我的MQ气体传感器似乎卡住了

Question

所以我一直致力于制作空气质量传感器的一些项目并遇到问题。任何使用过NodeMCU的人都知道，芯片只有一个模拟引脚。不幸的是，我有两个MQ气体传感器，MQ2和MQ7，所以我必须按照这里的指南为芯片安装两个模拟传感器：http://www.instructables.com/id/Multiple-Analog-Inputs-on-Only-One-Analoge-Pin/

现在，MQ传感器工作有点奇怪。当我从Arduino IDE上传代码时，它们输出非常高的值，并且在转换为ppm（生成0）时通常没有意义。 Dunno，如果是因为传感器中的加热器没有预热或什么。

/*

Multiple Analog inputs on one Analoge pin

Show input of two sensors on one analog pin. 
The vaues of both sensors will be displayed in the serial monitor.

The circuit:
* center pin of both Potentiometer/Sensors attached via a diode to analog input 0
* one side pin (either one)of both potentiometers/sensors to ground
* the other side of both potentiometers/sensors pin to +5V
* pull-down resitor (10k) between analog pin 0 and ground


Created by Vincent Verheggen
Ingenerare

based on:
*example sketch analog input by David Cuartielles
*http://www.arduino.cc/en/Tutorial/AnalogInput
*sketch breagan 22 
*http://www.instructables.com/id/ESP8266-with-Multiple-Analog-Sensors/

 */

const int analogpin = A0;
const int mq2pin = 4;
const int mq7pin = 5;

void setup() {


  Serial.begin(115200);
  // declare the enable and ledPin as an OUTPUT:
  pinMode(mq2pin, OUTPUT);
  pinMode(mq7pin, OUTPUT);
}

void loop() {
    //read from mq sensors

    float mq7_value;
    float mq7_volt;
    float mq7_gas;
    float mq7_ratio;
    float mq7_hold;
    float mq7_ppm;
    //Serial.print("reading mq7...");
    digitalWrite(mq7pin, HIGH);
    mq7_value = analogRead(analogpin);
    digitalWrite(mq7pin, LOW);
    //Serial.print("done!");
    mq7_volt = (float)mq7_value / 1024 * 5.0;
    mq7_gas = (5.0-mq7_volt)/mq7_volt;
    mq7_ratio = mq7_gas/0.18;
    mq7_hold = 24.671324557143727/(mq7_ratio-0.021209244624595787);
    mq7_ppm = pow(mq7_hold, (1/0.7));
    Serial.println(mq7_ppm);

    delay(100);

    float mq2_value;
    float mq2_volt;
    float mq2_gas;
    float mq2_ratio;
    float mq2_hold;
    float mq2_ppm;
    //Serial.print("reading mq2...");
    digitalWrite(mq2pin, HIGH);
    mq2_value = analogRead(analogpin);
    digitalWrite(mq2pin, LOW);
    //Serial.println("done!");
    mq2_volt = (float)mq2_value / 1024 * 5.0;
    mq2_gas = (5.0-mq2_volt)/mq2_volt;
    mq2_ratio = mq2_gas/0.40;
    mq2_hold = 16.177347074757936/(mq2_ratio+1.1016286306095602);
    mq2_ppm = pow(mq2_hold, (1/0.245));
    Serial.println(mq2_ppm);
    Serial.println("----------------------------------------");
    delay(2000);
}