PID control - air pressure - Devicenet -160Bulletin Analog drive

Daggi

Member
Join Date
Apr 2003
Posts
3
Here is my project (using DeviceNet):

I have a machine hall and a warehouse. I have to try to keep the air pressure differentials as follows:
- machine hall to warehouse: 0.15"WC
- warehouse to outside of building: 0.05" WC.

I am using two air pressure transmitters connected to a AB IE2C analog input module (4-20 mA). I can pick up these two inputs with my DeviceNet SDN scanner (Inputs I:2.0 for mc hall/ warehouse and I:2.1 for warehouse/outside)

I have 5 fans: 3 exhaust fans and 2 pressure fans.

The exhaust fans will come 'ON' when the pressure differential between machine hall and warehouse drops under 0.15 " WC.

The two pressure fans will have to come 'ON' when there is a need to pump air into the building because the differential between the outside of the building and the warehouse falls below the 0.5" WC.

Because this is all new to me, I am planning to start of simple and write my PLC program with the exhaust fans only. Furthermore, I will not attempt to control each of the exhaust fan drives (160 drives) individually, but I am planning to run them all at the same time.
Does this make sense at all or am I running off in the wrong direction?


I started writing the program for the scaling of the inputs, the PID instruction, and manual mode input of control variable, however, the PID instuction gives me only one control variable. How do I use this variable to control all three exhaust fans? Each drive needs a speed reference (O:2.2, O:2.4, O:2.6)

Any help is welcome. Maybe my approach to the problem is completely wrong, I don't know.

Daggi
 

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