The programmable logic controller, more commonly known as the PLC, plays a role in almost all automated manufacturing processes. The PLC is a programmable electronic device capable of almost infinite combinations of relays, contacts, calendar and circuits used to control industrial machinery of all types and sizes. This is essentially a computer designed to withstand harsh manufacturing environment. It was designed to replace complex system of relays, cam switches and other electromechanical circuits. The PLC first introduced in the 1970s and continued to grow in popularity since the day of his release.

PLC today are produced by many major manufacturers including Siemens, Allen Bradley, Koyo, Fuji, Telemecanique, and Mitsubishi, as well as a host of others. The PLC programming is done through proprietary software produced by the specific manufacturer. Software is not compatible between PLC and logic programming, although very similar, has many subtle differences between brands. The program stored in the PLC program is called the Ladder. Problems in the ladder program can be a bit complicated and it is a totally different subject altogether. Hardware problems however, are quite similar and can be easily diagnosed if you knows a little about the particular model and input and output configuration.

Hardware failure of the brain, or the main processor, is rare. It can be easily more often diagnosed visually by an error indicator light on the face of the PLC. An internal failure of power supply would be a possibility if the screen of a PLC or power indicator is not lit and the technician verify that the correct voltage is applied to the supply terminals. Some of PLC's are equipped with an internal fuse that can be unreliable. These problems are not as common as the failure of a terminal input or output. The modules I / S are more likely to fail due to load problems.

The inputs and outputs are available in multiple configurations and voltages. AC and DC are available separately and sometimes in the same unit. These inputs / outputs can be both digital and analog and can be configured as a transistor output or dry contact relay. In both entry and exit is essential to determine the specifications of the first PLC. Having the appropriate PLC software available at the time of troubleshooting is also required. The first recommendation would be to compare the entrances and exits, illuminated against the real-time software. An illuminated entry is not displayed correctly as an input energy in the software is an indication of an input terminal or not open. On the output side, a public enlightenment does not carry out proper output voltage can make a two things, the production has failed in an open position, or an improper voltage is applied to the common output terminal. The only way to verify this would be through the use of a multimeter set at the proper voltage level. In general, hardware troubleshooting PLC is not complex, however, needs be addressed in an orderly manner, because both hardware and software are required to work in harmony for a PLC to perform its intended tasks.

About the Author:

Chet is a longtime associate of Obsolete Industrial Parts, an informational site dedicated to locating obsolete industrial parts including plc hardware and io modules as well as other used obsolete parts. Their official website obsoleteindustrial.com is owned and operated by Val Marketing of Carbondale, PA.

Article Source: ArticlesBase.com – How to Troubleshoot PLC Hardware and PLC IO

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