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Static Detector

Discussion in 'General Electronics Discussion' started by yllawwally, Nov 4, 2016.

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  1. yllawwally

    yllawwally

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    Nov 4, 2016
    This circuit detects Negative and Positive Static Fields. However sometimes, if the field is high enough, it will cause the circuit to latch(The LED remains lit even if static field is removed). There is a physical switch to clear it. I'm hoping someone here, would know a way to modify this circuit, such that it won't latch. I don't want to have to push the button to clear it.
    FDS89s8A.jpg
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    What is an FDS8589A? Can you point me at the datasheet you're working from?
     
  3. yllawwally

    yllawwally

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    Nov 4, 2016
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,448
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    Jan 21, 2010
    Hmmm... I've seen schmitt trigger inverters used in circuits like this. They have a much lower gate charge, and the inputs are slightly better protected.

    That gate capacitance is the reason the LED stays turned on. The switch should discharge it nicely, but beware that if the gate voltage gets too high, the mosfet will be destroyed.

    You probably want to be very careful near the gates of these devices to ensure that the board resistance (or residue of flux, etc) don't provide a lower impedance path to ground. This will at the very least reduce the sensitivity, but may stop it working altogether.
     
  5. Colin Mitchell

    Colin Mitchell

    1,417
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    Aug 31, 2014
    Have you tried putting 1M to 10M on each probe to positive or negative.
    I use 4069UB with 20M
    see talking electronics.com website for circuit

    Mains Tracer
     
  6. yllawwally

    yllawwally

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    Nov 4, 2016
    I tried a 10M ohm before the antenna. It didn't help. I also tried that resistor plus another 10M going to ÷ or -, which also didn't do much.
     
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