Thursday, December 18, 2008

Open loop controller at home

In my house the heating system is made of electrical heaters that are mainly connected during the night (electricity is cheaper at night where I live). And during the day the heat accumulated in ceramic materials is slowly released.

To control when the heater should be connected I have a clock timers in the electrical plugs with the scheduled night hours.

This clock device is an open loop controller (a controler that makes decisions without information of the controlled variable). It is also a good example of the disadvantages of such systems. Since there is no feedback loop, the temperature will vary depending on the external conditions, since the heat input will remain constant. Sometimes it becomes too cold in the house and I need to connect it manually some more hours. When the winter is coming to an end temperature increases, and then I know it is time to reduce the programmed number of hours.

This system has some advantages but it's terrible if one wants to have good control of the temperature. And it would be expensive if I was to spend time analyzing the measured temperatures and manually trying to adjust the number of hours to adjust the system to the external conditions changes. It would be expensive because my time is limited.

Looking at what comes with the SAP standard, gATP PAL is an open loop controller (to be continued).

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