Security is a big challenge everywhere because thefts are increasing day by day owing to the unsafe and insecure security systems in homes, commercial complexes and industries. Several conventional technologies are available to keep home properties safe from intruders, but most common smart home security systems work on wireless GSM communication. Such systems provide security from natural, incidental, intended, unintended, accidental and human made problems by continuously monitoring homes with different sensory systems like motion, smoke, gas, temperature, glass break or door break detectors and fire alarm systems.
GSM Based Home Security System
Home security or home automation can be achieved by adopting central controllers to control home devices or appliances that sense different variables using appropriate sensors. The main aspect of such a system is a sensory system that collects the parameter information like temperature, fire, human presence, gas, etc., and sends the corresponding data to the microcontroller or any other processor. This controller is programmed such that when these parameters cross their prescribed limits, it sends the command signals to various final controlling devices like relays, motors and buzzer devices.
This system can be implemented with the use of the following functional blocks:
Sensory System: It consists of various sensors like IR sensors for detecting human presence to open or close the doors; LPG gas sensor to detect the gas leakage in kitchens – and, a smoke detector to detect the presence of fire. It is also possible to add temperature sensor, camera and other sensing devices for improving the security of homes. These sensing values are sent to the microcontroller with intermediate circuitry like Analog to Digital Converter (ADC).
Microcontroller: This is the heart of the system wherein central processing of data takes place. 8051 microcontroller collects the data or information from various sensors and compares it with appropriate prescribed limits. It is programmed by embedded C or assembly language in Keil software. By receiving the sensor signals, it takes the corresponding course of action by sending commands to the output devices.
GSM Modem: GSM modem allows the computer to communicate over the mobile network through calls, SMS and MMS messages. It consists of a SIM card and operates over a subscription through a mobile network. It is a highly flexible plug-and-play device capable of connecting to a PC or any microcontroller’s serial port through MAX232IC. This IC is used to convert the TTL logic levels of the microcontroller to a RS232 logic level for enabling serial communication.
Final Control Devices: These devices include buzzers and motors with driver ICs and LCDs display. Final control devices generate alarms of different kinds by using buzzers; doors and fire exhauster operations are controlled by using motors. All these devices act upon the commands directed from a microcontroller.
Circuit Diagram and Operation of a GSM-Based Home Security System Project
- In the below figure, you can observe the connections of various devices like sensors, ADC, relays, keypad, etc., to a microcontroller. In this system, an LCD is connected to the port1 of the microcontroller; ADC to the port0 and a matrix keypad to the port2.
- Smoke detector is connected to the port 2.3; a temperature sensor LM35 and a Light Dependent Resistor (LDR) are connected to the channel 1 and 2 of the ADC, respectively.
- This system continuously monitors the prevailing conditions of the homes at a given time by getting the sensor values. Analog sensor values of temperature and light illumination are sent to the ADC where these are then converted to the microcontroller understandable language as digital values. These digital values are compared with the pre-stored values of the microcontroller.
Read more: Home Security System with GSM Using 8051 Microcontroller