Current sensing circuit

Discussion in 'General Electronics Chat' started by aris, Jun 4, 2010.

  1. aris

    Thread Starter Member

    May 5, 2010
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    Hi all,

    continuing from my previous posts let me give an explanation of what I want to do.
    I already have built a circuit that gives me an interrupt on a 12V input for 2 minutes through a 555 timer and a relay, as well as a 2 minute delay based upon a CMOS 4000 series and a selection of resistors and capacitors. What I wan to do is to trigger this circuit with a threshold of 1A. If current Is lower than 1A to have an output of 12V or 11V otherwise when current is higher than 1A to have an output of 0V.
    The purpose of this circuit is to build a circuit that will detect is a pc box is on or off. When the box is off I want to cut-off the voltage supply(current 1A or less) for 1 minute and then give it back to the circuit, otherwise the circuit should stay neutral for.
     
  2. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    Where is the sensor part, or am I missing this.
    The current sensor that is.
     
  3. aris

    Thread Starter Member

    May 5, 2010
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    I am after the circuit that will sense the current and give an output towards the rest of the circuit I already have.
     
  4. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    so basically u want a way to sense load current and produce a proportional output voltage for the circuit above
     
  5. aris

    Thread Starter Member

    May 5, 2010
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    Yes that's what I am after!
    What do you mean by proportional?
     
  6. achilez

    New Member

    Mar 23, 2010
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    1
    He probably means

    E.g., a current through a small sense resistor will cause a voltage drop over the resistor. The voltage drop will be proportional to the current, as per Ohm's Law.
     
  7. cagriaksu

    New Member

    Jun 7, 2010
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    it took my attention that you are gonna integrate this circuit to a pc right?
    Are you trying to auto-boot a pc whenever it shuts down?
     
  8. aris

    Thread Starter Member

    May 5, 2010
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    ok I see what you mean achilez and that is exactly what I want to do along with the spec I have set on my first post!

    What I want to do cagriaksu is to have a system that would perform a power cut to the box when the box is detected to be off. I found that when the box I have is of consumes 1A and while operating more than that (max 3.6A). this would get in line with the 12V power supply of my box.
     
  9. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    1A at standby is not possible. Are u sure about this?
     
  10. aris

    Thread Starter Member

    May 5, 2010
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    When the box is off(not in stand by/hybernate or something similar) the current consumption is 1A. I know that this sounds weird but it is true...
     
  11. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,771
    971
    Just buy a properly rated current shunt. Typically they have a 0-50mv (or 60 or 100mv) output depending on the amount of current through them. Your shunt should be derated by 33% to avoid overheating which will throw off the calibration of the shunt.
     
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