int set_point = 300; // change int sensorPin = A0; int output_pin = 3; int sensorValue = 0; void setup() { Serial.begin(9600); pinMode(output_pin, OUTPUT); } void loop() { sensorValue = analogRead(sensorPin); //Serial.println(sensorValue); if( sensorValue <= set_point) digitalWrite(output_pin, LOW); else digitalWrite(output_pin, HIGH); }