20-12-2012, 01:12 PM
A Project On INVISIBLE BROKEN WIRE DETECTOR
1INVISIBLE.docx (Size: 52.57 KB / Downloads: 36)
INTRODUCTION
portable loads such as video cameras, halogen flood lights, electrical irons, hand drillers, grinders, and cutters are powered by connecting long 2- or 3-core cables to the mains plug .
Due to prolonged usage, the power cord wires are subjected to mechanical strain and stress ,which can lead to internal snapping of wires at any point.
In such a case most people go for replacing the core/cable, as finding the exact location of a broken wire is difficult.
In 3-corecables, it appears almost impossible to detect a broken wire and the point of break without physically disturbing all the three wires that are concealed in a PVC jacket
Working
The circuit presented here can easily and quickly detect a broken/faulty wire and its breakage point in 1-core, 2-core, and 3-core cables without physically disturbing wires. It is built usinghex inverter CMOS CD4069. Gates N3 and N4 are used as a pulse generator that oscillates ataround 1000 Hz in audio range.
The frequency is determined by timing components comprising resistors R3 and R4, and capacitor C Gates N1 and N2 are used to sense the presence of 230V AC field around the live wire and buffer weak AC voltage picked from thetest probe. The voltage at output pin 10 of gate N2 can enable or inhibit the oscillator circuit.When the test probe is away from any high-voltage AC field, output pin 10 of gate N2remains low. As a result, diode D3 conducts and inhibits the oscillator circuit fromoscillating. Simultaneously, the output of gate N3 at pin 6 goes ‘low’ to cut off transistor T1.As a result, LED1 goes off. When the test probe is moved closer to 230V AC, 50Hz mainslive wire, during every positive half cycle, output pin 10 of gate N2 goes high. Thus duringevery positive half-cycle of the mains frequency, the oscillator circuit is allowed to oscillateat around 1 kHz, making red LED (LED1) to blink. (Due to the persistence of vision, theLED appears to be glowing continuously.)