A circuit that can help you identify breaks in wires without needing to physically expose the wires themselves.
That is a broken cable detector circuit, it works like a metal detector for wires, but instead of metal it sniffs out AC electricity around the wire.
The circuit uses a special chip called a CD 4069, which has tiny switches that can light up an LED or make a buzzer beep.
When the detector finds a good wire with electricity flowing, it beeps or lights up.
But if there is a break, the electricity stops and the detector stays silent and dark.
Circuit Working:
Parts List:
| Component Type | Description | Quantity | Notes |
|---|---|---|---|
| Resistors | All 1/4 watt unless specified | ||
| 1M | 1 | ||
| 10k | 1 | ||
| 220k | 1 | ||
| 470k | 1 | ||
| 330Ω | 1 | ||
| 1.2k | 1 | ||
| Preset 20k | 1 | ||
| Capacitors | |||
| Ceramic | 100nF | 1 | |
| 470pF | 1 | ||
| Semiconductors | |||
| IC | CD4069 | 1 | |
| Transistor | BC547 | 1 | |
| LEDs | |||
| Red Green 5mm 20mA | 1 | ||
| Green 5mm 20mA | 1 | ||
| Diode | |||
| 1N4007 | 1 | ||
| Miscellaneous | |||
| Buzzer | 5V | 1 | |
| Antenna | 1 | ||
| Battery | 9V | 1 |
With a CD 4069 IC, we may construct a simple broken cable detecting circuit.
This chip, which is frequently utilized in electronic applications, has six inverter circuits.
The circuit can identify the electromagnetic field EMF produced by an AC current carrying wire, but it cannot determine the precise site of the break.
The circuit wont detect the EMF and wont provide a sound or light alarm if the wire is severed.
The resistors R3, R4 and capacitor C2 enable the CD 4069 to function as an oscillator.
This generates a signal at around one kilohertz kHz.
Transistor Q1 is a switch that is managed by pin 12 of the CD4069.
LED1 illuminates when the circuit senses an EMF on the test wire.
LED2 on the other hand illuminates when no EMF is detected.
The EMF detecting antenna is a specifically formed wire with a spiral shape that is about 15 cm long and should not come into contact with the AC supply directly.
It is possible to modify the sensitivity of the circuit by using a variable resistor VR1.
When checking AC cables, keep safety as your first priority.
Never put your naked hands near live wires!
Formulas:
Here are some recommendations and formulae to help you create a Broken Cable Detector Circuit utilizing the IC CD4069 and the needed components:
Current Limiting Resistor for LEDs:
To restrict the current, figure out the resistor RLED for each LED.
RLED = Vsupply − VLED / ILED
where,
- Vsupply, which stands for supply voltage 9V battery
- VLED which stands for forward voltage drop of the LED (usually about 2V for Red and Green LEDs)
- ILED, which stands for required LED current (20mA).
Base of Transistor resistor
To guarantee appropriate saturation, calculate the base resistor Rbase for the BC547 transistor.
Rbase = Vin − Vbe / Ib
where,
- Vbe is the base emitter voltage of the transistor, which is around 0.7V
- Vin is the input voltage (from the IC output)
- Ib is the base current needed for saturation.
Timing capacitor, if used:
For every timing circuit, get the value of the timing capacitor C using
C = T / 1.1 × R
where,
- T is the desired timing interval in seconds and R is the resistor value in ohms.
Note:
The particular specifications and working principles of the broken cable detection circuit will determine the precise circuit layout and component quantities.
Depending on the results of real testing and performance requirements, experimentation and modifications can be required.
You may start efficiently building and testing your Broken Cable Detector Circuit by using these formula and considerations.
To obtain desired functionality and maximize performance, make necessary adjustments to component values and settings.
How to Build:
To build a Broken Cable Detector Circuit using IC CD 4069 follow the below mentioned steps for connections
- Gather all the components as mentioned in the diagram above.
- Connect pin 1 of IC CD 4069 to antenna.
- Connect pin 2 to pin 3 of IC CD 4069 .
- Connect a series of resistor R1, R2 and preset VR1 from pin 1 of IC CD 4069 to ground.
- Connect pin 3 of IC CD 4069 between resistor R1 and resistor R2.
- Connect pin 4 to pin 5 of IC CD 4069, and again connect same pin 4/5 to pin 13 of IC CD 4069.
- Connect pin 6 to pin 11 of IC CD4069, through capacitor C2, diode D1, and resistor R3 in series.
- Connect pin 7 of IC CD 4069 to ground.
- Connect pin 9 of IC CD 4069 between diode D1 and resistor R3.
- Connect pin 10 of IC CD 4069 between capacitors C1 and anode of buzzer.
- Connect pin 11 of IC CD 4069 to ground in series through resistor R4, capacitor C1, and buzzer 5V.
- Connect pin 12 of IC CD 4069 to base of transistor Q1.
- Connect pin 14 to positive supply of of 9V battery.
- Connect collector of transistor Q1 to positive supply, base of transistor Q1 to pin 12 of IC CD 4069, and emitter of transistor Q1 to ground through resistor R5 and LED1.
- Connect an LED1 and series resistor R6 across the positive and negative supply lines.
Safety Notes:
- Keep in mind that working with electricity requires the utmost caution.
- Seek expert assistance if you are uncomfortable or unsure about any step.
Conclusion:
To conclude, the CD 4069 IC based broken wire detector circuit provides an easy method of locating wire breaks without requiring direct physical contact.
It is not able to locate the break precisely, but it is able to identify the existence of an AC electromagnetic field surrounding the wire.
This circuit is a useful tool for doing simple troubleshooting.
It is essential to bear in mind that seeking the advice of a certified electrician is always advised when doing electrical repairs or handling high voltage.
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