From the course: Learning PLC Ladder Logic: 1 The Basics

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Field devices and program instructions

Field devices and program instructions - Ladder Logic Tutorial

From the course: Learning PLC Ladder Logic: 1 The Basics

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Field devices and program instructions

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- [Instructor] Let's take a look on how the field devices and the program instructions work together and how to differentiate between them. To differentiate input devices and input instructions, we refer to the physical devices as a field input devices or contacts and the input within the PLC program as input instructions. There are two common types of field devices relay that we usually deal with. A normally open and a normally closed relay. This can apply to any field device. This is how a normally open pushbutton looks like and this is how a normally closed pushbutton looks like. You can check this document for more details about the different symbols by simply going to page 38, you can find the different symbols for the contacts, switches, and relays. This is the example that we covered for the pushbutton. A normally open pushbutton contact and a normally closed pushbutton contacts. In the simulation software, you can change the type of the contact by right click on the device…

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