PID for greenhouse

I am a software engineer, and I was assigned a project for developing a PID control for a greenhouse.

I plan to use an Industrial PC and .NET. But I haven't got much experience in PIDs!!

I appreciate any guidance from people exposed to greenhouse control, and PC coding for PIDs!

Well, I've got both greenhouse and PID experience. And so do dozens of other people on this list. But my answer here is what you need instead of what you want.

PID control from a PC isn't really as much about the "code for the PID math" as it is about the interfacing hardware. Writing code to do the math for a PID algorithm "demonstrator" is pretty trivial (search Google), but if you really need to control heater fans and dampers from a PC you've got to interface with the real world hardware, which isn't necessarily so trivial. Especially if your background is .NET software and not industrial hardware.

Forget about the PID functions until you can accurately read the sensor for your measured variable, i.e. temperature, moisture, conductivity or humidity for a greenhouse most likely, and until you can adequately command the position of your end effector for the manipulated variable, most probably a valve position or pump motor speed. Without the measuring and manipulating parts your project is merely a show and tell exercise. Once you can accurately read the measured variable and control the manipulated variable, then worry about the control algorithm.

Michael

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Michael Batchelor

www.IndustrialInformatics.com