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Thread: Please analyze this circuit.....for energy meter testing

  1. 7th November 2005 11:14 AM #1
    tkvenki
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    Default Please analyze this circuit.....for energy meter testing

    HI everybody

    i have a circuit which intends to:-(the bmp file is attached)
    1) act as a inductive load to ac current(variable ac current).
    2) phase shift the input current.

    the circuit has 2 parts:-
    1) Phase shifter circuit....using opamp
    2)power amplifier circuit...(using TIP147 and TIP142)

    I'am writing my explaination for the circuit......
    1) The transformer output(the input is 230VAC) is given to a bridge which will get us +12V and -12V. This voltages help us as power supply for opamps(LM324)..and are also given to TIP147 and TIP142...this is to acheive amplification.

    2) the signal comes at TP1 and that is attenuated by the 2K preset and the attenuated (it may be also left as it is) signal is given to phase shifter circuit which will result in a phase shifted signal at TP3.

    3)Then the signal is somehow amplified and we get ac current at TP6.


    My doubts:
    1)According to my analysis the output of the darlington pair(TIP147 and TIP142) must be a square wave...But i need a sine wave for my analysis.

    2)Explaination for darlington pair.

    3)So i want you to tell me what will be the output at TP5??....If it is a square wave..then what i must do to get a sine wave??

    4)The circuit may have some faults.....inform me if you find any of them.

    Thanking you....
    Venkatesh T.K
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  2. 7th November 2005 12:08 PM #2
    audioguru
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    Hi Venkatesh,
    With your darlington transistors swapped in the wrong places and labelled wrong, and the top diode backwards, I think your circuit might have produced smoke instead of a sine-wave.

    I corrected your sketch. If the input resistor's value is high enough, it will produce the same sine-wave waveform as the mains, except with a very small "crossover distortion" notch at zero crossings.

    The darlington transistors are "complimentary emitter-followers" and boost the current output of the opamp. :lol:
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    Uncle $crooge
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  3. 7th November 2005 12:19 PM #3
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    Oh yeah, I forgot.
    The darlingtons are rated for only 10A max so keep the peak-to-peak voltage of the sine-wave output into your 0.5 ohm load at or below 10V.
    With 10V p-p the load will dissipate 25W and each darlington transistor will dissipate about 10W.
    Uncle $crooge
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  4. 7th November 2005 01:19 PM #4
    tkvenki
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    Default Thanks a lot

    Hi,

    Thanks a lot for your help.

    Venkatesh T.K
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  5. 8th August 2008 12:13 PM #5
    zozi
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    Hi All

    Would you please assist I need to do a small elecronics energy meter to perform energy audit for home(tv, dvd) appliances to determine the impact they have on the bill .
    This is my college project and I have no idea on how to go about starting it.

    Can yuo please help with ideas
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  6. 8th August 2008 05:34 PM #6
    crutschow
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    Quote Originally Posted by zozi View Post
    Would you please assist I need to do a small elecronics energy meter to perform energy audit for home(tv, dvd) appliances to determine the impact they have on the bill .
    This is my college project and I have no idea on how to go about starting it.
    This should be in a new thread.

    Analog Devices makes several devices that monitor power http://www.analog.com/en/analog-to-d...cts/index.html. One of those should do what you need.
    Carl
    Curmudgeon Elektroniker
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  7. 11th August 2008 12:08 PM #7
    zozi
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    Default Many Thanks Carl

    Will have a look at it.

    Thanks
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