Electrochemical Gas Sensors O3, NO, NO2 configuration and I2C addressing

Soldered_Bot · March 25, 2025, 7:11am

Customer:

I purchased three electrochemical gas sensors (O3, NO, NO2) but did not receive documentation with them. Can you provide technical documentation and tutorials for these sensors?

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Originally submitted via email support on 25 March 2025. Migrated to the forum for community visibility.

Soldered_Bot · March 25, 2025, 12:17pm

Soldered Support:

You can use the Arduino library to get started. The single sensor example is at:

github.com/SolderedElectronics/Soldered-Electrochemical-Gas-Sensor-Arduino-Library

examples/singleSensor/singleSensor.ino

main

/**
 **************************************************
 *
 * @file        singleSensor.ino
 * @brief       See how to init one sensor and make a simple reading of PPM of gas.
 *
 *              To successfully run the sketch:
 *              - Connect the breakout to your Dasduino board via easyC
 *              - Connect LMPEN pin to GND or a GPIO pin so the breakout can be configured
 *              - Run the sketch and open serial monitor at 115200 baud!
 *
 *              Electrochemical Gas Sensor Breakout: solde.red/333218
 *              Dasduino Core: www.solde.red/333037
 *              Dasduino Connect: www.solde.red/333034
 *              Dasduino ConnectPlus: www.solde.red/333033
 *
 * @authors     Robert @ soldered.com
 ***************************************************/

// Include the required library

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The configuration example is at:

github.com/SolderedElectronics/Soldered-Electrochemical-Gas-Sensor-Arduino-Library

examples/customConfig/customConfig.ino

main

/**
 **************************************************
 *
 * @file        customConfig.ino
 * @brief       Create a custom config for the LMP91000 and upload it to the device.
 *              This enables you to use this breakout with any electrochemical sensor.
 *
 *              To successfully run the sketch:
 *              - Edit the custom configuration
 *              - Connect LMPEN to any GPIO pin
 *              - Connect the breakout to your Dasduino board via easyC
 *              - Run the sketch and open serial monitor at 115200 baud!
 *
 *              Electrochemical Gas Sensor Breakout: solde.red/333218
 *              Dasduino Core: www.solde.red/333037
 *              Dasduino Connect: www.solde.red/333034
 *              Dasduino ConnectPlus: www.solde.red/333033
 *
 * @authors     Robert @ soldered.com
 ***************************************************/

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Configurations for CO, NO2 and SO2 sensors are available at:

github.com/SolderedElectronics/Soldered-Electrochemical-Gas-Sensor-Arduino-Library

src/sensorConfigData.h

c691a805d


      
              uint8_t BIAS;
              uint8_t FET_SHORT;
              uint8_t OP_MODE;
          };
          
          // NOTE: The reference voltage is always 2.5V
          // The internal zero voltage has an offset in the PPM calculation - internalZeroCalibration
          // This is due to the fact high gains amplify the noise as well so it's best to further calibrate it
          
          // SGX-4CO - Carbon Monoxide sensor
          const sensorType SENSOR_CO = {
              70.0F,                    // nanoAmperesPerPPM
              0.078,                    // internalZeroCalibration
              ADS_GAIN_4_096V,          // adsGain
              TIA_GAIN_350_KOHM,        // TIA_GAIN_IN_KOHMS
              RLOAD_10_OHM,             // RLOAD
              REF_EXTERNAL,             // REF_SOURCE
              INTERNAL_ZERO_20_PERCENT, // INTERNAL_ZERO
              BIAS_SIGN_NEGATIVE,       // BIAS_SIGN
              BIAS_0_PERCENT,           // BIAS
              FET_SHORT_DISABLED,       // FET_SHORT

You will need to create configurations yourself for O3 and NO sensors using the datasheets:

Soldered_Bot · March 25, 2025, 1:08pm

Customer:

I’m not using the easyC port but connecting the SCL/SDA/VCC and GND pins directly. For addressing the three sensors, what is the operating voltage of the sensor board - 3.3 or 5 VDC?

Soldered_Bot · March 25, 2025, 1:55pm

Soldered Support:

You can use the SCL, SDA, VCC, and GND pins. If you use the same microcontroller for all three sensors, you will have address conflicts since the addresses will be the same.

The board has on-board regulators and can be connected via these pins or via easyC cable at 3.3V or 5V.

Start by testing one sensor at a time using the single sensor example. To use multiple sensors, refer to the twoSensors example in the library.

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Soldered_Bot · March 25, 2025, 2:15pm

Customer:

I want to use all three sensors with the same microcontroller. If I understand correctly, I need to set jumpers on jumper 5, 6, or 7 to change each sensor’s I2C address, so I can address them separately in my program?

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Soldered_Bot · March 25, 2025, 2:37pm

Soldered Support:

Yes, you are correct about using the three jumpers. However, you also need to connect the LMPEN pins to different microcontroller pins. The microcontroller must pull the LMPEN pin to GND to configure the onboard LMP91000 chip. If all LMPEN pins connect to the same microcontroller pin, you won’t be able to configure the sensors correctly.

I recommend testing each sensor one by one first. When testing each sensor individually, connect its LMPEN to GND temporarily to enable it.

Soldered_Bot · March 31, 2025, 5:40am

Customer:

I found an issue in the Electrochemical-Gas-Sensor-SOLDERED.h file. The includes were:

#include "libs/ADS1X15/ADS1X15.h"
#include "libs/LMP91000/LMP91000.h"

Changing them to:

#include "ADS1X15.h"
#include "LMP91000.h"

Fixed the problem and it now works.

Soldered_Bot · March 31, 2025, 11:43am

Soldered Support:

This appears to be an Arduino compiler issue. I will note this with our team that maintains the libraries.

Soldered_Bot · April 2, 2025, 1:51pm

Customer:

I2C is now fully functional with all three sensors and one LCD liquidCrystal display. Can you help me verify the sensorConfigData.h configuration for the O3 and NO sensors? I’m not confident in my configuration.

Here is what I created:

// NOTE: The reference voltage is always 2.5V
// The internal zero voltage has an offset in the PPM calculation - internalZeroCalibration
// This is due to the fact high gains amplify the noise as well so it's best to further calibrate it

// SGX-NO - Monoxide d'azote sensor
const sensorType SENSOR_NO = {
400.0F, // nanoAmperesPerPPM
0.078, // internalZeroCalibration
ADS_GAIN_4_096V, // adsGain
TIA_GAIN_350_KOHM, // TIA_GAIN_IN_KOHMS
RLOAD_10_OHM, // RLOAD
REF_EXTERNAL, // REF_SOURCE
INTERNAL_ZERO_20_PERCENT, // INTERNAL_ZERO
BIAS_SIGN_NEGATIVE, // BIAS_SIGN
BIAS_0_PERCENT, // BIAS
FET_SHORT_DISABLED, // FET_SHORT
OP_MODE_3LEAD_AMP_CELL, // OP_MODE
};

// SGX-4NO2 - Nitrogen Dioxide sensor
const sensorType SENSOR_NO2 = {
-600.0F, // nanoAmperesPerPPM
-0.015, // internalZeroCalibration
ADS_GAIN_2_048V, // adsGain
TIA_GAIN_350_KOHM, // TIA_GAIN_IN_KOHMS
RLOAD_10_OHM, // RLOAD
REF_EXTERNAL, // REF_SOURCE
INTERNAL_ZERO_67_PERCENT, // INTERNAL_ZERO
BIAS_SIGN_NEGATIVE, // BIAS_SIGN
BIAS_0_PERCENT, // BIAS
FET_SHORT_DISABLED, // FET_SHORT
OP_MODE_3LEAD_AMP_CELL, // OP_MODE
};

// SGX-4O3-20 - Ozone sensor
const sensorType SENSOR_O3 = {
1000.0F, // nanoAmperesPerPPM
0.1, // internalZeroCalibration
ADS_GAIN_2_048V, // adsGain
TIA_GAIN_350_KOHM, // TIA_GAIN_IN_KOHMS
RLOAD_10_OHM, // RLOAD
REF_EXTERNAL, // REF_SOURCE
INTERNAL_ZERO_20_PERCENT, // INTERNAL_ZERO
BIAS_SIGN_POSITIVE, // BIAS_SIGN
BIAS_0_PERCENT, // BIAS
FET_SHORT_DISABLED, // FET_SHORT
OP_MODE_3LEAD_AMP_CELL, // OP_MODE
};
#endif

Attachment omitted in migration: sensorConfigData.h

Soldered_Bot · April 3, 2025, 10:33am

Soldered Support:

Glad to hear I2C is working with multiple sensors on one microcontroller!

Configuring sensorConfigData is more involved. To create the existing configurations, we used the sensor datasheets and the Texas Instruments LMP91000 software as a starting point:

The sensor database contains similar sensors. These two data points - the sensor datasheet and the TI LMP software - were used to approximate the parameters. We are currently improving the library, and an update with all sensor configurations is planned for the coming weeks.

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