API for the MQ4 Gas Sensor. More...

Detailed Description

ID: mq4
Name: MQ4 Methane and Connecticut Natural Gas (CNG) Sensor
Category: gaseous
Manufacturer: dfrobot
Connection: analog
Link: https://www.dfrobot.com/index.php?route=product/product&product_id=683

The MQ4 Gas Sensor module is useful for detecting CH4 (Methane), and natural gas concentrations in the air. It has a detection range of 100-10000 ppm.

For optimum use, it requires calibration after a pre-heat time of at least 24 hours. See the datasheet for details.

int
main(int argc, char** argv)
{
    // Attach gas sensor to Analog A0
    upm::MQ4 sensor(0);
    signal(SIGINT, sig_handler);
    uint16_t buffer[128];
    thresholdContext ctx;
    ctx.averageReading = 0;
    ctx.runningAverage = 0;
    ctx.averagedOver = 2;
    // Infinite loop, ends when script is cancelled
    // Repeatedly, take a sample every 2 microseconds;
    // find the average of 128 samples; and
    // print a running graph of asteriskss as averages
    while (shouldRun) {
        int len = sensor.getSampledWindow(2, 128, buffer);
        if (len) {
            int thresh = sensor.findThreshold(&ctx, 30, buffer, len);
            sensor.printGraph(&ctx, 5);
            if (thresh) {
                // do something ....
            }
        }
    }
    cout << "Exiting" << endl;
    return 0;
}

Public Member Functions
	MQ4 (int gasPin)

	~MQ4 ()

std::string	name ()

Public Member Functions inherited from Gas
	Gas (int gasPin)

virtual	~Gas ()

virtual int	getSampledWindow (unsigned int freqMS, int numberOfSamples, uint16_t *buffer)

virtual int	findThreshold (thresholdContext ctx, unsigned int threshold, uint16_t buffer, int len)

virtual int	getSampledData (thresholdContext *ctx)

virtual int	getSample ()

virtual void	printGraph (thresholdContext *ctx, uint8_t resolution)