After the first use of the heater in a real world environment, for a thirteen hour print at 12° C, something was clear. Just controlling the temperature of the PCB heaters is not enough. Two things became apparent. First one is that the PCB heaters will come up to temperature before the resin even has a chance to worm up. The second is that if we run the heaters up to 35° it will take for ever to heat the hole vat. 

We need to run the heaters at 60° in the beginning (this is the maximum that I have set for safety) to warm up the vat as quickly as possible. After set amount of time switch to mode to maintain the temperature. The question is what is this amount of time? 

Now can we just add a user defined timer to run the heater on max power before it goes to temperature keeping mode. The answer is yes, but is any fun - no.

We need to simulate the vat + resin combo how they heat up and how much heat they loose to the environment. How much heat can the heaters themselves produce. And the last major player is the interface between the heaters and vat. We do have a sensor for ambient temperature and with this info we can make a formula that will give us the amount of time we need to run the heaters at 60° to reach the user set temp. We have a few assumption, the vat is full and we have not run the heater before. 

I already modeled the heater using GNU Octave. I also made a test using a real heater and logged its temperature. 

Math works... who would know. I think this is quite nice. Now I need to model the rest and work out the formula.

Cheers,

M