Run block of code periodically

Question

Hello,
I am writing a program which controls the temperature in a room. The user enters the "Start Temp", and "Goal Temp". First the program checks the "Cur Temp". THe program compares this temp with the "Start Temp"; if (Cur Temp < Start Temp) then I turn  on heaters. Once the StartTemp has been reached I am ready to move on to the next portion of my code which is cooling the room down at a user defined rate of cooling. I would like to compare the temperatures periodically. This is where I run into a problem. I have tried setting a delay before the cooling down portion of my code but it delays the hole while loop (all code in one while loop). I would like the temperature comparions to only occur every x amount of seconds (configurable by the user). So for arguments sake, I set the comparison rate at 10 seconds, every ten seconds I want to compare the previous value with the current value and determine the rate of at which it is cooling. If that rate is within in the desired rate of cooling then everything is ok. Ideally this code would not interfer with other program funcitons I have going on. Does anyone have any ideas on how I can have this code run perioically?
Thanks

Answer 1

There are plenty solutions possible, and they depend a little bit on what else the code does.
rchaoua wrote:
Once the StartTemp has been reached I am ready to move on to the next portion of my code which is cooling the room down at a user defined rate of cooling.
Well, the right thing is to do all in the same portion of code using a state machine architecture. There should only be one main loop with a case structure that depends on the state.
Here are some possibilities:
You can place your periodic code inside another case and only activate it whenever the loop counters is an integer multiple of some number or if a certain time has elapsed
for every 10th iteration, you would divide [i] by 10 using "quotient&remainder" and check if the remainder is zero.
Use the "elapsed time" express VI.
Do your own time tracking (e.g. using tick count and a shift register.
You can also place your slow periodic code in its seperate, parallel while loop.
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