Help requested with Mitsubishi FX2N PLC for PID control

[lw3eov]

Dear all,

I am a student trying to make a project to finish my studies as a Technician in Automation. I have a FX2N PLC which is a chinese semi-clon of a Mitsubishi. It only has digital inputs and outputs and addional module extensions cannot be added. I want to make a PID control to heat up liquid in a little container with a heating element. My idea is to use a external ADC circuit that sends bits in parallel to 4 inputs of my PLC. Those bits will be telling my PLC the temperature registered by my temperature sensor inside the liquid container. As my PLC has transistor outputs I want to use one of those to send PWM to my heating element in order to achive better results than using it as an on/off output.
The PLC's manual from Mitsubishi has over 700 pages but only a very few about PID and for my limited knowledge and understanding those are not really enough
I have a Mitsubishi PID specific manual but it is only for other series, not for the FX.
I will appreciate if you help me with the programming of this PLC to make my project as I cannot find anyone in this area who has any experience with Mitsubishi and the people with experience in Siemens are not willing to have a look at my project.

Many thanks
Best Regards

Marcelo