如何在循环中锁定10秒前的值(使用按钮)？

Question

我一直在创建一个涉及Mq-3传感器的项目。当传感器增加51%时，RedLED就会闪烁。关于这一点，我根据比率和我从答复者收集的数据建立了一个使用的公式。

sensorVal=analogRead(sensorPin);  //read SensorPin
sensorCalc51=(322./150.)*sensorVal; //This is the 51% value that the arduino makes that is dependent on the sensorVal

if (sensorVal >= sensorCalc51) {           //the condition involves both the sensorVal and sensorCalc51
    for (int i=0; i<=20; i=i+1) {       
        analogWrite(redPin,255);
        delay (500);
        analogWrite(redPin,000);
        delay (500);
    }

正如您在代码中所看到的，该条件永远不会为真，因为公式总是使sensorCalc51高于sensorVal。我需要通过一个按钮使sensorCalc51锁定它的最新值，这样当用户在传感器上呼吸时，它不会变得更高，而且它实际上使条件成为现实。

Answer 1

您应该将sensorCalc51封装在if语句中，并将值存储在全局或静态本地：

void test() {
  static float sensorCalc51 = 10000.0;  //to insure it doesn't fire before it's set properly
  int sensorVal;

  sensorVal = analogRead(sensorPin); //read SensorPin

  // now check if the button is pressed.  If so update sensorCalc51
  // the digitalRead will be HIGH or LOW when switch is pressed
  // depending on the type of switch
  if (digitalRead(mySwitch)) {
    sensorCalc51 = (322. / 150.) * sensorVal;
  }

  if (sensorVal >= sensorCalc51) {
    for (int i = 0; i <= 20; i = i + 1) {
      analogWrite(redPin, 255);
      delay (500);
      analogWrite(redPin, 000);
      delay (500);
    }
  }
}