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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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    how to do it in lt spice??
     
  2. audioguru

    audioguru Well-Known Member Most Helpful Member

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    Your output transistors are emitter-followers that have voltage loss not voltage gain.
    When Q2 turns off its collector is floating then nothing turns on Q3.

    You need a transistor circuit that has +5V and 0V inputs and 12V outputs. An H-Bridge circuit will work like this:
     

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  3. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    No idea, but what would be the point? - would you simulate a resistor and LED in series across a battery?. The result is blindingly obvious in both cases.
     
  4. dave

    Dave New Member

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  5. Sceadwian

    Sceadwian Banned

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    To take a differential reading in LTSpice simple click and drag the two points you're trying to measure. You can aso manually type in an equation that can calculate pretty much anything you want (including LisaJouse patterns) by right clicking on the plot window and adding a trace manually. The LTSpice help file has all the information about functions that you can use in the plot window.
     
  6. MrDEB

    MrDEB Active Member

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    NOW I am confuissed, NEED advice
    I thought I had this figured out (http://www.kpsec.freeuk.com/images/555leds.gif) but implementing to make amplifier work?
    here is what I have tried and thought I was getting an mirror signals for the amp but no.
    any ideas as to how to do this?
    http://www.electro-tech-online.com/attachments/555-pump-amp-png.42284/
    End result, feed the piezo tweeter both the 2-8khz frequencies and the 15-20khz frequencies. Maybe have one output for the 2-8khz and another pin with the 15-20khz but still need to alternate the inputs to the amp?
     
  7. MrDEB

    MrDEB Active Member

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    I think I figured it out?

    Now to actually build it.
    Looks ok in LT SPICE but will it really work?
    using two 4 ohm resistors to help indicate voltage output
     

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  8. audioguru

    audioguru Well-Known Member Most Helpful Member

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    Your switching amplifier will work if you remove Q1 and the two LEDs and replace them with an NPN transistor inverter for one input signal to the amplifier.

    Mix two frequencies together then feed the mixed signal to one input of the amplifier and the transistor inverter.
     
  9. MrDEB

    MrDEB Active Member

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    Lost?

    The LEDs are there to indicate that ( for testing) the 555 outputs a signal.
    The Leds were / are to make an alternating signal that the amp requires( At least thats what I think as it is a push pull amp.
    The amp works as the posted schematic but only get 3.6v on output (meter across piezo tweeter) and power supply for amp is 9v.
    I used 50 ohm resistors for the 33 ohm ( all I had)
    Have the 555 outputting a signal that pulses one of the LEDs faster than the other (need to get a 50% duty cycle) but your mentioning using the NPN as an inverter? and only one signal input?
    Need more info.
    ONE big reason I conjured the 555 circuit was its basically the circuit that alternates the LEDs.
    I think I posted a link to schematic
     
  10. MrDEB

    MrDEB Active Member

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    DUH it dawned on me

    Here is what I THINK your talking about?
    Now to mix the signals so I still get the alternating inputs?
     

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  11. audioguru

    audioguru Well-Known Member Most Helpful Member

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    The resistor values for your inverter transistor are too high.
    Your generator signal is +5V and 0V but the output of an ordinary 555 (with a 5V supply) is only +3.5V and close to 0V. Then the amplifier input transistor connected to the 555 has an base current of (3.5V - 1.5V)/150 ohms= 13.3mA and the amplifier input transistor connected to your inverter transistor will have a base current of only (5V - 1.5V)/(150 ohms + 1k ohms)= 3mA which might not be enough current. The 1k collector resistor and 10k base resistor of the inverter should have their values reduced to 270 ohms at the collector and 2.7k ohms at the base and the 150 ohm series resistor to the base of the amplifier input transistor should be removed.

    A 555 makes an output that is close to a square-wave when the resistor that connects from pin7 to pin2, pin6 and the capacitor is at least 10 times more than the other timing resistor.

    If you mix two frequencies together then the loudness of each frequency is reduced quite a lot. Maybe you should alternate the frequencies at full loudness instead.
     
  12. MrDEB

    MrDEB Active Member

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    It works as posted BUT the voltage across the piezo is only 1.6v w/ amp powered
    1.2v directly off the 555/inverter circuit.
    will reduce the resistors as suggested and re test.
    As for mixing the frequencies, maybe just alter the pic code to randomly output all desired frequencies.
    Will get back to you. WE ARE MAKEN PROGRESS
    LOOK OUT DEER here I come
     
  13. audioguru

    audioguru Well-Known Member Most Helpful Member

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    What does this mean?: "the voltage across the piezo is only 1.6v w/ amp powered 1.2v directly off the 555/inverter circuit."
     
  14. MrDEB

    MrDEB Active Member

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    meter readings and hearing aids going bezerk!!

    First the voltage readings- The meter leads across the piezo
    the 1.6 with power applied to amp
    the 1.2 the piezo with meter still across but amp not powered on = 1.2
    changed the resistor values on the 555 (calculated at 7khz) and my hearing aids start getting static. Adjust the pot (connected across pins 6/7 and got one LOUD shrill.
    Turned off hearing aids and at aprox 7khz the voltage across the piezo is 8v with amp powered with 9v. wal wart.
    that one shreak really got my attention as well as my dog.
    Now to assemble and program a 18F1320 PIC and connect this deer pulverizer amp.
    Be just my luck, run into a heard of deer with hearing disabilities ---LOL
    Thanks for the circuit Audioguru.
    This thing is LOUD. I just have to be careful as my hearing aids start going bezerk
    Any other suggestions to circuit?
    I should measure current draw of the inverter transistor base as well as the amp itself. The wall wart is only rated 9vdc 200ma
     
  15. audioguru

    audioguru Well-Known Member Most Helpful Member

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    You list numbers, not voltages.
    A multimeter cannot measure high frequencies since it is made to measure only 50Hz or 60Hz mains hum. The capacitance across the voltage divider resistors at its input cuts high frequencies.

    Hearing aids overload much sooner than normal hearing.

    The base current of the inverter transistor is simply calculated.

    A wall wart that has a rating of only 200mA is junk. Its output will be 18V or more with a light load and will vary all over the place when loaded.

    Loudness decreases a lot with distance. The deer might be too far away to be bothered by it.
     
  16. MrDEB

    MrDEB Active Member

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    Being optisimistic at best

    The transformer was part of a set of 3 different AC adapters. Its what I grabed first.
    Here is my schematic that I hope works.
    Not real sure about power supply as I have never worked with LDO power supply.
    Hopefully this contraption works??
    I wish I had a frequency meter.
    Never worked with piezos either but it appears that the higher the frequency, the higher the voltage across the piezo?
     

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  17. audioguru

    audioguru Well-Known Member Most Helpful Member

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    R10 in your latest schematic should be replaced by a piece of wire.

    The amplifier does not increase its output voltage due to magic nor due to a piezo load. The output voltage should be an alternating square-wave that is about 11V p-p but since its polarity alternates then it is like 22V p-p. It is the same as a sine-wave that produces only 7.6W into 8 ohms.

    The datasheet of a piezo tweeter shows peaks and valleys at different frequencies caused by resonances. A peak is loud and a valley is not.
     
  18. MrDEB

    MrDEB Active Member

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    Well it's pretty dang loud. I included some aditional frequencies Now I get a random 2-8KHZ and 15-20KHZ.
    I can tell when it hits a 7KHZ as my hearing aids start making noise, only briefly. Must be a resonant thing.
    WHY replace the 150 with a wire.
    The mirror input (first input)has a 350 ohm resistor. Should these be equal? Am thinking maybe yes?
    Got to add more wire to tweeter as well as a second tweeter.
    THen look out deer, I is coming about 9am to scare the s_it out of all yous trouble makers. But boy do you taste good.
     
  19. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi Deb,
    I hope you are wearing ear defenders while you are experimenting with this high intensity sound.?

    I permanently damaged my ears back in the 1980's working on SMPS, I have had tinnitus in both ears ever since.
     
    Last edited: May 7, 2010
  20. MrDEB

    MrDEB Active Member

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    Am just turning OFF hearing aids and not running the device very long (my dog dosn't like it )
    Will be running experiment at about 9am MST
    If you listen real close you might hear this device. The amp that Audioguru posted works real well.
    NEWS FLASH!!! The Idaho deer population are leaving the state due to hearing problems caused by a CRITTER RIDDER
    FILM AT 11
     
  21. audioguru

    audioguru Well-Known Member Most Helpful Member

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    The 270 ohm resistor turns on the right side of the amplifier and the 350 ohm resistor should also be 270 ohms to turn on the left side of the amplifier.
    The 150 ohm resistor reduces the current to the input of the amplifier which is not wanted.
     

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