int solenoidPin = 4;    //This is the output pin on the Arduino we are using

void setup() {
  // put your setup code here, to run once:
  pinMode(solenoidPin, OUTPUT);           //Sets the pin as an output
}

void loop() {
  // put your main code here, to run repeatedly:  
  digitalWrite(solenoidPin, HIGH);    //Switch Solenoid ON
  delay(2000);                      //Wait 1 Second
  digitalWrite(solenoidPin, LOW);     //Switch Solenoid OFF
  delay(2000);                      //Wait 1 Second
  }

/*
* Ultrasonic Sensor HC-SR04 and Arduino Tutorial
*
* by Dejan Nedelkovski,
* www.HowToMechatronics.com
*
*/
// defines pins numbers
const int trigPin = 0;
const int echoPin = 1;
// defines variables
long duration;
int distance;
void setup() {
pinMode(trigPin, OUTPUT); // Sets the trigPin as an Output
pinMode(echoPin, INPUT); // Sets the echoPin as an Input
pinMode(2,OUTPUT);
//Serial.begin(9600); // Starts the serial communication
}
void loop() {
// Clears the trigPin
digitalWrite(trigPin, LOW);
delayMicroseconds(2);
// Sets the trigPin on HIGH state for 10 micro seconds
digitalWrite(trigPin, HIGH);
delayMicroseconds(10);
digitalWrite(trigPin, LOW);
// Reads the echoPin, returns the sound wave travel time in microseconds
duration = pulseIn(echoPin, HIGH);
// Calculating the distance
distance= duration*0.034/2;
if (distance<10){
  digitalWrite(2,HIGH);
}
else{
  digitalWrite(2,LOW);
}
}

* Ultrasonic Sensor HC-SR04 and Arduino Tutorial
*
* by Dejan Nedelkovski,
* www.HowToMechatronics.com
*
*/
// defines pins numbers
const int trigPin = 0;
const int echoPin = 1;
// defines variables
long duration;
int distance;
void setup() {
pinMode(trigPin, OUTPUT); // Sets the trigPin as an Output
pinMode(echoPin, INPUT); // Sets the echoPin as an Input
pinMode(2,OUTPUT);
//Serial.begin(9600); // Starts the serial communication
}
void loop() {
// Clears the trigPin
digitalWrite(trigPin, LOW);
delayMicroseconds(2);
// Sets the trigPin on HIGH state for 10 micro seconds
digitalWrite(trigPin, HIGH);
delayMicroseconds(10);
digitalWrite(trigPin, LOW);
// Reads the echoPin, returns the sound wave travel time in microseconds
duration = pulseIn(echoPin, HIGH);
// Calculating the distance
distance= duration*0.034/2;
if (distance<10){
  digitalWrite(2,HIGH);
}
else{
  digitalWrite(2,LOW);
}
}