Current sense amplifier with lm358

Discussion in 'General Electronics Chat' started by blind2_man, Jan 20, 2012.

  1. blind2_man

    Thread Starter Active Member

    May 12, 2008
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    Hello,

    I am working on a testbench power supply and one block is current sense amplifier to display the current consumption.
    Is it posible to design a current sense amplifier with lm358 and read the voltage with ADC block in microcontroller?
    If you have any reference would be great.
     
  2. t06afre

    AAC Fanatic!

    May 11, 2009
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    Can you post your current design?
     
  3. blind2_man

    Thread Starter Active Member

    May 12, 2008
    33
    1
    my_design.JPG
    This is what I have done, but it is not working, in simulation is ok but implemented on PCB is not working, output remains close to 0 for currents in range [0 1.5A].
    The current measurement is on resitor 0.1Ohm used also for current measurement on series regulator with LM723, output of LM723 is driving a darlignton configuration made by BD135 and 2N3055.
     
  4. t06afre

    AAC Fanatic!

    May 11, 2009
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    Your schematics was somewhat hard to read. But anyway this will be your basic circuit http://www.allaboutcircuits.com/vol_3/chpt_8/10.html This circuit will give out (V2-V1) times the amplification factor. The 0.1 ohms resistor will give a voltage drop equal to I*R. Use the circuit above to measure this voltage drop. Select a proper amplification factor and feed this voltage to the ADC on the micro. It is important that the power supply voltage used by the opamps is higher than the output voltage from the LM723
     
  5. blind2_man

    Thread Starter Active Member

    May 12, 2008
    33
    1
    My prototype containts only output stage.
    This realy a useful link, thank you t06afre.
    What operational amplifier to you recomend?
     
    Last edited: Jan 20, 2012
  6. t06afre

    AAC Fanatic!

    May 11, 2009
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    As for now use the one you have. It can be used in a single supply configuration. And that would be ideal in your setting
     
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