8051 based gas detection system is a prototype of the industrial gas detector system. The system is equipped with an MQ sensor which can sense the presence of LPG. The sensor detects the presence of LPG and alerts the microcontroller. The microcontroller then perform the plant shutdown option if necessary. The system consists of a relay which is meant to shut down the plant if gas is present. Necessary warnings are displayed on the LCD. The user can set the desired trigger level, that is, the gas intensity point at which the shutdown should take place by adjusting the potentiometer in the system.
1) Power Supply: This section is responsible for providing required power for the working of entire project. This section consist of 12V step-down transformer, bridge rectifier with capacitor filter, 7805 voltage regulator and an indication LED.
2) Micro controller: The project contains AT89S52 microcontroller as central processor. The microcontroller have three timers and two of them are used in this project. Timer 1 is configured as a counter.
3) LCD display: Liquid Crystal Display which is commonly known as LCD is an Alphanumeric Display it means that it can display Alphabets, Numbers as well as special symbols, thus LCD is a user friendly Display device which can be used for displaying various messages unlike seven segment display which can display only numbers and some of the alphabets. The only disadvantage of LCD over seven segment is that seven segment has a robust display and can be visualized from a longer distance as compared to LCD. Here we have used 16×2 Alphanumeric Display which means it can display four lines with maximum of 16 characters in one line.
4) Oscillator: The system uses a 12MHz crystal oscillator for clocking.
5) Reset: There is a reset circuitry by which we can restart the system if any error occurs. The circuit also prevents unnecessary clocking when controller is powering up.
6) MQ sensor: it is a tin diode based sensor which can change the conductivity in the presence of certain gases at certain temperature. There is a heating coil in the sensor which keep the sensing material at a suitable temperature to react with LPG. The sensor output is fed to a comparator which gives a digital output suitable for processing. Comparator reference voltage can be changed using a potentiometer.