Portable loads such as video cameras,halogen flood lights, electricalirons, hand drillers, grinders,and cutters are powered by connectinglong 2- or 3-core cables to the mainsplug. Due to prolonged usage, the powercord wires are subjected to mechanicalstrain and stress, which can lead to internalsnapping of wires at any point. Insuch a case most people go for replacingthe core/cable, as finding the exact locationof a broken wire is difficult. In 3-corecables, it appears almost impossible to detecta broken wire and the point of breakwithout physically disturbing all the threewires that are concealed in a PVC jacket.The circuit presented here can easilyand quickly detect a broken/faulty wireand its breakage point in 1-core, 2-core,and 3-core cables without physically disturbingwires. It is built using hex inverterCMOS CD4069. Gates N3 and N4are used as a pulse generator that oscillatesat around 1000 Hz in audio range.The frequency is determined by timingcomponents comprising resistors R3 andR4, and capacitor C1. Gates N1 and N2are used to sense the presence of 230V ACfield around the live wire and buffer weakAC voltage picked from the test probe.The voltage at output pin 10 of gate N2can enable or inhibit the oscillator circuit.When the test probe is away from anyhigh-voltage AC field, output pin 10 ofgate N2 remains low. As a result, diodeD3 conducts and inhibitsthe oscillator circuit fromoscillating. Simultaneously,the output of gateN3 at pin 6 goes ‘low’ tocut off transistor T1. As aresult, LED1 goes off.When the test probe ismoved closer to 230V AC,50Hz mains live wire, duringevery positive halfcycle,output pin 10 of gateN2 goes high.Thus during everypositive half-cycle of themains frequency, the oscillatorcircuit is allowedto oscillate at around 1 kHz, making redLED (LED1) to blink. (Due to the persistenceof vision, the LED appears to beglowing continuously.) This type of blinkingreduces consumption of the currentfrom button cells used for power supply.A 3V DC supply is sufficient for poweringthe whole circuit. AG13 or LR44type button cells, which are also used insidelaser pointers or in LED-based continuitytesters, can be used for the circuit.The circuit consumes 3 mA during thesensing of AC mains voltage.For audio-visual indication, one mayuse a small buzzer (usually built insidequartz alarm time pieces) in parallel withone small (3mm) LCD in place of LED1and resistor R5. In such a case, the currentconsumption of the circuit will bearound 7 mA. Alternatively, one may usetwo 1.5V R6- or AA-type batteries. Usingthis gadget, one can also quickly detectfused small filament bulbs in serial loopspowered by 230V AC mains.The whole circuit can be accommodatedin a small PVC pipe and used as ahandy broken-wire detector. Before detectingbroken faulty wires, take out any connectedload and find out the faulty wirefirst by continuity method using any multimeteror continuity tester. Then connect230V AC mains live wire at one end ofthe faulty wire, leaving the other end free.Connect neutral terminal of the mainsAC to the remaining wires at one end.However, if any of the remaining wires isalso found to be faulty, then both ends ofthese wires are connected to neutral. Forsingle-wire testing, connecting neutralonly to the live wire at one end is sufficientto detect the breakage point.In this circuit, a 5cm (2-inch) long,thick, single-strand wire is used as thetest probe. To detect the breakage point,turn on switch S1 and slowly move thetest probe closer to the faulty wire, beginningwith the input point of the live wireand proceeding towards its other end.LED1 starts glowing during the presenceof AC voltage in faulty wire. When thebreakage point is reached, LED1 immediatelyextinguishes due to the non-availabilityof mains AC voltage. The pointwhere LED1 is turned off is the exactbroken-wire point.While testing a broken 3-core roundedcable wire, bend the probe’s edge in theform of ‘J’ to increase its sensitivity andmove the bent edge of the test probe closerover the cable. During testing avoid anystrong electric field close to the circuit toavoid false detection.

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