Download PLC Programming: Architecture, Components, and Applications and more Exams Health sciences in PDF only on Docsity!
PLC COMPREHENSIVE FINAL LATEST PRACTICE EXAM UPDATED FOR
2025 PRACTICE WITH 100% CERTIFIED SOLUTIONS 2023- 2025
What are the major parts of a plc? The CPU, I/O, power supply, and programming device Architecture Refers to PLC hardware or software Open architecture Allows the system to be connected easily to devices and programs made by other manufacturers Closed architecture A system whose design is proprietary making it difficult to connect to other systems Fixed I/O Small PLC that comes in one package with not separate removable units. The processor and I/O are packaged together Modular I/O A PLC that is divided by compartments into which separate modules can be plugged Power supply Provides DC power to all modules that plug into the rack CPU or processor A microprocessor for implementing the logic and controlling the communications among the modules PLC scan cycle Reads inputs - > executes program - > diagnostics & communication - > updates outputs I/O (Input/Output) system Forms the interface by which field devices are connected to the controller. I/O (Input/Output) system Forms the interface by which field devices are connected to the controller
Programming device Used to enter the desired program into the memory of the processor Personal computer (PC) The most commonly used programming device Program A series of instructions that directs the PLC to execute actions Relay ladder logic The standard programming language, is based on electromagnetic relay control Address Where an input or output device is conncected PC vs PLC PLC is designed to operate in the industrial environment with wide ranges of ambient temperature and humidity Human machine interface (HMI) Software that allows the user to monitor and control the process Programmable Automation Controllers (PACs) Combine PLC ruggedness with PC functionality Nano Smallest size with less than 15 I/O Micro 15 - 128 I/O Medium 128 - 512 I/O Large Over 512 I/O Single ended application
hardware assembly that houses I/O modules, processor modules, and power supplies logical rack an addressable unit consisting of 128 input points and 128 output points remote rack A rack that is located away from the processor module address a label or number that indicates where a certain piece of information is located in a PLC's memory Rack/slot-based addressing schemes used with Allen-Bradley PLC-5 and SLC 500 controllers Tag- based addressing used with Allen-Bradley ControlLogix controllers Combination I/O modules can have both input and output connections in the same physical module points refers to the number of inputs or outputs available discrete I/O interface module connects field input devices of the ON/OFF nature discrete I/O module is powered by some field
supplied voltage source Backplane power Used to power the electronics that reside on the I/O module circuit board optical isolator used to provide electrical isolation between the power and logic circuitry Interposing relay used to control a larger load or motor starter Output modules can be purchased with Transistor,triac, or relay output If the module is a current-sourcing module then the input or output device must be a current-sinking device If the module is a current-sinking module, then the input or output device must be a current-sourcing device The two basic types of analog input modules are voltage sensing and current sensing Bipolar input modules Accept signals that swing between a negative and positive value Unipolar input modules Accept an input signal that varies in the positive direction only Resolution refers to
runs user written BASIC and C programs BCD-output module enables a PLC to operate devices that require BCD-coded signals such as seven-segment displays proportional-integral-derivative (PID) module used in process control applications that incorporate PID algorithms Motion and position control modules used in applications involving accurate high-speed machining and packaging operations Serial communications modules used to establish point-topoint connections with other intelligent devices for the exchange of data Nominal Input Voltage Specifies the magnitude (e.g., 5 V, 24 V, 230 V) and type (AC or DC) of user-supplied voltage that a module is designed to accept Input Threshold Voltages Specifies the minimum ON-state voltage at which logic 1 is recognized and the maximum OFF-state voltage at which logic 0 is recognized Nominal Current Per Input Specifies the minimum input current that the discrete input devices must be capable of driving to operate the input circuit Ambient Temperature Rating
Specifies what the maximum temperature of the air surrounding the I/O modules should be for best operating conditions Input ON/OFF Delay (response time) Specifies the maximum time duration required by an input module's circuitry to recognize that a field device has switched ON (input ON-delay) or switched OFF (input OFF-delay) Output Voltage This AC or DC value specifies the magnitude (e.g., 5 V, 115 V, 230 V) and type (AC or DC) of user-supplied voltage at which a discrete output module is designed to operate Output Current Specifies the maximum current that a single output and the module as a whole can safely carry under load (at rated voltage) Inrush Current Specifies the maximum inrush current and duration (e.g., 20 A for 0.1 s) for which an output circuit can exceed its maximum continuous current rating Short Circuit Protection Specifies whether the particular output module's design has individual protection for each circuit or if fuse protection is provided for groups (e.g., 4 or 8) of outputs Leakage Current This value specifies the amount of current still conducting through an output circuit even after the output has been turned off Electrical Isolation
The resolution specifies how accurately an analog value can be represented digitally. This will determine the smallest measurable unit of current or voltage change that can be detected Input Impedance and Capacitance For analog I/Os, these values must be matched to the external device connected to the module. Typical ratings are in the Megohm and Picofarad range Common-Mode Rejection Noise is generally caused by electromagnetic interference, radio frequency interference, and ground loops input status files or tables Sections of memory used to store the status of inputs output status files or tables Sections of memory used to store the status of outputs Nonvolatile memory memory that has the ability to retain stored information when power is removed accidentally or intentionally Volatile memory memory that will lose its stored information if all operating power is lost or removed Nonvolatile Read Only Memory (ROM) stores programs, and data that cannot be changed after the memory chip has been manufactured Random Access Memory (RAM) designed so that information can be written into or read from the memory Erasable Programmable Read-Only Memory (EPROM)
memory designed so that data stored in them can be read, but not easily altered without special equipment Electrically erasable programmable read-only memory (EEPROM) a nonvolatile memory that offers the same programming flexibility as does RAM programming terminal device needed to enter, modify, and troubleshoot the PLC program radix or base determines the total number of different symbols or digits used by that system Output status file made up of single bits grouped into 16 - bit words One 16-bit output file word reserved for each slot in the chassis "0" indicates that the number is positive "1" indicates negative method of expressing a negative number complement of a binary number 2's complement the binary number that results when 1 is added to the 1's complement.
based on the basic logic functions, which are programmable and easily changed Program files the areas of processor memory where ladder logic programming is stored Data file portion stores input and output status, processor status, the status of various bits, and numerical data The time it takes to complete a scan cycle is measure of how fast the controller can react to changes in inputs scan time is a function of
- The speed of the processor module
- The length of the ladder program
- The type of instructions executed
- The actual ladder true/false conditions PLC programming language refers to the method by which the user communicates information to the PLC Ladder diagram language the most commonly used PLC language and is designed to mimic hardwired relay logic Instruction list programming language consists of a series of instructions that refer to the basic AND, OR, and NOT logic gate functions Functional block diagram programming uses instructions that are programmed as blocks wired together to accomplish certain functions
Sequential function chart programming language similar to a flowchart of your process Structured text a high level language primarily used to implement more complex procedures Examine If Closed (XIC) instruction looks and operates like a normally open relay contact Examine If Open (XIO) operates like a normally closed relay contact main function of the ladder logic diagram control outputs based on input conditions contactor a special type of relay designed to handle heavy power loads that are beyond the capability of control relays selector switch operator rotated (instead of pushed) to open and close contacts of the attached contact block Dual in-line package (DIP) small switch assemblies designed for mounting on printed circuit board modules mechanically operated switch
places the transmitter and receiver in direct line with each other a retroreflective scan technique the transmitter and receiver are housed in the same enclosure Fiber optic sensors a flexible cable containing tiny fibers that channel light from emitter to receiver. completely immune to all forms of electrical interference ultrasonic sensor operates by sending high- frequency sound waves toward the target and measuring the time it takes for the pulses to bounce back strain gauge converts a mechanical strain into an electric signal Thermocouples operate on the principle that when two dissimilar metals are joined, a predictable DC voltage will be generated Flow measurement
involves converting the kinetic energy that the fluid has into some other measurable form Tachometer generators convert rotational speed into an analog voltage signal that can be used for control applications encoder used to convert linear or rotary motion into a binary digital signal optical encoder uses a light source shining on an optical disk with lines or slots that interrupt the beam of light to an optical sensor. An electronic circuit counts the interruptions of the beam and generates the encoder's digital output pulses actuator a device that converts an electrical signal into mechanical movement electromechanical solenoid is an actuator that uses electrical energy to magnetically cause mechanical control action Stepper motors rotate in discrete increments when electrical command pulses are applied to it in the proper sequence Servo motors operate in closed-loop mode stepper motors operate in open-loop mode
