current sensing using ADC of microcontroller

Discussion in 'General Electronics Chat' started by bishal, Mar 31, 2013.

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  1. bishal

    Thread Starter New Member

    Oct 12, 2011
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    I need a current sensor for MPPT based charge controller of max 10A current flowing.
    Since the controller shouldn't be expensive, I don't want dedicated current sensors. So I have 2 alternatives:
    1) Measuring voltage across Rsense using Op-amp.
    2) Measuring voltage across Rsense by ADC of microcontroller.
    I was wondered why no one is talking about using micro-controller for current sensing.
    Upto now I plan to go for option 2. But please if there are certain things I must consider or if you have a better option, please suggest.

    Bishal Paudel
     
  2. WBahn

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    Mar 31, 2012
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    The input voltage range of the ADC is almost certainly more than you want to drop across a current sense resistor.
     
  3. bishal

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    Oct 12, 2011
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    I think I will use 0.001 ohm resistor or lower. SO the drop will be less than 0.1V.
     
  4. t06afre

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    May 11, 2009
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    You will have to use an opamp to amplify the voltage across Rsense anyway. But using a ground based Rsense in this case will work just fine. And it will be much simpler than using a differential approach. Like option 1.
    For precession current measurement. A 10 bit ADC will not be quite optional. And I guess that is why you can not find much about it. But again in your application. If you can utilize the full of the ADC measurement span. I guess it will work fine
     
  5. WBahn

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    And the input voltage range of a microcontroller's ADC is typically going to be 10 to 50 times that, meaning that you will be losing 3 to 6 bits of resolution right off the bat. Unless you go back to option #1 and use an opamp to amplify the signal to something that better matches the MCU's input range.
     
  6. bishal

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    Oct 12, 2011
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  7. ErnieM

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    Apr 24, 2011
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    Not the worst idea... though the national code does not allow resistors in the return leg so this is a hobby use only design.

    Your amp has a gain of about 134. The sense resistor will have it's max drop of 10A * .01 ohms or 0.01 volts. So it's output is 13.4 volts... a little large don't you think?

    I didn't check the specs of the LM2904 but it must include a voltage range down to ground, as that is the low end of your signal.

    When I do this I use a high side current sense chip. Maxim and several other places make them.
     
  8. bishal

    Thread Starter New Member

    Oct 12, 2011
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    i modified my design as that of 3A, sorry for that as I am now doing only for 40 watt panel. so I think the voltage out max will be 4V.
     
  9. bug13

    Well-Known Member

    Feb 13, 2012
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    I think its a lot nicer to just use a high side current sensing chip.
     
  10. Engr_KHAN

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    Apr 13, 2014
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    I want a circuit which will sense the current input from PV or a 12 volt battery plus the output current drawn by load. A microcontroller has to sense the current and switch accordingly..... Is there any efficient method.... As to ADC usually a voltage is input and to be compared and digitized.... any idea or sensing circuit in proteus plz???????????
     
  11. nsaspook

    AAC Fanatic!

    Aug 27, 2009
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    For complete isolation use a Hall effect sensor. Most will directly interface with the ADC. http://ampsolution.com/AMPSOLUTION.html
     
  12. praj3328

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    Jan 29, 2015
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    how to detect blockage in seeder nozzle using sensoro_O. option of using light and photodiode is not allowed:(
    plz inform me if any other option is there:)
     
  13. MrChips

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    Oct 2, 2009
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    Please start a new thread.
     
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