Sunday, May 19, 2024

Building a PC Control System Using Wonderware InTouch SCADA and Allen Bradley PLC


Fig. 12: A typical address for AB PLC
Fig. 12: A typical address for AB PLC
Fig. 13: Setting RS232 channel configuration
Fig. 13: Setting RS232 channel configuration

MicroLogix 1400 PLC system. The 1766 MicroLogix 1400 PLC system (Fig. 3) is built upon critical MicroLogix 1100 features, including EtherNet/IP, online editing and a built-in LCD panel. These controllers feature a higher I/O count, faster high-speed counters, pulse train output, enhanced network capabilities and a backlight on the LCD panel. Controllers without embedded analogue I/O points provide 32 digital I/O points, while analogue versions offer 32 digital I/O points and six analogue I/O points. You can expand all versions with up to seven 1762 expansion I/O modules.

The Ethernet port provides Web server capability, email capability and protocol support for DNP3 protocol support. The built-in LCD with a backlight lets you view the controller and I/O status. It also provides a simple interface for messages, bit/integer monitoring and manipulation.

Application capabilities can be expanded through support for up to seven 1762 MicroLogix Expansion I/O modules with 256 discrete I/Os, up to six embedded 100kHz high-speed counters (only on controllers with DC inputs), two serial ports with DF1, DH-485, Modbus RTU, DNP3 and ASCII protocol support.

There are 10kB words in the user program memory with 10kB words in the user data memory, and up to 128kB for data logging and 64kB for recipe.

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PLC connections
One can buy a compact AB Allen Bradley MicroLogix 1400 PLC 1766, with eight DIO and two built-in serial ports (model 1766) for initial development. We used MicroLogix 1400 controllers, which are suitable for use in an industrial environment. Specifically, this equipment is intended for use in clean, dry environments.

Typical PLC connections for automation of an experimental facility are shown in Fig. 5. Allen Bradley Micro Logix 1400 has various digital input and digital output pins operated by +24V DC. An analogue input module is added separately. Another high-current 1000A power supply device is connected via RS232 protocol, where only three lines, namely, TX, RX and GND, are used for communication via a PLC serial port. Finally, AB PLC is connected to the PC via an Ethernet port.

RS232. RS232 is a serial protocol that converts parallel data to serial bits (pulses) and sends these across three wires, that is, TX, RX and GND. In most cases, the number of wires required is just three, but in special circumstances it may go up to nine wires, say, an RS232 modem.

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Allen Bradley 1400 series has two serial ports. The first one is through a PPI cable with a 9-pin D connector at the other end. This needs a NULL modem connector to connect to any PC having a serial port or USB serial adaptor. NULL modem connections are shown in Fig. 4.

Interfacing the PLC to a computer. MAX1400 has three ports. First is COM1 (round connector); second is COM2 (9-pin D connector), which is for RS485/RS232 communications; and the third is Ethernet for Ethernet/IP driver based communications. Therefore it is pretty easy for anyone to configure Ethernet as download port and COM1 as serial port for RS232 communications.

Allen Bradley PLC is connected to the computer via the Ethernet. We need to interface the programmable controller in order to configure and program (Fig. 6).

Adding drivers. Adding a driver is required for RSLOGIX classic software. To do so, you need to click on the middle icon and add RS232 DF1 driver to it.

Software for interfacing. RSLinx Classic is a software tool from Rockwell Automation Networks and Devices. It is a comprehensive factory communication solution, providing Allen Bradley PLC access to a wide variety of Rockwell Software and Allen Bradley applications, ranging from device programming and configuration applications such as RSLogix.

Fig. 14: Downloading the Ladder program to the PLC
Fig. 15: PLC in Run mode

BOOTP server is a suitable server to establish communication between PC and Rockwell PLC.


  1. Hi,
    This is very good forum for me to learn a lot about Automation and instrumentation. I just wanna ask that if u can provide PDF files of projects so we can learn from them and make similar projects in our student activities and professional life as well. Hope u will take it seriously.

  2. It woulde be easy & better to understand for all if a you post a step by step video showing a simple thing like on/off a motor by using GUI button of Wonderware through Allen Bradley PLC using KEPSersver.


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