PLC / SCADA / HMI Controllers: Name : Muhammad Zunair Comsats University Date: 28-October-2018

PLC (Programmable Logic Controller):  It is used for the automation of various electro-mechanical processes in industries.  These controllers can automate a specific process, machine function, or even an entire production line.  These controllers are specially designed to survive in harsh situations and shielded from heat, cold, dust, and moisture etc.  PLC consists of a microprocessor which is programmed using the computer language.

How does a PLC work?  The PLC receives information from connected sensors or input devices, processes the data, and triggers outputs based on pre- programmed parameters.  Depending on the inputs and outputs, a PLC can monitor and record run-time data.  Such as machine productivity or operating temperature, automatically start and stop processes, generate alarms if a machine malfunctions, and more.  Programmable Logic Controllers are a flexible and robust control solution, adaptable to almost any application.

PLC Hardware:  The hardware components of a PLC system are CPU, Memory, Input/Output, Power supply unit, and programming device. Below is a diagram of the system overview of PLC.

Difference between PLC and HMI:  PLC (Programmable Logic Controller)  Most modern control systems employ a PLC (Programmable Logic Controller) as a means to control motors, pumps, valves and various other equipment used in a process.  HMI (Human Machine Interface)  Computer based HMI (Human Machine Interface) products provide the means by which process personnel interact with the PLC control system

HMI ( Human Machine Interface):  A Human-Machine Interface (HMI) is a user interface or dashboard that connects a person to a machine, system, or device.  While the term can technically be applied to any screen that allows a user to interact with a device.  HMI is most commonly used in the context of an industrial process.  It is sometimes referred to as Man-Machine Interface (MMI),  Operator Interface Terminal (OIT),  Local Operator Interface (LOI), or Operator Terminal (OT).  HMI and Graphical User Interface (GUI) are similar but not synonymous.

How HMI works:  HMIs communicate with Programmable Logic Controllers (PLCs) and input/output sensors to get and display information for users to view.  HMI screens can be used for a single function, like monitoring and tracking.  For performing more sophisticated operations, like switching machines off or increasing production speed, depending on how they are implemented.  HMIs are used to optimize an industrial process by digitizing and centralizing data for a viewer.  By leveraging HMI, operators can see important information displayed in graphs, charts, or digital dashboards, view and manage alarms.  It reduces many costly problems caused by lack of information or human error.

Difference Between HMI and SCADA?  Supervisory Control and Data Acquisition (SCADA) and HMI are closely related, and often referred to in the same context since they are both part of a larger industrial control system.  They each offer different functionality and opportunities.  While HMIs are focused on visually conveying information to help the user supervise an industrial process.  SCADA systems have a greater capacity for data collection and control- system operation.  Unlike SCADA systems, HMIs do not collect and record information or connect to databases. Rather, HMI provides an effective communication tool that functions as part of, or alongside, a SCADA system.

SCADA (Supervisory control and data acquisition) System:  Supervisory control and data acquisition (SCADA) is a system of software and hardware elements that allows industrial organizations to:  Control industrial processes locally or at remote locations  Monitor, gather, and process real-time data  Directly interact with devices such as sensors, valves, pumps, motors, and more through human-machine interface (HMI) software  Record events into a log file

Example:  For example, the SCADA system quickly notifies an operator that a batch of product is showing a high incidence of errors. The operator pauses the operation and views the SCADA system data via an HMI to determine the cause of the issue. The operator reviews the data and discovers that Machine 4 was malfunctioning. The SCADA system’s ability to notify the operator of an issue helps him to resolve it and prevent further loss of product.

Thank you