A gas detector is a device which detects the presence of gases within an area, usually as part of a safety system. This type of equipment is used to detect a gas leak and interface with a control system so a process can be automatically shut down.
Gas Sensor
Features
- High sensitivity to LPG, natural gas , town gas
- Small sensitivity to alcohol, smoke.
- Fast response .
- Stable and long life
- Simple drive circuit
Applications
- Detection of harmful gases in mines.
- Home safety
Using
The Sensor
- Connect regulated DC power supply of 5 Volts to pin 3 and GND to pin2.
- When gas is detected LED is ON or else it is OFF.
- The output from pin1 can be given directly to microcontroller for interfacing applications.
Working
As shown in, standard measuring circuit of MQ-7 sensitive components consists of 2 parts. one is heating circuit having time control function (the high voltage and the low voltage work circularly ). The second is the signal output circuit, it can accurately respond changes of surface resistance of the sensor.
operation principle:
The surface resistance of the sensor Rs is obtained through effected voltage signal output of the load resistance RL which series-wound. The relationship between them is described:
Rs\RL = (Vc-VRL) /
VRL
below fig shows alterable situation of RL signal
output measured by using above circuit output signal when the sensor is shifted from clean air to carbon monoxide (CO) , output signal measurement is made within one or two complete heating period (2.5 minute from high voltage to low voltage ). Sensitive layer of MQ-7 gas sensitive components is made of SnO2 with stability, So, it has excellent long term stability. Its service life can reach 5 years under using condition.
For Code Click Here.
ARM Schematic:
For Code Click Here.
PIC Schematic:
For Code Click Here.
