How to Troubleshoot PLC Hardware


The programmable logic controller, a lot more frequently identified as the PLC, plays a function in virtually every single automated manufacturing method. The PLC is an electronically programmable device capable of practically infinite combinations of relays, contacts, and timing circuits utilized to handle industrial machinery of all varieties and sizes. It is basically a laptop designed to withstand a harsh manufacturing atmosphere. It was developed to replace complicated system of relays, cam switches, and other electromechanical circuits. The first PLC’s have been introduced in the late 1970’s and they continued to develop in recognition because the day of their release.

PLC’s are produced nowadays by many major companies which includes Siemens, Allen Bradley, Koyo, Fuji, Telemecanique, and Mitsubishi as nicely as a host of other individuals. The programming of the PLC is performed by means of proprietary software program developed by the certain manufacturer. Software among PLC’s is not compatible and the logic programming, though it is extremely related, has a lot of subtle differences across the diverse brands. The program stored in the PLC is named the ladder logic program. Troubles in the ladder program can grow to be quite involved and that is an entirely distinct topic altogether. Hardware difficulties even so, are fairly comparable and can be effortless to diagnose if you know a little about the certain model and it’s input and output configuration.

Hardware failure of the brain, or major processor, is rare. It can be easily diagnosed visually most usually by an illuminated fault indicator on the face of the PLC. An internal energy supply failure would be a possibility if the PLC screen or energy indicator had been not lit and the technician verified that the right voltage is applied to the power terminals. Some PLC’s are equipped with an internal fuse which can also fail. These issues are not very as common as a failure of an input or output terminal.

Inputs and outputs are offered in several configurations and voltages. Each AC and DC are accessible separately and often in the same unit. These input/outputs can be each digital and analog and can be configured as a transistor output or as a dry relay contact. On each the input and output side it is critical to figure out the specifications of the PLC first. Obtaining the acceptable PLC application obtainable at the time of troubleshooting is also required.

The 1st recommendation would be to examine the illuminated inputs and outputs against the computer software in true time. An illuminated input not displaying properly as an energized input in the software is an indication of a failed or open input terminal. On the output side, an illuminated terminal not conducting the appropriate output voltage can mean one particular of two issues, the output has failed in an open position, or an improper voltage is getting applied to the widespread output terminal. The only way to confirm this would be by means of the use of a multimeter set on the correct voltage scale.

Overall, PLC hardware troubleshooting is not complex, but it needs to be approached in an orderly fashion due to the fact each hardware and software are necessary to work in harmony for a PLC to carry out its intended tasks.