Electro-Pneumatics
Module 3: Logic Operations in ElectroPneumatics
PREPARED BY
Academic Services
August 2012
© Applied Technology High Schools, 2012
ATM-414 – Electro-Pneumatics
Module 3: Logic Operations in Electropneumatics
Module Objectives
After the completion of this module, the student will be able to:
1- Explain the concept of logic operation (OR circuits).
2- Explain the concept of logic operation (AND circuits).
3- Describe, Explain and construct a simple AND/OR circuits.
4- Describe and use the latching circuits.
Module Contents
1
Logic operations-OR circuit
3
2
Truth table of the OR circuit
4
3
Logic operations-AND circuit
5
4
Truth table of the AND circuit
6
5
Practical Task 1
7
6
Practical Task 2
9
7
Latching Circuits
15
8
Types of latching
16
9
Practical Task 3
17
10 References
2
Module 3: Logic Operations in Electro-pneumatics
22
ATM-414 – Electro-Pneumatics
Logic Operations
In
order
to
produce
the
required
movements by pneumatic cylinders under
certain conditions, it is often necessary to
combine
signals
from
several
control
4
elements through some logic operations
such as:
2
Y1
5
1. OR circuits
1
3
2. AND circuits.
1- Logic operation - OR circuit
The OR circuit has two inputs and a single
(a)
output. 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
1
+24V
2
3
3
arranged in parallel
S1
branches in the circuit diagram as shown
3
S2
4
4
in Fig. 3.1.b.

As long as no pushbutton is pressed,
the solenoid valve remains in the
Y1
0V
normal position. The piston rod is
retracted.

(b)
If at least one of the two pushbuttons
is pressed, the solenoid valve switches
to the actuated position. The piston rod
advances.

Fig. 3.1:
(a): Pneumatic circuit
When both switches are released. The (b): Parallel connection
of two contacts (OR circuit)
solenoid valve switches to the normal
position. The piston rod is retracted.
Module 3: Logic Operations in Electro-pneumatics
3
ATM-414 – Electro-Pneumatics
Truth table of the OR circuit:
The truth table depicts the status of the output in relation with specific
inputs. Let us assume the following

0: push buttons are not pressed and thus there is no input signal.

1: push button pressed and thus the input signal exists.

Y1 is 0 means the solenoid valve is not activated

Y1 is 1 means the solenoid valve is activated
The table below shows the possible outputs based on the input operating
conditions.
S1
S2
Y1
0
0
0
1
0
1
0
1
1
1
1
1
Fig. 3.2: Truth table of the OR circuit.
4
Module 3: Logic Operations in Electro-pneumatics
ATM-414 – Electro-Pneumatics
2- Logic operation - AND circuit
The AND circuit has two inputs and a
single output. The output of the AND
circuit exists only when both inputs are
existing. In this case the piston rod of a
cylinder will be advanced only if both
pushbuttons S1 and S2 are pressed at the
4
Y1
2
5
1
same time. The Two pushbutton switches
3
are arranged in series in the circuit
diagram as shown in Fig.3.3.b

(a)
As long as neither or only one of the
two
pushbuttons
is
pressed,
the
solenoid valve remains in the normal

1
+24V
position and the piston rod is retracted.
3
If both pushbuttons are pressed at the
S1
4
3
same time, the solenoid valve switches
to the actuated position and the piston
S2
4
rod advances.

Y1
When at least one of the switches is
0V
released, the solenoid valve switches
to the normal position and the piston
rod retracted.
(b)
Fig. 3.3:
(a): Pneumatic circuit
(b): Series connection
of two contacts (AND circuit)
Module 3: Logic Operations in Electro-pneumatics
5
ATM-414 – Electro-Pneumatics
Truth table of the AND circuit:
The truth table depicts the status of the output in relation with specific
inputs. Let us assume the following

0: push buttons are not pressed and thus there is no input signal.

1: push button pressed and thus the input signal exists.

Y1 is 0 means the solenoid valve is not activated

Y1 is 1 means the solenoid valve is activated
The table below shows the possible outputs based on the input operating
conditions.
S1
S2
Y1
0
0
0
1
0
0
0
1
0
1
1
1
Fig. 3.2: Truth table of the AND circuit.
Practical Task 1
Title: Operating a pneumatic press directly
Objectives:
Upon the completion of this task, the student should
1- Explain and use the AND connection practically to ensure a safe
operation.
2- Explain and use the OR connection practically.
3- Explain the direct (without using relays) control circuit with AND/OR.
4- Be able to use the FluidSIM software as well as workstations.
6
Module 3: Logic Operations in Electro-pneumatics
ATM-414 – Electro-Pneumatics
Problem description:
The pneumatic press that is shown in the Fig.3.3 has to be operated by
two switches at the same time in order to protect the operator hands
from any possible injury during the press operation. The press will be
released automatically by a limit switch. However, another switch has to
be provided to release the press in case of the limit switch malfunction.
Fig.3.3
Module 3: Logic Operations in Electro-pneumatics
7
ATM-414 – Electro-Pneumatics
Required components:
1- Double acting cylinder
2- 5/2 Directional control valve, double solenoid
3- Power supply
4- Switch blocks
Required procedures:
1. Draw the elector-pneumatic circuit using the FluidSim software
2. The speed of the forward and backward stroke of the cylinder rod is
adjustable
3. Test the circuit functions against any errors or mistakes.
4. Construct the circuit on the workstation
5. Write down your notes and observations.
Pneumatic circuit
8
Electric circuit
Module 3: Logic Operations in Electro-pneumatics
ATM-414 – Electro-Pneumatics
Observations and notes
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Practical Task 2
Title: Operating a pneumatic press indirectly
Objectives:
Upon the completion of this task, the student should
1- Explain and use the AND connection practically to ensure a safe
operation.
2- Explain and use the OR connection practically.
3- Explain the indirect (using electric relays) control circuit with AND/OR.
4- Be able to use the FluidSIM software as well as workstations.
Problem description:
The problem description for this task is the same as for the above task
(task 1)
Required components:
1- Double acting cylinder
2- 5/2 Directional control valve, double solenoid
3- Power supply
4- Switch blocks
5- Relay blocks
Module 3: Logic Operations in Electro-pneumatics
9
ATM-414 – Electro-Pneumatics
Required procedures:
1- Draw the elector-pneumatic circuit using the FluidSim software
2- Test the circuit functions against any errors or mistakes.
3- Construct the circuit on the workstation
4- Write down your notes and observations.
Pneumatic circuit
Electric circuit
Observations
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10
Module 3: Logic Operations in Electro-pneumatics
ATM-414 – Electro-Pneumatics
Class work (1)
1. Give an application example of where an AND circuit is used.
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2. Give an application example of where an OR circuit is used.
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3. The circuit below illustrates an electro-pneumatic system, answer the
following questions :
a) Explain how to extend and retract the cylinder.
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Module 3: Logic Operations in Electro-pneumatics
11
ATM-414 – Electro-Pneumatics
b) For the electro- pneumatic system above, write the truth table.
S1
S2
S3
Y1
c) Convert the above electric circuit to control the pneumatic circuit
directly.
12
Module 3: Logic Operations in Electro-pneumatics
ATM-414 – Electro-Pneumatics
Home Work (1)
1. The circuit below illustrates an electro-pneumatic system. Answer the
following questions:
a) Is the above electric circuit direct or indirect control? Explain why.
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b) What is the name of the part which is labeled as Y1?
…………………………………………………………………………………………………………………
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c) What is the difference between K1 in branch 2 and K1 in branch 4?
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d) What is the difference between K1 in branch 2 and Y1 in branch 4?
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Module 3: Logic Operations in Electro-pneumatics
13
ATM-414 – Electro-Pneumatics
e) How to extend the piston of the above cylinder?
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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
.
14
Module 3: Logic Operations in Electro-pneumatics
ATM-414 – Electro-Pneumatics
Latching Circuits
Definition of latching: It is a process where the relay contacts remain on
without keeping the relay coil energized. In other words, it is required
sometimes to keep the circuit powered for a certain function even though
a pushbutton switch is released to the open position. Fig. 3.4 illustrates
the concept of latching before activating the switch S1 and Fig.3.5 after
activating switch S1.
Fig.3.4 Before latching
Fig.3.5 After latching
Module 3: Logic Operations in Electro-pneumatics
15
ATM-414 – Electro-Pneumatics
Way of operation:
When the “ON” pushbutton switch is
actuated as shown in Fig.3.5.a, the relay
coil is energized and thus the contact K1
closes. Even after the “ON” pushbutton
switch is released the electric current
continues to flow via contact K1 through
the coil, and the relay remains in the
actuated position. The “on” signal is
stored. When the OFF pushbutton is
pressed the current flow is interrupted
(a)
and the relay becomes de-energized.
Types of latching:
1- dominant ON:
In Fig.3.5.a, if the “ON” and “OFF”
pushbuttons are both pressed at the
same time, the relay coil is energized.
That’s why the circuit in Fig.3.5.a is
called a dominant ON latching circuit.
1- dominant OFF:
In Fig.3.5.b, If both pushbuttons are
pressed simultaneously: the relay coil is
not energized. That’s why the circuit in
Fig.3.5.b
is
called
latching circuit.
a
dominant
OFF
(b)
Fig. 3.5: Relay circuit with
latching
(a): Dominant ON
(b): Dominant OFF
16
Module 3: Logic Operations in Electro-pneumatics
ATM-414 – Electro-Pneumatics
Practical task 3
Title: Latching circuit
Objectives:
Upon the competition of this task, the student should be able to control
an electro-pneumatic system by using an electrical latching circuit.
Problem description:
Parts are to be pushed away from a multi-track gravity feed magazine
into a clamping device as shown below in Fig.3.6. By pressing a
pushbutton switch the parts are pushed out of the multi-track gravity feed
magazine by a slide. After the slide has reached the forward end position
it has to return to its start position.
Hint: A relay with latching function is to be used for signal storage.
Fig3.6
Required components:
1-
Double acting cylinder
2-
5/2 DCV, single solenoid
3-
Power supply
4-
Switches block
5-
Relay block
6-
Limit switch
Module 3: Logic Operations in Electro-pneumatics
17
ATM-414 – Electro-Pneumatics
Required procedures:
1- Draw the electro-pneumatic circuit using the FluidSim software
2- Test the circuit functions against any errors or mistakes.
3- Construct the circuit on the workstation
4- Write down your notes and observations.
Pneumatic circuit
Electric circuit
Observations and notes
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18
Module 3: Logic Operations in Electro-pneumatics
ATM-414 – Electro-Pneumatics
Class work (2)
1. Explain briefly the meaning of latching in electrical circuits
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2. The circuit below illustrates an electro-pneumatic system. Answer the
following questions.
1
+24V
S1
4
2
S2
Y1
5
1
3
K1
13 K1
14
2
3
3
4
K1
1
2
A1
3
4
Y1
A2
0V
2
3
a) Which one is the latching circuit? Indicate the circuit number.
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b) What type of switch are switches S1 and S2?
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c) What is the meaning of the symbol shown under circuit 1?
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Module 3: Logic Operations in Electro-pneumatics
19
ATM-414 – Electro-Pneumatics
d) What is the function of switch S2?
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e) How to extend and retract the cylinder piston?
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f) State whether the above electro-pneumatic system is controlled
directly or indirectly. Justify your answer
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20
Module 3: Logic Operations in Electro-pneumatics
ATM-414 – Electro-Pneumatics
Home Work (2)
The circuit below illustrates an electro-pneumatic system. Answer the
following questions:
a) Is the electric circuit above directly or indirectly controlled? Why?
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b) Which switch is used to operate the circuit?
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c) Which branch represents the latching circuit?
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Module 3: Logic Operations in Electro-pneumatics
21
ATM-414 – Electro-Pneumatics
d) Which switch is used to release (unlatch) the circuit?
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e) Explain, how to extend the piston of the above cylinder?
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f) Explain, how to retract the above cylinder?
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References
22
1.
Electro-pneumatic text book TP 201 2005 – Festo
2.
Electro-pneumatic work book TP201 2005 – Festo
3.
Electro-pneumatic work book TP202 advanced level – Festo
Module 3: Logic Operations in Electro-pneumatics