PLC Ladder Logic Flashcards
What is a PLC?
Programmable Logic Controller, is a digital computer widely used to automate industrial processes
These controllers are often combined with other automation technologies, such as sensors, actuators, and human-machine interfaces (HMIs), to create fully automated systems.
How do we program a PLC?
PLCs are programmed using specialized software and a programming language designed specifically for this type of device
The programming language is typically
adder logic, a graphical programming language, or a text-based programming language.
What is PLC Ladder Logic?
two vertical rails and horizontal rungs in between. This programming language is graphical and visually represents the control process.
How Does Ladder Logic Work?
each rung represents a specific action or operation the PLC will perform. The rungs are arranged in a logical sequence, starting from the top and proceeding downward. Each rung contains instructions that guide the PLC’s actions. Unlike a ladder diagram, ladder logic is the actual programming.
linked by logic symbols known as
contacts and coils.
What are Contacts,
represent inputs or conditions that must be met for the instruction to execute
What are coils
represent outputs or actions that occur upon execution, are connected to create various logical operations like AND, OR, and NOT.
What are PLC Ladder Logic Inputs
signals that control the behavior of a PLC system.
inputs are classified into two main categories
digital and analog.
Digital inputs are binary signals that are either
on or off
used to detect the presence or absence of a signal and commonly sense the state of switches, sensors, and other digital devices
Digital inputs are depicted in ladder logic diagrams using
normally open (NO) or normally closed (NC) contacts.
What are Analog inputs
ontinuous signals with values within a specified range, used to measure and control parameters like temperature, pressure, flow rate, and voltage.
pecial inputs are represented in ladder logic diagrams using
dedicated function blocks.
What are PLC Ladder Logic Outputs
signals that control the behavior of devices connected to the PLC system.
Digital outputs are
binary signals, either “on” or “off,” used to control the state of switches, relays, and other digital devices, and are represented in ladder logic diagrams using output coils.
Analog outputs are
continuous signals that can range within specified values, used to control parameters such as temperature, pressure, flow rate, and voltage.
Analog outputs are illustrated in ladder logic diagrams using
function blocks like digital-to-analog converters (DACs) and proportional-integral-derivative (PID) controllers.
Special outputs are represented with
dedicated function blocks.
What is A PID process loop controller
generates an output to apply corrective effort to a process, driving a measurable process variable toward the desired set-point value. The controller employs an “actuator” to influence the process and a “sensor” to measure the results, providing the same functionality as an external PID controller
The scale factor maps the process value to the output value, with the span typically ranging from
0-100 percent
