PLC Special Points

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5/23/2012 1Mohammed Ekram


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Less wiring.

Wiring between devices and relay contacts are done in thePLC program.

Easier and faster to make changes. Trouble shooting aids make programming easier and

reduce downtime. Reliable components make these likely to operate for years

before failure.

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1. SMALL - it covers units with up to 128 I/Os and

memories up to 2 Kbytes.- these PLCs are capable of providing

simple to advance levels or machinecontrols.

2. MEDIUM- have up to 2048 I/Os and memories upto 32 Kbytes.

3. LARGE - the most sophisticated units of the PLCfamily. They have up to 8192 I/Os andmemories up to 750 Kbytes.

- can control individual productionprocesses or entire plant.



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Solenoid


A

B

C

FS

MOTOR

TIMER


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DC INPUT MODULE

OPTO -ISOLATOR

IS NEEDED TO:Prevent voltage

transients fromdamaging theprocessor.Helps reduce the

effects ofelectrical noise

CurrentLimiting

Resistor

FROM

INPUTDEVICE

USE TODROP THEVOLTAGETO LOGIC

LEVEL

Buffer,Filter,

hysteresisCircuits

TOPROCESSOR


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AC INPUT MODULE

OPTO -ISOLATOR


transients fromdamaging theprocessor.

Helps reduce theeffects ofelectrical noise

Rectifier,ResistorNetwork

FROMINPUTDEVICE

CONVERTS THE ACINPUT TO DC ANDDROPS THEVOLTAGE TO LOGIC

LEVEL

Buffer,Filter,HysteresisCircuits

TOPROCESSOR


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DC / AC OUTPUT MODULE

OPTO -ISOLATOR


transients fromdamaging theprocessor.Helps reduce the

effects ofelectrical noise

FROMPROCESSOR

TTLCircuits

AmplifierRELAYTRIAC

XSISTOR

TO

OUTPUTDEVICE


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1. Pilot Duty Outputs

Outputs of this type typically are used to drive high-currentelectromagnetic loads such as solenoids, relays, valves, and motorstarters.These loads are highly inductive and exhibit a large inrush current.Pilot duty outputs should be capable of withstanding an inrushcurrent of 10 times the rated load for a short period of time withoutfailure.

2. General - Purpose OutputsThese are usually low- voltage and low-current and are used todrive indicating lights and other non-inductive loads. Noisesuppression may or may not be included on this types of modules.

3. Discrete InputsCircuits of this type are used to sense the status of limit switches,push buttons, and other discrete sensors. Noise suppression is ofgreat importance in preventing false indication of inputs turning onor off because of noise.


4 A l I/O


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4. Analog I/OCircuits of this type sense or drive analog signals.Analog inputs come from devices, such as thermocouples,strain gages, or pressure sensors, that provide a signal

voltage or current that is derived from the process variable.Standard Analog Input signals: 4-20mA; 0-10VAnalog outputs can be used to drive devices such asvoltmeters, X-Y recorders, servomotor drives, and valvesthrough the use of transducers.

Standard Analog Output signals: 4-20mA; 0-5V; 0-10V

5. Special - Purpose I/OCircuits of this type are used to interface PLCs to very specifictypes of circuits such as servomotors, stepping motors PID(proportional plus integral plus derivative) loops, high-speedpulse counting, resolver and decoder inputs, multiplexeddisplays, and keyboards.This module allows for limited access to timer and counterpresets and other PLC variables without requiring a program

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Troubleshooting

1. Look at the process

2. PLC status lightsHALT - something has stopped the CPURUN - the PLC thinks it is OK (and probably is)ERROR - a physical problem has occurred with the PLC

3. Indicator lights on I/O cards and sensors4. Consult the manuals, or use software if available.5. Use programming terminal / laptop.



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1. Basic Instruction:XIO, XIC, OTE, OTL, OUT, OSR, TON, TOF, RTO,CTU, CTD, HSC, REST4,C5,B3 registers. Effect on Status file of these instructions. Statusfiles no change is possible neither add nor delete.

2. Comparison Instructions:EQU, NEQ, LES, LEQ, GRT, GEQ, MEQ, LIM

3. Math Instructions:

ADD, SCP(Scale with parameters), SCL(Scaledata), ABS(Absolute), CPT(Compute), XPY(X tothe power Y)

4. Data Handling Instructions: MOV, AND, OR etc..



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5. Program Flow Instructions: JMP, LBL etc...

6.Application specific Instructions:BSL, BSR, SQO (Sequencer Output) etc.

7.HSC Instructions8.Communication Instruction:

MSG.9. PID Instructions10.ASCII Instruction



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1. RS 232 communication interface

2. DF1 Full Duplex3. DF1 Half Duplex4. DH 485



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Thanks & Expecting new things to learn fromyou..


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PLC Special Points