#define buttonPin  2 // the number of the pushbutton pin
#define solenoidPin 4 // the number of the solenoid pin
#define potPin A0 // Pot should be connected to this analog pin
#define shutterMinTime 500 // min shutter millis
#define shutterMaxTime 2000 // mas shutter millis



int selnoidOpenTime = 2000;
unsigned long TimerStart;
bool Timer_Started; // is set when Timer is started

// variables will change:
boolean buttonState; // variable for reading the pushbutton status

void setup() {
  // initialize the LED pin as an output: pin as an output:
  pinMode(solenoidPin, OUTPUT);
  // initialize the pushbutton pin as an input:
  pinMode(buttonPin, INPUT);
}

void loop() {
  // read the state of the pushbutton value:
  buttonState = digitalRead(buttonPin);

  // check if the pushbutton is pressed. If it is, the buttonState is HIGH:
  if (buttonState == HIGH) {

    if (!Timer_Started) {
      int analogReadValue = analogRead(potPin);
      selnoidOpenTime = map(analogReadValue,0,1024,shutterMinTime,shutterMaxTime);

      digitalWrite(solenoidPin, HIGH); // Open // turn LED ON
      TimerStart = millis(); // starting Timer
      Timer_Started = true;
    } //end if
  } //end if


  // if timer already started
  if (Timer_Started) {
    if (  TimerStart  + selnoidOpenTime <= millis()) {
      digitalWrite(solenoidPin, LOW); // Open // turn LED OFF
      Timer_Started = false;
    } //end if
  } //end if
}