我正在尝试检测 PIR 传感器何时触发连续运动超过 8 秒。这是我所拥有的。当传感器处于低电平时，"无运动..."，然后短动作触发第一个"<8 秒"IF 语句。当传感器返回到 LOW 时 - 没有显示应有的运动，但当第二次检测到运动时，代码似乎冻结并且没有任何反应。
unsigned long startMillis;
boolean timingFlag = false;
const int buttonPin = 2;
int buttonState = 0;
void setup() {
pinMode(buttonPin, INPUT);
Serial.begin(19200);
delay(500);
}
void loop() {
buttonState = digitalRead(buttonPin);
if (buttonState == HIGH && millis() - startMillis <= 8000UL)
{
Serial.println("Motion Detected but less than 8");
delay(1000);
//the PIR timed out with in the three seconds so cancel timing
timingFlag = false; //disable timing
}
if (buttonState == LOW)
{
Serial.println("No Motion...");
delay(1000);
timingFlag = true; //enable timing
}
//when nine seconds have gone by with consistant detection do something
if (timingFlag == false && millis() - startMillis >= 9000UL)
{
//There has now been nine seconds of constant PIR detection
Serial.println("Motion Detected and greater than 9 sec");
delay(1000);
//Do Something
}
}
正如 Scheff 在评论中已经提到的，您当前的代码存在一个非常明显的问题：您从未真正将startMillis设置为任何内容，因此它们可能(但不一定(始终为 0。
这意味着，语句if (buttonState == HIGH && millis() - startMillis <= 8000UL)在 8000 毫秒后将始终false(直到millis()流过，大约 50 天后*(，因此在此之后timingFlag永远不会重置为false。这最终会导致您的"冻结"情况。
我试图找到一个好地方在你的代码中设置startMillis，但老实说我觉得它有点混乱，所以我允许自己重写你的逻辑，希望你不要介意。(请注意，我还将变量名称从按钮更改为检测器，因为它似乎更适合我(：
(此版本在从高到低的转换时触发(
// define the threshold, after which an action shall be triggered
const int detectionThreshold = 8000;
const int detectorPin = 2;
unsigned long startTime = 0;
int lastDetectorState = LOW;
void setup() {
pinMode(detectorPin, INPUT);
Serial.begin(19200);
delay(500);
}
void triggerDetectionAction(){
// do whatever needs to be done after 8 seconds of motion in here
}
void loop() {
int currentDetectorState = digitalRead(detectorPin);
// if detector is low, no motion is detected
if( currentDetectorState == LOW ){
// when the detector is LOW, we want to check if the last state was HIGH
// because then we just arrived at the transition from HIGH to LOW =>
// "something was detected" to "there is no longer something detected"
if( lastDetectorState == HIGH ){
// then, we can get the total duration, the detection lasted
unsigned long detectionDuration = millis() - startTime;
// and print it for easier debugging
Serial.print("Detection ended after ");
Serial.print(detectionDuration);
Serial.println(" milliseconds");
// finally, we check if the durations was more than
// or equal to our threshold
if( detectionDuration >= detectionThreshold ){
// and trigger stuff if necessary
triggerDetectionAction();
}
}
// if last detector state was LOW too,
// we don't want to do anything
}else{
// here we wan't to check for the transition of LOW to HIGH,
// so we check our last detector state
if( lastDetectorState == LOW ){
// if we caught the transition,
// set the start time to the current millis
startTime = millis();
// we could also set an indicator LED
// or Serial.print something here
Serial.println("Detection started");
}
// otherwise, we don't wan't to do anything
}
// finally, we save our current state into the last state,
// so we have it available in the next loop
lastDetectorState = currentDetectorState;
// do your other loop stuff here
}
请注意，我在编写时无法测试代码，因此可能存在(语法(错误
*更多关于米利斯和溢出的信息：https://www.arduino.cc/reference/en/language/functions/time/millis/
更新：达到阈值时，此版本将立即触发。它还包括一个示例，如何在达到阈值后触发操作一次且每个循环。
// define the threshold, after which an action shall be triggered
const int detectionThreshold = 8000;
const int detectorPin = 2;
unsigned long startTime = 0;
int lastDetectorState = LOW;
bool actionTriggered = false;
void setup() {
pinMode(detectorPin, INPUT);
Serial.begin(19200);
delay(500);
}
void triggerOnce(){
// this will be called once, when the threshold is reached
}
void triggerEveryLoop(){
// this will be called every loop, after the threshold was reached
// for as long as the detector stays high
}
void loop() {
int currentDetectorState = digitalRead(detectorPin);
if( currentDetectorState == LOW ){
if( lastDetectorState == HIGH ){
// since we want to trigger immediately when the threshold is reached,
// we actually don't need this transition any longer.
// We can still keep it for debugging reasons thought.
// If you don't need this, you can simply remove the entire block
unsigned long detectionDuration = millis() - startTime;
Serial.print("Detection ended after ");
Serial.print(detectionDuration);
Serial.println(" milliseconds");
}
}else{
// Check for LOW => HIGH transition change
if( lastDetectorState == LOW ){
// if we caught the transition,
// set the start time to the current millis
startTime = millis();
// and reset the flag
actionTriggered = false;
// we could also set an indicator LED
// or Serial.print something here
Serial.println("Detection started");
}else{
// otherwise we want to check the duration
unsigned long detectionDuration = millis() - startTime;
// and trigger immediatley when the threshold is reached
if( detectionDuration >= detectionThreshold ){
// as long as it wasn't already triggered before
if( !actionTriggered ){
Serial.println("Threshold reached, triggering");
// now we also need to set a flag, so we know we already triggerd this action once
actionTriggered = true;
triggerOnce();
}
// we can also do something every loop
// this can be handy for e.g. blinking a light or playing a sound or something
triggerEveryLoop();
}
}
}
// finally, we save our current state into the last state,
// so we have it available in the next loop
lastDetectorState = currentDetectorState;
// do your other loop stuff here
}