Page 11 - AutomationNotebook-Issue46-digital

Tech Thread
Tech Thread
The PLC Scan
With PLC control, it’s important to understand the sequence of opera- tions for the CPU. Some may think when an output is set to ON in the ladder code, that this output change is immediately reflected in the out- put card. Or that when an input is activated, the CPU instantly sees it. While it may seem that way to the naked eye, that is not actually the case.
Tech Thread
Logic Circuits
For a better understanding of PLCs, let’s take a closer look at one of the fundamentals of automated control – logic circuits. Electrical components can be hardwired in a way to allow cer- tain decisions to be made electrically. They can provide physical “If, then” statements that systems can use in their decision making.
Sinking and Sourcing Circuits
Two of the most important fundamentals to understand when it comes to sensors is sinking and sourcing circuits. To properly wire your control device, you need to first know whether the sen- sor you are using is switching the positive or negative connection.
PLC Speaking
PLC Package Handling
PLCs play a major role when it comes to material or package han- dling operations. Conveyors, motors, drives, object detection sen- sors and of course controllers are used quite often when it comes to delivering your suitcase to the right airplane or getting the lap- top you ordered to the right delivery truck. But how would you go about coding the PLC for a package handling application?
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