Transcript Example 12
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