Automationcontrol4
- 1. PLC programming for applications and maintenance By Dr. Palitha Dassanayake
- 2. Content Programming a simple application Faultfinding and maintenance Programming application for sequential operations Another program application
- 3. Constructing a PLC Program Methodology in programming a PLC are given as follows. 2.Write down or draw the requirements, logics or/and sequences in an understandable format using pseudocodes, flowcharts or UML (in some special cases). This may be skipped for smaller tasks, but essential when that the task becomes large or complicated. However, it is good practice to conduct this step to avoid unnecessary logical errors. 1. Identify the requirements or logical sequences that are going to be handled by a PLC.
- 4. Draw the necessary tables or maps to illustrate the PLC ogic that match with the requirement, but independent om the language code (ladder, logo or statement list) 4. Connect the PLC to the system to be controlled and to the computer that PLC is going to get programmed Identify the input and output cables that are connected in der to program.
- 8. 1. When Os detects an item, it should be pushed by A0 and conveyor should start moving 2. If the item is metal, it has to be identified by Is. 3. Metal items are to be pushed by A1 and collected in C1. 4. Non-metal items are to be collected at the end of the belt to C2 5. If an item is in process, even if Os detects an item, it should not be pushed by A1 until the previous item is fully processed.
- 9. Start -No item Os=0 Os=1 A0 should be ejected provided no other item is in process If the item is metal, it is sensed by Is. If Is=1 item is metal, this should be remembered If Is had been 1 it has to pushed by A1 after a time interval If the item is not metal, it should not be pushed and collected at the end. The time required to travel is also required.
- 10. Amplifier Electro-pneumatic valve PLC Operating Voltage –24 v I0.1 I0.0 Q0.0 Q0.1 I s- C C2 Gear Box m Os If output the sensor is in mv A/C motor RelayA0 Q0.2 Electro-pneumatic valve A1
- 11. Os - I0.0 Is - I0.1 A1 - Q0.0 M - Q0.1 A0 - Q0.2 Input-output connections M0.0 - An item is in process M0.1- The item is Metallic 0.3 sec time is required for a pneumatic actuator to activate Operation Time(s) Activate A0 0 Near A1 10 End of the belt 15
- 12. Start -No item Os=0 Os=1 A0 should be ejected provided no other item is in process Time=0.3 sec T33 Q0.2 R M0.0 S Q0.2 T33 30+ IN PT TON Q ET I0.0 M0.0 Q0.2 S
- 13. If the item is metal, it is sensed by Is. If Is=1 item is metal, this should be remembered I0.1 M0.1 S If Is had been 1 it has to pushed by A1 after a time interval T37 T34 30+ IN PT TOF Q ET T34 T34 Q0.0M0.1 M0.0 T37 100+ IN PT TON Q ET T37
- 14. If the item is not metal, it should not be pushed and collected at the end. The time required to travel is also required. You must reset already set items once the process is completed M0.0 T38 150+ IN PT TON Q ET T38 Q0.0 T38 M0.1 R M0.0 R
- 15. Fault in a system System is not working at all 1. Check whether PLC is in the run mode Stop mode, change Error Mode, Restart PLC again error go to Step 2 2. Check inputs No input working check input power supply, connections etc Some inputs not working, check the connected wires, sensors or switches and interfaces All inputs working go to Step 3 3. Check outputs Check the outputs in the order it should work Check the LED of the PLC, if it is working find the fault in the connection or device No LED output is on, down load the program Communication with PLC is not possible replace PLC After downloading the programming Not working replace PLC
- 16. Faults and causes Os Fault A0 –Not work and Motor not work Is Fault A1-Not work Motor Fault Motor not work A0 Fault A0 Not Work A1 Fault A1 Not Work Sensor Faults Nothing Work Pneumatic problem A0 and A1 Not work PLC Fault Nothing Work
- 17. Fault Finding A/C Motor is not working, but the pneumatic actuator A0 pushes the item into conveyor Check the output of the PLC connected to the relay of the PLC That is Q 0.1 if it is on (LED on) fault is from that point If it is off (Generally not possible) check the program or check all sensors Pneumatic Actuator A0 is not working, but the A/C motor is working Check the output of the PLC connected to the electro-pneumatic valve of the PLC That is Q 0.2 if it is on (LED on) fault is from that point If it is off, Place a metal onto the conveyor and check A1 is working A1 Not working Pneumatic problem A1 is working (Generally not possible) check the program or check all sensors
- 18. Fault Finding Contd. A0 and A/C Motor is working, but the pneumatic actuator A1 does not sort items Check the output of the PLC connected to the electro-pneumatic valve of the PLC That is Q 0.0 if it is on (LED on) fault is from that point If it is off, check the sensor Is Working generally not possible check the program or check all sensors or sensor Is System is not working at all Check electrical connections, check sensor failure, No program in PLC Pneumatic failure+ Motor is not working PLC is at fault
- 19. Setting and Resetting a Memory I0.0 M0.0 S I0.1 M0.0 R Another method with one ladder I0.0 M0.0 I0.1 M0.0
- 20. Cylinders are in the original position A B C D Cylinder 2 X2 Cylinder 1 X1
- 23. Cylinders are in the original position A B C D Cylinder 1 X1 Cylinder 2 X2
- 24. Cylinders are in the original position A B C D Cylinder 2 X2 Cylinder 1 X1 =1 =1
- 25. Cylinders are in the original position A B C D Cylinder 2 X2 Cylinder 1 X1 =0 =1
- 27. ABC Pneumatic Actuator Product A=0 B=0 C=0 Product A=1 B=0 C=0 Product Time 1 sec after C=1 Product A=1 B=1 C=0 If short when B=1 A=0 Product A=0 B=1 C=1 If long when C=1 A=1 Product Time 1.3 sec after C=1 If the product is long or short
- 28. A B M0.0 S T34 M0.1 100+ IN PT TON Q ET T33 30+ IN PT TOF Q ET 34T T33 M0.1 S M0.0 A C C PLC programming using S7 Version
- 29. apT33 T34 M0.0 R T33 T34 M0.1 R C
- 30. END