Digital code lock or digital combination lock are a type of digital locks where a combination of digits/characters or both are used for unlocking the lock. This article is about a simple digital code lock using arduino. Here the code consists of a combination of digits from 1 to 6.
There are separate keys for locking and unlocking the system. The system can be unlocked by pressing the unlock button after entering the correct combination of digits. A hex key pad is used as the input device. Only the first two rows of key (1, 2, 3, A, 4, 5, 6, B) are used in this project. A is used for locking the system and B is used for unlocking the system. Read this article Interfacing hex keypad to arduino for knowing more about hex keypad and its interfacing to the arduino. The circuit diagram of the digital code lock using arduino is shown in the figure below.
Row pins R1 to r4 are interfaced to digital pins 6 to 9 of the arduino. Column pins C1 to C4 are interfaced to digital pins 10 to 13 of the arduino. Digital pin 3 of the arduino is configured as the output pin for delivering the control signal for the solenoid lock. The program and circuit is designed on the assumption that the solenoid lock will “lock” for a low signal at its input and “unlock” for a high signal at its input. In this circuit the solenoid is represented by the LED D1. LED ON means “unlocked” and LED OFF means “locked”. 330 ohm resistor R1 limits the current through the LED.
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