CO, O2, NH3, H2S, NO2, HCL, H2, PH3, SO2, O3, CL2, HF Gas Sensor Wiki - DFRobot

Introduction

The gas sensor series is designed to detect various flammable, combustible, and toxic gases in the environment. With pre-calibrated sensors, it can measure the concentration of specific gases quickly and accurately. Supporting multiple output modes, including Analog, I2C, UART, and digital alarm signals, it offers flexibility in different applications. The probes in this series use electrochemical principles, providing strong stability and sensitivity with a lifespan of up to two years.

Using the simple and user-friendly Gravity interface, you can easily build various gas concentration detectors. This sensor series has widespread applications in safety production, industrial manufacturing, and environmental protection, making it the ideal choice for settings such as coal mines, chemical industries, chemical laboratories, and environmental management.

Precautions for use

• The white waterproof and breathable membrane of the sensor on the module is strictly forbidden to open, otherwise it is regarded as artificial damage.
• It is forbidden to plug or unplug the probe with power on.
• It is forbidden to directly solder the pins of the module, but the sockets of the pins can be soldered.
• The module should avoid contact with organic solvents (including silica gel and other adhesives), paints, pharmaceuticals, oils and high-concentration gases.
• The module must not be subjected to excessive shock or vibration.
• The module needs to be warmed up for more than 5 minutes when powered on for the first time. It is recommended to warm up for more than 24 hours if it has not been used for a long time.
• Do not apply this module to systems involving personal safety.
• Do not install the module in environment with strong air convection.
• Do not leave the module in high-concentration organic gas for a long time.
• The data returned by the serial port of the module is the real-time concentration value in the current environment. If there is no standard gas, please do not try the calibration command. This command will clear the calibrated data, and the data returned by the serial port will be inaccurate.
• To judge whether the module communication is normal, it is recommended to use a USB to TTL tool (communication level 3V) to observe and judge according to the communication protocol through the serial debugging assistant software.

Features

• Factory calibrated, accurate measurement
• High sensitivity, low power consumption
• Excellent stability and anti-interference
• Three output modes: I2C, UART and analog
• Long service life(2 years)
• Compatible with 3.3~5.5V main controllers
• 32 modifiable I2C addresses
• Reverse connection protection
• Temperature compensation
• Threshold alarm

Specification

• Detection Gas: CO, O2, NH3, H2S, NO2, HCL, H2, PH3, SO2, O3, CL2, HF(Need to change different probe)
• Working Voltage: 3.3～5.5V DC
• Working Current: <5mA
• Output Signal: I2C, UART output (0~3V), analog voltage (see the characteristic parameters of specific probe)
• Detection error: ±10% of output value or ±5% of full scale (whichever is greater)
• Working Temperature: -20～50℃
• Working Humidity: 15～90%RH (non-condensing)
• Storage Temperature: -20～50℃
• Storage Humidity: 15～90%RH (non-condensing)
• Lifespan: >2 years (in the air)
• Adapter Plate Size: 37×32mm

Characteristic Parameters

Explanation of VO use:

VO: It means original voltage (linear) after amplifying circuit, rather than concentration value of current environment.

Calculation method: concentration in the current environment N= 200/(Vout1-Vout0)*(Voutx-Vout0)

Where Vout1 corresponds to Vout1 in the table and Vout0 corresponds to the voltage value of the gas at 0 ppm in the table. Take CO as an example: zero point voltage Vout0 = 0.6V, Vout1 = 0.9V, the current voltage of VO Voutx = 1.2V, then the current concentration in the environment N = 400ppm

Note: The analog output is the original uncalibrated voltage of the probe, the UART/I2C data is factory calibrated, if there is no special requirement, it is recommended to use the calibrated UART/I2C data.

Board Overview

Smart Gas Sensor Terminal

Tutorial for Arduino

Download the program to UNO and open the serial monitor to check the gas concentration.

Note:

• The initial power-on requires more than 5 minutes of preheating. It is recommended to preheat more than 24 hours if it has not been used for a long time.
• After switching the communication mode or changing the I2C address, the system needs to be powered off and on again.

Requirements

• Hardware

  • DFRuino UNO R3 x1
  • DFR0784 Smart Gas Sensor Terminal x1
  • Gas probe x1
  • Jumper wires

• Software

  • Arduino IDE
  • Download and install the DFRobot_GasSensor Library (About how to install the library?)

Acquire data in passive mode

Connection

Sample code

• Connect the module to the Arduino according to the connection diagram above. Of course, you can also use it with Gravity I/O Expansion Board to build the project prototype more conveniently and quickly.
• Set the DIP switch SEL on the sensor to 0, and use I2C communication by default.
• The default I2C address is 0x74. If you need to modify the I2C address,You can configure the hardware I2C address through the DIP switch on the module, or run the code to modify the address group to modify the address. The corresponding relationship between the DIP switch and the I2C address parameter is as follows:
  • ADDRESS_0: 0x74, A0=0, A1=0
  • ADDRESS_1: 0x75, A0=1, A1=0
  • ADDRESS_2: 0x76, A0=0, A1=1
  • ADDRESS_3: 0x77, A0=1, A1=1
• Download and install the DFRobot_GasSensor Library (About how to install the library?)
• Open Arduino IDE and upload the following code to Arduino UNO.
• Open the serial port monitor of Arduino IDE, adjust the baud rate to 115200, and observe the serial port print result.

Statement

• In this routine, the controller needs to request data from the sensor every time, and then the sensor returns the data.
• Default use I2C communication, mask #define I2C_COMMUNICATION in the code, and set the dip switch SEL to 1, the sensor is connected to the corresponding port defined by the controller, if use UNO, the blue line is connected to D3 and the green line is connected to D2, if use ESP32, the blue line is connected to IO17 and the green line is connected to IO16. After re-uploading the code, the whole system will be re-powered and will switch to UART communication.
• Turn off temperature compensation by default, modify the code gas.setTempCompensation(gas.ON);, turn on temperature compensation after re-uploading the code

/*!
  * @file  initiativereport.ino
  * @brief The sensor actively reports all data
  * @n Experimental method: Connect the sensor communication pin to the main control, then burn codes into it. 
  * @n Communication mode selection, dial switch SEL:0: IIC, 1: UART
@n I2C address selection, the default I2C address is 0x74, A1 and A0 are combined into 4 types of IIC addresses
                | A1 | A0 |
                | 0  | 0  |    0x74
                | 0  | 1  |    0x75
                | 1  | 0  |    0x76
                | 1  | 1  |    0x77   default i2c address
  * @n Experimental phenomenon: Print all data via serial port
*/
#include "DFRobot_MultiGasSensor.h"

//Enabled by default, use IIC communication at this time. Use UART communication when disabled
#define I2C_COMMUNICATION

#ifdef  I2C_COMMUNICATION
#define I2C_ADDRESS    0x74
  DFRobot_GAS_I2C gas(&Wire ,I2C_ADDRESS);
#else
#if (!defined ARDUINO_ESP32_DEV) && (!defined __SAMD21G18A__)
/**
  UNO:pin_2-----RX
      pin_3-----TX
*/
  SoftwareSerial mySerial(2,3);
  DFRobot_GAS_SoftWareUart gas(&mySerial);
#else
/**
  ESP32:IO16-----RX
        IO17-----TX
*/
  DFRobot_GAS_HardWareUart gas(&Serial2); //ESP32HardwareSerial
#endif
#endif

void setup() {

  Serial.begin(115200);

  while(!gas.begin())
  {
    Serial.println("NO Deivces !");
    delay(1000);
  }
  Serial.println("The device is connected successfully!");

  gas.changeAcquireMode(gas.PASSIVITY);
  delay(1000);

  gas.setTempCompensation(gas.OFF);
}

void loop() {

  Serial.print("Ambient ");
  Serial.print(gas.queryGasType());
  Serial.print(" concentration is: ");
  Serial.print(gas.readGasConcentrationPPM());
  Serial.println(" %vol");
  //The measurement unit will only be %vol when the sensor is SEN0465
  //Otherwise the unit will be PPM
  Serial.print("The board temperature is: ");
  Serial.print(gas.readTempC());
  Serial.println(" ℃");
  Serial.println();
  delay(1000);
}

Result

Open the serial monitor to get the gas type, concentration and temperature.

• The initial power-on requires more than 5 minutes of preheating. It is recommended to preheat more than 24 hours if it has not been used for a long time.
• After switching the communication mode and changing the I2C address, the system needs to be powered off and on again.

Acquire data in initiative mode

Connection

• Sample code

• Connect the module to the Arduino according to the connection diagram above. Of course, you can also use it with Gravity I/O Expansion Board to build the project prototype more conveniently and quickly.

• Set the DIP switch SEL on the sensor to 0, and use I2C communication by default.

• The default I2C address is 0x74. If you need to modify the I2C address,You can configure the hardware I2C address through the DIP switch on the module, or run the code to modify the address group to modify the address. The corresponding relationship between the DIP switch and the I2C address parameter is as follows:

  • ADDRESS_0: 0x77, A0=0, A1=0
  • ADDRESS_1: 0x76, A0=1, A1=0
  • ADDRESS_2: 0x75, A0=0, A1=1
  • ADDRESS_3: 0x74, A0=1, A1=1

• Download and install the DFRobot_GasSensor Library (About how to install the library?)

• Open Arduino IDE and upload the following code to Arduino UNO.

• Open the serial port monitor of Arduino IDE, adjust the baud rate to 115200, and observe the serial port print result.

  Statement

  • In this routine, the sensor will actively return data once a second, and the controller will receive and parse the data.

• Default use I2C communication, mask `#define I2C_COMMUNICATION in the code, and set the dip switch SEL to 1, the sensor is connected to the corresponding port defined by the controller, if use UNO, the blue line is connected to D3 and the green line is connected to D2, if use ESP32, the blue line is connected to IO17 and the green line is connected to IO16. After re-uploading the code, the whole system will be re-powered and will switch to UART communication.

• Turn off temperature compensation by default, modify the code gas.setTempCompensation(gas.ON);, turn on temperature compensation after re-uploading the code

/*!
  * @file  readGasConcentration.ino
  * @brief Obtain the corresponding gas concentration in the current environment and output the concentration value
  * @n Experiment method: Connect the sensor communication pin to the main control and burn codes into it. 
  * @n Communication mode selection, dial switch SEL:0: IIC, 1: UART
    @n i2c address selection, the default i2c address is 0x74, A1 and A0 are combined into 4 types of IIC addresses
                | A1 | A0 |
                | 0  | 0  |    0x74
                | 0  | 1  |    0x75
                | 1  | 0  |    0x76
                | 1  | 1  |    0x77   default i2c address  
  * @n Experimental phenomenon: You can see the corresponding gas concentration value of the environment at this time by printing on the serial port
  */
#include "DFRobot_MultiGasSensor.h"

//Enabled by default, use IIC communication at this time. Use UART communication when disabled
#define I2C_COMMUNICATION

#ifdef I2C_COMMUNICATION
#define I2C_ADDRESS 0x74
DFRobot_GAS_I2C gas(&Wire, I2C_ADDRESS);
#else
#if (!defined ARDUINO_ESP32_DEV) && (!defined __SAMD21G18A__)
/**
  UNO:pin_2-----RX
      pin_3-----TX
*/
SoftwareSerial mySerial(2, 3);
DFRobot_GAS_SoftWareUart gas(&mySerial);
#else
/**
  ESP32:IO16-----RX
        IO17-----TX
*/
DFRobot_GAS_HardWareUart gas(&Serial2); //ESP32HardwareSerial
#endif
#endif

void setup() {

  Serial.begin(115200);

  while(!gas.begin())
  {
    Serial.println("NO Deivces !");
    delay(1000);
  }

  gas.setTempCompensation(gas.OFF);  

  gas.changeAcquireMode(gas.INITIATIVE);
  delay(1000);
}

void loop() {
  if(true==gas.dataIsAvailable())
  {
    Serial.println("========================");
    Serial.print("gastype:");
    Serial.println(AllDataAnalysis.gastype);
    Serial.println("------------------------");
    Serial.print("gasconcentration:");
    Serial.print(AllDataAnalysis.gasconcentration);
    if (AllDataAnalysis.gastype.equals("O2"))
      Serial.println(" %VOL");
    else
      Serial.println(" PPM");
    Serial.println("------------------------");
    Serial.print("temp:");
    Serial.print(AllDataAnalysis.temp);
    Serial.println(" ℃");
    Serial.println("========================");
  }
  delay(1000);
}

Result

Open the serial monitor, then you can get the corresponding gas concentration.

• The initial power-on requires more than 5 minutes of preheating. It is recommended to preheat more than 24 hours if it has not been used for a long time.

• After switching the communication mode and changing the I2C address, the system needs to be powered off and on again.

Threshold alarm function

Connection

• Sample code

• Connect the module to the Arduino according to the connection diagram above. Of course, you can also use it with Gravity I/O Expansion Board to build the project prototype more conveniently and quickly.

• Set the DIP switch SEL on the sensor to 0, and use I2C communication by default.

• The default I2C address is 0x74. If you need to modify the I2C address,You can configure the hardware I2C address through the DIP switch on the module, or run the code to modify the address group to modify the address. The corresponding relationship between the DIP switch and the I2C address parameter is as follows:

  • ADDRESS_0: 0x74, A0=0, A1=0
  • ADDRESS_1: 0x75, A0=1, A1=0
  • ADDRESS_2: 0x76, A0=0, A1=1
  • ADDRESS_3: 0x77, A0=1, A1=1

• Download and install the DFRobot_GasSensor Library (About how to install the library?)

• Open Arduino IDE and upload the following code to Arduino UNO.

• Open the serial port monitor of Arduino IDE, adjust the baud rate to 115200, and observe the serial port print result.

/*!
  * @file  setThresholdAlarm.ino
  * @brief Set the threshold alarm of the sensor
  * @n Experiment method: Connect the sensor communication pin to the main control and burn codes into it. 
  * @n Communication mode selection, dial switch SEL:0: IIC, 1: UART
*/
#include "DFRobot_MultiGasSensor.h"

//Enabled by default, use IIC communication at this time. Use UART communication when disabled
#define I2C_COMMUNICATION

#ifdef  I2C_COMMUNICATION
#define I2C_ADDRESS    0x77
  DFRobot_GAS_I2C gas(&Wire ,I2C_ADDRESS);
#else
#if (!defined ARDUINO_ESP32_DEV) && (!defined __SAMD21G18A__)
/**
  UNO:pin_2-----RX
      pin_3-----TX
*/
  SoftwareSerial mySerial(2, 3);
  DFRobot_GAS_SoftWareUart gas(&mySerial);
#else
/**
  ESP32:IO16-----RX
        IO17-----TX
*/
  DFRobot_GAS_HardWareUart gas(&Serial2); //ESP32HardwareSerial
#endif
#endif

#define ALA_pin 4

void setup() {

  Serial.begin(115200);

  while(!gas.begin())
  {
    Serial.println("NO Deivces !");
    delay(1000);
  }

  while (!gas.changeAcquireMode(gas.PASSIVITY))
  {
    delay(1000);
  }
  Serial.println("change acquire mode success!");

  while (!gas.setThresholdAlarm(gas.ON, 2, gas.HIGH_THRESHOLD_ALA ,gas.queryGasType()))
  {
    Serial.println("Failed to open alarm!");
    delay(1000);
  }
  pinMode(ALA_pin,INPUT);
}

void loop() {

  Serial.print(gas.queryGasType());
  Serial.print(":");
  Serial.println(gas.readGasConcentrationPPM());
  if (digitalRead(ALA_pin) == 1)
  {
    Serial.println("warning!!!");
  }
  else
  {
    Serial.println("nolmal!!!");
  }
  delay(200);
}

Result

-*After uploading the code successfully, open the serial monitor and you can observe the alarm message. *

-ALA outputs low level by default when no alarm is triggered. Modify the HIGH_THRESHOLD_ALA parameter in the gas.setThresholdAlarm function to LOW_THRESHOLD_ALA, then ALA outputs high level when no alarm is triggered

API description

DFR0784 Gravity: Electrochemical Smart Gas Sensor Terminal There are two data reading modes: active upload and passive response. The factory default is active upload mode, and users can adjust them in the code according to their needs.

Mode selection function "changeAcquireMode()"

Modify the parameters in brackets of the "changeAcquireMode()" function to adjust the data sending mode.

"INITIATIVE" is the active upload mode. In the active upload mode, the sensor will automatically upload parameters every 1 second;

"PASSIVITY" is the passive response mode. In the passive response mode, the sensor will feedback the parameters only every time the data reading function is called.

gas.changeAcquireMode(gas.INITIATIVE)
/*
      gas.INITIATIVE            // Active upload mode
      gas.PASSIVITY             // Passive response mode
*/

Set the probe type function "setGasType()"

Set the probe type by the "setGasType()" function.

gas.setGasType(/*Gas type*/gas.O2);

Read the probe type function "queryGasType()"

Through the "queryGasType()" function, You can get the type of current gas probe.

gas.queryGasType();

For probe compatible types and corresponding parameters, please refer to the table below.

Gas concentration reading function "readGasConcentrationPPM()"

The feedback gas concentration value of the gas sensor can be read through the "readGasConcentrationPPM()" function.

gas.readGasConcentrationPPM();

Temperature reading function "readTempC()"

The onboard temperature sensor data can be read through the "readTempC()" function.

gas.readTempC();

Voltage reading function "getSensorVoltage()"

The original voltage output V0 of the gas probe can be read through the "getSensorVoltage()" function.

gas.getSensorVoltage();

Configure temperature compensation function "setTempCompensation()"

You can enable/disable the temperature compensation function through the "setTempCompensation()" function.

gas.setTempCompensation();
/*
      gas.ON      Turn on
      gas.OFF        Turn off
*/

Threshold alarm function "setThresholdAlarm()"

You can configure the threshold alarm information through the "setThresholdAlarm()" function

gas.setThresholdAlarm(gas.ON, 200, gas.LOW_THRESHOLD_ALA ,gas.queryGasType());
/*
    gas.ON      Turn on
      gas.OFF        Turn off
      200            Set threshold
      gas.LOW_THRESHOLD_ALA Jump to low level when alarming
      gas.HIGH_THRESHOLD_ALA Jump to high level when alarming
      gas.queryGasType() Set alarm gas type
*/

I2C address group configuration function "changeI2cAddrGroup()"

You can configure the I2C address group code and switch between different address groups through the "changeI2cAddrGroup()" function.

In order to prevent address conflicts when using multiple sensors, we have prepared 8 groups with a total of 23 addresses. If necessary, You can use "change_sensor_iic_addr.ino" in the library file "example",to switch by modifying the group serial number configuration of "changeI2cAddrGroup()". After the serial port information displays "IIC addr change success!", power on again.

gas.changeI2cAddrGroup(i);
 /* 
     i            Group number

  //Group serial number and DIP switch configuration table
  A0 A1Dial level    00    01    10    11
  Group number          Group address
    1            0x60  0x61  0x62  0x63
    2            0x64  0x65  0x66  0x67
    3            0x68  0x69  0x6A  0x6B
    4            0x6C  0x6D  0x6E  0x6F
    5            0x70  0x71  0x72  0x73
    6（Default address group） 0x74  0x75  0x76  0x77
    7            0x78  0x79  0x7A  0x7B
    8            0x7C  0x7D  0x7E  
 */

Serial port protocol usage tutorial

Through the UART serial communication protocol, you can connect DFR0784 Gravity: Electrochemical Smart Gas Sensor Terminal to any controller with UART for data reading and sensor configuration. Note: At this time, the SEL end of the DIP switch on the sensor must be placed in the "1" position

Serial port parameter setting

Communication protocol description

① 0x78——Modify terminal communication mode

The terminal has two communication modes, active uploading and question and answer. The factory default is active uploading mode, and data is sent every 1s.

Send

EXP.FF 01 78 03 00 00 00 00 84 (switch to initiative mode)

EXP.FF 01 78 04 00 00 00 00 83 (switch to passive mode)

Return

EXP.FF 78 01 00 00 00 00 00 87

② Initiative mode，Data Format

In the active upload mode, the terminal will return data every 1s. The data format is as follows.

Return

Note:

• Gas concentration value = (high gas concentration x 256 + low gas concentration) x resolution
• The decimal place is 0, the resolution is 1; the decimal place is 1, the resolution is 0.1; the decimal place is 2, the resolution is 0.01
• For the calculation method of temperature value, please refer to the sample code below: "Calculation of temperature value"

Gas Type Table

③ 0x86——Passive mode,Read gas concentration data

In the question and answer mode, you need to send commands to read various parameters of the terminal. The method of reading the gas concentration is as follows.

Send

EXP.FF 01 86 00 00 00 00 00 79

Return

EXP.FF 86 00 00 00 00 00 00 7A

Note:

• Gas concentration value = (high gas concentration x 256 + low gas concentration) x resolution
• The decimal place is 0, the resolution is 1; the decimal place is 1, the resolution is 0.1; the decimal place is 2, the resolution is 0.01

④ 0x87——Passive mode,Read temperature data

In the question and answer mode, you need to read various parameters of the terminal by sending commands. The terminal integrates the thermistor, which can obtain the real-time temperature of the terminal. The way to read the terminal temperature is as follows.

Send

EXP.FF 01 87 00 00 00 00 00 78

Return

EXP.FF 87 00 00 00 00 00 00 79

Note:

For the calculation method of temperature value, please refer to the sample code below: "Calculation of temperature value"

⑤ 0x88——Passive mode,Read temperature and gas concentration data

In the question and answer mode, you need to read various parameters of the terminal by sending commands, and the way to read the temperature and gas concentration data of the terminal is as follows.

Send

EXP.FF 01 88 00 00 00 00 00 77

Return

EXP. FF 88 00 00 00 00 00 00 78

Note:

• Gas concentration value = (high gas concentration x 256 + low gas concentration) x resolution
• The decimal place is 0, the resolution is 1; the decimal place is 1, the resolution is 0.1; the decimal place is 2, the resolution is 0.01
• For the calculation method of temperature value, please refer to the sample code below: "Calculation of temperature value"

⑥ 0x89——Configure threshold alarm function

The terminal has a threshold alarm function, the alarm threshold and judgment logic can be configured. The configuration method is as follows,After the configuration is successful, the entire system needs to be powered on again to take effect.

Note: When no external controller is connected and only the sensor is used to achieve this function, the sensor must be set to active upload mode after the parameters related to the threshold alarm function are configured.

Send

EXP. FF 01 89 00 00 05 00 00 71 (turn off the alarm function)

EXP. FF 01 89 01 00 05 00 00 70 (open the alarm function)

Please refer to ⑤ for how to calculate the concentration.

Return

To configure the threshold alarm by code using a controller such as Raspberry Pi, you can use this python code: GAS_ALA.zip

Checksum calculation

Check value = (inverted (byte 1 + byte 2 + ··· ··· + byte 7) + 1

The reference routine is as follows:

/****************************************************************** 
* Function name: unsigned char FucCheckSum(uchar *i,ucharln)
* Function description: Sum check (reverse the sum of 1\2\3\4\5\6\7 of the sending and receiving protocol  + 1)
* Function description: reverse the sum of the array element 1 to the penultimate element and plus 1 (the number of elements must be greater than 2)
******************************************************************/
char data[] = {0xFF,0x01,0x89,0x00,0x00,0x05,0x00,0x00};

unsigned char FucCheckSum(unsigned char *i,unsigned char ln)
{ 
    unsigned char j,tempq=0; 
    i+=1; 
    for(j=0;j<(ln-2);j++) 
    { 
        tempq+=*i; 
        i++; 
    } 
    tempq=(~tempq)+1; 
    return(tempq); 
}

void setup() {
  Serial.begin(115200);
  Serial.println(FucCheckSum(data,8),HEX);
}

void loop() {

}

Calculation of temperature value

byte Temp_H = 0x01;//Temperature data high bit
byte Temp_L = 0xD9;//Temperature data low bit

void setup() {
  Serial.begin(115200);
  uint16_t temp_ADC = (Temp_H << 8) + Temp_L;
  float Vpd3 = 3 * (float)temp_ADC / 1024;
  float Rth = Vpd3 * 10000 / (3 - Vpd3);
  float Temp = 1 / (1 / (273.15 + 25) + 1 / 3380.13 * log(Rth / 10000)) - 273.15;
  Serial.println(Temp);
}

void loop() {

}

FAQ

If you have any questions about using this product, please check the FAQ list for that product for a corresponding solution. For any questions, advice or cool ideas to share, please visit the DFRobot Forum.

More Documents

• DFRobot-Electrochemical Module .pdf

• Dimension.pdf

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