Cooling and Heating



  • Hi All,

    I’m trying to put together some control logic to both cool and heat using a dead band. Currently I’m using a CMP block for cooling, this works really well. Now need to add heating to this. I was think about using two relay blocks but I’m sure there is a better way.

    Thoughts?

    Cheers

    Mike



  • Hi Mike,
    how about using the PWM block?

    If u=-1, then UP will be ON and you can use it for heating. If u=0 then both outputs are off. And if u=-1 then DN will be ON and you can use it for cooling.

    The PWM:offtime parameter defines the minimum delay between heating and cooling phases.

    Let me know.

    Kind regards
    Jaroslav



  • Hi Jaroslav,

    What would work but wouldn't I then have to use a PIDU block (or similar) for the main process control? I don't need the accuracy of a PID controller.

    This is my current cooling solution.

    0_1571428686770_70df882c-0931-4f10-bb0e-974a55c504f4-image.png

    I'm guessing keeping it simple now I require heating isn't so easy 🙂 Other people need use this after myself so I trying to not over complicate it. But if I need to then I will, no problem.

    Cheers

    Mike



  • Hi Mike,
    I see. In that case the simplest approach is to use the TSE block (three state element), which moreorless combines two comparators with hysteresis.
    0_1571645853248_rexygen_tse_cooling_heating.png

    Kind regards
    Jaroslav