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Infrared CO2 Sensor Module(Model: MH-Z19B)

User’s Manual(Version: 1.5)
Valid from: 2019.09.23

Zhengzhou Winsen Electronics Technology Co., Ltd
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StatementThis manual’s copyright belongs to Zhengzhou Winsen Electronics Technology Co., LTD. Without
the written permission, any part of this manual shall not be copied, translated, stored in databaseor retrieval system, also can’t spread through electronic, copying, record ways.
Thanks for purchasing our product. In order to let customers use it better and reduce the faults
caused by misuse, please read the manual carefully and operate it correctly in accordance with theinstructions. If users disobey the terms or remove, disassemble, change the components inside of
the sensor, we shall not be responsible for the loss.
The specific such as color, appearance, sizes &etc., please in kind prevail.
We are devoting ourselves to products development and technical innovation, so we reserve theright to improve the products without notice. Please confirm it is the valid version before using thismanual. At the same time, users’ comments on optimized using way are welcome.
Please keep the manual properly, in order to get help if you have questions during the usage in thefuture.

Zhengzhou Winsen Electronics Technology CO., LTD.

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MH-Z19B NDIR CO2 Module
1. Profile
MH-Z19B NDIR infrared gas module is a common type, small size sensor, using non-dispersive infrared (NDIR)
principle to detect the existence of CO 2 in the air, with good selectivity, non-oxygen dependent and longlife. Built-in temperature compensation; and it has UART output and PWM output. It is developed by thetight integration of mature infrared absorbing gas detection technology, precision optical circuit design andsuperior circuit design.

2. Applications*HVAC refrigeration*Smart home

*Air cleaner device*Ventilation system*Indoor air quality monitoring*School

3. Main Features
Chamber is gold plated, water-proof and anti-corrosion
High sensitivity, low power consumption

Good stability
Temperature compensation, excellent linear output
Multiple output modes: UART, DAC, PWM
Long lifespanAnti-water vapor interference, anti-poisoning

4. Structure

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Terminal connection type:
Unit: mm

Pins connection type:

Pins connection type:

PinVinGNDVo
PWM
HdRxTxPin Definition
Positive pole of power (Vin)Negative pole of power (GND)
Analog output(0.4~2V)
PWM
HD(zero point calibration, low levellasting for over 7s is effective)
UART(RXD)TTL Level data input
UART(TXD)TTL Level data output

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Terminal connection type:
Pin

Terminal pin Definition

Pin 1
Pin 2Pin 3
Pin 4
Pin 5

Anolog Output Vo (0.4~2V)
None
Negtive Pole(GND)
Positive Pole(Vin)
UART(RXD)TTL Level data input
UART(TXD)TTL Level dataoutput
None

Pin 6
Pin 7

Note: The analog output Vo has a default output range of 0.4V~ 2V. It is configurable from 0V to 3V.

5. Detection range and accuracy
Detection GasFormulaCarbon Dioxide

CO2Detection Range
0~2000ppm0~5000ppm
0~10000ppm

Accuracy± (50ppm+5% reading value)

6. Main parameters
Model No.

MH-Z19B

Detection Gas

CO2Working voltage

4.5 ~ 5.5 V DC

Average current< 20mA (@5V power supply)

Peak current

150mA (@5V power supply)

Interface level

3.3 V (Compatible with 5V)

Detection Range

0~2000/5000/10000ppm(optional)
Serial Port (UART) (TTL level 3.3V)

Output signal

PWM
Analog output(DAC) (default 0.4~2V)(0~3V range could be customized)

Preheat time

3 min

Response TimeT90 < 120 s

Working temperature-10 ~ 50 ℃

Working humidity

0 ~ 90% RH (No condensation)

Weight5g

Lifespan> 5 years

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7. Output
PWM output
Take 0~2000ppm for example
CO2 output range

0~2000ppm

Cycle

1004ms±5%

Cycle start high level output

2ms(theoretical value)

The middle cycle

1000ms±5%cycle end low level output

2ms(theoretical value)

CO2 concentration: Cppm=2000×(TH-2ms)/(TH+TL-4ms)
Cppm: CO2 concentration could be calculated by PWM output

TH high level output time during cycle
TL low level output time during cycle

Serial port output (UART)
Hardware connection
Connect module’s Vin-GND-RXD-TXD to users’ 5V-GND-TXD-RXD.
(Users must use TTL level. If RS232 level, it must be converted.)

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Software setting
Set serial port baud rate be 9600, data bit 8 bytes, stop bit 1byte, parity bit null.

Commands
0x86

Read CO2 concentration

0x87

Calibrate Zero Point (ZERO)

0x88

Calibrate Span Point (SPAN)

0x79

ON/OFF Self-calibration function for zero point

0x99

Detection range setting

0x86- Read CO2 concentration
Sending command
Byte0

Byte1

Byte2

Byte3

Byte4

Byte5

Byte6

Byte7

Byte8

Start Byte

ReservedCommand-----

Checksum

0xFF

0x01

0x86

0x00

0x000x00

0x00

0x00

0x79

Byte0

Byte1

Byte2

Byte3

Byte4

Byte5

Byte6

Byte7

Byte8

Start Byte

CommanConcentration

Concentration----

Checksumd(High 8 Byte)(Low 8 Byte)

0x86

HIGH

LOW----

Checksum

Return value

0xFF

CO2 concentration = HIGH * 256 + LOW
For example:
Send command FF 01 86 00 00 00 00 00 79, Return value FF 86 02 20 00 00 00 00 58
How to calculate concentration: convert hexadecimal 02 into decimal 2, hexadecimal 20 into decimal 32, then 2*256+32=544ppm

0x79- On/Off Self-calibration for Zero Point
Send command-No return value
Byte0

Byte1

Byte2

Byte3

Byte4

Byte5

Byte6

Byte7

Byte8

Start Byte

ReservedCommand-----

Checksum

0xFF

0x01

0x79

0xA0/0x00

0x00

0x00

0x00

0x00

ChecksumFor example:
ON this function, send command: FF 01 79 A0 00 00 00 00 E6
OFF this function, send command: FF 01 79 00 00 00 00 00 86
NOTE: This function is on when Byte3 is 0xA0 while this function is off when Byte3 is 0x00.
Default status is “this function is on”.

0x99- Detection range setting
Send command-No return value
Byte0

Byte1

Byte2

Byte3

Byte4

Byte5

Byte6

Byte7

Byte8

StartReserved

CommandReserved

Detection range

Detection range

Detection

DetectionCheck

24~32 bit

16~23 bitrange 8~15 bit

range 0~7 bit

sum

Data 1

Data 2

Data 3

Data 4

Check

Byte
0xFF

0x01

0x99

0x00

sum

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Note: Detection range should be 0~2000, 0~5000, or 0~10000ppm.
For example:

set 0~2000ppm detection range, send command: FF 01 99 00 00 00 07 D0 8F
set 0~10000ppm detection range, send command: FF 01 99 00 00 00 27 10 2F

Analog Voltage Output(Vo)Conversion between analog voltage output and concentration, take 0.4V~2V as an example:
Vo(V)=0.4V+(2.0V-0.4V)*C(concentration ppm) / detection range(ppm)

1. Checksum calculation method
Checksum = (Negative (Byte1+Byte2+Byte3+Byte4+Byte5+Byte6+Byte7))+1
For example:
Byte0

Byte1

Byte2

Byte3

Byte4

Byte5

Byte6

Byte7

Byte8

Start Byte

Reserved

Command-----Checksum

0xFF

0x01

0x86

0x00

0x00

0x00

0x00

0x00

ChecksumCalculating Checksum：
1、Add Byte 1 to Byte 7: 0x01 + 0x86 + 0x00 + 0x00 + 0x00 + 0x00 + 0x00 = 0x87
2、Negative: 0xFF - 0x87 = 0x78
3、Then+1：0x78 + 0x01 = 0x79

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;}

8.Zero Point Calibration
About zero point calibration:
This module has three methods for zero point calibration: hand-operated method, sending command method
and self-calibration. All the zero point is at 400ppm CO2.
Hand-operated method: Connect module’s HD pin to low level(0V), lasting for 7 seconds at least. Before
calibrating the zero point, please ensure that the sensor is stable for more than 20 minutes at 400ppm ambientenvironment.

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Sending command method:
Zero and Span point calibration can be achieved by sending a calibration command to the sensor via the serial
port (URAT). Zero and SPAN point calibration commands are as follows:

Self-calibration:
After the module works for some time, it can judge the zero point intelligently and do the zero calibrationautomatically. The calibration cycle is every 24 hours since the module is power on. The zero point is 400ppm.
This method is suitable for office and home environment, not suitable for agriculture greenhouse, farm,refrigerator, etc.. If the module is used in latter environment, please turn off this function.

9. Notes
9.1 Please avoid the pressure of its gilded plastic chamber from any direction, during welding, installation, anduse.
9.2 When placed in small space, the space should be well ventilated, especially for diffusion window.
9.3 The module should be away from heat, and avoid direct sunlight or other heat radiation.
9.4 The module should be calibrated termly, the suggested period is not longer than 6 months.
9.5 Do not use the sensor in the high dusty environment for long time.
9.6 To ensure the normal work, the power supply must be among 4.5V~5.5V DC rang, the power current must be
not less than 150mA. Out of this range, it will result in the failure of the sensor. (The concentration output is low,or the sensor can not work normally.)
9.7 During the zero point calibration procedure by manual, the sensor must work in stable gas environment
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www.winsen-sensor.com(400ppm) for over 20 minutes. Connect the HD pin to low level (0V) for over 7 seconds.
9.8 Forbid using wave soldering for the sensor.
9.9 When soldering with soldering iron, set the temperature to be (350 ± 5) °C, and soldering time must bewithin 3 seconds.
9.0 As for pin version sensor, it is recommended to use soldering socket to directly insert or remove sensors forconvenient maintenance.

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