CO2Sensor.ino

/*
 * The MySensors Arduino library handles the wireless radio link and protocol
 * between your home built sensors/actuators and HA controller of choice.
 * The sensors forms a self healing radio network with optional repeaters. Each
 * repeater and gateway builds a routing tables in EEPROM which keeps track of the
 * network topology allowing messages to be routed to nodes.
 *
 * Created by Henrik Ekblad <[email protected]>
 * Copyright (C) 2013-2019 Sensnology AB
 * Full contributor list: https://github.com/mysensors/MySensors/graphs/contributors
 *
 * Documentation: http://www.mysensors.org
 * Support Forum: http://forum.mysensors.org
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * version 2 as published by the Free Software Foundation.
 *
 *******************************
 *
 * DESCRIPTION
 *
 *  MH-Z14 CO2 sensor
 *
 *  Wiring:
 *   Pad 1, Pad 5: Vin (Voltage input 4.5V-6V)
 *   Pad 2, Pad 3, Pad 12: GND
 *   Pad 6: PWM output ==> pin 6
 *
 *  From: http://davidegironi.blogspot.fr/2014/01/co2-meter-using-ndir-infrared-mh-z14.html
 *    MH-Z14 has a PWM output, with a sensitivity range of 0ppm to 2000ppm CO2, an accuracy of ±200ppm.
 *    The cycle is 1004ms±5%, given the duty cicle Th (pulse high), Tl is 1004-Th, we can convert it to CO2 value using the formula:
 *    CO2ppm = 2000 * (Th - 2ms) /(Th + Tl - 4ms)
 *  From: http://airqualityegg.wikispaces.com/Sensor+Tests
 *    - response time is less than 30 s
 *   - 3 minute warm up time
 *  datasheet: http://www.futurlec.com/Datasheet/Sensor/MH-Z14.pdf
 * Contributor: epierre
 */
 
// Enable debug prints to serial monitor
#define MY_DEBUG
 
// Enable and select radio type attached
#define MY_RADIO_RF24
//#define MY_RADIO_NRF5_ESB
//#define MY_RADIO_RFM69
//#define MY_RADIO_RFM95
 
#include <MySensors.h>
 
#define CHILD_ID_AIQ 0
#define AIQ_SENSOR_ANALOG_PIN 6
 
uint32_t SLEEP_TIME = 30*1000; // Sleep time between reads (in milliseconds)
 
float valAIQ =0.0;
float lastAIQ =0.0;
 
MyMessage msg(CHILD_ID_AIQ, V_LEVEL);
MyMessage msg2(CHILD_ID_AIQ, V_UNIT_PREFIX);
 
void setup()
{
    pinMode(AIQ_SENSOR_ANALOG_PIN, INPUT);
}
 
void presentation()
{
    // Send the sketch version information to the gateway and Controller
    sendSketchInfo("AIQ Sensor CO2 MH-Z14", "1.0");
 
    // Register all sensors to gateway (they will be created as child devices)
    present(CHILD_ID_AIQ, S_AIR_QUALITY);
    send(msg2.set("ppm"));
}
 
void loop()
{
 
    //uint32_t duration = pulseIn(AIQ_SENSOR_ANALOG_PIN, HIGH);
    while(digitalRead(AIQ_SENSOR_ANALOG_PIN) == HIGH) {
        ;
    }
    //wait for the pin to go HIGH and measure HIGH time
    uint32_t duration = pulseIn(AIQ_SENSOR_ANALOG_PIN, HIGH);
 
    //Serial.print(duration/1000); Serial.println(" ms ");
    //from datasheet
    //CO2 ppm = 2000 * (Th - 2ms) / (Th + Tl - 4ms)
    //  given Tl + Th = 1004
    //        Tl = 1004 - Th
    //        = 2000 * (Th - 2ms) / (Th + 1004 - Th -4ms)
    //        = 2000 * (Th - 2ms) / 1000 = 2 * (Th - 2ms)
    long co2ppm = 2 * ((duration/1000) - 2);
    //Serial.print(co2ppm);
    if ((co2ppm != lastAIQ)&&(abs(co2ppm-lastAIQ)>=10)) {
        send(msg.set((int32_t)ceil(co2ppm)));
        lastAIQ = ceil(co2ppm);
    }
 
    //Serial.println();
 
    // Power down the radio.  Note that the radio will get powered back up
    // on the next write() call.
    sleep(SLEEP_TIME); //sleep for: sleepTime
}