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

[flashclass]

Hi again Idaho-

The delay is actually for a kill button, which when pressed puts all components of the system in a state which is safe to shut down the controller. The 60 seconds just gives me time to turn it off. This feature is actually working pretty well.

An example of the code I'm having trouble with is below.

@flashclass

if (psi<=Start){
 {digitalWrite (ConcRelay1 , HIGH);} // if psi is less than start setpoint turn on concentrator1
 {digitalWrite (ConcRelay2 , HIGH);} // if psi is less than start setpoint turn on concentrator2
 {digitalWrite (ValveRelay4 , HIGH);} // if psi is less than than start setpoint turn on solenoid valve
 psiStartTime = currentMillis; 
  }
 if ((unsigned long)(currentMillis - psiStartTime) >= warmInterval){ // allows concentrators to warm up prior to starting compressor, O2 purged through valve
 {digitalWrite (ValveRelay4 , LOW);}   //cuts power to solenoid after warmInterval time 
 {digitalWrite (CompRelay3 , HIGH);}         // if psi is less than start setpoint turn on compressor after warmInterval
 }

In this case the psi has fallen below the start threshold. What should happen is the unloader solenoid (ValveRelay4) activates, stays on for 15 seconds (warmInterval) and then turns off, and stays off.

What is actually happening is that the unloader solenoid is on, and turns off briefly every 15 seconds in a loop. I can see the error in my logic in the code but I'm unsure of the best way to get it to perform as I expect. I was thinking of using while conditions, but I don't have experience with them. If using a while loop do I need to have the pressure monitoring and LCD setup in each while condition?