Measuring Voltage from the Mains

Discussion in 'The Projects Forum' started by Viann, Jun 24, 2009.

  1. Viann

    Thread Starter New Member

    Jun 16, 2009
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    My project is to build a digital watt meter, to measure the Voltage, Current, Power, etc. from an appliance connected.

    My question is, is there a way I could measure voltage from a 240V/50Hz mains connecting to an appliance?
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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    Generally speaking, a voltmeter works extremely well. In your case, using a transformer to reduce the voltage by some known factor and to provide galvanic isolation might be a start. Rectifying and filtering the voltage makes applying it to an ADC much simpler.

    Use a current transformer for that function, and you have your instrument under way.
     
  3. studiot

    AAC Fanatic!

    Nov 9, 2007
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  4. n9352527

    AAC Fanatic!

    Oct 14, 2005
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  5. Tahmid

    Active Member

    Jul 2, 2008
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    You can use a sense resistor that creates a specific voltage across it at a specific current. Use the formula V=IR, thus R = V/I.
    Then amplify this voltage using a non-inverting amplifier and then send this to a PIC to sense the voltage, thus you know how much current passed through. Then sense the voltage before the resistor. Amplify and send to PIC. Now you know the voltage. Use software to calculate the Wattage and you know everything.
    Hope this helps.
     
  6. studiot

    AAC Fanatic!

    Nov 9, 2007
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    Phase angle?
     
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