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Energy meter using ADE 7763

Discussion in 'General Electronics Discussion' started by aravindmgcee, Jun 11, 2012.

  1. aravindmgcee

    aravindmgcee

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    0
    Jun 11, 2012
    Hi,
    I am trying to do an single phase energy monitoring project. The voltage and current I want to measure is 240Vrms and 20A rms respectively.
    I am planning to use a voltage divider for voltage measurement and ACS 712 -20A for current measurement . Micro controller planning to use is pic 18f series. Energy meter Ic planning to use is ADE 7763.
    But i have no idea about how to design circuit of energy meter( i am at level 0 at energy meter). So please provide me with circuit diagram of energy meter using the components and specifications given above.


    thanks in advance....
     
    Last edited: Jun 12, 2012
  2. john monks

    john monks

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    Mar 9, 2012
    What is a ADE 7763?
     
  3. aravindmgcee

    aravindmgcee

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    Jun 11, 2012
    ADE 7763 is an energy meter ic manufactured by Analog devices.
     
  4. CocaCola

    CocaCola

    3,635
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    Apr 7, 2012
    Have you read the ADE 7763 datasheet? It contains working 'test' circuits as well as 50 some odd other pages of relevant info... They also sell an already built evaluations board that is fully documented...
     
  5. aravindmgcee

    aravindmgcee

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    Jun 11, 2012

    My doubt is that can I use acs 712 hall effect sensor ic for current measurement in ADE 7763??
     
  6. CocaCola

    CocaCola

    3,635
    5
    Apr 7, 2012
    I only did a quick glance at the datasheet (and I'm probably not going to read much more) but the ADE 7763 appears to have built in current and voltage sensing ability, why do you plan to use additional external devices?
     
  7. aravindmgcee

    aravindmgcee

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    Jun 11, 2012
    No... ADE 7763 can sense current and voltage through some external devices
     
  8. CocaCola

    CocaCola

    3,635
    5
    Apr 7, 2012
    Are you sure? Like I said I only quickly glanced over the info but it appears it has the capability to measure by itself... I have included a few cut and paste from the developer board datasheet...

    http://www.analog.com/static/imported-files/eval_boards/ADE7763EB.pdf
     

    Attached Files:

  9. aravindmgcee

    aravindmgcee

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    Jun 11, 2012

    Ya,, I'm sure about that...ade 7763 needs an external current sensor like shunt,current transformer or di/dt sensor.
     
  10. CocaCola

    CocaCola

    3,635
    5
    Apr 7, 2012
    I asked why you planned on using an external device like the ACS 712 -20A... Yes, the ADE 7763 needs a few external components to sense current but it doesn't require a complete solid state device like the ACS 712 -20A to do it...
     
  11. aravindmgcee

    aravindmgcee

    8
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    Jun 11, 2012
    Because ACS 712 is very small ic ,so my device will be small and it can measure upto 20A . Cost is also comparitively less.
     
  12. Harald Kapp

    Harald Kapp Moderator Moderator

    9,396
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    Nov 17, 2011
    Not knowing what's on the EVAL board in terms of additional circuitry, I looked at the datasheet.
    The AD7763 has "current sense" inputs, but these are voltage inputs that are meant to receive a voltage proportional to the current (or to di/dt). Therefore you need an external "current sensor" which will do the translation from current to voltage.

    1) put a small series resistor into the mains wire and use the voltage drop acrosss the resistor as input to the AD.
    advantage: very simple, low-cost, good accuracy
    disadvantage: no potential separation, AD will be on high potential (dangerous)

    2) put a current transformer into the mains wire. A current transformer with e.g. 1 primary winding and 1000 turns of secondary winding will give a 1:1000 current ratio. Thus 1 A of primary current forces 1mA of secondary current through the transfomer. Put a burden resistor across the secondary terminals of the transformer, then the current will generate a voltage drop across the resistor which is proportional to the secondary current or to 1/1000*primary current.
    advantage: sav due to potential separation
    disadvantage: costly, bulky, less accuracy, risk of transformer saturation in case of overcurrent, no measurement of DC components

    3) use a hall sensor to convert the magnetic field from the primary current to a proportional voltage.
    advantage: safe (potential separation), smaller than a transformer, can transfer DC components of the current, too, typically higher bandwidth than a transformer
    disadvantage: costly

    From the original specs I assume the device is to be operated at life potential of a 240 V mains. Therefore I suggest using one of methods 2) or 3) for safety reasons.
    I also suggest using a transformer (or more transformers for more than 1 phase) for the voltage input(s) instead of a voltage divider. Thus the AD is completely isolated from the mains and you can safely handle it.

    Furthermore there are two aspects to building a power meter.
    1) hardware
    2) software

    If you are going to build both from scratch, you are likely o have a hard time getting both set up correctly simultaneously. CocaCola's suggestion of using the eval board is a fairly good compromise, although at a prize, I admit. By using the eval board you can concentrate on getting the SW part right. Once this works and you have developed an understanding of the AD7763, you can still build your own hardware - but now you have a working reference.
    You will need to build the sensors (aka transfomer interfaces) for the eval board anyway and can reuse them for your later hardware project.

    Harald
     
    Last edited: Jun 12, 2012
  13. aravindmgcee

    aravindmgcee

    8
    0
    Jun 11, 2012
    Thanks Harald for the reply.
    I cant buy an evaluation board because of its cost. So I'm planning to make one. My idea is to use acs 712 for current sensing and voltage divider for voltage measurement. For isolation between ADE 7763 and pic I'm planning to use an optocoupler. Please provide me with circuit diagram if you have done this type of project.
     
  14. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    Sorry, I don't have a circuit diagram.
    But there is a complete schematic in the manual of the eval board (http://www.analog.com/static/imported-files/eval_boards/ADE7763EB.pdf page 13). you can use this for reference.

    I also strongly recommend using a transformer for voltage measurement, not a voltage divider.
    It is your own responsibility to observe all required safety measures when dealing with dangerous voltages and currents as in this case.

    Harald
     
  15. aravindmgcee

    aravindmgcee

    8
    0
    Jun 11, 2012
    thanks harald :)
     
  16. Harald Kapp

    Harald Kapp Moderator Moderator

    9,396
    1,919
    Nov 17, 2011
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