temp regulating and timing module 16x2 lcd

iv been playing with a few ideas but cant quite get it all to work together.
module should have inputs from a lm 35 and a probe.

outputs should be LCD and ssr to switch an external supply.

here is what i am after.

lm35 measures temp
probe measures coolant level (input is pulled up when water is low and pulled down when water level is fine)

the lcd should display coolant temp, overtemp warning at a given temp and coolant low warning if coolant is low.
ssr should switch on at a set temp to turn on a cooling fan (i had this work linear to temp in a given range, but even on and off will work)

i get most of this working correctly but there are a few features i want to add and i want to be able to use a push-button to scroll through the other readings.

line 0 on the display should be reserved for temp reading and warnings only.

line 1 on the display i want to add the following and be able to scroll through them by push button.

total run time in hours (minute increments) ... this must be saved to rom somehow so that the run time is never lost.
run time since last reset in hours (minute increments) .. this must also be saved to rom so that it is not lost if there is power lost , but must be resistible somehow.
cycle time in minutes (second increments) should work something like a stop watch. push button to start and stop and saves last 10 cycle times to rom for review.

im not sure if all of this is going to require a real time clock though ??

You need a RTC for two purposes.

  • Logging. If you need to know exactly when something happened, other than merely in respect to the last time of reboot.

  • Accuracy. You need to know exactly how long something was in use.

If neither of these is critical, then using the resonator time is sufficient.

Your main concern is "data massage", figuring what the data needs to look like as you write it to the EEPROM.

im still a noob..... so alot of this is still very new to me.

The logging and display you describe doesn't need any form of RTC, just careful coding to manage how frequently you save your accumulators to EEPROM.

The temperature and level controls don't actually need a microcontroller at all as far as I can see, just a thermostatic switch for the fan and a level sensor for the warning lamp. All the microcontroller is needed for is the runtime logging. You could choose to use digital sensors and transistors and driver circuits and so on to control everything, and that would make it possible to display the temp and level status on your LCD module if you want, but do consider the simpler analog electrical solution before you add that complexity to your project.