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Pneumatic Systems

Module 3: Logic Operations in Electro-

pneumatics

PREPARED BY

IAT Curriculum Unit

August 2008

© Institute of Applied Technology, 2008

AT0000 – Pneumatic Systems

Module 3: Logic Operations in Electro-pneumatics 2



Module 3: Logic Operations in Electro-

pneumatics

Module Objectives

The students will be familiar with:

1- A range of electric components.

2- A range of electro-pneumatic components.

3- Simple AND/OR circuits.

4- Latching circuits.

Module Contents

1 Logic operations-OR circuit P4

2 Logic operations-AND circuit P5

3 Experiment 1 P6

4 Experiment 2 P9

5 Experiment 3 P12

6 Assignments P15

7 Latching P18

8 Experiment 4 P19

9 Assignments P21



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 S2.

The contacts of the pushbuttons S1 and

S2 are arranged in parallel in the circuit

diagram, Fig. 3.1-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. 3.2

a)Pneumatic circuit

b)Electric circuit

Fig. 3.1: Parallel connection of two contacts (OR circuit).

S1 S2 Y1

0 0 0

1 0 1

0 1 1

1 1 1

Fig. 3.2: Truth table-OR circuit.

+24V

0V

S1

3

4

Y1

S2

3

4

1 2 3

4 2

51

3

Y1



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 S2 are pressed. The Two

pushbutton switches are arranged in

series in the circuit diagram, Fig. 3.3-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. 3.4.

a)Pneumatic circuit

b)Electric circuit

Fig. 3.3: Series connection of two contacts (AND

circuit).

S1 S2 Y1

0 0 0

1 0 0

0 1 0

1 1 1

Fig. 3.4: Truth table-AND circuit

+24V

0V

S1

3

4

Y1

S2

3

4

1

4 2

5 1 3

Y1



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.

3- 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

3 Power supply 1

4 Switches block 1



Procedure

1. Connect the pneumatic circuit

according to the pneumatic circuit

a).

2. Connect the electric circuit

according to the electric circuit b).

3. Check that all the parts are

connected properly with each

other.

4. 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

S2, does the cylinder extend?

Why?

………………………………………………………

………………………………………………………

………………………………………………………

………………………………………………………

………………………………………………………

………………………………………………………

7. Press the two switches S1 and S2

together. Does the cylinder

extend? Why?

………………………………………………………

………………………………………………………

……………………………………………………..

`

a) Pneumatic circuit

b) AND circuits

+24V

0V

S1

3

4

Y1

S2

3

4

1

4 2

5 1

3

Y1



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.


extend? Why?

…………………………………………………………………

…………………………………………………………………

…………………………………………………………………


S2. Does the cylinder extend? Why?

…………………………………………………………………

…………………………………………………………………

………………………………………………………………


together. Does the cylinder extend?

Why.

…………………………………………………………………

…………………………………………………………………

…………………………………………………………………

14. Turn the power off and close the

service unit.

15. Dismantle and tidy up

c) OR circuit

Conclusion ………………………………………………………………………………………………………………………

………………………………………………………………………………………………………………………

………………………..………………………………………………………………………………………….…

…………………………………………………………………………………………………………………….…

…………………………………………………..……………………………………………………………….…

…………………………………………………………………………………………………………………….…

……………………………………………………………………………..…………………………………….…

…………………………………………………………………………………………………………………….…

……………………………………………………………………………………………………………………….

+24V

0V

S1

3

4

Y1

S2

3

4

1 2 3



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.

3. Direct control circuit with AND/OR.




circuit).

Required components


2 5/2 way valve, double solenoid 1

3 Power supply 1

4 Switches block 2



Procedure 1. Connect the pneumatic circuit

according to the pneumatic circuit a).

2. Connect the electric circuit according

to the electric circuit b).




the service unit.


extend? Why?

……………………………………………………………

……………………………………………………………

……………………………………………………………

……………………………………………………………

……………………………………………………………



……………………………………………………………

……………………………………………………………

……………………………………………………………

……………………………………………………………



Why.

……………………………………………………………

……………………………………………………………

……………………………………………………………

……………………………………………………………

8. If the cylinder piston extended from

the previous steps, propose how to

retract it.

……………………………………………………………

……………………………………………………………

……………………………………………………………

……………………………………………………………

……………………………………………………………


b) AND circuit

+24V

0V

S1

3

4

Y1

S3

3

4

Y2

S2

3

4

S4

3

4

1 2

4 2

5 1

3

Y1 Y2



Procedure

9. For the same pneumatic circuit,

connect the electric circuit

according to the electric circuit c).



other.



12. Press switch S1. Does the

cylinder extend? Why.

………………………………………………………

………………………………………………………

………………………………………………………

13. Release Switch S1 and press

switch S2, does the cylinder

extend? Why?

………………………………………………………

………………………………………………………

………………………………………………………

14. Press the two switches S1 and

S2 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.

17. Dismantle and tidy up.

c) OR circuit

Conclusion ………………………………………………………………………………………………………………………

………………………………………………………………………………………………………………………

………………………..………………………………………………………………………………………….…

…………………………………………………..……………………………………………………………….…

+24V

0V

S1

3

4

Y1

S3

3

4

Y2

S2

3

4

S4

3

4

1 3 4 6



Experiment # 3

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.

3. Direct control circuit with AND/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

3 Power supply 1

4 Switches block 1

5 Relays block 1



Procedure








the service unit.


extend? Why?

……………………………………………………………

……………………………………………………………

……………………………………………………………

……………………………………………………………

……………………………………………………………



……………………………………………………………

……………………………………………………………

……………………………………………………………

……………………………………………………………



Why?

……………………………………………………………

……………………………………………………………

……………………………………………………………

……………………………………………………………

……………………………………………………………

8. If the cylinder piston extended from

the previous steps, propose how to

retract it.

…………………………………………………………………

…………………………………………………………………

…………………………………………………………………

…………………………………………………………………


b) AND circuit

+24V

0V

Y1

S3

3

4

Y2K1

A1

A2

S1

3

4

K1

3

4

K2

A1

A2

K2

3

4

S2

3

4

S43

4

1 2 3 4

2 4

4 2

51

3

Y1 Y2



Procedure

9. For the same pneumatic circuit,

connect the electric circuit

according to the electric circuit c).



other.



12. Press switch S1, does the

cylinder extend? Why?

……………………………………………………….

.………………………………………………………

.………………………………………………………

13. Release switch S1 and press

switch S2. Does the cylinder

extend? Why?

…………………………………………………….…

…………………………………………………….…

……………………………………………………….

14. Press the two switches S1 and

S2 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.


c) OR circuit

Conclusion ………………………………………………………………………………………………………………………

…..…………………………………………………………………………………………………………………

……………………………..………………………………………………………………………………………

+24V

0V

Y1

S3

3

4

Y2 K1

A1

A2

S1

3

4

K1

3

4

K2

A1

A2

K2

3

4

S2

3

4

S4

3

4

1 2 3 4 5 6 7 8

4 8



Assignment 1: Class work

1. Give an application example of where an AND circuit is used.

………………………………………………………………………………………………………………………

………………………………………………………………………………………………………………………

………………………………………………………………………………………………………………………

……………………………………………………………………………………………………………………..

2. Give an application example of where an OR circuit is used.

………………………………………………………………………………………………………………………

………………………………………………………………………………………………………………………

………………………………………………………………………………………………………………………

3. The circuit below illustrates an electro-pneumatic system, answer the

following questions :

a) Explain how to extend and retract the cylinder.

…………………………………………………………………………………………………………………

…………………………………………………………………………………………………………………

…………………………………………………………………………………………………………………

…………………………………………………………………………………………………………………

…………………………………………………………………………………………………………………

b) For the electro- pneumatic system above, write the truth table.

…………………………………………………………………………………………………………………

...……………………………………………………………………………………………………………

…………………………………………………………………………………………………………………

…………………………………………………………………………………………………………………

…………………………………………………………………………………………………………………

4 2

513

Y1

+24V

0V

Y1K1

A1

A2

S1

3

4

K1

3

4

S3

3

4

S2

3

4

1 2 3 4

4



Assignment 2: Home Work

1. The circuit below illustrates an electro-pneumatic system. Answer the

following questions:

a) Is the electric circuit above direct or indirect? Explain why.

…………………………………………………………………………………………………………………

…………………………………………………………………………………………………………………

b) What is the name of the part which is labeled as Y1?

…………………………………………………………………………………………………………………

…………………………………………………………………………………………………………………

………………………………………………………………………………………………………………..

c) How to extend the piston of the above cylinder?

…………………………………………………………………………………………………………………

…………………………………………………………………………………………………………………

…………………………………………………………………………………………………………………

…………………………………………………………………………………………………………………

d) How to retract the piston above cylinder?

…………………………………………………………………………………………………………………

…………………………………………………………………………………………………………………

…………………………………………………………………………………………………………………

…………………………………………………………………………………………………………………

…………………………………………………………………………………………………………………

4 2

513

Y1 Y2

+24V

0V

S1

3

4

Y1

S2

3

4

K1

A1

A2

K1

3

4

Y2K2

A1

A2

K2

3

4

S3

3

4

Pneumatic circuit Electric circuit

1 2 3 4 5 6

4 6



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 S2 S3 Y1 0 0 0 0

1 0 0 0

0 1 0 0

0 0 1 0

1 1 0 0

1 0 1 1

0 1 1 1

1 1 1 1

………………………………………………………………………………………………………………………

…..…………………………………………………………………………………………………………………

………………………………………………………………………………………………………………………

………………………………………………………………………………………………………………………

………………………………………………………………………………………………………………………

……………………………………………………………………………………………………………………..

………………………………………………………………………………………………………………………

…..…………………………………………………………………………………………………………………

………………………………………………………………………………………………………………………

………………………………………………………………………………………………………………………

………………………………………………………………………………………………………………………

……………………………………………………………………………………………………………………..

………………………………………………………………………………………………………………………

…..…………………………………………………………………………………………………………………

………………………………………………………………………………………………………………………

………………………………………………………………………………………………………………………

………………………………………………………………………………………………………………………

……………………………………………………………………………………………………………………..



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. 3.5. When the “ON” pushbutton is actuated

Fig. 3.5-a, the relay coil is energized.

The relay is energized, and contact K1

closes. After the “ON” pushbutton is

released, current continues to flow via

contact K1 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.

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. 3.5-a is called a dominant ON latching circuit.

The circuit in Fig. 3.5-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.

a) Dominant ON

b) Dominant OFF

Fig. 3.5: Relay circuit with latching

+24V

0V

ON

13

14

K1

A1

A2

K13

4

OFF

1

2

1 2

2

+24V

0V

ON

13

14

K1

A1

A2

K1

3

4

OFF

1

2

1 2

2



Experiment # 4

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 S2 is pressed. A

relay with latching function is to be used for signal storage.

Required components


2 5/2 DCV, single solenoid 1

3 Power supply 1

4 Switches block 1

5 Relays block 1



Procedure








the service unit.


extend? Why?

.……………………………………………………………

……………………………………………………………

6. Release switch S1. Does the cylinder

retract? Why?

……………………………………………………………

……………………………………………………………

……………………………………………………………

7. Press the switch S2. 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.



b)

b) Electrical circuit

Conclusion ………………………………………………………………………………………………………………………

………………………………………………………………………………………………………………………

………………………..………………………………………………………………………………………….…

…………………………………………………………………………………………………………………….…

…………………………………………………..……………………………………………………………….…

+24V

0V

S113

14

K1A1

A2

K13

4

S21

2

Y1

K13

4

1 2 3

23

4 2

5 1

3

Y1



Assignment 3: Class work

1. Explain briefly the meaning of latching.

………………………………………………………………………………………………………………………

………………………………………………………………………………………………………………………

………………………………………………………………………………………………………………………

……………………………………………………………………………………………………………………..

2. The circuit below illustrates an electro-pneumatic system. Answer the

following questions.

a) Which one is the latching circuit? Indicate the circuit number.

…………………………………………………………………………………………………………………

…………………………………………………………………………………………………………………

b) What type of switch are switches S1 and S2?

…………………………………………………………………………………………………………………

…………………………………………………………………………………………………………………

c) What is the meaning of the symbol shown under circuit 1?

…………………………………………………………………………………………………………………

…………………………………………………………………………………………………………………

d) What is the function of switch S2?

…………………………………………………………………………………………………………………

…………………………………………………………………………………………………………………

e) How to extend and retract the cylinder piston?

…………………………………………………………………………………………………………………

…………………………………………………………………………………………………………………

…………………………………………………………………………………………………………………

…………………………………………………………………………………………………………………

+24V

0V

S113

14

K1A1

A2

K13

4

S21

2

Y1

K13

4

1 2 3

23

4 2

5 1

3

Y1



Assignment 4: Home Work

The circuit below illustrates an electro-pneumatic system. Answer the

following questions:

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?

…………………………………………………………………………………………………………………

…………………………………………………………………………………………………………………

…………………………………………………………………………………………………………………

+24V

0V

S2

13

14

K1

A1

A2

K1 3

4

4 2

5 1

3

Y1

Y1

K2 3

4

S3

1

2

K2

A1

A2

S1

13

14

1 2 3 4

3 4

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