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PLC LADDER DIAGRAM
-BY
Shruti Bhatnagar Dasgupta
A Ladder diagram is a symbolic and schematic
representation of both the process hardware and
process control.
Its called a...
Normally Open Normally Closed
Push button Switches PB1 PB2
Limit Switches LS1 LS2
Temperature Limit
Switches
TS1 TS2
Press...
OUTPUT DEVICES
Contact Relay Normally closed
CR1
Normally Open
CR2
Relay
Contactor
Motor
Solenoid Valve SOV1
Indicating La...
RUNG
Condition Area Result Area
Active Supply Neutral Supply
Physical or Relay Ladder Example
Gate Input Output Logic PLC Ladder
OR A
B
Y A.B=Y A Y
B
AND A
B
Y A+B=Y A B Y
NOT A Y
__
A=Y
A X
X Y
Basic Logic Gates Usi...
Water Level Control:
i. It’s a single point level control.
ii. When the Level is above set point the output pump should be...
The number of inputs are Pump ‘ON’, Pump ‘OFF’ and
Level Switch; I/P=3
The number of outputs; O/P=1
The conditions for inp...
Supply Line Neutral
X1 X2 R1
R1
R1 X3 Y1
Here relay R1 acts as a Latch.
Ladder Diagram 1
Temperature Control
i. A temperature control system consists of four
thermostats. The system operates three heating units....
There are four thermostats; assume them be
in NC state when the set point is not reached.
Let there be a control relay (CR...
Solution 2
Teperature Thermostats Heater 1 Heater 2 Heater3
Below 55°C TS1
TS2
TS3
TS4
Closed
Closed
Closed
Closed
ON ON O...
Ladder Diagram 2
CR1
Star
t
Sto
p
TS4
CR1
H1
H2
H3
TS1
TS2
TS3
CR1
Safety
Shutoff
Heater 1
Heater 3
Heater 2
THANK YOU
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PLC LADDER DIAGRAM

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PLC Ladder Diagram basics, with two solved examples
For more information go to
http://shrutizpresentations.blogspot.in/2014/04/plc-ladder-diagram-basics.html

Publié dans : Technologie, Business

PLC LADDER DIAGRAM

  1. 1. PLC LADDER DIAGRAM -BY Shruti Bhatnagar Dasgupta
  2. 2. A Ladder diagram is a symbolic and schematic representation of both the process hardware and process control. Its called a ‘Ladder’ because all the devices are connected across the supply lines making it look like a ladder. Each parallel connection is called a ‘Rung’, it can contain many inputs but only one output. What is a Ladder Diagram
  3. 3. Normally Open Normally Closed Push button Switches PB1 PB2 Limit Switches LS1 LS2 Temperature Limit Switches TS1 TS2 Pressure Limit Switches PS2 Level Limit Switches LLS1 LLS2 On Delay Switches Delayed closed Delayed open Off Delay Switches (Timer Contacts) Logic Symbols:
  4. 4. OUTPUT DEVICES Contact Relay Normally closed CR1 Normally Open CR2 Relay Contactor Motor Solenoid Valve SOV1 Indicating Lamp Timer Counter Up Counter Down Counter CR1 R M1 R TR CT D CTR
  5. 5. RUNG Condition Area Result Area Active Supply Neutral Supply Physical or Relay Ladder Example
  6. 6. Gate Input Output Logic PLC Ladder OR A B Y A.B=Y A Y B AND A B Y A+B=Y A B Y NOT A Y __ A=Y A X X Y Basic Logic Gates Using PLC
  7. 7. Water Level Control: i. It’s a single point level control. ii. When the Level is above set point the output pump should be OFF iii. When the Level is below set point the output pump should be ON Example 1 TANK Pump Set Point
  8. 8. The number of inputs are Pump ‘ON’, Pump ‘OFF’ and Level Switch; I/P=3 The number of outputs; O/P=1 The conditions for inputs and outputs are: Solution 1 X1 (Pump ON) X2 (Pump OFF) X3 (Limit Switch) Y1 (Output) High Low Low High --- High --- Low High Low High Low
  9. 9. Supply Line Neutral X1 X2 R1 R1 R1 X3 Y1 Here relay R1 acts as a Latch. Ladder Diagram 1
  10. 10. Temperature Control i. A temperature control system consists of four thermostats. The system operates three heating units. The thermostats are set at 55°C, 60°C, 65°C and 70°C. ii. Below 55°C three heater are to be in ON state iii. Between 55°C - 60°C two heaters are to be in ON state. iv. Between 60°C - 65°C one heater is to be in ON state. v. Above 70°C all heaters are to be in OFF state, there is a safety shutoff in case any heater is operating by mistake. vi. A master switch turns the system ON and OFF. Example 2
  11. 11. There are four thermostats; assume them be in NC state when the set point is not reached. Let there be a control relay (CR1) to work as a safety shutoff. The Start switch is NO and Stop switch NC type. Solution 2
  12. 12. Solution 2 Teperature Thermostats Heater 1 Heater 2 Heater3 Below 55°C TS1 TS2 TS3 TS4 Closed Closed Closed Closed ON ON ON 55°C-60°C TS1 TS2 TS3 TS4 Open Closed Closed Closed OFF ON ON 60°C-65°C TS1 TS2 TS3 TS4 Open Open Closed Closed OFF OFF ON 65°C-70°C TS1 TS2 TS3 TS4 Open Open Open Closed OFF OFF ON Above 70°C TS1 TS2 TS3 TS4 Open Open Open Open OFF OFF OFF
  13. 13. Ladder Diagram 2 CR1 Star t Sto p TS4 CR1 H1 H2 H3 TS1 TS2 TS3 CR1 Safety Shutoff Heater 1 Heater 3 Heater 2
  14. 14. THANK YOU

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