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D2-250 CPU maintains water pressure for city water system

by John Neiswanger,
Industrial Electronics
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We created a water pressure controller for a local city water system. We used a pressure transducer to feed a water pressure signal into the DL205 PLC system analog card. The output from an analog card is used to vary the speed of a 75 HP well pump, controlled by a variable frequency drive, to keep the city water system at a more constant pressure. Setpoints are entered with a touch panel and the pressure is displayed as well. The system controls the startup sequence, releasing the well flow to a drain and slowly cutting into the system to prevent a pressure spike on startup. It also controls the shutdown to prevent a pressure dip. System pressure is maintained with a PID loop in the D2-250 processor.
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