MHZ-19B with wemos D1 mini v3.0

Other Hardware Sensors
1

Hi,

I have this CO2 sensor, datasheet: here
I'm trying to get with wemos d1 mini v3.0 the values of ppm and temp out of the sensor but i just can't get it to work.

I have found some one who sais he has i running. this is his blog: here
and the corresponding github files: here

Difference is that he has MHZ-19 and i have MHZ-19B sensor.
Where the TX and RX are on different pins.

My wiring:

VCC: to external 5 volt
GND: to externa GND (grounds of sensor and external vcc NOT connected)
RX to D3 on wemos d1 mini
TX to D4 on wemos d1 mini

Wemos to USB -> PC

The problem is that when i power everything the arduino serial console seem to see the sensor but i just get this:

MH-Z19 now warming up... status:-1
MH-Z19 now warming up... status:-1
MH-Z19 now warming up... status:-1
MH-Z19 now warming up... status:-1
MH-Z19 now warming up... status:-1
MH-Z19 now warming up... status:-1
co2: -1
temp: -1
co2: -1
temp: -1
co2: -1
temp: -1
co2: -1
temp: -1
co2: -1
temp: -1
co2: -1

This is the simple test scatch that i have now:

/*----------------------------------------------------------
    MH-Z19 CO2 sensor  SAMPLE
  ----------------------------------------------------------*/

#include <MHZ19_uart.h>

const int tx_pin = D3;  //Serial tx pin no
const int rx_pin = D4;	//Serial rx pin no


MHZ19_uart mhz19;

/*----------------------------------------------------------
    MH-Z19 CO2 sensor  setup
  ----------------------------------------------------------*/
void setup() {
  Serial.begin(9600);
  mhz19.begin(rx_pin, tx_pin); 
  mhz19.setAutoCalibration(false);
  while( mhz19.isWarming() ) {
    Serial.print("MH-Z19 now warming up...  status:");Serial.println(mhz19.getStatus());
    delay(1000);
  }
}

/*----------------------------------------------------------
    MH-Z19 CO2 sensor  loop
  ----------------------------------------------------------*/
void loop() {
  int co2ppm = mhz19.getPPM();
  int temp = mhz19.getTemperature();

  Serial.print("co2: "); Serial.println(co2ppm);
  Serial.print("temp: "); Serial.println(temp);
  
  delay(5000);
}

This is the liberary that i use: here

Has anyone have this configuration running?
Whats is wrong?
Why are all values -1??

hope someone can help me.

tnx

2

So found this on github and it works. So for the others here is the link.
Seems to be a difference between MHZ-19A and MHZ-19B.
This workt for my MHZ-19B

link

3

I'd like to confirm that MHZ-19 works with WeMos. Feed it with 5V and use logic on 3.3 (no other circuits are requered). But sometimes you need to change RX to TX because it depends on which side to look on the terminal :slight_smile:

Here is my blog post about this sensor and even with an example of connection Отслеживаем содержание CO2 в воздухе при помощи WeMos D1 Mini Pro, ThingSpeak и MHZ-19 | Многобукфф