‫بسم هللا الرحمن الرحيم‬
‫(وقل رب زدني علما )‬
‫( رب اشرح لي صدري ويسر لي امري‬
‫واحلل عقدة من لساني يفقهوا قولي )‬
The Islamic University Of Gaza
Faculty Of Engineering
Electrical Engineering Department
Advanced Technical English
Programmable Logic controllers (PLC)
BY : Marwan Hammouda
Sabri Mohammed Radi
To : Dr . Basil Hamad
120030606
120030171
Functions of Controllers :
 On-off control
 Sequential control
 Feedback control
 Mation control
Control Devices:
 Mechanical control
 Pneumatic control
 Electromechanical control
 Electronic control
 Computer control
Programmable Logic controllers
PLCs
 Were introduced in 1968
 Were primarily intended to replace relay
devices , so it is appropriate to be familiar
with the components used in relay devices
PLCs (continue)
 The National Electrical Manufacturing Associatioin
(NEMA) defines the PLC as
“A digitally operating electronic apparatus which uses a
programmable memory for the internal storage of
instructions by implementing specific functions such as
logic sequencing, timing, counting, and arithmetic to
control, through digital or analog input/output modules,
various types of machines or processes. The digital
computer which is used to perform the functions of a
programmable controller is considered to be within this
scope. Excluded are drum and other similar mechanical
sequencing controllers."
Why is the PLC ?
 Cost effective for controlling complex systems.
 Flexible and can be reapplied to control other
systems quickly and easily
 Computational abilities allow more sophisticated
control.


Trouble shooting aids make programming easier
and reduce downtime
Reliable components make these likely to
operate for years before failure
PLC Architecture
Program
Loader
PC
Switches
Printer
Processor
I/O
Modules
Memory
Power
Supply
Machines
Cassette
Loader
EPROM
Loader
Peripherals
External Devices


PLC Components :
Processor : The processor (CPU) scans the status of the
input peripheral , examines the control logic to see what
action to take , and then excute the appropriate output
response
Memory : the control program and the peripheral status
are stored in the memory
ROM( Read Only Memory )
RAM (Random Access Memory),
PROM (Programmable Read Only Memory),
EEPROM (Electric Erasable Programmable
ROM),
EPROM (Erasable Programmable Read
Only
Memory),
EAPROM (Electronically Alterable
Programmable
PLC Components (continue)
 Input/Output :
modular plug-in periphery
Ac voltage input and output
Dc voltage input and output
Low level analog input
High level analog input and output
Specail purpose modulas
 Powre supply : Ac power
 Peripherals : Hand-Held Programmer ( HHP)
CRT programmer
Operetor console
Printer
Simulator
EPROM loader
Graphics processor
A Hand Held Programmer
An Allen-Bradley hand-held programmer for MicroLogix 1000
PLC Programming
 Ladder Diagram - most common
 Structure Text Programming (ST)
 Functional Block Programming (FB)
 Instruction List (IL)
 Sequential Function Chart (SFC)
Ladder Diagram
A ladder diagram (also called contact symbology)
is a means of graphically representing the logic
required Rail
in a relay logic system.
start
PB1
emergency stop
PB2
R1
Rung
R1
R1
A
PLC Ladder Diagram
INSTRUCTIONS
1) Relay,
2) Timer and counter,
3) Program control,
4) Arithmetic,
5) Data manipulation,
6) Data transfer, and
7) Others, such as
sequencers.
 Hint : Relay , timer
and counter
instructions are the
most fundemental
because they
correspond to what
is on a ladder
diagram and are
avaliable on all
PLCs so we limit our
disscusion to them
Relay
A Relay consists of two parts, the coil and the contact(s).
Contacts:
a. Normally open
-| |-
b. Normally closed
-|/|-
c. Positive transition sensing -|P|-
contact
d. Negative transition sensing -|N|Coil:
a. Coil
-( )-
b. negative coil
c. Set Coil
d. Reset Coil
coil
-(/)-(S)-
input
-(R)-
Relay (continue)
Coil:
e. Retentive memory Coil
f. Set retentive memory Coil
g. Reset retentive memory Coil
h. Positive Transition-sensing Coil
h. Negative Transition-sensing Coil
-(M)-(SM)-(RM)-(P)-(N)-
(set coil latches the state, reset coil deenergize the set coil.
retentive coil retain the state after power failure.)
TIMERS AND COUNTERS
Timers:
a. Retentive on delay
(RTO)-
-
b. Retentive off delay
(RTF)-
-
c. Reset
Input
True
False
RTO counting stop
-(RST)RTF
stop
True
counting
resume
counting stop
Counter:
a. Counter up
-(CTU)-
b. Counter down
-(CTD)-
c. Counter reset
-(CTR)-
RTO reach PR value, output ON
RTF reach PR value, output OFF
PR value in 0.1 second
TIMERS AND
COUNTERS(continue)
Clock
input
Register
5
Accumulator
reset
Accumulator
reset
Register
contact
contact
Contact
output
output
COUNTER
TIMER
THANKS
ALL