Programmable logic controller, better known as PLC, plays a role in almost every automated manufacturing process. PLC programmable electronic device capable of almost infinite combinations of relays, contacts, and the timing circuits used to control industrial equipment of all types and sizes. Essentially, this is computer designed to withstand the harsh conditions of production. It was designed to replace a complex system of relays, cam switches, electromechanical and other schemes. The first PLC was introduced in the late 1970’s, and they continue to grow in popularity since their release.
PLC manufactured today many major manufacturers, including Siemens, Allen Bradley, Koyo, Fuji, Telemecanique, and Mitsubishi, as well as many others. PLC programming through its own software manufacturing a specific manufacturer. Software among the PLC are not compatible and logic programming, although it’s very similar, many subtle differences between different brands. The program is stored in the PLC ladder logic program is called. Problems in the ladder program can become very involved, and it is quite another matter altogether. Hardware Troubleshooting problems however, are quite similar and can be easily diagnosed, if you know a little about the specific model and its input and output configuration.
A hardware failure of the brain, or main processor, is rare. It can be easily diagnosed visually often illuminated malfunction indicator on the face of PLC. Internal power failure will have an opportunity, if PLC screen or the power were not addressed and techniques to verify that the correct voltage is supplied to the power terminals. Some PLCs have an internal fuse that can fail. These problems are not as common as a waiver of terminal input or output.
Inputs and outputs are available in several configurations and voltages. Both AC and DC supplied separately, and sometimes in the same units. These inputs / outputs can be both digital and analog, and can be configured as an output transistor or as a dry contact relay. On both sides of the entrance and exit is essential to determine specifications PLC in the first place. Having the proper software PLC, available at the time of troubleshooting is necessary.
The first recommendation would be to compare the coverage of entrances and exits to the software in real time. Illuminated entry appears incorrect, as under voltage input to the software instructions, or could not open input terminal. At the exit, lit terminal does not carry out proper output voltage can mean one of two things, the yield could not be in the open position, or improper voltage applied to the total output to the terminal. The only way to test it would be with a multimeter set to the proper voltage level.
In general, PLC diagnostic equipment is not complicated, but it must come in an orderly manner, because the hardware and software needed to work in harmony for the PLC to perform its intended tasks.
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