CREATING LADDER DAIGRAM FOR PROCESS CONTROL

When a PLC is used primarily to replace relays, timers, and counters, it's hard to beat the simplicity and usefulness of ladder diagram programming.

Their ability to accept programming in ladder diagram format is one of the reasons for the success of programmable logic controllers (PLCs) in the industry. The many similarities between the ladder diagrams used to program PLCs and the relay ladder logic formerly used to control industrial systems eased the transition from hardwired relay systems to PLC-based systems for many people in the electrical industry. And, the ability to monitor PLC logic in ladder diagram format also made troubleshooting easier for those already familiar with relay-based control systems. Although there are many higher-level languages now available for PLC programming, the majority of systems are still programmed in ladder diagram format because of these advantages.



The logic in a ladder diagram typically flows from left to right. The diagram can be divided into sections called rungs, which are roughly analogous to the rungs on a ladder. Each rung typically consists of a combination of input instructions. These instructions lead to a single output instruction; however, rungs containing function block instructions may be more complicated.
When a PLC is used primarily to replace relays, timers, and counters, it's hard to beat the simplicity and usefulness of ladder diagram programming.

Their ability to accept programming in ladder diagram format is one of the reasons for the success of programmable logic controllers (PLCs) in the industry. The many similarities between the ladder diagrams used to program PLCs and the relay ladder logic formerly used to control industrial systems eased the transition from hardwired relay systems to PLC-based systems for many people in the electrical industry. And, the ability to monitor PLC logic in ladder diagram format also made troubleshooting easier for those already familiar with relay-based control systems. Although there are many higher-level languages now available for PLC programming, the majority of systems are still programmed in ladder diagram format because of these advantages.

The logic in a ladder diagram typically flows from left to right. The diagram can be divided into sections called rungs, which are roughly analogous to the rungs on a ladder. Each rung typically consists of a combination of input instructions. These instructions lead to a single output instruction; however, rungs containing function block instructions may be more complicated.