MH-z19 giving -1 value after some time - arduino-esp8266

Question

I'm trying make an mqtt co2 sensor for home assistant. And I got it to work, but only for a couple of hours. At some point it starts giving me -1 values instead of the proper co2 value. What could this be?
Below my code:
#include <Arduino.h>
#include <Mhz19.h>
#include <SoftwareSerial.h>
SoftwareSerial softwareSerial(D3, D4);
Mhz19 sensor;
#include <ESP8266WiFi.h>
#include <PubSubClient.h>
const char* ssid = "ID";
const char* password = "pw";
const char* MQTT_BROKER = "192.168.1.25";//"test.mosquitto.org";
int mqttPort = 1883;
const char* mqttUser ="mqtt-user";
const char* mqttPassword ="pw";
WiFiClient espClient;
PubSubClient client(espClient);
void setup_wifi() {
delay(100);
// Connect to Wi-Fi network
Serial.println();
Serial.print("Connecting to ");
Serial.println(ssid);
WiFi.begin(ssid, password);
while (WiFi.status() != WL_CONNECTED) {
delay(500);
Serial.print(".");
}
randomSeed(micros());
Serial.println("");
Serial.println("Connected to Wi-Fi");
}
void reconnect() {
// Loop until connected
while (!client.connected()) {
Serial.print("Connecting to MQTT...");
if (client.connect("Test1", mqttUser, mqttPassword )) {
Serial.println("Connected to MQTT");
} else {
Serial.print("Failed MQTT connection with state: ");
Serial.println(client.state());
// Re-try in 3 seconds
delay(3000);
}
}
// Once connected, publish an announcement, and subscribe
client.publish("sensor/test", "Hello from ...");
client.subscribe("sensor/test");
}
void setup() {
Serial.begin(115200);
setup_wifi(); // Connect to Wi-Fi network
client.setServer(MQTT_BROKER, mqttPort);
//client.setCallback(callback);
reconnect(); // Connect to MQTT broker
softwareSerial.begin(9600);
sensor.begin(&softwareSerial);
sensor.setMeasuringRange(Mhz19MeasuringRange::Ppm_5000);
sensor.enableAutoBaseCalibration();
Serial.println("Preheating..."); // Preheating, 3 minutes
while (!sensor.isReady()) {
delay(50);
}
Serial.println("Sensor Ready...");
}
void loop() {
if (!client.connected()) { reconnect(); }
//client.publish("Time", ctime(&now));
auto carbonDioxide = sensor.getCarbonDioxide();
if (carbonDioxide >= 0) {
Serial.println(String(carbonDioxide) + " ppm");
}
char co2String[8];
dtostrf(carbonDioxide, 1,0, co2String);
//Serial.println(co2String);
client.publish("Floating/climate/CO2", co2String);
delay(2000);
}
I also tried flashing it via ESPHome, but then I run into issues from UART. The chip doesn't work propperly as long as the sensor is connected to it.

Answer 1

The sensor may not be receiving enough current. Try connecting the sensor directly to a separate breadboard power supply. The sensor seems to have a warm up time. Try waiting for longer with the independent power supply connected. I hope this will solve your issue.
Thank You,
Naveen PS