Working of Intelligent Electronic Lock System with Applications

In the present scenario of the world, security is a major concern for all, and the security problem is being faced by every person. The usual means of securing anything is through mechanical locks, which operate with a specific key or a few keys; but, for locking a large area many locks are necessary. However, conventional locks are heavy and do not offer the desired protection as they can be easily broken down by using some tools. Therefore, security breaching problems are associated with the mechanical locks.However to decide the electronic security system problems that are associated with the mechanical locks.

Nowadays, many devices’ operations are based on digital technology. For example, digital based door lock systems for auto door opening and closing, token-based-digital-identity devices are all based on digital technology. These locking systems are controlled by a keypad and are installed at the side hedge of the door. Here, intelligent electronic security lock system offers freedom from physical and mental stress faced by a person while moving away from their home. In this article we have explained about three different types of intelligent electronic lock projects.

1. Intelligent Electronic Lock Circuit Diagram:

The below shown circuit represents an intelligent electronic lock project, which is built using transistors only. To open this electronic lock, one has to press switches S1 through S4 serially. For dishonesty, you may explain these switches with different numbers on the keypad. For example, if you want to use 10 switches 0 to 9 on the keypad, use any four arbitrary numbers out of these switches and remaining 6 numbers may be explained on the leftover switches. These switches may be wired in parallel to disable S6 switch. When four password digits are mixed with remaining 6 digits, which are connected across disable switch terminals, energization of the RL1 relay by unknown person is prohibited.

For authorized persons or known persons, a four-digit password is very easy to remember. To strengthen the relay RL1, one has to press the switches S1 to S4 in sequence within six seconds. Each of the switches will take 0.75 to 1.25 seconds time duration. The relay will not work if time duration is less than 0.75 Sec or above 1.25Sec. A special characteristic of this electronic lock circuit is the pressing of any switch wired across the switch S6 which will guide to disable of the whole circuit for about one minute. This circuit comprises sequential switching, relay latch up sections and disabling. The disabling section consists of Transistors T1, T2 and Zener diode ZD5. The function of the disabling section is such that- when the disable switch S6 is pressed, it cuts off the positive supply to the sequential switching and the relay latches up sections for one minute.

During idle state, the C1 capacitor is discharged and the voltage is less than 4.7V. Thus, T1 transistor and Zener diode are in non-conduction state. So the collector voltage of the T1 transistor is higher than transistor T2. Therefore, +12V is extended to the relay latch up and sequential switching sections. The sequential switching includes Transistors: T3, T4, T5; Zener diodes ZD1, ZD2, ZD3;  Tactile switches S1 to S4; and, Timing capacitors: C2 to C4. In this electronic switch, when the tactile switches are activated, then the timing capacitors are charged through resistors. Thus, while activating tactile switches sequentially, transistors T3, T4 and T5 remain in conduction for a few seconds (T3 for 6 seconds, T4 for 3 seconds, and T5 for 1.5 seconds).

To activate the tactile switches, the time taken is greater than 6 seconds, and the T3 transistor stops performing due to the time lapse. Thus, Sequential switching is not achieved and it is not possible to energize the relay RL1. However, on correct operation of sequential switches S1, S2, S3 and S4, the capacitor C5 is charged through R9 resistor, and the voltage across it increases above 4.7 volts. Next the  transistors T6, T7, T8 as well as the Zener diode start conducting and the RL1 relay gets energized. Next, if you turn on the reset switch S5 for a moment, the C5 capacitor is instantly discharged through the R8 resistor, and the voltage across it falls below 4.7 volts. Therefore the transistors T6, T7, T8 and the Zener diode ZD4 stop conducting again and the RL1 relay de-energizes.

2. Password Based Door Locking System:

In this password based door locking system project, a keypad is arranged to open and close the door. After entering a password, if it matches with the stored one, then the door will unlock for a limited period of time. After extending the unlocking process for a fixed period of time, the relay energizes, and then the door gets locked again. If any unauthorized person enters a wrong password in an attempt to open the door, then this system immediately switches a buzzer

Block diagram:

The working of this project can be described by the above block diagram. It consists of blocks as a microcontroller, a keypad, a buzzer, an LCD, a stepper motor and a motor driver.

The keypad is an input device which helps to enter a password to open the door. Then, it gives the entered code signals to the microcontroller. The LCD and buzzer are the indicating devices for alarming and displaying the information. The stepper motor moves the door to open and close and the motor driver drives the motor after receiving the code signals from the microcontroller.

The microcontroller which is used in this project is from 8051 families and that is programmed with the Keil software. When a person enters a password through a keypad, then the microcontroller reads the data and contrasts it with the stored data. If the entered password matches with the stored data, then the microcontroller sends the information to the LCD, which displays this information: the code is valid. Also, it sends the command signals to the motor driver to rotate the motor in a particular direction such that the door opens. After some time, the spring system with a particular time delay closes its relay, and then the door gets to its normal position,

If a person challenging to open the door enters a wrong password, then the microcontroller switches the buzzer for further action. In this way, a simple door-electronic-lock system can be implemented with the use of a microcontroller

3. ATmega Based Garage Door Opening:

This is an advanced project compared to the above project. This project uses android technology instead of a keyboard for opening and closing the door. Hence, users can use their Android mobiles for opening and closing the door.

The main intention of this project is to unlock a garage door with an Android-OS-based device such as mobile or tablet by entering a single password through the Android application. This system uses a microcontroller, a Bluetooth modem, a buzzer, an Android mobile, a relay driver, lamps and relays for attaining the remote-controlled operations of the door.

The Android based device is connected to this system through a Bluetooth device. The Bluetooth device is arranged to the microcontroller which  is programmed with a particular password for opening and closing the garage door.

Before sending this information to the microcontroller, the Bluetooth on the phone is attached to the control device which is paired to the Bluetooth modem. After entering the password in the android device, it sends the data to the microcontroller through a Bluetooth. Then it compares that data with the password stored in the microcontroller. If the two passwords match, then the microcontroller sends the control signals to the relay driver.

Then, the relay performs mechanical operations to open and close the garage door through the motor. Here, the motor is replaced with the lamp for visualization purpose. If the entered password is wrong, then the system generates an alarm.

Thus, this is all about intelligent electronic lock and basic projects based on electronic door lock system. We hope that you have got a better understanding of this concept with the above examples. Please share your views on this article in the comment section below.

Photo Credits:

• Intelligent Electronic Lock by brownsafe
• Intelligent Electronic Lock Circuit Diagram by projectsjugaad