search

tobiasschuerg / MH-Z-CO2-Sensors

Arduino imeplementation for CO2 sensors of the MH-Z series (Intelligent Infrared CO2 Module)
MIT License
75 stars 40 forks source link

adjust measurement range (5000 ppm or 2000 ppm) #15

Closed PaulMerk closed 3 years ago

PaulMerk commented 3 years ago

I would like to adjust the measurement range from 5000 to 2000. quote:According to the MH-Z19B datasheet, you can configure the measurement range by putting the desired range in byte 3 and 4. However, unlike what the MH-Z19B datasheet says, you can set the range using the following command (in this case 0x07d0 = 2000 ppm in byte 6 and 7):
0xFF 0x01 0x99 0x00 0x00 0x00 0x07 0xD0 0x8F

^-range-^ unquote How would a sketch look like to send this command to the MH-Z19B ? ``` #include #include // pin for pwm reading #define CO2_IN 10 // pin for uart reading #define MH_Z19_RX D7 // D7 D4 #define MH_Z19_TX D6 // D6 D0 MHZ co2(MH_Z19_RX, MH_Z19_TX, CO2_IN, MHZ19B); void setup() { Serial.begin(9600); pinMode(CO2_IN, INPUT); delay(100); Serial.println("MHZ 19B"); // enable debug to get addition information // co2.setDebug(true); if (co2.isPreHeating()) { Serial.print("Preheating"); while (co2.isPreHeating()) { Serial.print("."); delay(5000); } Serial.println(); } } void loop() { ??? 0xFF 0x01 0x99 0x00 0x00 0x00 0x07 0xD0 0x8F ??? } ```
tobiasschuerg commented 3 years ago

You need to create a byte array with the command that you want to send and then pass it over serial. Something like:

byte command[9] = {0xFF, 0x01, 0x99, 0x00, 0x00, 0x00, 0x07, 0xD0, 0x8F};
serial->write(command, 9);

Like in https://github.com/tobiasschuerg/MH-Z-CO2-Sensors/blob/master/MHZ.cpp#L116 Hope that helps.

See also the official documentation: https://www.arduino.cc/reference/en/language/functions/communication/serial/write/