Plc Fundamental Theory
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COMPONENTS & THEIR SYMBOLS
The following are most commonly used components. Control transformers. Fuses/MCBs. Switches/Sensors. Relays/Contactors
Contnu…..
CONTROL TRANSFORMER Transformer is a component which converts electrical voltage/current from one circuit to the other circuits at the same frequency. If the person were to touch any part of metal bulb the shock could be lethal.However if the bulb is powered by 110VAC or less the resulting shock would likely be much less severe. In order to make large ,powerful machines effective and cost effective and reduce line Current, most are powered by high voltages (230 VAC,440VAC). This means line voltage must be reduce to 230VAC or less for the controls. This is done using a Control Transformer.
Contnu…..
TRANSFORMER CIRCUIT DIAGRAM
420VAC or 230VAC
Primery winding Secondary winding 230VAC
0VAC
24VAC
0VAC
The secondary windings are generally rated at 230VAC,110VAC,or 24VAC.
MCB MCB (Miniature Circuit Breaker) MCB is a device which cuts of the circuit if the current is more than predetermined value,flows in a circuit. Control circuits are always protected by MCB. This prevents damage to the control components in the event of short circuit in the control circuit. MCB must be rated at a current that is less than or equal to the rated Current of control circuit. MCB must be connected in series with the circuit.
USES OF SWITCHES Switches are used to send instruction/signals to the control logic. Switches are installed on the moving parts of a machine to provide automatic feedback to the control logic.
TYPES OF SWITCH & SENSOR Push buttons Selector switches Limit switches Pressure switches Float switches Liquid Level switches
TYPES OF SWITCH & SENSOR Proximity sensors Optical sensors Encoders Transducers Thermocouples (RTD) Resistance Temperature Device
TYPES OF PUSHBUTTON & LAMP Momentary Maintained Mushroom Head
Contacts and Coils Contacts have two states ,ON and OFF.In PLCs two type of contacts. Normally open (NO) This type of contact does not allow current to flow through it when it is switched OFF. When the contact is switched ON,the circuit is completed and current flows through the circuit.
Normally close (NC) This type of contact allows current to flow through it when it is switched OFF. When the contact is switched ON,the circuit is broken and stops the current flow in the circuit.
Coils Coils are output devices that are controlled By PLC as per the input conditions of ladder logic is True or ON value.The coil is set to the ON status and device performs its function.
FUNCTION OF SWITCHES The contacts (Rear blocks ) on push button can be of two types. Normally Open (N/O) Normally Close (N/C) Description
Symbol
Comment
Push Button (N/O)
It is Normally Open (N/O). When external force is applied it becomes closed. It is used to switch ON equipments.
Push Button (N/C)
It is Normally Close (N/C). When external force is applied it becomes open. It is used to switch OFF equipments.
FUNCTION OF SWITCHES Description
Symbol
Selector Switch
EXAMPLE: Selection of Manual Mode. Selection of Auto Mode.
Comment It is normally open condition, it selects the mode of operation of work.
FUNCTION OF SWITCHES Limit Switch: Limit switches are not operator accessible,instead they are Activated by moving part on the machine. They are usually mechanical switches.
Example: Mechanically operated limit switch is the switch on the refrigerator Doors that turns on inside the light.
Description Limit Switch
Symbol
Comment It is normally open condition when any object is in contact of its CAM then it becomes closed. Its application is to limit the continuous signal by sensing it.
FUNCTION OF SWITCHES Description Pressure Switch
Float Switch
Symbol
Comment It is normally open condition it works on the pressure level, it becomes on when pressure level reaches up to preset value. It is normally closed condition it consists a long lever arm with a float attached. As the liquid level rises,the lever arm presses on the switch’s actuator knob.
FUNCTION OF SENSORS Type of Proximity Sensors. Inductive proximity sensor. Capacitive proximity sensor. Inductive proximity sensor It operates on the principle that the inductance of a coil and the power losses in the coil vary as a metallic (or inductive) object is passed near by it. Because of this operating principle ,inductive proximity sensors are only used for sensing metal objects. They will not work with non-metallic materials.
FUNCTION OF SENSORS Inductive proximity sensors are available in both AC and DC powered types. Most sensors available built in LED that indicates when the sensor output is on while the object is sensed.
Capacitive proximity sensor The principle of operation of the sensor is that internal oscillator will not oscillate until a target material is moved near to the sensor face. This will work with Non-metallic objects.
SENSORS Description
Symbol
Proximity Sensor
Comment
Output
+VE
Optical Sensor
It is normally open Condition, when any metallic object is sensed from specified distance then it becomes on.
-VE
Output +VE -VE
It is normally open Condition, It is capable of sensing any type of material whether it is metallic, Conductive or porous. It operates over longer distances.
SENSORS Description
Symbol
Comment
Output
Read Switch +VE
-VE
Read switch and proximity switch are similar in function but it is mounted on the pneumatic cylinders only.
CONTACTORS/RELAYS A relay or Contactor is an electromagnetic device assembled of a frame, electromagnetic coil and contacts (Movable and Fixed). The movable contacts are mounted via an insulator to a plunger that moves with in a bobbin. A coil of copper wire is wound on the bobbin to create an electromagnet. A spring holds the plunger up and always from the electromagnet. When the electromagnet is energized by passing an electric current through coil,the magnetic field pulls the plunger into the core,which pulls the movable contacts downwards. Two fixed pairs of contacts are mounted to the relay frame on electrical insulator so that when movable contacts are not being pulled towards the core (The coil is de-energized) they physically touch the upper fixed pair of contacts And,when being pulled towards the coil,touch the lower pair of fixed contacts.
CONTACTORS&RELAYS Description
Symbol
Comment
Contactor
It is a device to make and break the circuit. It is mainly used to control the motors and heaters etc. on/off
Relay
It is a device to make and break the circuit. It is mainly used to control the solenoid coils, magnetic clutches etc.. on/off
CONTACTORS/RELAYS Following figure shows the three most common Contactor or Relay symbols. These are used in electrical control logic diagrams.
Normally open contact (N/O) %QX0.3
R1
Normally close contact (N/C) R1
Coil
R1
Normally open and normally closed contacts of above figures have lines extending from both sides of the symbols.These are the connecting lines which,on a real relay would be the connection points for wires
OVER LOAD RELAY Over load relay is component used to break the circuit and over loaded caution automatically if there is short circuit or power over loaded in the power circuit. Over load relay will have NO/NC contacts to inter lock the control circuit. Mainly it is mounted under the Power contactor (L1,L2,L3 terminals) of 3-Phase induction motors. Restarting of OLR is very easy ,just pressing the RESET knob.
INDICATING LAMPS LAMPS The lamps are used to indicate present operation status of the machine or fault conditions. The indicators are generally white,they generally covered with colored lenses.
INDICATING LAMPS The colors are usually RED,GREEN or AMBER etc. RED LAMP This is used for Power is ON,the machine is running. the machine door is open or other important faults. GREEN LAMP This is used for safety conditions (power to the motion controllers OFF status etc). AMBER LAMP This indicates that are important but not dangerous. Fluid getting low,Machine paused,etc.
INDICATING LAMPS Description Indicating Lamp
Symbol
Comment All control panels provided indicator lamps. It is provided at important diagnostic points to monitor. Know the present operating status of the machine.
FUNDAMENTALS OF BASIC DIAGRAMS All electrical control circuit diagrams are designed using a standard format call the Relay Logic Circuit (RLC). Ladder diagram begin with control transformer and protective MCB on the left side. As mentioned earlier,From transformer and MCB combination, horizontal lines are extended to both sides and then drawn vertically down the page as shown in Figure in next slide.
BASIC CONTROL CIRCUIT
420VAC
R
Y
Primery Secondary 1
230VAC
0VAC
MCB 230VAC
2
0
These vertical lines are called power lines. The voltage deference between the two vertical lines is equal to the control transformer secondary voltage.
WIRING AND NUMBERING Total wires in a control circuit are numbered. In our circuit,the left line number is 2 and right line number is 0. When the circuit is designed,the actual wires used to connect the components will have a ferrule(Number) on each end called a wire numbering. Numbering makes easier to design,troubleshoot and modify the circuitry. By using wire ferrule numbers,all the wires in the control panel will be identified and unnecessary to use more than one color wire to wire the circuit (except for ground wire).
SWITCH GEAR NOMENCLATURE PREFIX Some of the most commonly used reference nomenclature prefixes are listed below. T/F ------------ Transformer MCB ----------- Miniature Circuit Breaker CR ------------ Control Relay PB ------------ Push Button LS ------------ Limit Switch PX ------------ Proximity Switch OS ------------ Optical Sensor SS ------------Selector Switch OLR ------------ Over Load Relay FWD ------------ Forward REV ------------ Reverse L1 ------------ Lamp1 Etc….. The number of the nomenclature is assigned by designer beginning with the number 1.
CIRCUIT REFERENCE NOMENCLATURE All electrical circuits and every switch gear is given a reference nomenclature. This is a label assigned to the switch gear so that it can be easily located. The reference nomenclature for each switch gear appears on the schematic diagram. The reference nomenclature consists of an alphabetical prefix followed by a number. The prefix identifies that the kind of switch gear it is (Viz Control transformer,Relay,Pushbutton…etc).
CONVENTIONAL RLC CIRCUIT 2
From Control Transformer (230V AC) 3 PB1
0
4 PB2
CR1
Wire ferrule number
CR1
Label 5
6
7
8 FWD
PB3
CR1
Label 9 PB4
LS1 10
CR1
REV 11
LS2
12 FWD
REV
RELAY LOGIC Since the relays in a machine perform some type of control operation,it can be set that they perform a logic function. As with all logic functions, these control circuits must consist of the fundamental AND,OR,and compliment logic operations. N/O,N/C contacts and relay coils can be wired to perform these Same fundamental logical functions. By properly wiring relay contacts and coils together ,we can develop any logic function as required.
AND Lamp Circuit This slide shows the actual wiring connection for two switches a lamp and voltage source.
PUSHBUTTON-1
PUSHBUTTON-2
LAMP-1
230V AC
The LAMP1, will glow only when PUSHBUTTON-1,PUSHBUTTON-2 are pressed while the voltage sours is there.
AND Lamp Ladder diagram To represent the previous diagram in ladder logic form an electrical Machine diagram,we will utilize the power from the vertical lines and simply add the two Pushbuttons and Lamp in series between the two vertical power lines as shown in next slide. The switches are on the left and lamp is on the right. This is a standard convention when designing and drawing machine circuits.The controlling devices are always positioned on the left side of the power line,and the controlled devices are always positioned on the right side of the power line
AND Lamp Ladder diagram 420VAC
R
Y
Primery Secondary 1 MCB 230VAC
2
4
3 PB-1
0
PB-2
L-1
OR Lamp Circuit This circuit shown in below figure illustrates two pushbuttons wired as an OR logic controlling a lamp. The lamp will glow if either PUSHBUTTON-1OR PUSHBUTTON-2 is pressed,That is depressing either of switches will cause LAMP-2 to glow while the voltage sours is there.
PUSHBUTTON-1 LAMP-2
PUSHBUTTON-2
230V AC
LADDER DIAGRAM WITH “AND,OR” LOGIC The next slide shows the combined ladder diagram (AND,OR logic). Note that since the pushbuttons PB-1 and PB-2 same ones used in the top line ,they will have the same names and the same reference nomenclature when drawn in bottom. When two or more components in parallel,each parallel path is called branch. In our diagram AND,OR logic has two branches,it is possible to exchange branches 1and 2 without changing the way the lamps operate. The branches can be arranged in any order without changing the way the machine operates. It allows the designer to group and organize the control circuitry so that it is easier to understand and troubleshoot.
420VAC
R
Y
Primery Secondary 1 AND Lamp Ladder diagram
MCB 230VAC
2
4
3 PB-1
0
PB-2 L-1
5 PB-1 L-2 PB-2
AND-OR Lamp Circuit
PB-1
PB-2 L-3
PB-3
PB-4
230V AC LAMP- 3 will glow if PB-1 and PB-2 are both ON, or PB-3 and PB-4 are both ON. This circuit is called AND-OR logic.
OR-AND Lamp Circuit
PB-1
PB-3 L-4
PB-2
PB-4
230V AC
This circuit is called OR- AND logic.
OR-AND Circuit combination chart LAMP- 4 will glow when the following combination of pushbuttons are ON. LAMP- 4 ON PB-1 AND PB-3 are ON PB-1 AND PB-4 are ON PB-2 AND PB-3 are ON PB-2 AND PB-4 are ON LAMP- 4 ON PB-1 OR PB-2 AND PB-3 are ON PB-1 OR PB-2 AND PB-4 are ON PB-2 OR PB-1 AND PB-3 are ON PB-2 OR PB-1 AND PB-4 are ON
LADDER DIAGRAM WITH COMBINATION BRANCHES 230VAC 2
0 4
3 PB-1
PB-2 L-1 5
PB-3 L-2
PB-4 7
6 PB-5
PB-6
L-3
8 PB-7
PB-8 10
9 PB-9
PB-10
L-3 L-3
PB-11
PB-12
INCH Circuit 2
0
3
INCH
CR1
SELF LATCH Circuit 2
3
START
4
CR1
0
STOP
CR-1
When power is applied to the vertical lines,CR1 is de-energized and the N/O of CR1 contact in parallel with START pushbutton is also open. CR1 is energized when START pushbutton is pressed and CR1 remain ON,if release START PB because power will flow through CR1 (NO) contact. CR1 is de-energized when STOP PB is pressed. Since we are assuming START PB not been pressed,there is no path for power flow through the branch and it will be OFF.
INVENTION OF PLC The first PLC systems evolved from conventional computers in the early 1970 s. These first PLCs were installed in automotive plants. Traditionally automotive plants had to be shut down for a month to change the model . The PLC keyboard reprogramming procedure replaced rewiring of panel full of wires, relays, counters and other components. The new PLCs helped to reduce the changeover time to a matter of few days.
PLC DEFINITION The Programmable Logic Controller is a solid state equipment, designed to perform the function of logic made for industrial control applications.
INTRODUCTION OF PLC The PLC acts as a total replacement for hardwired relay logic with an effective reduction in wiring and panels. With the coming of microprocessor and associated peripheral chips the whole process of control & automation went for a radical change. Instead of achieving the desired control or automation through physical wiring of control components, in PLC it is achieved through a program or say software. As the desired logic control is achieved through a program, these controllers are referred to a Programmable Logic Controllers (PLC).
BLOCK DIAGRAM OF PLC PB1 I PB2
LS1 R1
N P U T
POWER SUPPLY
CPU USER PROGRAM MEMORY SERIAL PORT
Computer
PROGRAMMING DEVICE
O U T P U T
FWD CONT
REV CONT
LAMP
CONNECTING CODEYSYS TO THE NEXGEN 2000 PLC Computer
CABLE CODE:PRG CAB 2910
DETAILS OF PLC BLOCK DIAGRAM INPUT MODULE The input module acts as an interface between the field components (viz pushbuttons, selector switches, limit switches, proximity switches, pressure switches etc) and CPU.
POWER SUPPLY UNIT The power supply module delivers the power required for the electronic components in the modules of the PLC.
CPU It is a Central Processing Unit which masterminds the operation of PLC.
DETAILS OF PLC BLOCK DIAGRAM OUTPUT MODULE The Output Module receives commands from CPU inorder to control various field elements like power contactors, solenoid coils, indicating lamps etc.
SERIAL PORT It is a hardware device used to transfer a program from PC to PLC and PLC to PC.
PROGRAMMING DEVICE Used for storing, editing, inserting, deleting of the logic diagram and transferring the same to PLC and PC devices like PC or Hand-Held programmer and also used to monitor the status of inputs, outputs and flags in online mode.
PLC CONFIGURATION EXAMPLE Slot
Slot
2113
2211 2616
P S U
C P U
Slot-0 Slot-1
Slot-2 Slot-3
2716
2616
2716
16
16
16
16
I N P U T
O U T P U T
I N P U T
O U T P U T
M O D U L E
M O D U L E
M O D U L E
M O D U L E
PLC CONFIGURATION EXAMPLE Slot
Slot
Slot-0
Slot-1
Slot-2 Slot-3 Slot-4 Slot-5 Slot-6
Slot-7
2113
2211
2616
2414
2416
SPARE
P S U
C P U
16
8
I N P U T M O D U L E
2716
2708
2708
2712
8
16D
8D
8D
12R
I N P U T +
I N P U T +
O U T P U T
O U T P U T
O U T P U T
O U T P U T
6R
8D
O U T P U T
O U T P U T
M O D U L E
M O D U L E
M O D U L E
M O D U L E
M O D U L E
M O D U L E
S P A R E S L O T
16 Pt 24 VDC Input Module Sr.No SPECIFICATIONS
Details
1
No of inputs
16
2
Voltage rating
24 VDC (18 to 30 VDC)
3
Indication for inputs
Provided on CPU module via Multiplexed dot matrix display
4
ON voltage
18 VDC Minimum
5
OFF voltage
5 VDC Maximum
6
Current per input channel 7mA (Maximum) @24 VDC
7
Ordering code
2616
Contnu…..
16 Pt 24 VDC Output Module Sr.No SPECIFICATIONS
Details
1
No of outputs
16
2
Voltage rating
24 VDC (18 to 30 VDC external supply)
3
Current rating
250 mA per output
4
Indication for inputs
Provided on CPU module via Multiplexed dot matrix LED display
5
ON voltage
22 VDC Minimum
6
OFF voltage
1.5 VDC Maximum
7
Response time
OFF to ON---- 0.1ms ON to OFF---- 0.4ms
8
Inrush Current
600mA for 700 micro second Contnu…..
16 Pt 24 VDC Output Module Sr.No SPECIFICATIONS
Details
9
Protections
Reverse voltage Over voltage Output short circuit protection
10
Ordering code
2716
DETAILS OF ADDRESSING Following slides explain the input/output/Memory addressing.
BASICS IN DIGITAL ELECTRONICS Numbering Systems Bit, Nibble, Byte, Word Bit: Bit means binary digit. It is smallest piece of digital information. It can be either 0 (OFF) or 1(ON). Nibble: Four bits grouped together form nibble. Byte: Eight bits or two nibbles grouped together form one byte. Word: It is the maximum number of bits that are processed or handled at a time. Sixteen bits or four nibbles or two byes grouped together form one word.
B15 B14 B13 B12 B11 B10 B9 B8
1
0
1
0
1
0
1
1
B7
B6
B5
0
0
1
B4 B3 B2 B1 B0
0
1
0
1
0 Bit
Byte Word
Nibble
NUMBERING SYSTEM Binary Hexadecimal Binary Coded Decimal (BCD) Binary Numbering System: The binary numbering systems uses a number set that consist of two digits VIZ., numbers 0 AND 1. Each digit in a binary number has a weightage expressed as a power of “2”. The decimal equivalent of binary number is computed by multiplying each binary digit by its corresponding weightage and adding these number together. 2 2 2 2 2 Binary Number: 4 3 2 1 0
1 1 0 1 0
Decimal equivalent = =
0
1
2
3
4
2X0 + 2X1 + 2X0 + 2X1 + 2X1 0+ 2 +0 + 8 + 16 = 26
NUMBERING SYSTEM Hexadecimal Numbering System: The hexadecimal numbering system has a number set of 16 digit VIZ.The number 0-9 and the letter of A to F (Decimal number 10-15 respectively). Each digit in a hexadecimal has a weightage expressed as a’16’. A hexadecimal number can be converted to a decimal number by multiplying the hexadecimal digit by its corresponding weightage,expressed as power of ’16’ and the adding these numbers together.
Binary Number:
4 16
16
3
16
2
1 16
16
0
1 0 1 0 1
Decimal equivalent = = 2X0 + 2X1 + 2X0 + 2X1 + 2X1 0+ 2
+0
+8
+ 16 = 26
ADDRESSING CODE Hexadecimal Decimal Octal (Base 16) (Base 10) (Base 8) 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F
00 01 02 03 04 05 06 07 08 09 10
000 001 002 003 004 005 006 007
Binary (Base 2) 00
INPUTS ADDRESSING RANGE WORD %IW0
%IW2
%IW4
%IW6
BYTE
BITS
%IB0
%IX0.0
%IX0.1
%IX0.2
%IX0.3
%IX0.4
%IX0.5
%IX0.6
%IX0.7
%IB1
%IX1.0
%IX1.1
%IX1.2
%IX1.3
%X1.4
%IX1.5
%IX1.6
%IX1.7
%IB2
%IX2.0
%IX2.1
%IX2.2
%IX2.3
%IX2.4
%IX2.5
%IX2.6
%IX2.7
%IB3
%IX3.0
%IX3.1
%IX3.2
%IX3.3
%IX3.4
%IX3.5
%IX3.6
%IX3.7
%IB4
%IX4.0
%IX4.1
%IX4.2
%IX4.3
%IX4.4
%IX4.5
%IX4.6
%IX4.7
%IB5
%IX5.0
%IX5.1
%IX5.2
%IX5.3
%IX5.4
%IX5.5
%IX5.6
%IX5.7
%IB6
%IX6.0
%IX6.1
%IX6.2
%IX6.3
%IX6.4
%IX6.5
%IX6.6
%IX6.7
%IB7
%IX7.0
%IX7.1
%IX7.2
%IX7.3
%IX7.4
%IX7.5
%IX7.6
%IX7.7
INPUTS ADDRESSING RANGE WORD BYTE %QW0
%QW2
%QW4
%QW6
BITS
%QB0
%QX0.0
%QX0.1
%QX0.2
%QX0.3
%QX0.4
%QX0.5
%QX0.6
%QX0.7
%QB1
%QX1.0
%QX1.1
%QX1.2
%QX1.3
%QX1.4
%QX1.5
%QX1.6
%QX1.7
%QB2
%QX2.0
%QX2.1
%QX2.2
%QX2.3
%QX2.4
%QX2.5
%QX2.6
%QX2.7
%QB3
%QX3.0
%QX3.1
%QX3.2
%QX3.3
%QX3.4
%QX3.5
%QX3.6
%QX3.7
%QB4
%QX4.0
%QX4.1
%QX4.2
%QX4.3
%QX4.4
%QX4.5
%QX4.6
%QX4.7
%QB5
%QX5.0
%QX5.1
%QX5.2
%QX5.3
%QX5.4
%QX5.5
%QX5.6
%QX5.7
%QB6
%QX6.0
%QX6.1
%QX6.2
%QX6.3
%QX6.4
%QX6.5
%QX6.6
%QX6.7
%QB7
%QX7.0
%QX7.1
%QX7.2
%QX7.3
%QX7.4
%QX7.5
%QX7.6
%QX7.7
DEFINITION OF FLAG/MEMORY BIT Storage of intermediate results of one Rung, ( as internal relay in PLC software) In Relay logic it is defined as Auxiliary contactor %IX0.0 Motor on PB input
%IX0.1
Motor off PB input
%IX0.2
Safety inter lock
%MX0.0
Motor on flag
%MX0.0 Motor on flag %MX0.0
Motor on flag
%QX0.6
Motor on output
MEMORY ADDRESSING RANGE WORD BYTE %MW0 %MW2 %MW4 %MW6 %MW8 %MW10 %MW12
%MW14
BITS
%MB0
%MX0.0
%MX0.1
%MX0.2
%MX0.3
%MX0.4
%MX0.5
%MX0.6
%MX0.7
%MB1
%MX1.0
%MX1.1
%MX1.2
%MX1.3
%MX1.4
%MX1.5
%MX1.6
%MX1.7
%MB2
%MX2.0
%MX2.1
%MX2.2
%MX2.3
%MX2.4
%MX2.5
%MX2.6
%MX2.7
%MB3
%MX3.0
%MX3.1
%MX3.2
%MX3.3
%MX3.4
%MX3.5
%MX3.6
%MX3.7
%MB4
%MX4.0
%MX4.1
%MX4.2
%MX4.3
%MX4.4
%MX4.5
%MX4.6
%MX4.7
%MB5
%MX5.0
%MX5.1
%MX5.2
%MX5.3
%MX5.4
%MX5.5
%MX5.6
%MX5.7
%MB6
%MX6.0
%MX6.1
%MX6.2
%MX6.3
%MX6.4
%MX6.5
%MX6.6
%MX6.7
%MB7
%MX7.0
%MX7.1
%MX7.2
%MX7.3
%MX7.4
%MX7.5
%MX6.6
%MX7.7
%MB8
%MX8.0
%MX8.1
%MX8.2
%MX8.3
%MX8.4
%MX8.5
%MX8.6
%MX8.7
%MB9
%MX9.0
%MX9.1
%MX9.2
%MX9.3
%MX9.4
%MX9.5
%MX9.6
%MX9.7
%MB10
%MX10.0
%MX10.1
%MX10.2
%MX10.3
%MX10.4
%MX10.5
%MX10.6
%MX10.7
%MB11
%MX11.0
%MX11.1
%MX11.2
%MX11.3
%MX11.4
%MX11.5
%MX11.6
%MX11.7
%MB12
%MX12.0
%MX12.1
%MX12.2
%MX12.3
%MX12.4
%MX12.5
%MX12.6
%MX12.7
%MB13
%MX13.0
%MX13.1
%MX13.2
%MX13.3
%MX13.4
%MX13.5
%MX13.6
%MX13.7
%MB14
%MX14.0
%MX14.1
%MX14.2
%MX14.3
%MX14.4
%MX14.5
%MX14.6
%MX14.7
%MB15
%MX15.0
%MX15.1
%MX15.2
%MX15.3
%MX15.4
%MX15.5
%MX15.6
%MX15.7
MEMORY ADDRESSING RANGE WORD BYTE %MW16 %MW18 %MW20 %MW22 %MW24 %MW26 %MW28
BITS
%MB16
%MX16.0
%MX16.1
%MX16.2
%MX16.3
%MX16.4
%MX16.5
%MX16.6
%MX16.7
%MB17
%MX17.0
%MX17.1
%MX17.2
%MX17.3
%MX17.4
%MX17.5
%MX17.6
%MX17.7
%MB18
%MX18.0
%MX18.1
%MX18.2
%MX18.3
%MX18.4
%MX18.5
%MX18.6
%MX18.7
%MB19
%MX19.0
%MX19.1
%MX19.2
%MX19.3
%MX19.4
%MX19.5
%MX19.6
%MX19.7
%MB20
%MX20.0
%MX20.1
%MX20.2
%MX20.3
%MX20.4
%MX20.5
%MX20.6
%MX20.7
%MB21
%MX21.0
%MX21.1
%MX21.2
%MX21.3
%MX21.4
%MX21.5
%MX21.6
%MX21.7
%MB22
%MX22.0
%MX22.1
%MX22.2
%MX22.3
%MX22.4
%MX22.5
%MX22.6
%MX22.7
%MB23
%MX23.0
%MX23.1
%MX23.2
%MX23.3
%MX23.4
%MX23.5
%MX23.6
%MX23.7
%MB24
%MX24.0
%MX24.1
%MX24.2
%MX24.3
%MX24.4
%MX24.5
%MX24.6
%MX24.7
%MB25
%MX25.0
%MX25.1
%MX25.2
%MX25.3
%MX25.4
%MX25.5
%MX25.6
%MX25.7
%MB26
%MX26.0
%MX26.1
%MX26.2
%MX26.3
%MX26.4
%MX26.5
%MX26.6
%MX26.7
%MB27
%MX27.0
%MX27.1
%MX27.2
%MX27.3
%MX27.4
%MX27.5
%MX26.6
%MX27.7
%MB28
%MX28.0
%MX28.1
%MX28.2
%MX28.3
%MX28.4
%MX28.5
%MX28.6
%MX28.7
%MB29
%MX29.0
%MX29.1
%MX29.2
%MX29.3
%MX29.4
%MX29.5
%MX29.6
%MX29.7
RANGE OF WORDS
RANGE OF BYTES
%MW0 TO %MW 7678
%MB0 TO %MB7679
PLC CONFIGURATION EXAMPLE Slot
Module
Slot
PSU
Nil
Nil
Slot
CPU
Nil
Nil
I/o Slot-0 16 Pt DC Input
Input addressing
%IB0 & %IB1
I/o Slot-1 12Pt Relay Output
NIL
I/o Slot-2 16 Pt DC Input
%IB2 & %IB3
I/o Slot-3 8Pt DC input+6Pt Relay Output
%IB4
I/o Slot-4 8Pt Relay Output
Nil %QB0 & %QB1 Nil %QB2
NIL
I/o Slot-5 16 Pt DC Input
%IB5 & %IB6
I/o Slot-6 8Pt DC input+6Pt Relay Output
%IB7
I/o Slot-7 12Pt Relay Output
Output addressing
%QB3 Nil %QB4
NIL
%QB5 & %QB6
Types of PLC Basically PLCs are two types. Brick type. Modular type.
BRICK TYPE PLC is housed in a single box with all power supply,CPU,Inputs and out puts & connection terminals. These are generally chosen according to a available program memory and required number of I/Os to suit he application. This type of PLC generally has an expansion port. This type of PLC will have limited I/Os. These ports allow the addition of Digital Inputs/outputs or analog Inputs/ Outputs. These expansion units are either plugged directly or connected it with ribbon cable.
PLC Configurations MODULAR TYPE More sophisticated units,with a wider range of options,are MODULAR. Modular type PLC can be connected consist following Modules. CPU (Central Processor Unit). I/O Rack. Power supply Module (PSU). Digital Input Module. Digital Output Module. Analog I/O Modules High speed counter Module. Other type of modules may be available depending up on the manufacture of the PLC. Function of communication modules is transfer the data from one device to another. One module allows the serial transfer of data to remote I/O modules which is some feets away.
Modular Type PLC with 8 I/O Rack Figure RACK Slot
Slot
P O W E R Supply
C P U
I/O Slot-0
I/O Slot-1
I/O Slot-2
I/O Slot-3
I/O Slot-4
I/O Slot-5
I/O Slot-6
I/O Slot-7
Expansion Port
The RACK is a framework into which the Input/outputs modules are inserted. The size of the Rack depends on the number of slots ,such as 3, 5,8. (Source: MESSUNG)
Fundamentals of PLC Programming Symbols used in ladder logic. Rungs. Contacts and Coils.
Symbols Used in Ladder Logic A PLC takes input from field devices and based on the programming instructions controls output devices. Ladder logic diagrams are used in PLCs to write programming instructions below figure illustrates a simple ladder diagram.
Input
Rung
Output
As shown in above figure,a ladder logic diagram consists of three elements. Input Output Rung A ladder logic diagram consists of one or more horizontal lines,called RUNGS. The rungs contain the input and output elements.In a ladder logic diagram,the input elements referred as the contact and output element s referred as Coil.
Rungs The horizontal lines in a ladder logic diagram are called RUNGS. Each Rung of a ladder logic diagram represents a condition of the input/output/ memory bits. Each Rung ends with a coil and starts with a set of conditions. The two vertical lines at the two end of the rungs are called rails and are represented as L1 and L2. These rails represents the voltage potential of the ladder diagram. The below figure illustrates the rails and the rung of ladder logic diagram. L2 L1
Rung
Ladder Logic Specifications Input Conditions Arrange Inputs Ladder Logic Diagram All conditions should be met
Series
Any condition should be met
Parallel
A
B
C
D
M
M A B C
A combination of conditions
In combination
A B C
D
M
FUNDAMENTAL PLC PROGRAMMING Relay type instructions.
Function Block instructions. How to convert a simple relay logic diagram into PLC Ladder Program.
RELAY TYPE INSRTUCTIONS Symbol Instruction Comment
NO
This is a single Normally Opened contact. Its results is True if the input bit is 1 and the false if the input bit is 0.
NC
This is a single Normally Closed contact. Its results is True if the input bit is 0 and the false if the input bit is 1.
COIL
This represents the coil of output, memory bit etc. It becomes ON if the result of ladder programmed prior to it is 1 (true).
RELAY TYPE INSRTUCTIONS Symbol Instruction Comment
S
R
SET
This represents the latch type coil of the output, memory bit etc. It is SET to 1(true).
RESET
This represents the latch type coil of the output, memory bit etc. It RESETS the latched coil if the result of the ladder programmed prior to it is 1 (true).
FUNCTION BLOCK INSTRUCTION TIMERS COUNTERS TYPE OF TIMERS On delay timer Off delay timer
TYPE OF COUNTERS Up counter Down counter Up/Down counter
DETAILS OF FUNCTION BLOCKS ON DELAY TIMER T1 %IX0.1
T# 10M
DONE
TON IN
Q
PT
ET
T1_ET
PT- Preset time ET- Elapsed time When IN input becomes high , the elapsed time value increments on every rising edge. The DONE bit becomes on when elapsed time becomes equal to preset time. When IN input becomes low the elapsed time become 0. Cont….
DETAILS OF FUNCTION BLOCKS OFF DELAY TIMER T3 TOF
%MX10.0
T# 10S
DONE
IN
Q
PT
ET
T3_ET
PT- Preset time ET- Elapsed time When IN input becomes high , timer DONE bit also becomes high immediately. When IN input becomes low and the elapsed time value will get incremented by every rising edge of time base. When elapsed time becomes equal to preset time DONE bit goes low and elapsed time becomes 0.
Cont….
DETAILS OF FUNCTION BLOCKS BLINK/CYCLIC B10 %IX0.1
%QX0.6
BLINK ENABLE
T#5S
LOW TIME
T#3S
HIGH TIME
OUT
LOW TIME- Output OFF duration HIGH TIME- Output ON duration When the ENABLE input becomes high , BLINK begins to set OUTPUT for the time period TIMEHIGH to ON and then afterwards TIMELOW to OFF Cont….
DETAILS OF FUNCTION BLOCKS UP COUNTER C1 %MX0.1
DONE
CTU UP
%IX0.6 20
Q
RESET PV
CV
%MW00
PV- Preset value CV- Current value When the REST input becomes high , the current value of counter becomes zero. This is resetting of counter. When reset input is OFF the current value of the counter increments by one on every transition from OFF to ON at the UP input. The DONE bit goes high when the current value becomes equal to preset Cont…. value.
DETAILS OF FUNCTION BLOCKS DOWN COUNTER C10 %MX0.1
DONE
CTD DN
%IX0.6 20
Q
LOAD PV
CV
%MW100
PV- Preset value CV- Current value DN- Down When the LOAD input becomes high , the current value of counter becomes equal to preset value. This is presetting of counter. When LOAD input is OFF the current value of the counter decrements by one on every transition from OFF to ON at the DOWN input. The DONE bit goes high when the current value Cont…. becomes equal to zero.
PLC INPUTS AND OUTPUTS WIRING OF ‘AND’ LOGIC INPUT MODULE
OUTPUT MODULE
I0
I0
PB1 PUSH BUTTON-1
Q0
I1
I1
PB2 PUSH BUTTON-2
Q1
I2
L1
LAMP-1
Q2
Wire ferrule number
I3
Q3
G1
N1
Q0
Q4
Label
I4
Q5
I5
Q6
I6
Q7
I7
V1
G2
G1
I10
Q10
I11
Q11
I12
Q12
I13
Q13
G3
Q14
I14
Q15
I15
Q16
I16
Q17
I17
V2
G4
G2
24VDC
P1
P1
N1
24VDC
N1
CONVERSION OF RELAY LOGIC CIRCUIT TO PLC LADDER AND Relay Logic Diagram
PB-1
PB-2
L-1
230V AC
AND PLC Logic RUNG %IX0.0
%IX0.1
PB-1
PB-2
%QX0.0
L-1
PLC INPUTS AND OUTPUTS WIRING OF ‘OR’ LOGIC INPUT MODULE
OUTPUT MODULE
I0
I0
PB1 PUSH BUTTON-1
Q0
I1
I1
PB2 PUSH BUTTON-2
Q1
I2
L2
LAMP-2
Q2
Wire ferrule number
I3
Q3
G1
N1
Q0
Q4
Label
I4
Q5
I5
Q6
I6
Q7
I7
V1
G2
G1
I10
Q10
I11
Q11
I12
Q12
I13
Q13
G3
Q14
I14
Q15
I15
Q16
I16
Q17
I17
V2
G4
G2
24VDC
P1
P1
N1
24VDC
N1
CONVERSION OF RELAY LOGIC CIRCUIT TO PLC LADDER OR Relay Logic Diagram
PB-1
L-2
PB-2
230V AC OR PLC Logic RUNG %IX0.0 PB-1 %IX0.1 PB-2
%QX0.0
L-2
PLC INPUTS AND OUTPUTS WIRING OF ‘AND-OR’ LOGIC INPUT MODULE
OUTPUT MODULE
I0
I0
PB1 PUSH BUTTON-1
Q0
I1
I1
PB2 PUSH BUTTON-2
Q1
I2
I2
PB3 PUSH BUTTON-3
Q2
I3
I3
PB4 PUSH BUTTON-4
Q3
G1
L3
LAMP-3
Q4
Wire ferrule number
I4
Q5
I5
N1
Q0
Q6
Label
I6
Q7
I7
V1
G2
G1
I10
Q10
I11
Q11
I12
Q12
I13
Q13
G3
Q14
I14
Q15
I15
Q16
I16
Q17
I17
V2
G4
G2
24VDC
P1
P1
N1
24VDC
N1
CONVERSION OF RELAY LOGIC CIRCUIT TO PLC LADDER AND-OR Relay Logic Diagram PB-1
PB-2
PB-3
PB-4
L-3
230V AC %IX0.0
%IX0.1
PB-1
PB-2
%IX0.2
%IX0.3
PB-3
PB-4
AND-OR PLC Logic RUNG %QX0.0
L-3
PLC INPUTS AND OUTPUTS WIRING OF ‘OR-AND’ LOGIC INPUT MODULE
OUTPUT MODULE
I0
I0
PB1 PUSH BUTTON-1
Q0
I1
I1
PB2 PUSH BUTTON-2
Q1
I2
I2
PB3 PUSH BUTTON-3
Q2
I3
I3
PB4 PUSH BUTTON-4
Q3
G1
L4
LAMP-4
Q4
Wire ferrule number
I4
Q5
I5
N1
Q0
Q6
Label
I6
Q7
I7
V1
G2
G1
I10
Q10
I11
Q11
I12
Q12
I13
Q13
G3
Q14
I14
Q15
I15
Q16
I16
Q17
I17
V2
G4
G2
24VDC
P1
P1
N1
24VDC
N1
CONVERSION OF RELAY LOGIC CIRCUIT TO PLC LADDER OR-AND Relay Logic Diagram PB-1
PB-3 L-4
PB-2
PB-4
230V AC %IX0.0
%IX0.2
PB-1
PB-3
%IX0.1
%IX0.4
PB-2
PB-4
OR-AND PLC Logic RUNG %QX0.0
L-4
ADVANTAGES OF USING PLC OVER CONVENTIONAL ELECTRICAL PANEL Solid state devices reduce failures because there is no mechanical wear and tear. Power consumption is less. Easily programmed or reprogrammed with the help of programming device. PLC can be reused if no longer required in original application. Only application program is to be changed. Indicating lamps are provided at important diagnostic points to simplify troubleshooting. No external hardware timers and counters are required unless due to specific need. Unlimited NO and NC contacts of inputs, outputs and auxiliary relays (Memory Bits) are available. Smallest cabinet size leading to less floor requirement. Easy troubleshooting.
DISADVANTAGES OF RLC Life of components is limited because of wear and tear of mechanical components . No flexibility. Huge space is required. Required more no of Labors. Fault finding is very lengthy process (Some times it may take few days to solve the problem). Lot of time required to complete the Job of small logic.
THANK YOU TO ALL PARTICIPANTS AND KEEP ON UPDATE THE KNOWLEDGE OF PLC
THE END
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