The celebration is taking place at your house today. And at this very moment, your attention is focused on locating any malfunctions in the ornamental lights that are strung along the exterior of your home. It is important that the task be completed before the evening. However, daylight makes it more difficult for you to detect whether the neon bulb included within the tester is glowing or not, which adds to your sense of irritation. A neon bulb is typically utilized in traditional continuity testers for live-voltage testing in order to show the presence of live voltage. However, their brilliance is only noticeable when used inside. If it were an extremely bright LED or buzzer, it would be possible to see it in the daytime even when you were outside the house. The live-wire scanner that is being discussed in this article not only makes use of an LED, but also a piezobuzzer that makes a chirping sound like a bird when it locates the place of break in a wire that is located inside the sheath. The circuit is made up of a few discrete components in addition to a piezobuzzer that is wired all the way around a CMOS Johnson decade counter CD4017 (IC1). This decade counter/divider contains ten decoded outputs (Q0 through Q9), a divided (divide-by-10) output that is accessible at its pins 3, 2, 4, 7, 10, 1, 5, 6, 9 and 11, respectively, and a carryout bit at pin 12. At the positive edge of each input pulse that is received at pin 14, the count of the CD4017 advances by one. After Q9 at pin 11 gets high, this decade sequence will continue to repeat.

Fig. Continuity tester circuit Because of the extraordinarily high input impedance of CMOS integrated circuits and the fact that they are voltage-controlled devices, it is simple to set off a CMOS IC with even relatively weak stray signals, such as the electric field of a 220V live-wire. The same fundamental idea underlies the operation of this circuit. Even if a live wire is 20 centimeters distant from a metallic strip, the potential across clock input pin 14 of IC1 can still swing to high and low logic levels when it is attached to a small metallic strip. This is because the potential is connected to a small metallic strip. This causes the counter to start counting, and a squarewave output with a frequency of 50 tenths of a hertz, or 5 Hz, is generated at pin 12 of IC1. Now, this extremely high sensitivity of the clock input can be decreased to the required extent by connecting a voltage divider composed of passive components of the proper value. This, in turn, decreases the input impedance, which, in turn, lessens the sensitivity. The device is able to respond from up to 10 centimeters distant from the live wire in the event of an emergency. The wire can be scanned with this

configuration to look for any breaks or discontinuities inside the sheath where it is housed. Circuit operation When IC1's output pin 12 is driven high, a pulse is sent through capacitor C3 to make transistor T1 conduct, and it also charges capacitor C4 at the same time. Because of the charged capacitor C4, which is discharged through the resistor R3, transistor T1 continues to conduct for a little period of time after pin 12 is brought low. When capacitor C4 is discharged, there is an exponential movement of the transistor T1 from the saturation region to the active region and subsequently to the cut-off zone. Variations in the voltage across the buzzer cause corresponding shifts in the pitch of the sound produced by the buzzer. The chime of the buzzer is silenced at last. A chirping sound is produced as a result of the repetition of this operation at a frequency of 5 Hz. During this operation, LED1 will also blink. This continuity tester circuit does not require any ground terminal to be touched with a finger, as is required by traditional continuity testers. Therefore, it is quite safe in the event that a contact within the circuit becomes dysfunctional. Install all of the components, including a lithium battery, on a PCB designed for general use, then enclose the whole thing in a plastic cabinet.