Friday, August 28, 2009
Live-line Detector
If the unit is brought close to a live conductor (insulated, and even buried in plaster) capacitive coupling between the live conductor and the probe clocks the counter, and causes the LED to flash 5 times per second, because the 4017 IC divides the mains 50Hz frequency by 10.When remote from a live line, the unit stops counting, the LED resulting permanently off.
Parts:
C1____________100nF 63V Polyester or Ceramic Capacitor D1_____________Red LED (any type) IC1____________4017 Decade counter with 10 decoded outputs IC P1_____________SPST Pushbutton B1_____________3V Battery (two 1.5V AA or AAA cells in series etc.) Sensing probe__3 to 15 cm. long, stiff insulated piece of wire Notes: * Sensitivity can be varied using a more or less long sensing probe. * Due to 3V operation, the LED's current limiting resistor can be omitted.
.
.
.
.
.
0 comments: