I/O

Real inputs and outputs to the PLC

Forward/Reverse Motor Interlocking use the PLC

Figure 31 shows a hardwired forward/reverse circuit with push button and electrical interlockings. The simplified wiring diagram of this motor is shown in Figure 32. Figure 31: Hardwired forward/reverse motor circuit. This circuit must be implemented using the overload contacts in the PLC. They are used to monitor the existence of overload conditions. Auxiliary starter […]

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PLC wiring diagram of a three-phase motor

Simple Start/Stop Motor Circuit use the PLC

Figure 25 shows the wiring diagram of a three-phase motor and its three-wire control circuit. The starter push button is sealed by the auxiliary contacts. This circuit can be converted into a PLC program by first identifying which control devices will make up the PLC I/O systems. These are the items circled in Figure 26.

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Example PLC configuration

Control Programming and PLC Descriptions

Modernization is the process of moving a machine’s or process’s control over from traditional relay logic to a programmable controller. The control logic is housed in traditional hardwired relay panels. They can be difficult to maintain, including contact chatter and contact welding. The machine’s performance can be improved by switching to a PLC. It also

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I/O address assignment table for real inputs and outputs

Internal and Real I/O Assignment of PLCs

It is an important step in the implementation and programming organization stages. The I/O assignment tables documents and organizes all of the work done so far. It shows which PLC inputs are connected and which PLC outputs drive what output devices. Here is also where internals are assigned, including counters and timers. These are the

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