PLC

Retained Memory:

-Where PLC keeps info it has read about processes-Data maintained throughout power disruptions

A typical scan operations for most plcs

read inputs, execute program, diagnostics communication, update outputs

3 positions for the CPU key

run, remote, program,

4 different plc I/O cards not used on our plcs

thumbwheel, PID, TTL, HIgh speed counter, stepper motor

Job example where a plc is fast enough to work correctly

traffic light

An internal program that detects unusually long scan times that may be an endless loop and sets an alarm condition is called a

watch dog timer

What is the most important automation language in industry? IEC 61131-3 How are Codesys projects arranged?

IEC 61131-3

ABB Inputs and Outputs

Inputs• Analog• Digital• Pulsed (Fast Digital)Outputs• Analog• Digital• Pulsed (Fast Digital)

Most modern PLCs will either be...

Integrated (unitary) or modular in style

SFC is not a language in and of itself. T/F?

True-It is a way to use multiple smaller programs-Utilizes other languages in a logical order-Accomplish a large and complex task

We must use complementary PLC cards and sensors (eg. sinking PLC card with sourcing sensor) T/F?

TrueBecause there must be potential difference between the PLC card and Sensor in order to initiate current flow, we must therefore use complementary types. One must be sourcing and the other sinking.

Why was the first PLC developed?

As a replacer for relays for GM and Landis

job example where a plc with standard inputs and outputs is not fast enough to work correctly

digital encoder

What does PLC stand for?

Programmable Logic Controller

Cpu used in this class's labs?

sic 505

Acceptable Zelio Inputs

-Analog (0-10V or 0-power supply)-Digital (Fully-On or Full-Off)-Pulsed (Fast digital at power supply)

Acceptable Zelio Outputs

-Analog (0-10V)-Digital (Fully-On or Full-Off at rated voltages of relays or solid-state)-Pulsed (Fast digital)

What does the housekeeping step include?

-Communications-Self-tests-Internal diagnostics

Memory types in a PLC

-Executive-User-Retained

Purpose of optical isolation on inputs

-Isolates field wiring from PLC-Protects CPU from surgesProper grounding must be observed

Purpose of optical isolation on outputs

-Isolates field wiring from the PLC-Protects CPU from backfeedingProper grounding must be observed

Programming languages defined in IEC 61131-3

-Ladder Diagram (LD) -Function Block Diagram (FBD) -Structured Text (ST) -Instruction List (IL) aka machine language-Sequential Function Chart (SFC)

Executive Memory:

-Manufacturers code, tells PLC how to operate-Cannot be changed

What was the first PLC and who invented it?

-Model 084-Invented by Dick Morley in 1969

What was the first commercial PLC?

-Model 184 (introduced in 1973)-Designed by Michael Greenberg

Digital Outputs on the Zelio (Relay contacts)

-Relay contacts are dry-You can choose to switch negative or positiveRelays 08, 09, 0A share the same common

What is a PLC?

-Solid state control system-Continuously monitors status of input devices-Changes status of output devices based on the program in the PLC

User Memory:

-Where the program is stored-Can be volatile or non-volatile

3 different plc I/O USED on our plcs

input,output,analog

4 main components of PLC hardware

power supply, cpu, I/O modules, and rack

Why use a PLC?

• Cost Savings• Time Savings• Pre-testing of systems• System Replication• Save cabinet Space• Expandability and adaptability• Check and Interface with equipment online

First Programmable Logic Controllers were designed and developed by...

Modicon

Typical rule of thumb scan time

10 ms

What is an important part of the electrical code to keep in mind?

28-506 Grounded control circuit (Pertinent to Motors)When power for a control circuit for a motor controller is obtained conductively from a grounded system, the control circuit shall be arranged so that an accidental ground in the wiring from the controller to any remote or signal device will nota) start the motor; orb) prevent the stopping of the motor by the normal operation of any control or safety device in the control circuit.

Integrated PLC

An integrated PLC will have both the Inputs and Outputs on the same CPU that reads and runs the program.

A couple important safety conditions to remember when working with PLC IO cards?

Caution when using a sourcing input cardCable ground faults can activate inputCaution when using a sinking output cardcable ground faults can activate loads

Sinking field device (sensor)

It ties its output to the negative power leadNPN sensors

Sourcing field device (sensor)

It ties its output to the positive power leadPNP sensors

4 benefits of PLCs over Relay Logic

More reliable, can communicate with other devices, faster, cheaper

Name of the communication package to allow our programming environment to communicate with our lab PLCs

RS binx

Name of the programming environment that is used to program our lab PLCs?

RS logix 500

4 steps in PLC operations

Steps are repeated, looped1. Input Scan2.Program Scan3.Output Scan4.Housekeeping

Modular PLC

The addition of different modules needed:-To be able to accept specific inputs-Control different types of outputs.

Sinking PLC card

The connection internally on the card is from the Negative DC input to the Input or output screw

Sourcing PLC card

The connection internally on the card is from the Positive DC input to the Input or Output screw