Measurement of Current flowing through mains and sending value to micro-controller!

Discussion in 'The Projects Forum' started by withloveshyam, Mar 20, 2010.

  1. withloveshyam

    Thread Starter New Member

    Mar 20, 2010
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    Hi
    I am doing a home automation system project and in it I want to measure the current flowing through the mains wire of a device, say refrigerator(current consumed by the refrigerator)and send the value to a micro controller from time to time.

    I know that there are a lot of devices available in the market for doing this. But let me know the most efficient and cost effective device for this application.

    Thanks a lot for your help.
     
  2. hgmjr

    Moderator

    Jan 28, 2005
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    I have re-enabled this thread since you requested the other one deleted.

    hgmjr
     
  3. beenthere

    Retired Moderator

    Apr 20, 2004
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  4. hgmjr

    Moderator

    Jan 28, 2005
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    Here is a link to a clamp-on current transformer in the Digikey catalogue similar to the product that beenthere has suggested.

    hgmjr
     
  5. withloveshyam

    Thread Starter New Member

    Mar 20, 2010
    20
    0
    Hi
    thanks for the reply.

    1)I wanted to know if this transformer will directly measure the current consumed by appliances like TV, Refrigerator..

    2)What will be the output of this transformer..Will it give the current value or the voltage value..If so how to infer the current value from that?

    3)Then i saw this line in the datasheet of the digikey link "High secondary turn will develop signals up to 10.0 Vac across a burden resistor"

    What does this mean?

    4)Then do i need to provide power supply for it? If so how much?

    thanks...
     
  6. hgmjr

    Moderator

    Jan 28, 2005
    9,030
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    The output voltage from a current transformer is proportional to the peak amount of current that is to be monitored. Whether you need a power supply depends on what you intend to do with the output of the sensor.

    hgmjr
     
  7. DickCappels

    Moderator

    Aug 21, 2008
    2,650
    632
    Generally, and with respect to the current transformer in the Digikey link, the current to be observed or measured is passed through the current transformer primary. The secondary is loaded, often with a resistor. The most common application, such as yours, uses a current transformer to reduce the current.

    The transformer in the Digitkey link has a 1:3000 turns ratio, which means that for every 3 amps on the primary, there will be 1 milliamp on the secondary. That means you would dissipate very little power in the secondary, and loose very little voltage in the primary because of the insertion of the transformer.

    The output of the transformers mentioned in the links above are reduced current replicas of the input current waveform.

    For your application, the best way to measure the current is to use an A/D converter (preferably already on your microcontroller) and either sample the waveform and take the RMS value or simply assume the waveform is a sine wave and sample the waveform to find the maximum and minimum peaks, then divide by 2.82 to find the RMS.

    Here is a current transformer you can build yourself if you have access to the materials. More importantly, the link contains the formulas to calculate the number of turns, etc.

    http://tinyurl.com/ycn84l6
     
  8. withloveshyam

    Thread Starter New Member

    Mar 20, 2010
    20
    0
    thanks for the replies.....

    @ Mr.Alberto
    THanks for the reply.. I would like to know if i need to purchase the phidget interface kit also or if just the current sensor is enough.

    Then reg. the power supply to the current sensor. The analog input cable connectors are supposed to give the power right? If so how do i give the power connections? Simply connect the 5 V battery?

    Then reg. the getting the current sensor value to the microcontroller, how do i do it? As i dont think the cable connector will fit into the microcontroller's ADC input?

    I mean in all these questions i am concerned about the connectivity between the microcontroller and the current sensor.

    Kindly give me a detailed explanation.
    As i am new to this field.

    thanks..
     
  9. withloveshyam

    Thread Starter New Member

    Mar 20, 2010
    20
    0
    Thanks very much for the reply. I think i ll go with this product.

    Anyways is the site that u had given in the link the best one to get this product?

    Is there any other place where i can get it for cheap..I am in California..So shipping comes around 13$ as it is shipped from canada.

    then can i have ur email id. So that i can get in touch with u if i have any questions after i purchase the product.

    Then reg. the battery will a normal 5V DC battery serve the purpose?

    thanks for all ur help.
     
  10. withloveshyam

    Thread Starter New Member

    Mar 20, 2010
    20
    0
    thanks very much for the reply.

    I would like to know if the link given by u is the best place to buy this product?

    As it ships from Canada. the shipping cost around 13$

    I live in California.

    And can u also lemme know ur email id so that i can mail u if i have any doubts after i purchase the kit.

    thanks very much.
     
  11. withloveshyam

    Thread Starter New Member

    Mar 20, 2010
    20
    0
    Ignore my previous reply.

    then i went thru the link that u gave..

    it says that the current that it can measure is 5A ac/DC.

    but if i use it to measure the current of refrigerator/ TV i think i ll get an error as their current rating is more than 5A.

    Am i right?
     
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