PLC Logics and HMI Screens for Systems Automation Recipes: A pratical approach to systems and facilities automation using IEC 61131 - 3 Ladder Logic

This volume contains a complete and detailed collection of automation recipes for technological systems which is composed of 16 functional blocks, 8 subroutines and the associated graphic pages, expressly designed for monitoring and control, in a PLC-HMI-SCADA context.All the PLC logics and the HMI screens have been applied and extensively tested by the author in thirty years of experience on real automation systems. The PLC code uses the standard ladder 61131-3 language which was chosen to facilitate portability and universality of the code independently of the PLC manufacturer. Each control logic is associated with one or more HMI graphic pages that dynamically display values, texts and allow set-points and manual commands on the local operator panel.The book consists of four sections.The first section contains recipes specially designed for the equipment and sensors automation. It includes five functional blocks: ElectricMotor, very useful for managing commands, statuses, alarms, hours of operation and number of starts for an electric motor; Conv4_20mA a block to be used for the conversion from analog signal to engineering value when 4-20 mA transmitters are used; AnalogSts to be used for monitoring the HighOperating, LowOperating, HighAlarm, LowAlarm, HighReasonability statuses, the hysteresis and the alarm thresholds, depending on the set-point of analog quantities; Mot2Seq and Mot6Seq, twin and parallel sequencers for starting and stopping machinery (from 2 to 6 units).The section also contains three subroutines: VirtualDI, VirtualAI and VirtualDO for decoupling the input / output physical addresses from the internal registers distributed within all the application logic.The second section contains general purpose recipes. It includes three subroutines whose usage is always recommended to the developer: Init to set, at the first scan cycle, default values for the application set points, timers and counters; ScadaCmd to group together the remote command registers coming from the SCADA system; Alarms to set global alarm flags and to group alarm registers. The section also contains four function blocks: SecFlipFlop and Ctrl3P to generate pulse trains for three-point actuators, HighLimitTester to check compliance with the intervention thresholds, WatchDog to monitor the maximum time allowed for the execution of an action, Linear for a real-time linear interpolation within 8 predefined x-axis intervals. The third section exploits the capabilities of the PLC internal clock calendar: the subroutine RTC constructs convenient global flags and registers, for date and time management, to be consumed by other client routines. Six function blocks are also illustrated: TimeValidator verifies the correctness of the hours and minutes fields set by the user on HMI; Load1Enable and Load3Enable enable an output channel respectively on one or three daily bands; DayOfWeekEnabled supports the activation of a single load on the various days of the week, Zone function block aggregates Load1Enable and DayOfWeekEnabled to manage weekly irrigation tables and the last Room function block aggregates Load3Enable and DayOfWeekEnabled to manage building weekly occupancy tables for HVAC systems.Finally, the fourth section deals with issues related to user authentication and authorization. The access subroutine and the associated HMI screen manage the appropriate role and password fields. The navigation of the various pages of the operator panel can therefore be authorized or denied based on the authorized access role.A final chapter shows two examples of the usage of recipes within the main PLC program of a wastewater pumping station and a booster pump system.This book is addressed to a reader who, even if in possession of the basic knowledge on PLC programming, wants to develop, in a very short time, professional automation systems characterized by a great robustness and reliability of the source code.