-
7/29/2019 16650900-PLC-Basics
1/47
Programmable Logic Controllers(PLC)
-
7/29/2019 16650900-PLC-Basics
2/47
PLC Presentation Contents
Introduction
What is a PLC
PLC Types
Choosing PLCHardware
PLC Applications
Programming PLCs Advantages of PLCs
Questions
-
7/29/2019 16650900-PLC-Basics
3/47
What is a PLC?
-
7/29/2019 16650900-PLC-Basics
4/47
Nema Definition circa 1978
. The PLC, also known as programmable controller
is defined by the National Electrical ManufacturersAssociation
(NEMA) in 1978 as:
"a digitally operating electronic apparatus whichuses a
programmable memory for the internalstorage ofinstructions for
implementing specificfunctions, such as logic, sequencing,
timing,
counting and arithmetic, to controlthrough digitalor analog
input/output, various types ofmachines or process".
-
7/29/2019 16650900-PLC-Basics
5/47
Traditional PLC Concept
PLC performs relay equivalent functions
PLC performs ON/OFF control
Ladder diagram programming Designed for industrial
environment
-
7/29/2019 16650900-PLC-Basics
6/47
|/|
CR3
CR3 M1
PB1 LS1 SOL2
PB2LS1
LS3
LS4
I/8
I/4 I/6 O/0
O/1
| | | | ( )
I/5I/7 B/0
| | | | ( )
| |
|/|
B/0
( )
Relay Logic vs. PLC & Ladder Logic
| |
I/9
ProgrammableLogic
Controller
Inputs Outputs
CR
-
7/29/2019 16650900-PLC-Basics
7/47
Terminal
Block
1
2
3
4
5
6
7
89
Input Devices
L1
L1
L2
10
COM
PL
C
Isolation
Barrier
Input Wiring: PLC input is the load in thecircuit, sensing if
voltage is present
-
7/29/2019 16650900-PLC-Basics
8/47
Input Devices
Pushbuttons
Selector Switches
Limit Switches
Level Switches
Photoelectric Sensors
Proximity Sensors
Motor Starter Contacts
Relay Contacts
Thumbwheel Switches
120/230 VAC
24 VDC
Sourcing
Sinking
-
7/29/2019 16650900-PLC-Basics
9/47
OUT 1
Output Devices
L2
L2
L1
OUT 1
OUT 2
OUT 2
OUT 3
OUT 3
OUT 4
OUT 4OUT 5
OUT 5
OUT 6
OUT 6
CR
L1PL
C
Terminal
Block
Isolation
Barrier
Output Wiring: PLC output is the switch,controlling current flow
to load
-
7/29/2019 16650900-PLC-Basics
10/47
Output Devices
Valves
Motor Starters
Solenoids
Control Relays
Alarms Lights
Fans
Horns
Relays
120 VAC/VDC 240 VAC
24 VAC/VDC
Triac
120/230 VAC
Transistor MOSFET
24 VDC
-
7/29/2019 16650900-PLC-Basics
11/47
Inside a PLC
CR
IsolationBarrier
Isolation
Barrier
MEMORY
program data
HighVoltage
HighVoltage
Low Voltage
AC Power Supply85-264 VAC,
50/60Hz
O
u
t
p
ut
C
i
r
c
u
it
s
ExternalDC Power Supplyor
Communications
I
n
p
u
t
C
i
r
c
u
it
s
CentralProcessor
-
7/29/2019 16650900-PLC-Basics
12/47
Input Scan
Program ScanOutput Scan
Housekeeping
START
Each ladder rung is scannedusing the data in the Input file.
The resulting status (Logicbeing solved) is written to theOutput
file (Output Image).
The status of external inputs(terminal block voltage) is
writtento the Input image (Input file).
The Output Image datais transferred to the
external outputcircuits, turning theoutput devices ON orOFF.
Internal checks onmemory, speed andoperation. Serviceany
communicationrequests, etc.
PLC Operating Cycle
-
7/29/2019 16650900-PLC-Basics
13/47
PLC Hardware Types
M t B i f PLC S t
-
7/29/2019 16650900-PLC-Basics
14/47
Most Basic of PLC Systems
In the most basic of PLC systems, a self contained
(shoe box) PLC has 2 terminal blocks, one forInputs and one for
Outputs
Today, most PLCs in this category are know as
Micros. Typically they provide front panel LED
status indication of I/O and Processor states
ProgrammableController
Inputs Outputs
CR
M d l Ch i B d PLC
-
7/29/2019 16650900-PLC-Basics
15/47
Modular Chassis Based PLCs
The vast majority of PLCs installed today are
modular chassis based systems consisting of:1. Processor Module
(CPU)
2. Input & Output Modules
3. Chassis4. Power Supply
M d l Ch i l PLC S t
-
7/29/2019 16650900-PLC-Basics
16/47
Modular Chassis-less PLC Systems
Also available from many vendors are Chassis less
but still Modular PLC systems. These systems stillrequire a
Processor, I/O Modules, and Power
Supply, but in place of a chassis these
components mount directly onto a panel, din rail,
and many use a tongue and grove system to alloweasy insertion
and removal
-
7/29/2019 16650900-PLC-Basics
17/47
Choosing PLC Hardware
PLC Application Considerations
-
7/29/2019 16650900-PLC-Basics
18/47
PLC Application Considerations
Inputs/Outputs
Type, AC, DC, sourcing,
sinking, etc.
Number of
10, 16, 20, 32, 156
Memory
Type
Flash or Battery backed
Size 1k, 6k, 12k, 16k, 64k
Functions required Instruction set
Messaging
PID
PTO, PWM
Arithmetic
Communications
DeviceNet, Ethernet
Remote I/O, DH+ Report generation
SOURCING vs SINKING
-
7/29/2019 16650900-PLC-Basics
19/47
SOURCING vs. SINKING
+VDC
SOURCING Pushbutton(PNP)
SINKING Pushbutton(NPN)
DC
Power
Supply
+
- DC COM
DC
Power
Supply
+
-
SOURCING vs SINKING DC Inputs
-
7/29/2019 16650900-PLC-Basics
20/47
SOURCING vs. SINKING DC Inputs
DC
Power
Supply
FieldDevice
DC
Input
Module
+
- DC COM
IN1
DC
Input
Module
FieldDevice
DC
Power
Supply
+
-
+VDC
IN1
SOURCING
(PNP)
SINKING
(NPN)
Rules
-
7/29/2019 16650900-PLC-Basics
21/47
Rules
Field devices on the positive side (+VDC) of the field
powersupply are sourcing field devices.
Field devices on the negative side (DC COM) of the fieldpower
supply are sinking field devices.
Sourcing field devices must be connected to sinking I/O cardsand
vice versa.
Sinking field devices must be connected to sourcing I/O cardsand
vice versa.
RULES
-
7/29/2019 16650900-PLC-Basics
22/47
PLC Applications
Installed and Running Systems in RI
-
7/29/2019 16650900-PLC-Basics
23/47
Installed and Running Systems in RI
- Conveyors
- Curtain rods
- Deodorants
- Donuts
- Duplex Receptacles
- Fibers
- Filters
- Forged Parts
- Glass
- Goggles
- Grinding and Polishing
- Heat Treating Metal Products- Jails
- Lenses
- Nails
- Natural Gas
- Paper
- Pharmaceuticals
- Plastics
- Plating
- Plating Machines
- Power Generation
- Power Supplies
- Product Assembly Machines
- Rubber products
- Seafood Processing
- Soda
- Staples
- Warehouse Automation- Waste Water Systems
- Drinking Water Systems
- Water Heaters
- Web Handling (paper/plastic)
- Wire / Cable
Typical PLC Application
-
7/29/2019 16650900-PLC-Basics
24/47
MotorSolenoid 1Solenoid 2
Solenoid 3
Sensor 1
Sensor 2
Ingredient A Ingredient B
Typical PLC Application
Operation of Mixer (Sequence of Control)
-
7/29/2019 16650900-PLC-Basics
25/47
MotorSolenoid 1Solenoid 2
Solenoid 3
Sensor 1
Sensor 2
IngredientA
IngredientB
Operation of Mixer (Sequence of Control)
Solenoid 1 On = Sol 3 is off, and Motor is
off, and Sensor 2 is off, andAuto Switch is on
Off = Sol 3 is on, or Motor ison, or Sensor 2 is on
Solenoid 2 On = Sol 3 is off, and Motor is
off, and Sensor 2 is on
Off = Sol 3 is on, or Motor ison, or Sensor 1 is on
Motor On = Sensor 1 is on, and
Solenoid 2 is off, and Solenoid1 is off
Off = Solenoid 3 on
Solenoid 3
On = Sol 1 is off, and Sol 2 isoff, and Motor has run for 30
sec.
Off = Solenoid 3 has been on
for 60 sec.
PLC Applications: Packaging
-
7/29/2019 16650900-PLC-Basics
26/47
PLC Applications: Packaging
De-Palletizing, Washing, Filler, Capper, Case
Packaging, Wrapping, Cartoning, Labeling, &Bagging
Machines
PLC Application: SCADA & RTU
-
7/29/2019 16650900-PLC-Basics
27/47
PLC Application: SCADA & RTU
Supervisory Control and Data Acquisition
(SCADA)/Remote Terminal Unit (RTU) puts the remote site report
data at your fingertips, but also provides
affordable remote communications and control, minimizing the
likelihood of remote site issues.
PLC Applications: Material Handling
-
7/29/2019 16650900-PLC-Basics
28/47
PLC Applications: Material Handling
Control of rollerbed conveyors or towveyors, and
mobile equipment including transfer vehicles,elevated transfer
vehicles, lifts and hoists, and
stacker cranes.
PLC Applications: Distribution
-
7/29/2019 16650900-PLC-Basics
29/47
PLC Applications: Distribution
Start and stop conveyors, control traffic at merge
points, redirect packages at divert points, andcontrol a wide
assortment of OEM machines such
as palletizers and accumulators.
-
7/29/2019 16650900-PLC-Basics
30/47
PLC Programming
Programming PLCs
-
7/29/2019 16650900-PLC-Basics
31/47
Programming PLC s
The purpose of a PLC Program is to control the state
of PLC outputs based on the current condition ofPLC Inputs
Different PLCs support different languages, but the
most popular PLC language is know as LadderLogic.
PLC Ladder Logic purposely resembles Relay Logic
Ladder Logic Concepts
-
7/29/2019 16650900-PLC-Basics
32/47
Ladder Logic Concepts
| | |/|
Read / ConditionalInstructions
Write / ControlInstructions
| | |/|
| | |/|
| |
| | |/| ( )
| |
( )
( )
( )
( )
| |
Start (Rung #1)
End (Rung #5)
Ladder Logic Concepts
-
7/29/2019 16650900-PLC-Basics
33/47
Ladder Logic Concepts
Read / ConditionalInstructions
Write / ControlInstructions
No Logical Continuity
|/| | |T F F
|/| |/|
( )
( )
T T T
Logical Continuity
Logical AND Construction
-
7/29/2019 16650900-PLC-Basics
34/47
Logical AND Construction
IF input 4AND input 5 have powerTHEN energize output 0
| |I/4
| |I/5
( )O/0
Logical Continuity
T T T
On
Logical OR Construction
-
7/29/2019 16650900-PLC-Basics
35/47
Logical OR Construction
IF input 4OR input 5 have powerTHEN energize output 0
| |I/4
| |I/5
( )O/0
Logical Continuity
F
T
On
| |I/4
| |I/5
( )O/0
Logical Continuity
T
F
On
Complex Construction
-
7/29/2019 16650900-PLC-Basics
36/47
Complex Construction
|/|I/11
| |I/5 |/|I/7|/|I/1
| |I/3
| |I/2
| |I/4
|/|I/0
| |I/1
| |I/1
|/|I/8
| |I/9
( )O/0
| |I/10
Read Instructions
-
7/29/2019 16650900-PLC-Basics
37/47
Read Instructions
Unused I / 2I / 1I / 0COM I / 3 I / 6I / 5COMI / 4 I / 7 I / 9I
/ 8
Supply
Voltage
Unused
LS 1
False
True
Examine OFF
-|/|-XIO
False
The instruction is:
The inputbit is
Logic 0
Logic 1True
Examine ON
-| |-XIC
If theinput
device is
Open (0)
Closed (1)
Write Instruction
-
7/29/2019 16650900-PLC-Basics
38/47
Write Instruction
RungState
OutputBit
OutputTerminal
De-energized
TRUE
FALSE
ON
OFF
OTEOutput Energize
-( )-
| | |/| ( )T T T
ENERGIZED
GNDL 1 O / 0VAC
VDC
L 2 / N VAC
VDC
VAC
VDC
O / 2VAC
VDC
O / 1 O / 3 O / 5O / 4VAC
VDC
SupplyVoltage
Putting it Together
-
7/29/2019 16650900-PLC-Basics
39/47
Putting it Together
| | ( )
I/8 O/0
GNDL 1 O / 0VAC
VDC
L 2 / N VAC
VDC
VAC
VDC
O / 2VAC
VDC
O / 1 O / 3 O / 5O / 4VAC
VDC
Supply
Voltage
Unused I / 2I / 1I / 0COM I / 3 I / 6I / 5COMI / 4 I / 7 I / 9I
/ 8
Supply
Voltage
Unused
PB1
Addressing Example
-
7/29/2019 16650900-PLC-Basics
40/47
Addressing Example
L1 L2
PB1 LS1 PS2 SOL6
DEVICE
PB1
LS1
PS2
SOL6
| | ( )| | | |I/5 I/6 O/0I/7
HHPI/5
I/6
I/7
O/0
LogixI:0/5
I:0/6
I:0/7
O:0/0
ADDRESS
Relay Logic to Ladder Logic
-
7/29/2019 16650900-PLC-Basics
41/47
INPUT Address Assignment:
PB1- I/4 PB2- I/5
LS1- I/6 LS2- I/7
LS3- I/8 LS4- I/9
OUTPUT Address Assignment:
SOL2- O/0 M1- O/1
|/|
CR3
CR3 M1
PB1 LS1 SOL2
PB2LS1
LS3
LS4
I/8
I/4 I/6 O/0
O/1
| | | | ( )
I/5I/7 B/0
| | | | ( )
| |
|/|B/0
( )
Relay Logic to Ladder Logic
| |I/9
Advanced Instructions
-
7/29/2019 16650900-PLC-Basics
42/47
Advanced Instructions
SEQUENCERS
SHIFT REGISTERS
DATA HANDLING
HIGH SPEED COUNTER
SUBROUTINES
-
7/29/2019 16650900-PLC-Basics
43/47
Advantages of a PLC
Basic PLC Advantages
-
7/29/2019 16650900-PLC-Basics
44/47
Basic PLC Advantages
Ease of programming
Ease of maintenance
Designed for industrial environment Quick installation
Adaptable to change
Source: A-Bs Micro Solutions Presentation
Advantages over Relays
-
7/29/2019 16650900-PLC-Basics
45/47
Advantages over Relays
All the capabilities of the earlier systems
Dramatic performance increase over the relaylogic systems
Greater reliability
Little maintenance due to no moving parts No special programming
skills required by
maintenance personnel
Physical size of the PLC system is much smaller
than the conventional relay based logic
And most importantly much lower cost
Source: [email protected]
Advantages over SBCs (single board
mailto:%[email protected]:%[email protected]
-
7/29/2019 16650900-PLC-Basics
46/47
Advantages over SBC s (single boardcomputers)
SBCs have high design costs Contract or Staff with overhead and
maintenance issues associated with each
SBCs are Repair / Service nightmare for customers Depending on
markets served supplier must develop/support services
SBCs requires high level of technical expertise bytechnicians
Specialized circuit boards require specialized equipment and
technical staff
SBCs not stocked through local distributors Suppliers sell the
controller imbedded, replacement parts are not readily
available
even in emergency situations
SBCs typically do not meet worldwide standards Certifications
cost money, typically a single controller does not warrant the
investment. Volumes are not high enough and re-certification on
each revision isunrealistic
SBCs typically a Domestic product Because of these issues many
manufacturers limit themselves to a single market.
Source: A-Bs Micro Solutions Presentation
Advantages over Computer based Software
-
7/29/2019 16650900-PLC-Basics
47/47
Advantages over Computer based Software
Maintenance personnel already experienced in PLCtroubleshooting
and servicing relay latter logic
programming, not PC software
Better power failure response
Cost advantages for simple machine control
Higher reliability that minimizes the expense of
shutdown,troubleshooting, repair, & startup
Industrially hardened packaging
Long availability and support for product models withoutthe
rapid obsolescence of PCs.
