Inverter output is reading zero

Discussion in 'The Projects Forum' started by nobleman, Apr 18, 2015.

  1. nobleman

    Thread Starter New Member

    Apr 17, 2015
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    Hello house, Please I tried implementing this circuit, But after everything the output still reads zero.....what shall I do Please
     
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    bet you built it wrong, lets have a pic of the board you made...
     
  3. nobleman

    Thread Starter New Member

    Apr 17, 2015
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    Its on a bread board, the transformer is a 12v 1.5A. When I connect the battery. The transformer becomes hot withot any output ....thanks.
     
  4. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    It's unlikely to work properly on a breadboard :(. Wire inductance plus board capacitance are a recipe for spurious high-frequency oscillations, which in turn can result in excess current through the FETs and transformer. The IRF540 has significant gate capacitance which has to be charged up and discharged each cycle. The CD4047 can't source/sink enough current to do that quickly, and the complementary outputs of the CD4047 don't provide any dead-time, so there is a ~3uS period twice per cycle where both FETs are partly on at the same time. That results in a high current 'shoot-through', effectively shorting the 12V rail to ground.
    It's possible one of the connections to one of the FETs isn't properly made, preventing a FET switching properly. That would cause a net DC current through the transformer and hence heating.
     
  5. nobleman

    Thread Starter New Member

    Apr 17, 2015
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    Thanks for the update, guess maybe I should transfer or solder the components on a Vero board. For the transformer I joined their source pin and send it to ground I.e the third pin reading from top, connect both of the drain pin I.e the center pin to the primary part of the transformer and also connected the gate pin ie the first pin to the irf540 Hope I Did the connection rightly.
     
  6. wayneh

    Expert

    Sep 9, 2010
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    What is the purpose of R3?

    But anyway, if you don't have an oscilloscope, slow down the frequency so that you can use LEDs in place of the transformer to verify the switching. If that works, speed it up until you can barely see flashing - this will be 50Hz or so - and see if the transformer works at this low frequency.
     
  7. crutschow

    Expert

    Mar 14, 2008
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    The transformer will saturate and overheat if the frequency is less than about 100Hz since it's a 9Vrms transformer and a squarewave has a large low frequency component generating the magnetizing current.
    My simulations show that a ±12V, 91Hz square-wave generates about the same peak magnetizing current as a 9Vrms sinewave at 60Hz.
    The DC voltage should be reduced to 9V if you want to operate the transformer at its rated mains frequency.
     
  8. nobleman

    Thread Starter New Member

    Apr 17, 2015
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    Alright, will put all u have said into consideration and tell u How far I'm fairing ...Thanks So much for ur help.
     
  9. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    The schematic is stating "100 Watt inverter".
    This can not be the case, as the transformer in the schematic is 18 Volts at 1.5 Amps = 27 Watt.
    With some luck you will get about 20 Watts at the output, taking the losses in account.

    Bertus
     
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  10. nobleman

    Thread Starter New Member

    Apr 17, 2015
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    Do u mean the circuit is wrong or what can be done to correct this...Thanks
     
  11. bertus

    Administrator

    Apr 5, 2008
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  12. nobleman

    Thread Starter New Member

    Apr 17, 2015
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    hello house, this circuit is simple but I wonder y it refused to work... I even tried putting an led to replaced the transformer, nothing happened
    ..I then use my meter to test the output ie from the 4047 ic pin 11 is reading 2v while pin 10 reads 0v.. can anyone help...I really have little ideas on inverter making. Thanks
     
  13. gerty

    AAC Fanatic!

    Aug 30, 2007
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    Does your D7 led light up with power applied? If not try disconnecting transistors from either pin 10 or 11.
    Verify pinout on transistors.
     
  14. nobleman

    Thread Starter New Member

    Apr 17, 2015
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    yes d7 lights up when connected. How do I verify pin out on transistor, from data sheet it says pin 2.
     
  15. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Shouldn't pin 4 of the 4047 be grounded instead of tied high?
     
  16. nobleman

    Thread Starter New Member

    Apr 17, 2015
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    Hmmm, I really have quite a few idea on the 4047, I think pin 4 and 5 are the astable port... I really don't know if I should ground it...please help
     
  17. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    This table may give you information on how to connect the 4047:
    4047_functions_table.png

    I also have attached the full datasheet.

    What is the measured voltage between pin 7 and 14 of the 4047?

    Bertus
     
  18. nobleman

    Thread Starter New Member

    Apr 17, 2015
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    Thanks you for those attachment, they are indeed quite educative. well the voltage drop across pin 7 and 14 is 7.3v.
     
  19. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Is your powersupply 12 Volts?
    Then the current in R3 (330 Ohm) will be (12 - 0.7 - 7.3) volts / 330 Ohms = 12 mA.
    This is rather high.
    What is the voltage across pin 7 and 14 when the gates of the fets are disconnected(pins 10 and 11)?

    Bertus
     
  20. nobleman

    Thread Starter New Member

    Apr 17, 2015
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    the voltage when the gates are disconnected is 10.42v. and yes I'm using a 12v supply. Thanks.
     
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