AC Current Transducer project

Discussion in 'The Projects Forum' started by J.Green, Jul 8, 2010.

  1. J.Green

    Thread Starter Member

    Jul 15, 2008
    26
    0
    Hi,

    I have an AC current transducer that outputs either 10 mV per amp or 1 mV per amp. The range is selected by the user. Here is the transducer.

    http://www.dealexcel.com/old/ms3302-clamp-meter-transducer-ac-current-true-rms-product-442.html

    I want to build a circuit based on a PIC microcontroller. When the current through the wire to which the transducer is clamped to exceeds 0.5A, I would like to make one of the PIC inputs low. I am familiar with programing the PIC and should be ok there. I am not sure on what the best approach is to convert the mV from the transducer to something I can use to send the PIC. I am using a 12F675. I am familar with ADC if required.

    The transducer has a maximum rating of 400A. I would like to be able to send the PIC input low for any current between 0.5A and 400A. I would like to be able to do this for either the 10mV/A or the 1mV/A range.

    I have read about opamps, but never used on in a circuit before. Any suggestions on the best way of doing this would be appreciated.

    Thank you
    JG
     
  2. John P

    AAC Fanatic!

    Oct 14, 2008
    1,634
    224
    It seems as if there's nothing you need to do except set the current sensor for 10mV/Amp and send its output to the A/D input of the PIC. The only thing to be concerned about is the output impedance of the sensor: if it's above 1K or so, you might want to buffer it. Otherwise, I don't see a need for any added components.

    At 10mV/Amp and 400 Amps max, you'd get 4.0V at the A/D input, which is fine. At least, it's fine if the PIC power supply is as high as the A/D input, and you should be aware that the range of the A/D will be the power supply, so each "quantum" that you measure will be 1/1024 of the supply voltage.
     
  3. J.Green

    Thread Starter Member

    Jul 15, 2008
    26
    0
    The specs on the link are wrong. The transducer is spitting out AC voltage. Not sure on best way to make this usable for the PIC. Any suggestions.

    Thank you.
    JG
     
  4. Dx3

    Member

    Jun 19, 2010
    87
    7
    Build a precision rectifier with an op-amp. That will produce DC voltage in direct proportion to the AC voltage.

    That is, if you need DC. Do you need DC?
     
  5. J.Green

    Thread Starter Member

    Jul 15, 2008
    26
    0
    Yes, I need DC. Never worked with Op amps. Any suggestions on type to use and circuit?

    Thanks
    JG
     
  6. Dx3

    Member

    Jun 19, 2010
    87
    7
    One way is to google "precision rectifier schematic" and you'll get some of these.
     
  7. Dx3

    Member

    Jun 19, 2010
    87
    7
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