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York Jong

Build this simple "electronic electroscope," a FET electrometer - 0 views

www.amasci.com/...chargdet.html

circuit electrometer electronics electrostatics fet mpf102

shared by York Jong on 30 May 07 - Cached
  • This simple circuit can detect the invisible fields of voltage which surround all electrified objects
  • ...9 more annotations...
  • The Gate acts as an antenna, so leave it unconnected.
  • The 1-meg resistor helps protect the FET from being harmed by any accidental sparks to its Gate lead. The circuit will work fine without this resistor. Just don't intentionally "zap" the Gate wire with a charged object or your charged finger.
  • To test the circuit, charge up a pen or a comb on your hair, then wave it close to the little "antenna" wire. The LED should go dark. When you remove the electrified pen or comb, the LED should light up again.
  • If you suspect that humidity is very high, test this by rubbing a balloon or a plastic object upon your arm. If the balloon does not attract your arm hairs, humidity is too high.
  • This FET sensor is not an ideal educational device because it responds differently to positive than to negative.
  • negative objects turn the LED off, it lights again when removed. positive objects make the LED bright, then dark when removed.
  • Obtain a small capacitor with a value below 100 picofarads. Connect it between the FET gate lead and one of the other FET leads (doesn't matter which one.) This greatly reduces the sensitivity of the device
  • Now make the circuit MORE sensitive. Obtain an alligator clip-lead, and connect it to the Gate lead of the FET. Let it hang loose without touching anything. You'll find that this has vastly increased the sensitivity of your FET circuit.
  • York Jong on 30 May 07
     
    This simple circuit can detect the invisible fields of voltage which surround all electrified objects. It acts as an electronic "electroscope.
York Jong

BEAM Circuits -- Field sensors - 0 views

www.solarbotics.net/...sensors_field.html

4star beam circuit electrometer sensor

shared by York Jong on 29 May 07 - Cached
  • note that the human body is a good absorber of stray RF fields, so this sensor should be a good people-detector
    • York Jong
      York Jong on 14 Jun 07
       
      should be shield, not sheilduses two of six inverting Schmitt trigger in a 74HC14 IC
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