KY-021 Mini reed magnet – Учебка DF

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const int ledPin  = 13;  // on-board LED
const int reedPin = 2;   // KY-021 signal (S) pin

int reedState   = HIGH;          // debounced reed state (HIGH = no magnet)
int lastReading = HIGH;          // previous raw reading
unsigned long lastChange = 0;
const unsigned long debounceMs = 20;

void setup() {
  pinMode(ledPin, OUTPUT);
  pinMode(reedPin, INPUT);       // the KY-021 has an on-board pull-up resistor
}

void loop() {
  int reading = digitalRead(reedPin);

  // restart the debounce timer whenever the raw reading changes
  if (reading != lastReading) {
    lastChange = millis();
    lastReading = reading;
  }

  // accept the reading once it has stayed stable long enough
  if (millis() - lastChange > debounceMs) {
    reedState = reading;
  }

  // the KY-021 reads LOW when a magnet closes the reed switch
  if (reedState == LOW) {
    digitalWrite(ledPin, HIGH);  // magnet detected -> LED on
  } else {
    digitalWrite(ledPin, LOW);   // no magnet -> LED off
  }
}

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