Using Millis to Turn On/Off Relay for a set interval

[flashclass]

Oh wow, ok, you took this to a whole new level! Thank you so much for taking the time to clean up my chicken scratch and introduce me to some new functions! After spending a couple hours reviewing I think I have some questions...

I'm a little unsure of what's going on here. Why have you assigned const bytes to the inputs and outputs? I don't see where that's necessary later in the code. Again, I'm a beginner so I'm sure I've missed something. Also, in this chunk of code you define the Start and Stop ints, but further down they are redefined using the values I had set? I'm not understanding the significance of const int Start = 88 and
const int Stop = 92, why is it necessary and why have you specifically chosen those values? I have the same question about the solenoid and warm intervals?

@gcjr

const int  pressureInput = A0;

const byte RedEnd      = A1;

const byte ConcRelay1  = 10;
const byte ConcRelay2  = 11;
const byte CompRelay3  = 12;
const byte ValveRelay4 = 13;

const int Start = 88;
const int Stop  = 92;

const long solenoidInterval = 5000;
const long warmInterval     = 3000;

Your use of the delay is really very clever and I'm a little jealous I didn't think of it this way. I was dead set on using the millis function but looking at what you've done the delay makes much more sense because pressure does not need to be monitored during the solenoidInterval and warmInterval times, because it won't be changing!

I think I understand what's going on down in the loop but I just want to clarify. So on start up my "Hello there" message will be displayed and will be in ST_idle until I press the RedEnd button which will cause the program to enter into ST_Run? Once in ST_Run the program will loop through the monitor section until I hit the RedEnd again which will initiate the ST_shutdown case?

@gcjr

void loop ()
{
    enum { ST_IDLE, ST_RUN, ST_SHUTDOWN };
    static int state = ST_IDLE;

    switch (state)  {
    case ST_RUN:
        monitor ();
        break;

    case ST_SHUTDOWN:
        digitalWrite (ConcRelay1 ,  LOW);
        digitalWrite (ConcRelay2 ,  LOW);
        digitalWrite (CompRelay3 ,  LOW); 
        digitalWrite (ValveRelay4 , HIGH);

        lcd.clear ();
        lcd.setCursor (1,0); //sets cursor to column 1, row 0
        lcd.print ("Program Ended!"); //prints label

        state = ST_IDLE;
        break;

    case ST_IDLE:
        break;
    }

    byte but = digitalRead (RedEnd);
    if (butState != but)  {
        butState = but;
        delay (10);         // debounce

        if (LOW == but)  {  // press
            if (ST_IDLE == state)
                state = ST_RUN;
            else
                state = ST_SHUTDOWN;
        }
    }
}

Again, thanks so much for the guidance here. I understand where my mistake in using the millis function was and have added a couple new functions to my vocabulary.