MH-Z14 Intelligent Infrared Gas Module User’s Manual

MH-Z14 Intelligent Infrared Gas Module

Profile

Main functions and features：

• High sensitivity, High resolution
• Low power consumption
• Output modes: UART, analog voltage signal, PWM wave
• Quick response
• Temperature compensation, excellent linear output
• Good stability
• Long lifespan
• Anti-water vapor interference
• No poisoning

Main technical parameters

Structure

Definition for pins

Circuit

Operating instruction

Analog output connections

The output value of Vout1 is 0-2.5V, which stands for 0 to full range.The output value of Vout2 is 0.4-2V, which stands for 0 to full range.

Vin –5VGND- Power GroundVout2-ADC inputAfter preheating, the value of output voltage from Vout2 represents gas concentration.

PWM output (taking PWM output from 2000ppm as example):

CO2 output range: 0ppm-2000ppmCycle: 1004ms±5%

High level output for beginning: 2ms (in name)Middle of cycle: 1000ms±5%Low level output for ending: 2ms（in name）Account formula for CO2 concentration which gets through PWM:

Digital connects

Vin-5V powerGND- Power GroundRXD connect sensor TXDTXD connect sensor RXDYou can read gas concentration via Uart, no need to calculate.

Communication protocol

1. General Settings
   

   Baud rate	9600
   Date byte	8 byte
   Stop byte	1byte
   Calibrate byte	no

2. CommandEach command or return：Contains 9 bytes (byte 0 ~ 8) starting byte fixed 0 XFFcommand contains sensor number (factory default to 0 x01) to check and endCommand List:

   0x86	Gas concentration
   0x87	Calibrate zero point（ZERO）
   0x88	Calibrate span point（SPAN）

   Read gas concentration

   Send command
   Byte0	Byte1	Byte2	Byte3	Byte4	Byte5	Byte6	Byte7	Byte8
   Starting byte	Sensor No.	command	–	–	–	–	–	Check value
   0XFF	0x01	0x86	0x00	0x00	0x00	0x00	0x00	0x79

   Return value

   Return
   Byte0	Byte1	Byte2	Byte3	Byte4	Byte5	Byte6	Byte7	Byte8
   Starting byte	command	High level concentration	Low level concentration	–	–	–	–	Chec k value
   0XFF	0x86	0x02	0x60	0x47	0x00	0x00	0x00	0xD1

   Gas concentration= high level *256+low level

   Calibrate zero point

   Send command
   Byte0	Byte1	Byte2	Byte3	Byte4	Byte5	Byte6	Byte7	Byte8
   Starting byte	Sensor No.	command	–	–	–	–	–	Check value
   0XFF	0x01	0x87	0x00	0x00	0x00	0x00	0x00	0x78

   No return value

   Calibrate span point

   Send command
   Byte0	Byte1	Byte2	Byte3	Byte4	Byte5	Byte6	Byte7	Byte8
   Starting byte	Sensor No.	command	High level span point	Low level span point	–	–	–	Check value
   0XFF	0x01	0x88	0x07	0xD0	0x00	0x00	0x00	0xA0

   No return value

    

3. Calibration and calculationThe checksum = (invert (byte 1 +… + 7)) + 1Reading gas concentration:
   

   Send command
   Byte0	Byte1	Byte2	Byte3	Byte4	Byte5	Byte6	Byte7	Byte8
   Startingbyte	Sensor No.	command	–	–	–	–	–	Check value
   0XFF	0x01	0x86	0x00	0x00	0x00	0x00	0x00	0x79

   Except byte 0 ,add the other bytes together0x1 + 0x86 + 0 + 0 + 0 + 0 + 0 = 0x87Get the value from the first step, then invert it.0xff – 0x87 = 0x78The second value plus one0x78 + 0x01 = 0x79Program :C language

   char getCheckSum(char *packet){char i, checksum; for( i = 1; i < 8; i++){checksum += packet[i]; }checksum = 0xff – checksum;checksum += 1;return checksum;}

Notes for maintenance

7.1 The sensor should be calibrated regularly. The cycle time is better to be no more than 6 months.7.2 Do not use the sensor in the high dusty environment for long time.7.3 Please use the sensor with correct power supply.7.4 Forbidden to cut the sensor pin.

MH-Z14 Intelligent Infrared Gas Module User’s Manual – MH-Z14 Intelligent Infrared Gas Module User’s Manual –