Pneumatic Systems. Module 3: Logic Operations in Electropneumatics. IAT Curriculum Unit PREPARED BY. August 2008

Transcription

1 Pneumatic Systems Module : Logic Operations in Electropneumatics PREPARED BY IAT Curriculum Unit August 2008 Institute of Applied Technology, 2008

2 2 Module : Logic Operations in Electro-pneumatics

3 Module : Logic Operations in Electropneumatics Module Objectives The students will be familiar with: 1- A range of electric components. 2- A range of electro-pneumatic components. - Simple AND/OR circuits. - Latching circuits. Module Contents 1 Logic operations-or circuit P 2 Logic operations-and circuit P5 Experiment 1 P6 Experiment 2 P9 5 Experiment P12 6 Assignments P15 7 Latching P18 8 Experiment P19 9 Assignments P21 Module : Logic Operations in Electro-pneumatics

4 Logic Operations In order to produce the required movements by pneumatic cylinders, it is often necessary to combine signals from several control elements through logic operations such as: 1. OR circuits 2. AND circuits. The OR circuit The OR circuit has two inputs and a single output. The output will be at logic 1 if either or both inputs are 1. The aim is to be able to extend the piston rod of a cylinder with two different input elements, pushbutton S1 and. The contacts of the pushbuttons S1 and are arranged in parallel in the circuit diagram, Fig..1-b. As long as no pushbutton is pressed, the DCV remains in the normal position. The piston rod is retracted. If at least one of the two pushbuttons is pressed, the DCV switches to the actuated position. The piston rod advances. When both switches are released. The DCV switches to the normal position. The piston rod is retracted. Lets consider the following values are valid : 0: push buttons are not pressed, piston rod doesn t advance. 1: push button pressed or piston rod advances. Then above results are shown in the truth table, Fig..2 a)pneumatic circuit +2V S1 b)electric circuit Fig..1: Parallel connection of two contacts (OR circuit). S Fig..2: Truth table-or circuit Module : Logic Operations in Electro-pneumatics

5 Logic Operations The AND circuit The AND circuit has two inputs and a single output. The output is at logic 1 only when both inputs are only at logic 1. In this case the piston rod of a cylinder is to be advanced only if both pushbuttons S1 and are pressed. The Two pushbutton switches are arranged in series in the circuit diagram, Fig..-b. As long as neither or only one of the two pushbuttons is pressed, the DCV remains in the normal position. The piston rod is retracted. If both pushbuttons are pressed at the same time, the DCV switches to the actuated position. The piston rod advances. When at least one of the switches is released, the DCV switches to the normal position. The piston rod retracted. The truth table for the AND operation is illustrated in the table, Fig... a)pneumatic circuit +2V S1 2 5 b)electric circuit Fig..: Series connection of two contacts (AND circuit). 1 S Fig..: Truth table-and circuit Module : Logic Operations in Electro-pneumatics 5

6 Experiment # 1 Title An OR/AND electric circuit to directly control a double acting cylinder by using 5/2 DCV, single solenoid. Objectives Students to be familiar with: 1- Double acting cylinder. 2-5/2 way valve double solenoid. - Direct control circuit with AND/OR. Background The electric circuits OR/AND will replace the mechanical OR/AND valves to actuate a directional valve either by pressing any two switches together (AND circuit), or by pressing any one of two switches (OR circuit). Required components SR. Name Qty. 1 Double acting cylinder 1 2 5/2 Directional control valve, single solenoid 1 Power supply 1 Switches block 1 6 Module : Logic Operations in Electro-pneumatics

7 Procedure 1. Connect the pneumatic circuit according to the pneumatic circuit a). 2. Connect the electric circuit according to the electric circuit b).. Check that all the parts are connected properly with each other.. Switch the power supply on and open the service unit. 5. Press switch S1. Does the cylinder extend? Why? ` a) Pneumatic circuit +2V 1 6. Release switch S1 and press switch, does the cylinder extend? Why? 7. Press the two switches S1 and together. Does the cylinder extend? Why?.. S1 b) AND circuits Module : Logic Operations in Electro-pneumatics 7

8 Procedure 8. For the same pneumatic circuit, connect the electric circuit according to the electric circuit c). 9. Check that all the parts are connected properly with each other. 10. Switch the power supply on and open the service unit. 11. Press switch S1. Does the cylinder extend? Why? 12. Release switch S1 and press switch. Does the cylinder extend? Why? 1. Press the two switches S1 and together. Does the cylinder extend? Why. 1. Turn the power off and close the service unit. 15. Dismantle and tidy up +2V 1 2 S1 c) OR circuit Conclusion Module : Logic Operations in Electro-pneumatics

9 Experiment # 2 Title An OR/AND electric circuit to directly control a double acting cylinder by using 5/2 DCV, double solenoid Objectives Students to be familiar with: 1. Double acting cylinder. 2. 5/2 way valve, double solenoid.. Direct control circuit with AND/OR. Background The electric circuits OR/AND will replace the mechanical OR/AND valves to actuate a directional valve either by pressing any two switches together (AND circuit), or by pressing any one of two switches (OR circuit). Required components SR. Name Qty. 1 Double acting cylinder 1 2 5/2 way valve, double solenoid 1 Power supply 1 Switches block 2 Module : Logic Operations in Electro-pneumatics 9

10 Procedure 1. Connect the pneumatic circuit according to the pneumatic circuit a). 2. Connect the electric circuit according to the electric circuit b).. Check that all the parts are connected properly with each other.. Switch the power supply on and open the service unit. 5. Press switch S1. Does the cylinder extend? Why? 6. Release switch S1 and press switch. Does the cylinder extend? Why? 7. Press the two switches S1 and together. Does the cylinder extend? Why. 8. If the cylinder piston extended from the previous steps, propose how to retract it. 2 Y2 5 1 a) Pneumatic circuit +2V 1 2 S1 S S Y2 b) AND circuit 10 Module : Logic Operations in Electro-pneumatics

11 Procedure 9. For the same pneumatic circuit, connect the electric circuit according to the electric circuit c). 10. Check that all the parts are connected properly with each other. 11. Switch the power supply on and open the service unit. 12. Press switch S1. Does the cylinder extend? Why. 1. Release Switch S1 and press switch, does the cylinder extend? Why? 1. Press the two switches S1 and together. Does the cylinder extend? Why?. 15. If the cylinder piston extended from the previous steps, propose how to retract it. 16. Turn the power off and close the service unit. +2V c) OR circuit 17. Dismantle and tidy up. Conclusion S1 1 6 Module : Logic Operations in Electro-pneumatics 11 S Y2 S

12 Experiment # Title An OR/AND electric circuit to indirectly control a double acting cylinder by using 5/2 DCV, double solenoid. Objectives Students to be familiar with: 1. Double acting cylinder. 2. 5/2 way valve double solenoid.. Direct control circuit with AND/OR. Background The electric circuits OR/AND will replace the mechanical OR/AND valves to actuate a directional valve either by pressing any two switches together (AND circuit), or by pressing any one of two switches (OR circuit). The circuit is controlled indirectly using a relay. Required components SR. Name Qty. 1 Double acting cylinder 1 2 5/2 way valve single solenoid 1 Power supply 1 Switches block 1 5 Relays block 1 12 Module : Logic Operations in Electro-pneumatics

13 Procedure 1. Connect the pneumatic circuit according to the pneumatic circuit a). 2. Connect the electric circuit according to the electric circuit b).. Check that all the parts are connected properly with each other.. Switch the power supply on and open the service unit. 5. Press switch S1. Does the cylinder extend? Why? 6. Release switch S1 and press switch. Does the cylinder extend? Why? 7. Press the two switches S1 and together. Does the cylinder extend? Why? 8. If the cylinder piston extended from the previous steps, propose how to retract it. 2 Y2 5 1 a) Pneumatic circuit +2V1 2 S1 S K2 S K2 Y2 2 b) AND circuit Module : Logic Operations in Electro-pneumatics 1

14 Procedure 9. For the same pneumatic circuit, connect the electric circuit according to the electric circuit c). 10. Check that all the parts are connected properly with each other. 11. Switch the power supply on and open the service unit. 12. Press switch S1, does the cylinder extend? Why? Release switch S1 and press switch. Does the cylinder extend? Why? Press the two switches S1 and together. Does the cylinder extend? Why? 15. If the cylinder piston extended from the previous steps, propose how to retract it. 16. Turn the power off and close the service unit. +2V c) OR circuit 17. Dismantle and tidy up. Conclusion.... S1 S S K2 8 K2 Y2 1 Module : Logic Operations in Electro-pneumatics

15 Assignment 1: Class work AT0000 Pneumatic Systems 1. Give an application example of where an AND circuit is used Give an application example of where an OR circuit is used.. The circuit below illustrates an electro-pneumatic system, answer the following questions : +2V S1 S a) Explain how to extend and retract the cylinder. b) For the electro- pneumatic system above, write the truth table.... Module : Logic Operations in Electro-pneumatics 15

16 Assignment 2: Home Work 1. The circuit below illustrates an electro-pneumatic system. Answer the following questions: +2V S1 S K2 5 1 Y2 K2 Y2 Pneumatic circuit 6 Electric circuit a) Is the electric circuit above direct or indirect? Explain why. b) What is the name of the part which is labeled as?.. c) How to extend the piston of the above cylinder? d) How to retract the piston above cylinder? 16 Module : Logic Operations in Electro-pneumatics

17 2. The truth table below represents a logic circuit controlling a single solenoid 5/2 DCV, based on the table below draw the electric and the pneumatic circuit. S1 S Module : Logic Operations in Electro-pneumatics 17

18 Relay Circuits with Latching Sometimes, it is required to keep the circuit powered, for a certain function, even though a pushbutton switch is released to the open position. In order to achieve this latching circuit, a relay is introduced, see Fig..5. When the ON pushbutton is actuated Fig..5-a, the relay coil is energized. The relay is energized, and contact closes. After the ON pushbutton is released, current continues to flow via contact through the coil, and the relay remains in the actuated position. The on signal is stored. This is therefore a relay circuit with latching function. +2V ON 1 1 OFF 2 2 a) Dominant ON When the OFF pushbutton is pressed the flow of current is interrupted and the relay becomes de-energized. If the ON and OFF pushbuttons are both pressed at the same time, the relay coil is energized, that s why the circuit Fig..5-a is called a dominant ON latching circuit. The circuit in Fig..5-b has the same behavior as the previous circuit. The behavior is different when both pushbuttons are pressed simultaneously: the relay coil is not energized. The circuit is referred to as a dominant OFF latching circuit. +2V ON OFF b) Dominant OFF Fig..5: Relay circuit with latching 18 Module : Logic Operations in Electro-pneumatics

19 Experiment # Title Manual forward and return stroke control via relay with latching function. Objectives The student will be familiar with Latching. Background In this experiment the piston rod of a cylinder is to advance when pushbutton S1 is pressed and retract when pushbutton is pressed. A relay with latching function is to be used for signal storage. Required components SR. Name Qty. 1 Double acting cylinder 1 2 5/2 DCV, single solenoid 1 Power supply 1 Switches block 1 5 Relays block 1 Module : Logic Operations in Electro-pneumatics 19

20 Procedure 1. Connect the pneumatic circuit according to the pneumatic circuit a). 2. Connect the electric circuit according to the electric circuit b).. Check that all the parts are connected properly with each other.. Switch the power supply on and open the service unit. 5. Press switch S1. Does the cylinder extend? Why?. 6. Release switch S1. Does the cylinder retract? Why? 7. Press the switch. Comment about the cylinder movement. 8. Remove the circuit branch no. 2 (cancel latching), and press/release S1. Explain what happens to cylinder. 18. Turn the power off and close the service unit. 19. Dismantle and tidy up. +2V a) Pneumatic circuit b) b) Electrical circuit Conclusion S Module : Logic Operations in Electro-pneumatics

21 Assignment : Class work 1. Explain briefly the meaning of latching. AT0000 Pneumatic Systems.. 2. The circuit below illustrates an electro-pneumatic system. Answer the following questions. +2V 1 2 S a) Which one is the latching circuit? Indicate the circuit number. b) What type of switch are switches S1 and? c) What is the meaning of the symbol shown under circuit 1? d) What is the function of switch? e) How to extend and retract the cylinder piston? 2 Module : Logic Operations in Electro-pneumatics 21

22 Assignment : Home Work The circuit below illustrates an electro-pneumatic system. Answer the following questions: +2V S1 1 1 S K2 K2 a) Is the electric circuit above direct or indirect? Why? b) Which circuit is controlled by circuit no 2?.. c) Write down the latching circuit no... d) It is not possible to unlatch the above circuit, explain why?.. e) Explain, how to extend the piston of the above cylinder? f) Explain, how to retract the above cylinder, if possible? 22 Module : Logic Operations in Electro-pneumatics