Single sensor

What this example shows

The library's singleSensor example creates one sensor with only a preset, so the address and the pin keep their defaults, and prints the concentration in ppm every 2.5 s.

The example creates the sensor with SENSOR_CO, the carbon monoxide preset. The library calculates ppm from the preset's sensitivity and gain settings; the preset for this board's chlorine cell is SENSOR_CL2.

The example code

Select Board

singleSensor.ino

/**
 **************************************************
 *
 * @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 LMPEN pin to GND or a GPIO pin so the breakout can be configured
 *              - Run the sketch and open serial monitor at 115200 baud!
 *
 *
 * @authors     Robert @ soldered.com
 ***************************************************/

// Include the required library
#include "Electrochemical-Gas-Sensor-SOLDERED.h"

// Configurations for each of the sensor types are in sensorConfigData.h in the library's 'src' folder
// Create the sensor object with the according type
ElectrochemicalGasSensor sensor(SENSOR_CO);

// If you are using a custom I2C address (for multiple sensors) use:
// ElectrochemicalGasSensor sensor(SENSOR_SO2, 0x4B, 5);
// For more details on this, see customAddress.ino

void setup()
{
    Serial.begin(115200); // For debugging

    // Init the breakout
    if (!sensor.begin())
    {
        // Can't init? Notify the user and go to infinite loop
        Serial.println("ERROR: Can't init the sensor! Check connections!");
        while (true)
            delay(100);
    }

    Serial.println("Sensor initialized successfully!");
}

void loop()
{
    // Make the reading
    double reading = sensor.getPPM();

    // If PPB is more relevant for your sensor, you can use:
    // double reading = sensor.getPPB();

    // Print the reading with 5 digits of precision
    Serial.print("Sensor reading: ");
    Serial.print(reading, 5);
    Serial.println(" PPM");

    // Wait a bit before reading again
    delay(2500);
}

The header comment asks for LMPEN to be connected. On this board a 10 kΩ resistor holds LMPEN low and it is wired to the ATtiny404, so you leave it unconnected (see the pin table on Hardware details).

Expected result:

Serial MonitorAutoscrollShow timestampNewline115200 baud

Message (Enter to send message to the board)

Sensor initialized successfully!

Then a line every 2.5 s: Sensor reading: , the concentration in ppm with five decimals, and PPM. If begin() fails, the sketch prints ERROR: Can't init the sensor! Check connections! and stops.

Functions used

ElectrochemicalGasSensor(sensorType _t, uint8_t _adcAddr = DEFAULT_ADC_ADDR, int _configPin = -1)returns ElectrochemicalGasSensor

Creates the sensor object. It stores the settings only; nothing is sent to the board until begin().

ReturnsThe sensor object.

Parameters

Type	Name	Description
sensorType	_t	The cell preset. The example passes SENSOR_CO; this board's SGX-4CL2 cell has the preset SENSOR_CL2.
uint8_t	_adcAddr	The I2C address, DEFAULT_ADC_ADDR (0x49) when left out, as in the example. For an address from 0x30 to 0x37, the range of this board's ADDRESS switch, begin() talks to the board's ATtiny404; for any other address it looks for an ADS1115 at that address and the LMP91000 directly on the bus.
int	_configPin	A GPIO that begin() drives low while it configures the LMP91000 directly. -1 (none) when left out, as in the example. Unused for addresses 0x30 to 0x37.

bool begin()returns bool

Starts Wire, checks that the board answers, sets the preset's ADC gain and data rate, and configures the LMP91000 with the preset's settings. Call it once in setup() before reading.

Returnstrue when the board answered and both configuration steps succeeded, false otherwise.

double getPPM()returns double

Takes one reading and converts it to ppm: it subtracts the internal zero voltage (the 2.5 V reference times the preset's internal zero percentage), adds the zero calibration, divides by the amplifier gain and by the preset's sensitivity in nA per ppm. A result below zero is returned as 0.

ReturnsThe gas concentration in ppm.

double getPPB()returns double

Same reading as getPPM(), times 1000. The example shows it in a comment as the alternative to getPPM().

ReturnsThe gas concentration in ppb.

The example also uses Serial and delay(), which come with the Arduino core, not with this library.

Putting it together

begin() does all the setup, so loop() only calls getPPM() and prints the result. To read in ppb instead, swap the getPPM() line for the getPPB() line in the comment below it.

SourceOpen the verified Arduino exampleView the exact source used by this page.examples/singleSensor/singleSensor.ino