Programmable Logic Controllers

Question 1

Name some of the industries PLC’s can be found in:

Answer 1

Chemical and Petrochemical
Automobile manufacturing
Metal smelting and mining
Lumber, pulp and paper
Food and beverage production

Question 2

PLC’s are usually selected according to the number of ______ and _______ _______ they can service.

Answer 2

Input and Output points

Question 3

A control system of a PLC consists of:

Answer 3

Input devices - switches, thermostats
Controller - hard wired or software program
Output devices - relays, solenoids that control operating devices (pumps, fans, valves)

Question 4

State the four main advantages of PLCS

Answer 4

L.E.R.P.

Lower overall cost
Expandability
Reliability
Programmability

Question 5

Name the four main hardware components of a PLC:

Answer 5

Backplane
Power Supply
Processor (CPU)
Input/Output (I/O)

Question 6

Does a PLC have to be a chassis connected to the backplane?

Answer 6

No, the backplane can be disassembled and assembled with or without a chassis.

Question 7

A means is required for the CPU to communicate with other components and and to distribute power for internal operation. This is done through the _____________

Answer 7

Backplane

Question 8

A PLC that is a complete unit is often called a ____ ____

Answer 8

Shoe box PLC

Question 9

The 3 primary functions of a PLC processor are to:

Answer 9

Read and store the status of the input devices

Execute the user program by solving the program’s logic

Update the status of the output devices

Question 10

The processor of a PLC carries out its functions in a sequence called the ______________ _____

Answer 10

Processor Scan

Question 11

Whats does RAM, ROM and EEPROM stand for?

Answer 11

RAM
Random Access Memory

ROM
Read Only Memory

EEPROM
Electrically Erasable PROgrammable Memory

Question 12

Name an example of an EEPROM device

Answer 12

USB
Memory Cards

Question 13

Special I/O modules are used for a variety of control functions. Name an example:

Answer 13

Position Control
High Speed Counters
Temperature Controls
Proportional Integral Derivative Control (PID)
Fuzzy Logic Control
Identification Sensors (ID)
Analog I/O

Question 14

Describe a data highway.

Answer 14

A data highway is a local area network (LAN) cabling that connects a number of PLCS, or PLCs and PCs, allowing them to exchange programs and data.

Question 15

A Remote I/O is used to:

Answer 15

Reduce the amount of cabling between the PLC & I/O devices

Question 16

Discrete input and output circuits are electrically isolated from the actual circuitry that is internal to the processor module and backplane of the PLC. This is most often done by ____________ _______

Answer 16

Optoisolating devices - inputs/outputs from discrete device changed into lightbeam by the input/output modules.

Question 17

For output circuits that require large currents than can be handled by the solid state electronic switch, a relay coil is operated by the solid state switch instead. This relay is called an __________ _______

Answer 17

Interposing Relay

Question 18

You may be required to install analog cables for analog input and output devices. The most common type of cable is:

Answer 18

Shielded Twisted Pair (STP)
Conductor size may be as small as #22 AWG

Question 19

Name the five PLC programming languages,
And what two categories there are:

Answer 19

Graphics based -Ladder Diagrams (LD) , Function Block Diagrams (FBD) and Sequential Function (or flow) Chart (SFC)

Text based - Structured Text (ST) , Instruction Lists (IL)

Question 20

The most common PLC programming language is:

Answer 20

Ladder Diagram

Question 21

Function Block Diagrams are commonly used where in the world?

Answer 21

Europe

Question 22

Sequential Function/Flow Charts are used for large-process controls where complex functions take place. T or F?

Answer 22

True

Question 23

Hand-held PLC programmers at one time were commonly using what programs?

Answer 23

Text based programs

Question 24

What PLC language is similar to the computer programming language called Basic?

Answer 24

Structured Text (ST)

Question 25

Instruction List programs are similar to assembler language programs. T or F?

Answer 25

True

Question 26

Discrete means…

Answer 26

Electrically Isolated

(Inputs and Outputs)