Introduction: EAL- Embedded - Combination Lock

About: Tomasz Bojanowski

This project is one school project, which I have made to choose subject 2.1 C-programming in the EAL. It is the first time, when I made an Arduino project and C-programming. That is a project, which presenter a combination lock. A combination lock can we use in many places every day. We can use that among other in the safe or when we need to open some door.

Step 1: Components

To at create that project, I have used the following components:

  • Arduino mega 2560
  • LCD 2x16 HD44780 blue
  • Konverter LCD HD44780 I2C IIC
  • SERVO Tower Pro SG92 9g
  • Keypad 4x4 8pin
  • Led blue
  • Contact plade
  • Connection wires
  • Power bank

Step 2: Connection

The above picture and the following description presents how all components are connected to the Arduino Mega 2560.

LCD end KONVERTER - Arduino 2560 Mega


VCC - 5V



KEYPAD - Arduino 2560 Mega

conected A0 A1 A3 A4 A5 A6 A7

SERVO - Arduino 2560 Mega


VCC - 5V

SIGNAL - 8 Pin

Step 3: Programming

I have started programming in that way that I have found the library to LCD, password, keypad . Next, with help easy programs in Arduino I have checked, that my components working good. One of the biggest problem was, that converter has not communication with LCD. After one long day and evening I have found a problem. Problem was the wrong address in converter. Next step was to finish a program.

Keypad, I have used to entering the code. (1111)

Servo is working like an unlocking mechanism.

LCD is showing the code, which I have entered. (1111)

Program is working in that way that after I enter the correct code, the blue led lights up and servo performs a 90-degree movement.

Step 4: Testing

In the testing, I have entered code (1111), with I approved with the star. After I have entered the correct code on the LCD, I could see inscription OPEN, and the blue led lights up and servo make a 90-degree movement. When I have wrote a wrong code, I could see inscription WRONG.

The device is working properly and without any problems.

That is an easy project, which we can use in a lot of situation and places.