05-07-2013, 04:42 PM
Microcontroller Based LPG Gas Detector Using GSM Module
Microcontroller Based LPG.docx (Size: 99.54 KB / Downloads: 79)
Working
The entire circuit has two sections- the sensor and the power supply section.
(1)Sensor Side circuit
The circuit diagram shows the fire sensor circuit. The front end of the circuit has a sensitive signal amplifier built around IC1 (CA 3130). It gives a high output when temperature near the Piezo-element increases. IC CA3130 is a CMOS operational amplifier with gate protected p-channel MOSFETs in the inputs. It has high speed of performance and low input current requirements. There are two inputs – the non inverting input (pin 3) connected to the Piezo element that carries the voltage signal from the Piezo element and the inverting input (pin 2) that gets a preset voltage through VR1.By adjustingVR1,it is easy to set the reference voltage level at pin 2. In normal condition, IC1 gives a low output and the remaining circuitry is in a standby state. Capacitor C1keeps the non-inverting input of IC1 stable, so that even a slight change in voltage level in the inputs can change the output to high. Normally, IC1 gives a low output, keeping transistor T1 non-conducting. When the Piezo element gets heat from fire, asymmetry in its crystals causes a potential change, enabling capacitor C1to discharge. It momentarily changes the voltage level at pin 3 of IC1 and its output swings high. It give output to the buzzer for fire alarm and Transistor T1 conducts and start the switch of relay which already connected with ac-motor for water outlet and with ac-input for give input to the motor.