Mains Load Current and Voltage Measurement

Discussion in 'Embedded Systems and Microcontrollers' started by aneeshmp200745, Feb 24, 2010.

  1. aneeshmp200745

    Thread Starter New Member

    Feb 24, 2010
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    plz any one can help me to design a circuit using pic microcntroller to measure mains voltage and load current without using current transformer or volage transformer. actually i wish to measure with pic microcontroller's internal ADC ,so how can i convert this mains voltage and load current to DC plz suggest me a good circuit or good link
    thanks in advance
     
  2. t_n_k

    AAC Fanatic!

    Mar 6, 2009
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    If you are not intending to use any galvanic isolation between the mains and measurement sides, how do you propose to make your system safe?
     
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  3. aneeshmp200745

    Thread Starter New Member

    Feb 24, 2010
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    BUT SIR ITS just for demo model just to work for an hour thats enough
    can u help me
     
  4. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Without isolation it is DANGEROUS.
    All of the circuit will be connected to the mains.

    Bertus
     
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  5. aneeshmp200745

    Thread Starter New Member

    Feb 24, 2010
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    okie then how can i build galvanic circuit for isolation purpose
    atually i need to measure mains supply and load current and i need to get it as analog quantity
    can i use optocoupler ????
    and i dont to how to convert this to DC i tried to rectify with traditional bridge recifier but its not getting done
    any one plz help me
     
  6. Markd77

    Senior Member

    Sep 7, 2009
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  7. t_n_k

    AAC Fanatic!

    Mar 6, 2009
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    Perhaps you could provide a specification of the anticipated voltage and current you want to monitor.

    I'm not sure why a simple rectifier for the voltage component didn't work. You should be able to do that part quite easily using a relatively cheap step down transformer with a secondary side rectifier plus some capacitive filtering to obtain your scaled equivalent DC term for the AC voltage. Maybe you might also need a resistive divider to scale / range the input to your micro-controller.

    Provide some more information about the AC current term and you might get some further suggestions for a cost-effective solution.
     
  8. aneeshmp200745

    Thread Starter New Member

    Feb 24, 2010
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    sir actaully i need to build a prepaid energy meter using rfid so the mains voltage 230v and current need to dispaly on lcd ,im using pic microcontroller for this purpose so how can i convert these parameters to analog quantity so that i can directly take this to pic microcontroller usings piCs internal ADC and calculate power consumption plz help me sir
     
  9. n9352527

    AAC Fanatic!

    Oct 14, 2005
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    The simplest solution is to use an energy measurement IC. Such as ADE7753, or another from the same family http://www.analog.com/en/analog-to-digital-converters/energy-measurement/products/index.html. There are also other sources, such as Microchip.

    If you are going to design your own system, make sure you consider the power factor, linearity and the range of measured current. A power meter has to be accurate from low current, in mA range up to maybe tens of amperes.
     
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