Industrial control systems are always very complex and cumbersome to handle. For electronics engineers, it is becoming very essential to understand the computer control system using a programmable logic controller (PLC) and supervisory control and data acquisition (SCADA) system.

Here is a very efficient and expandable robust control system solution for industrial purposes. For the proposed system, we have used AB Allen Bradley MicroLogix 1400 PLC 1766, Wonderware InTouch 2012R2 SCADA system and KEPServer version 5 software for communicating between the PLC and SCADA. Wonderware InTouch SCADA is becoming increasingly popular due to its powerful user-friendly graphics as shown in Fig. 1.

Fig. 1: A typical Wonderware InTouch graphical user interface
Fig. 2: MicroLogix 1000 PLC (Model 1761-L10BWA features 120V/240V AC power, six 24V DC digital inputs and four relay outputs)
Fig. 2: MicroLogix 1000 PLC (Model 1761-L10BWA features 120V/240V AC power, six 24V DC digital inputs and four relay outputs)
Fig. 3: MicroLogix 1400 PLC (Model 1766-L32BWA features 12 digital fast 24V DC inputs, eight digital normal 24V DC inputs, 12 relay outputs, RS232 ports, 110V/240V AC power)
Fig. 3: MicroLogix 1400 PLC (Model 1766-L32BWA features 12 digital fast 24V DC inputs, eight digital normal 24V DC inputs, 12 relay outputs, RS232 ports, 110V/240V AC power)

The entire process can be summarised in the following steps:

Fig. 4: NULL modem connections
Fig. 4: NULL modem connections
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1. The RSLogix family of IEC-1131-compliant Ladder logic programming packages help you maximise performance, save project development time and improve productivity. This family of products has been developed to operate on Microsoft Windows operating systems. Supporting Allen Bradley SLC 500 and MicroLogix families of processors, RSLogix 500 was the first PLC programming software to offer unbeatable productivity with an industry-leading user interface. PLC is programmed using Ladder programming in RSLogix software. Different inputs and outputs have different addresses. Mostly the field devices, which are to be controlled, are connected to the PLC via digital input, analogue input, digital output and RS232, among others. The address of each device, module and register is specific to each PLC manufacturer, including Allen Bradley, Siemens, Schneider, Mitsubishi, Hitachi and Delta.

Fig. 5: Schematic diagram for PLC connections

2. The PLC is connected to the PC via the Ethernet. Since both PLC and SCADA are from different manufacturers, we used an intermediate OPC link (communicator) between these. This job is done by
KEPServer, which is installed on the PC.

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