Password Based Circuit Breaker

The Password-Based Circuit Breaker is a straightforward project designed to manage electrical lines using a password.

The increasing frequency of electrical accidents involving linemen during maintenance activities due to poor communication between the electrical substation and maintenance staff has prompted the need for a solution. This initiative addresses this issue by prioritizing the safety of linemen. In this proposed system, the control (ON/OFF) of electrical lines is entrusted to the lineman. The project is configured so that maintenance personnel or linemen are required to input a password to activate or deactivate the electrical line.

In the event of a fault in an electrical line, the lineman can deactivate the power supply to the line by entering the password, facilitating safe line repair. After completing the repairs, the lineman can return to the substation and reactivate the power supply to the line by entering the password again. Each electrical line is associated with its own unique set of passwords.

To delve deeper into this circuit, you may want to explore the informative article titled “Locking System Based on a Password.”


  • Construction and Output Video
  • Block Diagram
  • Principle of Operation
  • Circuit Diagram of Password based Circuit Breaker
  • Components Required
  • How to Design Password based Circuit Breaker Circuit?
  • Algorithm 
  • Simulation Video
  • How to Operate the Password based Circuit Breaker Project?
  • Download Project Code
  • Advantages
  • Applications

Construction and Output Video

Block Diagram

Principle of Operation

The central element of the circuit is the 8051 microcontroller. In this project, a 4×4 keypad is employed for entering the password. The input password is cross-referenced with a set of pre-established passwords. When the input matches a valid password, it results in the activation or deactivation of the corresponding electrical line. In this project, each electrical wire is assigned a distinct password. The status of the lines, indicating their activation or deactivation (acting as circuit breakers), is visually represented through load indicators, typically in the form of light bulbs.

Circuit Diagram of Password based Circuit Breaker

Password Based Circuit Breaker

Components Required

  • 8051 Microcontroller (AT89C52)
  • 8051 Development Board
  • 8051 Programming Board (Programmer)
  • 4 x 4 Matrix Keypad
  • 4 – Channel Relay Module
  • 16 x 2 LCD Display
  • 10KΩ Potentiometer
  • 4 Loads (Light Bulbs)
  • Power Supply
  • Connecting Wires
  • If 8051 Development Board is not used, then you need
    • 0592 MHz Crystal
    • 2 x 33pF Capacitor
    • 2 x 10KΩ Resistors (1/4 Watt)
    • Push Button
    • 10µF Capacitor (Electrolytic)
    • 1KΩ x 8 Pull – up Resistor Pack
  • If Relay Module is not used, then you need (components mentioned for one load)
    • 5V or 12V Relay
    • 1KΩ Resistor (1/4 Watt)
    • BC547 NPN Transistor
    • 1N4007 PN Junction Diode

How to Design Password based Circuit Breaker Circuit?

The circuit comprises several components, including the 8051 series controller (AT89C52), a 4×4 Matrix Keypad, a 16×2 LCD Display, a 4-Channel Relay Module, and four loads. The LCD data pins are connected to PORT1, while the control pins RS, RW, and EN are linked to P3.0, GND, and P3.1, respectively. In this setup, the LCD serves as a means to display load-related information.

The microcontroller’s PORT2 is interfaced with the keypad. The keypad’s four row pins are connected to P2.0 through P2.3, while the four column pins are attached to P2.4 through P2.7. The input password is entered using this keypad.

Four lamps, representing electrical lines, are connected to P0.0 to P0.3 through the 4-Channel Relay Module. These lamps serve as indicators for the circuit breaker state, with a lit lamp indicating an active line and an unlit lamp indicating an inactive line.

If the Relay Module is not being used, an alternative approach involves utilizing four BC547 NPN Transistors, each with its corresponding current-limiting base resistor, to control the relays.


  1. Initially declare the PORT1 to LCD data pins and its control pins RS and E to P3.0 and P3.2 and P3.7 respectively. Also declare PORT2 to keypad and use P0.0, P0.1, P0.2 and P0.3 to loads.
  2. Initially display “enter password” on LCD.
  3. Now read the five digit password from the user.
  4. Compare the entered password with stored password.
  5. If the password matches, correct then ON or OFF the particular load and display line or load status on LCD.
  6. If the password is wrong, then display “wrong password” on the LCD.
  7. After some delay, again ask to enter password.

Simulation Video

How to Operate the Password based Circuit Breaker Project?

  1. Write the program to the Password based Circuit Breaker in Keil software and create .hex file.
  2.  Burn program to the controller with help of 8051 Programming Board and Willar Software.
  3.  Now give the connections as per the circuit diagram.
  4. While giving the connections, make sure that there is no common connection between AC and DC supplies
  5. Use 5V power supply circuit to provide regulated 5V DC to the controller.
  6.  Switch on the both AC and DC supplies.
  7. Now relay output pins gets 230V. So, do not touch the load connected pins.
  8. LCD displays “enter password”.
  9. Enter the password with help of keypad.
  10.  Now, if the password is correct, then circuit breaker changes its state (i.e. if it is already ON, now it becomes OFF and if it is already OFF, now it becomes ON) and displays line (or load) status on LCD.
  11.  If the password is wrong, then the LCD displays “wrong password”.
  12. After some time, the microcontroller asks to enter password by displaying “enter password”.


  • Avoids electrical accidents to line man
  • Project is simple and easy
  • Uses commonly available components


  • Used in electrical substations to ensure line man safety
  • This system is used in buildings and houses
  • Used in hotels and shopping malls to save the power. 
  • Can also be used as Password based electrical appliance control or Password based Load Control system.

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