Introduction to mq-7 sensor:
The gas sensing material used in mq-7 gas sensor is SnO2 with low conductivity in clean air. The conductivity of the sensor increases with the increase of carbon monoxide concentration in the air. The stray gas adsorbed at low temperature is cleaned by high temperature (5.0V heating). Using a simple circuit, the change of conductivity can be converted into the output signal corresponding to the gas concentration. Mq-7 gas sensor has high sensitivity to carbon monoxide, which can detect a variety of gases containing carbon monoxide. It is a low-cost sensor suitable for a variety of applications
Brief description:
1、 Dimension: 32mm x 22mm x 27mm
2、 Main chips: LM393, mq-7 gas sensor
3、 Working voltage: DC 5 V
4、 Features:
1. With signal output indication.
2. Dual signal output (analog output and TTL level output)
3. TTL output valid signal is low level（ When the output level is low, the signal light is on, which can be directly connected to the single chip microcomputer.)
4. Analog output voltage is 0 ~ 5V, the higher the concentration, the higher the voltage.
5. It has high sensitivity and good selectivity for carbon monoxide.
6. It has long service life and reliable stability
5、 Application:
Carbon monoxide detector for home and environment. It is suitable for the detection of carbon monoxide and gas.
Electrical performance:
Input voltage: DC5V, power consumption (current): 150mA
Do output: TTL digital quantity 0 and 1 (0.1 and 5V)
Ao output: 0.1-0.3v (relatively pollution-free), maximum concentration voltage about 4V
Special reminder:After the sensor is powered on, it needs to be preheated for about 20s before the measured data is stable. The heating of the sensor is a normal phenomenon, because there is an electric heating wire inside, if it is hot, it is abnormal.
测试程序：
Implementation function: This version of supporting test program
Chip: AT89S52
Crystal oscillator: 11.0592Mhz
Baud rate: 9600
Compilation environment: Keil
[statement] this program is only for learning and reference. Please indicate the copyright and author information when quoting!
*********************************************************************/
/********************************************************************
Note: 1. When the measured concentration is greater than the set concentration, the IO port of MCU outputs low level
*********************************************************************/
#include//Library file
#define uchar unsigned char//Macro defines the type of unsigned character
#define uint unsigned int //Macro defines an unsigned integer
/********************************************************************
I/Odefinition
*********************************************************************/
sbit LED=P1^0;//Define the first bit (P1.0) of MCU P1 port as the indicating end
sbit DOUT=P2^0;//Define the first bit of MCU P2 port (p2.0) as the input of the sensor
/********************************************************************
Delay Functions
*********************************************************************/
void delay()//Delay program
{
uchar m,n,s;
for(m=20;m>0;m--)
for(n=20;n>0;n--)
for(s=248;s>0;s--);
}
/********************************************************************
Principal function
*********************************************************************/
void main()
{
while(1) //Infinite cycle
{
LED=1;//Turn off P1.0 port light
if(DOUT==0)//When the concentration is higher than the set value, the condition function is executed
{
delay();//Delay anti jamming
if(DOUT==0)//When the concentration is higher than the set value, the condition function is executed
{
LED=0;//Turn on P1.0 port light
}
}
}
}
/********************************************************************
end
*******************************************************************
