Electro-Pneumatics M1 Student - Quia · PDF fileATM-414 – Pneumatic systems Module 1: Introduction to electro-pneumatics 3 1 Introduction to electro-pneumatics Electro-pneumatic

Electro-Pneumatic

Module 1: Introduction to Electro-pneumatics

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August 2012

© Applied Technology High Schools, 2012

ATM-414 – Electro-Pneumatics

2 Module 1: Introduction to electro-pneumatics

Module 1: Introduction to Electro-pneumatics

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 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



9 References 24

ATM-414 – Pneumatic systems

Module 1: Introduction to electro-pneumatics 3

1 Introduction to electro-pneumatics

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 electro-

pneumatic machines.

In electro-pneumatics, the

pneumatic components 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.

(a)

(b)

Fig.1.1 (a): Milk filling machine (b): Yogurt filling machine



` 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



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.



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.

Whether it provides continuous or pulsed energy.



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

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.

(a) (b)



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. The circuit is

interrupted by pressing the

pushbutton. Fig.1.5.d shows the

ISO symbol of the push button N/C.

3 Changeover contact (two-

way)

The change over contact Fig. 1.9-c

combines the function of the

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.

(c) (d)

(e) (f)

(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

1

2 4



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

Fig.1.6.b show the ISO symbol of the

normally open detent switch and

normally closed detent switch

respectively.

Detent switches also designed to be as

normally open, normally closed 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 Limit switches

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)

(b)

(c)

Fig. 1.6:

(a): ISO symbol of normally

open detent switch

(b): ISO symbol of normally

closed detent switch

(c): Switch block

(a) (b)



contacts and can be connected

according to the 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



4.3 Relays

A 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

or opening them.

The spring returns the contacts to the

initial position immediately after

disconnecting the voltage at the coil

terminals.

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.

(a)

(b)

(c)

Fig. 1.8:

(a): Internal structure

(b): ISO symbol of the relay

(c): Relay block



5. Safety and operation The following points should be observed while working with electro-

pneumatic 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 may advance or

retract as soon as 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.



6. Practical Task 1

Title:

Controlling an electric bulb lighting

using different types of switches

Objectives:

Understanding and using the DC

power supply.

The student should be able to use of

the pushbutton switches (NO and

NC).


detent switches (NO and NC).


changeover switch.

The student should be able to

construct the circuit using 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.

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)

(a)

(b)

(c)

Fig. 1.9:

(a): Dc power supply

(b): Indicator block

(c): Switch block



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

what happens to lamp.

……………………………………………………………

……………………………………………………………

…………………………………………………………..

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 NC

(a)

N.O N.C.

(b)



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.

………………………………………………………………

………………………………………………………………

………………………………………………………………

………………………………………………………………

………………………………………………………………

………………………………………………………………

……………………………………………………………..

5. Turn the power off.

6. Dismantle and tidy up.

(c)

Fig. 1.10:

(a): Push button switch

(b): Detent switch

(c): Changeover switch

Conclusion ............................................................................................................

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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.


DC power supply.


the pushbutton switches (NO and

NC).


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

Relay block



Procedures:

1. Connect the circuit according to circuit

shown in Fig.1.11.a, so the relay is a

normally open.

2. Switch on /off the pushbutton switch

and observe the lamp and also the LED

of the relay block. Explain what

happens to the lamp?

……………………………………………………………………

……………………………………………………………………

………………………………………………………..……

3. Replace the pushbutton switch with a

detent switch and repeat the same

steps. Explain what happens to lamp.

………………………………………………………………

………………………………………………………………

………………………………………………………………

4. Connect the circuit according to circuit

shown in Fig.1.11.b, so the relay is in a

normally close mode.

5. Switch on/off the pushbutton switch

and observe the lamp and the LED of

the relay block. Explain what happens

to lamp.

……………………………………………………………..

………………………………………………………………

………………………………………………………………

(a)

(b)

Fig. 1.11:

(a): Relay-Normally open

(b): Relay-Normally closed

+24V

0V

3

4

K2

A1

A2

K2

1

2

3 4

4

0V

3

4

K1

A1

A2

K1

3

4

2

+24V 1 2



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



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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Student’s notes ............................................................................................................

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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.

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

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

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

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

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

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



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



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.

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

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

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



9. References

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

Electro-Pneumatics M1 Student - Quia · PDF fileATM-414 – Pneumatic systems Module 1: Introduction to electro-pneumatics 3 1 Introduction to electro-pneumatics Electro-pneumatic

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