Download ATM-414 – Pneumatic systems Electro

Electro-Pneumatic
Module 1: Introduction to Electropneumatics
PREPARED BY
Academic Services
August 2012
© Applied Technology High Schools, 2012
ATM-414 – Electro-Pneumatics
Module 1: Introduction to Electropneumatics
Module Objectives
After the completion of this module, the student will be able to:
1- Explain all safety precaution when working with electro-pneumatics.
2- Explain the concept of signal flowing in electro-pneumatics.
3- Identify the advantages and disadvantages of the elector-
pneumatics.
Module Contents
Sr
2
Topic
Page No.
1
Introduction to electro-pneumatics
3
2
Signal flow in electro-pneumatics
4
3
Advantages of electro-pneumatic systems
5
4
Components of electro-pneumatic system
6
5
Safety and operation
12
6
Practical task 1
13
7
Practical task 2
17
8
Practical task 3
18
9
References
24
Module 1: Introduction to electro-pneumatics
ATM-414 – Pneumatic systems
1
Introduction to electropneumatics
Electro-pneumatic is widely used in
many
areas
of
industrial
automation. Production, assembly,
and packaging systems worldwide.
These
systems
are
driven
by
electro-pneumatic control systems.
Fig.1.1 (a) and Fig1.1 (b) show
different applications of electropneumatic machines.
In
(a)
electro-pneumatics,
pneumatic
components
the
are
controlled by using electrical and
electronic circuits. Electronic and
electromagnetic sensors, electrical
switches and industrial computers
are used to replace the manual
control of a pneumatic system.
(b)
Fig.1.1
(a): Milk filling machine
(b): Yogurt filling machine
Module 1: Introduction to electro-pneumatics
3
ATM-414 – Electro-Pneumatics
`
2
Signal flow in electro-pneumatic control system
The signal flow diagram of Fig. 1.2 illustrates the signal flow within an
electro-pneumatic system.
1. Signal input: This signal is usually generated from sensor or switch.
2. Signal processing: the signal is processed in the processing station such
as OR gate, AND gate or time delay valve.
3. Signal output: the signal forms as a link between the signal control
section and the power section
4. Command execution: it takes place at high power level either for:

High speed-fast ejection of product.

Apply high force as in power presses.
Fig. 1.2: Signal flow and components of an electro-pneumatic control
system
4
Module 1: Introduction to electro-pneumatics
ATM-414 – Pneumatic systems
3
Advantages of electro-pneumatic systems:
Below are some advantages of electro-pneumatic systems
1. Greater reliability.
Less moving parts subjected to wear compared to mechanical
control systems.
2. Reduced installation complexity.
Less components and hoses, leads to less effort in planning and
commissioning especially with large and complex systems.
3. The control system can be easily modified and adapted.
It is easier to change wiring and modify programs rather than
changing mechanical components and hose networks.
Example: the AND gate is replaced with logic and through using
electrical switches.
4. Easy handling.
Less complexity
5. Secure mounting.
Fewer hoses
6. Environmentally-friendly coupling system.
Less lubrication require
4
Components of electro-pneumatic system
The electro pneumatic system is normally consists of the following items:
1. DC power supply.
2. Switches.
3. Relays.
4. Solenoid valves.
5. Sensor.
Module 1: Introduction to electro-pneumatics
5
ATM-414 – Electro-Pneumatics
4.1
DC Power Supply
The power supply is used to reduce and convert the 230 V AC to a 24 V DC
(inside ATHS laboratories) as shown in Fig.1.3
Figure 1.3 power supply
The power supply components which are shown in Fig. 1.4 have the
following functions:

The transformer reduces the main voltage (230 to 24 volt).

The rectifier converts the AC voltage to DC voltage.

The stabilizer is used to smooth and maintain constant voltage at the
output
Fig.1.4 electric diagram of the power supply
The following criteria play commonly an important role is selecting the
power supply:

The magnitude of voltage and current it can supply.

How stable its output voltage or current is under varying load
conditions.

6
Whether it provides continuous or pulsed energy.
Module 1: Introduction to electro-pneumatics
ATM-414 – Pneumatic systems
4.2
Switches
Switches are installed in an electric circuit to connect or interrupt the
electric current.
These switches are divided into:
1- Control switches: keep the selected position such as detent switches.
Push button switches: maintain the selected position as long as the switch
is activated.
In this module, three types of switches will be discussed:
a. Push button switches.
b. Detent switches.
c. Limit switches.
(a)
Push button switches
These switches are activated manually and used connect or disconnect the
electric current in he control circuit. There are three typed of the push
button switches:
1- Normally
open
contact
(make)
In the case of a normally open
switch Fig.1.5.a, the circuit is
open if the switch is in its initial
position
(a)
(b)
Pressing the pushbutton results in
closing the circuit and then the
current will flow to load. When
the plunger is released the spring
will returns the switch to it initial
position.
Module 1: Introduction to electro-pneumatics
7
ATM-414 – Electro-Pneumatics
2 Normally
close
contact
(break)
In the case of the normally closed
switch Fig. 1.5.c, the circuit is
closed when the switch is in its
initial
position.
interrupted
pushbutton.
by
The
circuit
pressing
Fig.1.5.d
shows
(c)
is
(d)
the
the
ISO symbol of the push button N/C.
2
3 Changeover contact (two-
4
way)
1
The change over contact Fig. 1.9-c
combines
the
function
of
the
(e)
(f)
normally open and normally closed.
Changeover contacts are used to
close one circuit and open another
circuit in one switching operation.
In the (ATHS) labs, these types of
switches are combined in one switch
block as illustrated in figure 1.5.g.
(g)
Fig.1.5:
(a): push button switch (N/O)
(b): ISO symbol of the normally
open push button switch
(c): push button switch (N/C)
(d): ISO symbol of the normally
closed push button switch
(e): changeover switch (two way)
(f): ISO symbol of the changeover
switch
(g): Switch block
8
Module 1: Introduction to electro-pneumatics
ATM-414 – Pneumatic systems
b
Detent switches
These
switches
keep
the
selected
position; the switch position remains
unchanged until a new switch position
is selected. It is called detent switch or
a
latching
switch.
Fig.1.6.a
and
(a)
Fig.1.6.b show the ISO symbol of the
normally
open
normally
detent
closed
switch
detent
and
switch
respectively.
Detent switches also designed to be as
normally
open,
normally
closed
(b)
or
changeover switches.
In the (ATHS) labs, the detent switches
are included in the same switch block
with pushbutton switches, as shown in
Fig. 1.6.c
(c)
Fig. 1.6:
(a): ISO symbol of normally
open detent switch
(b): ISO symbol of normally
closed detent switch
c
Limit switches
(c): Switch block
The limit switch (Fig.1.7.a) is actuated
when a machine part or a work-piece is
in
a
certain
position.
Normally,
actuation is affected by a cam or
cylinder piston.
Limit switches are normally changeover
(a)
Module 1: Introduction to electro-pneumatics
(b)
9
ATM-414 – Electro-Pneumatics
contacts
and
according
to
can
the
be
connected
required
control
circuit. The limit switch can be used in
circuit
according
to
one
of
the
following:
 Normally open switch
 Normally closed switch
 Changeover switch
.
Fig. 1.7
(a): internal construction of the
limit switch
(b): ISO symbol of the limit
switch
(c): picture of the limit switch
10
Module 1: Introduction to electro-pneumatics
ATM-414 – Pneumatic systems
4.3
A
Relays
relay
is
defined
as
an
electromagnetically actuated switch.
When the voltage
is applied to a
solenoid coil terminals (A1, A2) in
Fig.1.14,
it
will
become
an
electromagnet which in turn attracts
the contacts of the relay either closing
(a)
or opening them.
The spring returns the contacts to the
initial
position
immediately
after
disconnecting the voltage at the coil
terminals.
(b)
An ISO symbol of the relay and a lab
relay block is also illustrated in the
same figure.
Some advantages of a relay that:

It can be used to switch one or
more contacts.

To switch a high current circuit with
a low current circuit.
(c)
Fig. 1.8:
(a): Internal structure
(b): ISO symbol of the relay
(c): Relay block
Module 1: Introduction to electro-pneumatics
11
ATM-414 – Electro-Pneumatics
5. Safety and operation
The following points should be observed while working with electropneumatic systems:
1. Pressurized
air
lines
that
become detached can cause
accidents. Switch off pressure
immediately.
2. First connect all tubing and
secure before switching on
the compressed air.
3. Cylinders
retract
may
as
advance
soon
as
or
the
compressed air is switched
on.
4. Do not operate the electrical
limit switch manually during
fault
finding
(use
a
tools
only).
5. Limit switches should be fixed
in
such
a
way
that
they
contact the trip cam of the
cylinder
only
in
the
determined direction.
6. Do not exceed the permissible working pressure.
7. Use only low voltages of ≤ 24 V.
8. Switch off the air and voltage supply before disconnecting the
circuit.
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Module 1: Introduction to electro-pneumatics
ATM-414 – Pneumatic systems
6. Practical Task 1
Title:
Controlling an electric bulb lighting
using different types of switches
Objectives:

Understanding and using the DC
power supply.

(a)
The student should be able to use of
the pushbutton switches (NO and
NC).

The student should be able to use of
detent switches (NO and NC).

The student should be able to use of
changeover switch.

The
student
construct
the
should
be
circuit
able
using
to
(b)
the
FluidSim software
Background:
The student should know how to use
the Pushbutton, detent and changeover
switches that will be used to switch
on/off a lamp using different circuit
configurations.
(c)
Required components:
1- DC power supply (Fig.1.9.a)
2- Indicator unit (Fig.1.9.b)
3- Switch block (Fig.1.9 c)
4- Limit switch (Fig1.7 c)
Fig. 1.9:
(a): Dc power supply
(b): Indicator block
(c): Switch block
Module 1: Introduction to electro-pneumatics
13
ATM-414 – Electro-Pneumatics
Procedures:
1. Prepare the components according to
the components list.
2. From
the
switch
block,
use
a
pushbutton switch to connect the first
two circuits as in Fig.1.10.a

Pushbutton switch, normally open.
Press the switch on/off and explain
what happens to the lamp.
……………………………………………………………
……………………………………………………………
……………………………………………………………

Pushbutton, Normally closed switch.
Press the switch on/off and explain
N.O
what happens to lamp.
NC
(a)
……………………………………………………………
……………………………………………………………
…………………………………………………………..
3. From the switch block, use a detent
switch
to
connect
the
second
two
circuits as in Fig.1.10.b

Detent switch, normally open. Press
the switch and note what happens to
the lamp.
……………………………………………………………
……………………………………………………………
……………………………………………………………
N.O
N.C.
(b)
14
Module 1: Introduction to electro-pneumatics
ATM-414 – Pneumatic systems

Detent switch normally closed. Press
the switch and note what happens to
the lamp.
……………………………………………………………
……………………………………………………………
…………………………………………………………..
4. Use a limit switch (as a changeover
switch) to connect the circuit as in
Fig.1.10.c
Press the switch and see how the switch
is used to control two circuits at a time.
Write your comments.
(c)
………………………………………………………………
………………………………………………………………
Fig. 1.10:
………………………………………………………………
(a): Push button switch
………………………………………………………………
(b): Detent switch
………………………………………………………………
(c): Changeover switch
………………………………………………………………
……………………………………………………………..
5. Turn the power off.
6. Dismantle and tidy up.
Conclusion
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Module 1: Introduction to electro-pneumatics
15
ATM-414 – Electro-Pneumatics
7. Practical Task 2
Title:
Indirect control of a lamp using a
pushbutton switch and a relay.
Objectives:

Introduce the students to the use of
lab equipment.

Introduce the students to the use of
DC power supply.

Introduce the students to the use of
the pushbutton switches (NO and
NC).

Introduce the students to the use of
the relay and the associated
contacts (NO and NC).
Background:
The relay is an electromagnetically
operated switch; it will be used to
indirectly control a 24V lamp through
a pushbutton switch.
Required Components:
5- DC power supply
6- Indicator unit
7- Switch block
8- Relay block
16
Module 1: Introduction to electro-pneumatics
Relay block
ATM-414 – Pneumatic systems
Procedures:
1
+24V
2
1. Connect the circuit according to circuit
shown in Fig.1.11.a, so the relay is a
3
normally open.
4
2. Switch on /off the pushbutton switch
A1
and observe the lamp and also the LED
of
the
relay
block.
Explain
K1
what
3
K1
A2
4
happens to the lamp?
……………………………………………………………………
0V
……………………………………………………………………
2
………………………………………………………..……
(a)
3. Replace the pushbutton switch with a
detent switch and repeat the same
+24V
3
4
steps. Explain what happens to lamp.
3
………………………………………………………………
………………………………………………………………
4
………………………………………………………………
4. Connect the circuit according to circuit
K2
K2
shown in Fig.1.11.b, so the relay is in a
normally close mode.
1
A1
A2
2
0V
5. Switch on/off the pushbutton switch
and observe the lamp and the LED of
the relay block. Explain what happens
4
(b)
to lamp.
……………………………………………………………..
Fig. 1.11:
………………………………………………………………
(a): Relay-Normally open
………………………………………………………………
(b): Relay-Normally closed
Module 1: Introduction to electro-pneumatics
17
ATM-414 – Electro-Pneumatics
6. Turn off the power
7. Dismantle and tidy up.
Conclusion
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8. Practical Task 3:
Title: Opening/closing the flow in a pipeline
The double acting cylinder (1A) in Fig. 1.12 is used to open and close the
main valve in a pipeline. Draw an electro-pneumatic circuit to control the
movement of cylinder (1A).
Hint: The valve is opened by pressing the pushbutton switch. When the
pushbutton is released the valve is closed.
Fig. 1.12
18
Module 1: Introduction to electro-pneumatics
ATM-414 – Pneumatic systems
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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Module 1: Introduction to electro-pneumatics
19
ATM-414 – Electro-Pneumatics
Student’s notes
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20
Module 1: Introduction to electro-pneumatics
ATM-414 – Pneumatic systems
Class work
1. Name three electrical components that will be used in the lab.
………………………………………………………………………………………………………………………
………………………………………………………………………………………………………………………
………………………………………………………………………………………………………………………
2. What is the function of a D.C. power supply?
………………………………………………………………………………………………………………………
………………………………………………………………………………………………………………………
3. What are the main components of the D.C. power supply?
………………………………………………………………………………………………………………………
………………………………………………………………………………………………………………………
4. List the main types of switches in terms of function.
………………………………………………………………………………………………………………………
………………………………………………………………………………………………………………………
………………………………………………………………………………………………………………………
5. Explain the difference between a push button switch and a detent switch.
………………………………………………………………………………………………………………………
………………………………………………………………………………………………………………………
………………………………………………………………………………………………………………………
6. Explain the difference between a pushbutton normally open switch and a
pushbutton normally closed switch.
……………………………………………………………………………………………………………………
……………………………………………………………………………………………………………………
……………………………………………………………………………………………………………………
……………………………………………………………………………………………………………………
……………………………………………………………………………………………………………………
……………………………………………………………………………………………………………………
Module 1: Introduction to electro-pneumatics
21
ATM-414 – Electro-Pneumatics
7. Draw the ISO symbol of the following components:
a- Detent pushbutton switch, N/C and N/O
N/C
N/O
b- Changeover switch
c-Relay
22
Module 1: Introduction to electro-pneumatics
ATM-414 – Pneumatic systems
Home Work
The circuit below illustrates a relay controlling three lamps indirectly,
answer the following questions:
1. What is the type of switch S1?
………………………………………………………………………………………………………………………
………………………………………………………………………………………………………………………
2. How many relays are there in the circuit?
………………………………………………………………………………………………………………………
……………………………………………………………………………………………………………………..
3. What is the meaning of the symbols below circuit 1 and circuit 4?
………………………………………………………………………………………………………………………
……………………………………………………………………………………………………………………..
4. Explain what happens when switch S1 is activated.
………………………………………………………………………………………………………………………
………………………………………………………………………………………………………………………
………………………………………………………………………………………………………………………
Module 1: Introduction to electro-pneumatics
23
ATM-414 – Electro-Pneumatics
9. References
24
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 1: Introduction to electro-pneumatics