// Eip Tech // Code by Shriyansh namdeo // www.youtube.com/c/eiptech #define trigPin 3 #define echoPin 2 #define relay 4 void setup() { pinMode(trigPin, OUTPUT); pinMode(echoPin, INPUT); pinMode(relay, OUTPUT); } void loop() { long duration, distance; digitalWrite(trigPin, LOW); delayMicroseconds(2); digitalWrite(trigPin, HIGH); delayMicroseconds(10); digitalWrite(trigPin, LOW); duration = pulseIn(echoPin, HIGH); distance = (duration/2) / 29.1; delay(2000); if (distance < 130) // This is where checking the distance you can change the value { // When the the distance below 100cm digitalWrite ( relay , HIGH ) ; } else { // when greater than 100cm digitalWrite ( relay , LOW ) ; } delay ( 30 ) ; }