const int TRIG_PIN = 2; const int ECHO_PIN = 4; const int RELAY_PIN = 15; long duration, distance;
void setup() { Serial.begin(115200); pinMode(TRIG_PIN, OUTPUT); pinMode(RELAY_PIN, OUTPUT); pinMode(ECHO_PIN, INPUT);
}
void loop() {
distance = getDistanceInCentimeters(); if(distance <= 100)
digitalWrite(RELAY_PIN, HIGH);
else
digitalWrite(RELAY_PIN, LOW);
delay(1000); }
long  getDistanceInCentimeters() {
digitalWrite(TRIG_PIN,LOW); delayMicroseconds(2); digitalWrite(TRIG_PIN, HIGH); delayMicroseconds(10); digitalWrite(TRIG_PIN, LOW); duration = pulseIn(ECHO_PIN, HIGH); return (duration * 0.034 / 2) + 1;
}