Is that useful for your application?
     
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