Current Sensing IC

Discussion in 'The Projects Forum' started by markmelive, Dec 20, 2012.

  1. markmelive

    Thread Starter Member

    Aug 13, 2012
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    Hello Guys,


    Need Help!! I want to sense the current of the load and feed it back to the microcontroller ADC. So basically I want to sense the current driving by the load (flashing lights) and adjust the load current accordingly, like a diagnostic system which sense the load current and adjust it accordingly. In this, I am totaly confused whether to use current sensing switches or current sensing amplifiers. Kindly help me in this regard. The flashing lights drives 1.2A current and supply voltage is 12v.

    Thanks in advance
     
  2. John P

    AAC Fanatic!

    Oct 14, 2008
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    Let's see now, what did you find when you dropped the title of this thread, "Current Sensing IC" into Google?
     
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  3. markmelive

    Thread Starter Member

    Aug 13, 2012
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    I found many from Linear Technology, MAX4080 etc but didnt find the one which may be suitable or my project.
     
  4. John P

    AAC Fanatic!

    Oct 14, 2008
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    No, the MAX4080 is perfect! Buy a thousand of them immediately.

    Or perhaps you can explain why it isn't perfect.
     
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  5. BillB3857

    Senior Member

    Feb 28, 2009
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    Try a Google on LTS25-NP. It might work for you.
     
  6. markmelive

    Thread Starter Member

    Aug 13, 2012
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    Thank u . Max4080 works fine but, I am getting the output with large variation. :( Any idea????
     
  7. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    Your flux capacitor has gone bad.
    Seriously though, post the actual circuit and what you´re measuring. No one here is an oracle.
     
  8. RRITESH KAKKAR

    Senior Member

    Jun 29, 2010
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    I have listen about Ct...
     
  9. markmelive

    Thread Starter Member

    Aug 13, 2012
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    For example: The sense resistor used is 0.1 ohm (RSENSE) and voltage accross sense resistor is 0.07v. The gain of the max4080 used is 60. So, Vout should be 0.07 x 60 = 4.20V but infact I am getting Vout = 4.68. More variation. Can any one pls tell me to get less variation. So that I can measure the current more accurately.
     
  10. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    Except for Rritesh obviously, but no one understands what he means.
     
  11. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    For example, are you sure the sense resistor is exactly 0.1000ohms and the sensed voltage is exactly 0.070000V? What is the common mode voltage on the sense resistor?
    Do you have at least one 100nF ceramic bypass capacitor right next to the chip? Is the measured current truly DC?
     
  12. markmelive

    Thread Starter Member

    Aug 13, 2012
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    Here is the circuit attached!
     
  13. markmelive

    Thread Starter Member

    Aug 13, 2012
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    @kubeek: pls check the circuit which i have uploaded
     
  14. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    So, you are measuring some pwm current with an ordinary dc voltmeter, and expect to get accurate and consistent results? Or how fast are the lights flashing?
     
  15. markmelive

    Thread Starter Member

    Aug 13, 2012
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    light flashes twice in a second. Similar to ambulance vehicle flashing lights.
     
  16. markmelive

    Thread Starter Member

    Aug 13, 2012
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    @kubeek: I checked with the steady lights (drawing constant 0.74A current) not flashing lights.
     
  17. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    So, are you sure the current you measure is exactly 0.74A, the voltage on the sense resistor is exactly 70mV, etc.? Can you try it with different current, to see if what you get is just offset or the gain is different?

    Actually you could use a potentiometer and check what the output does as you vary the voltage on the sense pins.
     
  18. markmelive

    Thread Starter Member

    Aug 13, 2012
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    Yes, current drawn by the steady light is 0.74A and the voltage accross 0.1 sense resistor is 70mv. I am using a DC supply not battery of fixed 12v. So i can varry suppy voltage 0v-12v. By varying the supply voltage, the Vout changes. So wot do u think, is the circuit right? or wot else extra i have to add to the circuit, except the 100nf decoupling capacitor near the supply voltage ?.
     
  19. markmelive

    Thread Starter Member

    Aug 13, 2012
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    Or do u want me to change the resistor to 0.005 and check the output?. Because it is the lowest sense resistor i have got.
     
  20. markmelive

    Thread Starter Member

    Aug 13, 2012
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    Come on guys any one help!!!
     
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