Fundamentals of Electropneumatics

095011 GB

Fundamentals of

Electropneumatics

Collection of

Transparencies

2

1 3

33

11

22

Foreword

© Festo Didactic GmbH & Co. • Electropneumatics

The transparencies are designed from a didactical and methodological point of view.

For each transparency, there is a short accompanying text that provides the speaker

with a quick overview of the contents. More information you will find in the textbook

Electropneumatics.

� Physical fundamentals of electropneumatics

� Function and application of electropneumatic components

� Designation and drawing of electropneumatic symbols

� Drawing of pneumatic and electrical circuit diagrams in accordance with

standards

� Presentation of motion sequences and switching conditions

� Direct and indirect manual controls

� Direct and indirect direction-dependent controllers

� Logical AND/OR functions

� Pressure-dependent controls with pressure switches

� Troubleshooting in simple electropneumatic control systems

The text pages contain a complete picture of the transparency with some additional

explanations and items which the speaker can mark on the transparency during

instruction.

The advantages of this concept are:

� The speaker can add to the transparencies step-by-step during instruction.

� Instruction is livelier.

� The accompanying texts provided reduce preparation time.

Syllabus

New!

Electronic presentation

Contents

System Elements

Elements of a Control Chain __________________________________ Transparency 1

Pneumatic Components

Single-Acting Cylinder _______________________________________ Transparency 2

Double-Acting Cylinder ______________________________________ Transparency 3

Non-return, Flow Control and Pressure Control Valves_____________ Transparency 4

Pressure Regulating Valve____________________________________ Transparency 5

One-Way Flow Control Valve __________________________________ Transparency 6

Quick Exhaust Valve_________________________________________ Transparency 7

Electropneumatic Components

Conversion of Electrical Signals into Pneumatic Signals ___________ Transparency 8

Conversion of Pneumatic Signals into Electrical Signals ___________ Transparency 9

Switching Symbols for Valves ________________________________ Transparency 10

Directional Control Valves: Ports and Switching Positions_________ Transparency 11

Function Principle of a Solenoid Coil __________________________ Transparency 12

2/2-Way Solenoid Valve without Pilot Control __________________ Transparency 13

Solenoid Valves with Pilot Control ____________________________ Transparency 14

3/2-Way Single Solenoid Valve with Pilot Control _______________ Transparency 15

5/2-Way Single Solenoid Valve with Pilot Control _______________ Transparency 16

5/2-Way Double Solenoid Valve with Pilot Control_______________ Transparency 17

5/3-Way Solenoid Valve ____________________________________ Transparency 18

Electrical Components

Power Supply Units ________________________________________ Transparency 19

Switching Contacts and Types of Actuation_____________________ Transparency 20

Types of Actuation of Switching Elements ______________________ Transparency 21

Switching Symbols for Solenoid Coils and Relays________________ Transparency 22

The Relay ________________________________________________ Transparency 23

Magnetic Proximity Switches (Reed Switches) __________________ Transparency 24

Electrical Output Devices____________________________________ Transparency 25

Logic Functions

The AND Logic Function _____________________________________ Transparency 26

The OR Logic Function ______________________________________ Transparency 27

Contents

Electropneumatic Controller

Control Chain _____________________________________________ Transparency 28

Direct Actuation of a Single-Acting Cylinder ____________________ Transparency 29

Indirect Actuation of a Double-Acting Cylinder __________________ Transparency 30

Electrical Memory Circuit – Dominant Set ______________________ Transparency 31

Electrical Memory Circuit – Dominant Reset ____________________ Transparency 32

Electropneumatic Memory Circuit with Double Solenoid Valve _____ Transparency 33

Stroke-Dependent Control___________________________________ Transparency 34

Pressure-Dependent Control_________________________________ Transparency 35

Circuit Diagram Design

The Electropneumatic Circuit Diagram _________________________ Transparency 36

Circuit Diagram Structure ___________________________________ Transparency 37

Displacement-Step Diagram _________________________________ Transparency 38

Terminal Connection Diagram

Terminal Connection Diagram ________________________________ Transparency 39

Checklist for the Terminal Connection Diagram__________________ Transparency 40

Special Features with the Connection of Solenoid Coils

Protective Circuits for Inductive Loads _________________________ Transparency 41

Programmable Logic Controllers

Alterable Controls__________________________________________ Transparency 42

1

Elements of a Control Chain

The principle of the control chain is used for the preparation of the circuit diagram.

Every element of a control chain has a certain task to perform in the processing and

further transmission of signals.

This structuring of a system into functional blocks has proven itself in the following

tasks:

� Arrangement of the elements in the circuit diagram

� Definition of the nominal sizes, nominal current and nominal voltage of

components

� Set-up and commissioning of the controller

� Identification of the components for maintenance work

–

–

–

Electric motors

Solenoids

Linear motors

–

–

–

Power contactors

Power transistors

Power thyristors

–

–

–

–

–

Switches

Push button

actuators

Limit switches

Program

module

Sensors

Electrics/ Electronics

–

–

–

–

–

–

Switches

Push button actuators

Limit switches

Program module

Sensors

Indicators/generators

–

–

–

Contactors

Relays

Electronic modules

Pneumatics/ Hydraulics

– Directional

control valves

–

–

–

Directional

control valves

Isolating valves

Pressure valves

Working elements

Control elements

Processingelements

(Control elements)

Input elements

–

–

–

Cylinders

Motors

Components

TP 201, 01Transparency

Elements of a Control Chain

Electrics/Electronics

–

–

–

Power contactors

Power transistors

Power thyristors

–

–

–

–

–

–

Switches

Push button actuators

Limit switches

Program module

Sensors

Indicators/generators

–

–

–

Contactors

Relays

Electronic modules

–

–

–

Electric motors

Solenoids

Linear motors

Pneumatics/Hydraulics

– Directional

control valves

–

–

–

Directional

control valves

Isolating valves

Pressure valves

Working elements

Control elements

Processingelements

(Control elements)

Input elements

–

–

–

Cylinders

Motors

Components

–

–

–

–

–

Switches

Push button

actuators

Limit switches

Program

module

Sensors

2

Single-Acting Cylinder

Compressed air is applied to only one side of the single-acting cylinder.

The piston rod side of the cylinder is vented to atmosphere.

Single-acting cylinders can perform work in only in the advance direction of travel.

The piston rod is driven inwards by the force of a built-in spring or by external forces.

Piston

Reset spring

Piston rod

Bearing capEnd cap

Exhaust portSealing ring

Supply port Cylinder barrel

TP 201, Transparency 02

Single-Acting Cylinder

3

Double-Acting Cylinder

The double-acting cylinder is actuated in both directions with compressed air.

It can perform work in both directions of movement.

The force transmitted to the piston rod is greater during the advance stroke than

during the return stroke.

End cap

Piston Piston rod

Bearing cap

Scraper ring

Cylinder barrel


Double-Acting Cylinder

4

Non-return, Flow Control and Pressure Control Valves

Non-return valves block the flow in one direction and release it in the opposite

direction. A distinction is made between:

� Non-return valves

� Shuttle valves (OR)

� Dual pressure valves (AND)

� One-way flow control valves

� Quick exhaust valves

Pressure control valves influence the pressure or are controlled through the size of

the pressure. A distinction is made between:

� Pressure regulating valves

� Pressure relief valves

� Pressure sequence valves

Sloping arrow – the valve is adjustable

Non-return valves

Flow control valve

Pressure control

valve

– Non-return valve (check valve)

– Flow control valve (throttle valve), adjustable

– Non-return valve, spring-loaded

– Shuttle valve (OR function)

– Quick exhaust valve

– One-way flow control valve

– Adjustable pressure regulating valve without relief port

– Adjustable pressure regulating valve with relief port

– Pressure sequence valve with external supply line

– Pressure-relief valve

– Pressure sequence valve-combination

– Dual pressure valve (AND function)

12

3

2

2

2

2

1

1

1

1

3

12

2

1


Non-return, Flow Control and Pressure Control Valves

Non-return valves

Flow control valve

Pressure control

valve

– Non-return valve (check valve)

– Flow control valve (throttle valve),adjustable

– Non-return valve, spring-loaded

– Shuttle valve (OR function)

– Quick exhaust valve

– One-way flow control valve

12

3

– Adjustable pressure regulating valvewithout relief port

– Adjustable pressure regulating valvewith relief port

– Pressure sequence valvewith external supply line

– Pressure-relief valve

2

2

2

2

1

1

1

1

– Pressure sequencevalve-combination

3

12

2

1

– Dual pressure valve (AND function)

5

Pressure Regulating Valve

Pressure regulators have the function of keeping the output pressure mainly

constant, independent of variations in the input pressure and the air consumption.

If the pressure rises at the outlet, the diaphragm moves against the spring force and

the flow cross-section at the valve seat is reduced or closed.

If the pressure drops at the outlet, the spring presses against the diaphragm and the

passage cross-section at the valve seat is enlarged or opened.

The output pressure is adjustable.

The input pressure must be higher than the output pressure.

P1 P2 P1 P2

1

3

2

P1 P2


Pressure Regulating Valve

1

3

2

P1 P2

6

One-Way Flow Control Valve

The check element blocks the flow of air in one direction, so that it flows across an

adjustable throttle in this direction.

The air flow from the opposite direction lifts the seal of the check element from the

seat. The compressed air can flow almost unrestricted in this direction.

The valve should be installed as close as possible to the cylinder.

4

5

2

1Y1 1Y2

31

1A

1V2 1V3

1V1


One-Way Flow Control Valve

4

5

2

1Y1 1Y2

31

1A

1V2 1V3

1V1

7

Quick Exhaust Valve

Quick exhaust valves are used to achieve the maximum advance and retract speed

of pneumatic cylinders.

To increase the effectiveness of the valve, it should be mounted directly on the

cylinder or in the immediate vicinity of the supply or exhaust ports of the cylinder.

2

3

2

1Y1

1 3

1A

1

1V2

1V1 1V1

2

3

1Y2

13

1A

1

1V2

4

5

2

2

1

3

2

1

3

�

�


Quick Exhaust Valve

2

3

2

1Y11 3

1A

1

1V2

1V1 1V1

2

3

1Y2

13

1A

1

1V2

4

5

2

2

1 3

2

1

3

2

1

3

8

Conversion of Electrical Signals into Pneumatic Signals

If control systems are using compressed air and electricity as working mediums,

converter systems must be used.

Solenoid valves convert electrical signals into pneumatic signals.

Solenoid valves consist of:

� A pneumatic valve

� A coil which switches the valve

2

1 3

unactuated actuated

33

11

22

2

1 3

Conversion of Electrical Signals into Pneumatic Signals

unactuated actuated

33

11

22


9

Conversion of Pneumatic Signals into Electrical Signals

The PE converter is actuated with compressed air. When the pressure reaches a

preset value, an electric signal is generated.

The pressure of a pneumatic signal works against an adjustable spring.

If the pressure working against the diaphragm overcomes the spring force, a stem

actuates an electrical switch contact.

The electrical switching element can be normally closed, normally open or

changeover contact.

14

1414

unactuatedactuated


Conversion of Pneumatic Signals into Electrical Signals

14

1414

unactuatedactuated

10

Switching Symbols for Valves

Pneumatic components are normally shown in the deenergized condition in circuit

diagrams.

Valve switching positions are represented by a square.

The number of squares corresponds to the number of switching positions.

Functions and modes of operation are drawn inside the square:

� Lines indicate the flow paths.

� Arrows indicate the flow direction.

� Closed ports are represented by two lines drawn at right angles to one another.

The connecting lines are drawn outside on the square.

The valve switching position is shown by a square.


Lines indicate the flow paths, arrows indicate the direction of flow.

Closed ports are shown by two lines drawn at right angles to one another.

The connecting lines for supply and exhaust air are drawn outside the square.


Switching Symbols for Valves

The valve switching position is shown by a square.


Lines indicate the flow paths, arrows indicate the direction of flow.

Closed ports are shown by two lines drawn at right angles to one another.

The connecting lines for supply and exhaust air are drawn outside the square.

11

Directional Control Valves: Ports and Switching Positions

Information about the type of valve can be established from the following features:

� Number of ports

� Number of switching positions

� Port numbering

The following applies to the numbering of the ports:

� Air supply port 1

� Exhaust ports 3, 5

� Working or outlet ports 2, 4

2/2-way valve, normally open position

4/2-way valve flow from 1 2 and from 4 3� �

5/2-way valve flow from 1 2 and from 4 5� �

5/3-way valve, mid-position closed

3/2-way valve, normally closed position


Number of switching positions

Number of ports

4

4

4

2

2

2

2

2

2

3

3

3

3

3

1

1

1

1

1

1

5

5

Directional Control Valves:Ports and Switching Positions


4/2-way valveflow from 1 2 and from 4 3� �

5/2-way valveflow from 1 2 and from 4 5� �

5/3-way valve, mid-position closed

3/2-way valve, normally closed position


Number of switching positions

Number of ports

4

4

4

2

2

2

2

2

2

3

3

3

3

3

1

1

1

1

1

1

5

5


12

Function Principle of a Solenoid Coil

When an electric current flows through a coil, a magnetic field is generated.

The following applies to the strength of the magnetic field:

� Increasing the number of windings increases the field.

� Increasing the strength of the current increases the field.

� Lengthening the coil reduces the field.

A soft iron core (armature) is drawn into a coil through which a current is flowing.

Coil winding

Soft iron core


Function Principle of a Solenoid Coil

Coil winding

Soft iron core

13

2/2-Way Solenoid Valve without Pilot Control

Normally-closed position, spring return

Solenoid coil deenergized

� Port 1 is blocked.


� Exhausting is not possible.

Solenoid coil energized

� The armature is raised.

� Compressed air flows from port 1 to port 2.

2

1

1 12 2


2/2-Way Solenoid Valve without Pilot Control2

1

1 12 2

14

Solenoid Valves with Pilot Control

Solenoid valves with pilot control consist of:

� An electromagnetically-actuated pilot control valve.

� A pneumatically-actuated main valve.

In comparison with solenoid valves without a pilot control, solenoid valves with a

pilot control are distinguished by:

� Lower force required to actuate the armature.

� Smaller dimensions of the coil head.

� Lower power consumption.

� Less heat generated.

An electrical signal isapplied to the solenoidcoil

The solenoid coilactuates the pilotcontrol valve

The pilot controlactuates the valve


Solenoid Valves with Pilot Control

An electrical signal isapplied to the solenoidcoil

15

3/2-Way Single Solenoid Valve with Pilot Control

Normally-closed position, spring return, manual override



� Port 2 is vented to port 3.

� The pilot control channel is blocked by the armature seal on the valve side.

� The space above the valve piston is vented through the armature guide tube.


� The armature is lifted and the armature seal on the coil side blocks the vent hole

in the armature guide tube, while the armature seal on the valve side opens the

pilot control channel.

� Compressed air from port 1 flows through the pilot control channel and actuates

the valve piston.



2

1 3

33

11

22

2

1 3


33

11

22


16


Spring returned, manual override


� Compressed air flows from port 1 to 2.

� Port 4 is vented to 5.


� The pilot control channel is blocked.

� The space above the valve piston is vented through the armature guide tube.


� The armature is lifted and the armature seal on the coil side blocks the vent in

the armature guide tube, while the armature seal on the valve side opens the

pilot control channel.

� Compressed air from port 1 flows through the pilot control channel and actuates

the valve piston.




4

4

2

2

1

1

14

14

3

3

5

5

84

84

3

3

2

2

1

1

4

4

5

5

84

84

14

14



4

4

2

2

1

1

14

14

3

3

5

5

84

84

3

3

2

2

1

1

4

4

5

5

84

84

14

14

17

5/2-Way Double Solenoid Valve with Pilot Control

Manual override

Solenoid coil Y1 energized, solenoid coil Y2 deenergized

� The valve switches over.


� Compressed air flows from Port 1 to Port 2.

� Port 4 is vented to Port 5.

Both solenoid coils deenergized

� The valve retains its previous switching position.

Solenoid coil Y2 energized, solenoid coil Y1 deenergized

� The valve switches over.




4

4

2

2

1

1

14

14

12

12

3

3

5

5

84

84

82

82

3214584 82

14 12

3214584 82

14 12


5/2-Way Double Solenoid Valve with Pilot Control

4

4

2

2

1

1

14

14

12

12

3

3

5

5

84

84

82

82

3214584 82

14 12

3214584 82

14 12

18

5/3-Way Solenoid Valve

The three switching positions of an electrically-actuated pilot-controlled

5/3-way valve:

1. In the normal position, the solenoid coils are deenergized and the piston is

centered in its mid-position by the two springs. Ports 2 and 3 as well as 4 and 5

are connected. Port 1 is blocked.

2. If current is applied to the lefthand solenoid coil, the piston moves to the right.

Ports 1 and 4 as well as 2 and 3 are connected with each other.

3. If current flows through the righthand solenoid coil, the piston moves to the left.

In this position, Ports 1 and 2 as well as 4 and 5 are connected.

Each of the two actuated switching positions is held as long as current flows through

the corresponding solenoid coil. If the flow of current is interrupted, the piston

switches back to the mid-position.

4

4

2

2

5

5

3

3

1

1

12

12

14

14

84

84

82

82

4 2

5 31

1214

84 82

3

3

3

2

2

2

1

1

1

4

4

4

5

5

5

84

84

84

82

82

82

14

14

14

12

12

12


4

4

2

2

5

5

3

3

1

1

14

14

12

12

14

14

84

84

82

82

4 2

5 31

5/3-Way Solenoid Valve

14 1214

84 82

3

3

3

2

2

2

1

1

1

4

4

4

5

5

5

84

84

84

82

82

82

14

14

14

12

12

12

19

Power Supply Units

It is necessary to distinguish between an alternating current and a direct current

power supply.

� Is supplied from the mains

� 3-phase or single-phase form

� Sinusoidal-shaped voltage of fixed frequency

� Relatively constant amplitude

� Voltage change through transformers

� Is supplied by power supply devices

Modules of direct current power supply devices

� Mains transformer

� Rectifier

� Stabilization

Batteries and rechargeable batteries

� Used for buffering in case of mains failure.

� Used in portable devices.

+

Transformer StabilizerRectifier

Power supply unit

Alternating current Direct current Battery

Alternating current

Direct current


Power Supply Units

Transformer StabilizerRectifier

Power supply unit

Alternating current Direct current Battery

+-

20

Switching Contacts and Types of Actuation

The following switch contact designs are used as input and processing elements:

� Normally-open contact

� Normally-closed contact

� Changeover contact

Types of actuation for switching elements are:

� Manual

� Mechanical

� Relay

� Magnet field

Normally-opencontacts

Changeoverswitch

Mechanically connectedcontacts

Rotary switch withnormally open contactsmanually actuatedby turning

Push-button withnormally open contactsmanually actuatedby pushing

Limit switch with normally openor normally closed contacts,mechanically actuated

Normally-closedcontacts


Switching Contacts and Types of Actuation

Normally-opencontacts

Changeoverswitch

Mechanically connectedcontacts

Rotary switch withnormally open contactsmanually actuatedby turning

Push-button withnormally open contactsmanually actuatedby pushing

Limit switch with normally openor normally closed contacts,mechanically actuated

Normally-closedcontacts

21

Types of Actuation of Switching Elements

Frequently used types of actuation are

� Pushbuttons

� Roller levers

� Roller lever with idle return

Two types of actuation are shown

� Pushbutton, as changeover switch

� Latching rocker switch, as normally-open contact

Identifying letters in electrical circuit diagrams: S (S1, S2, ...)

Connection(normally-closed contact)

Connection(normally-open contact)

Switching element

Type of actuation(push-button)

4

3

2

1

4

3

4 4

3


Types of Actuation of Switching Elements

4

3

2

1

4

3

4 4

3

Connection(normally-closed contact)

Connection(normally-open contact)

Switching element

Type of actuation(push-button)

22

Switching Symbols for Solenoid Coils and Relays

In electropneumatics, the solenoid coil is the element that switches the valves.

Identifying letters in electrical circuit diagrams: Y (Y1, Y2, ...)

A relay switches 1, 2 or more contacts. The relay can also be a time or temperature-

controlled element.

Identifying letters in electrical circuit diagrams: K (K1, K2, ...)

Y1

K1

Electro-magneticallyactuated on both sides

Electro-magneticallyactuated,with pilot control

Contactor or relay with3 normally open contactsand 1 normally closed contact

Electro-magneticallyactuated on one side,with spring return

Representation inelectrical circuitdiagrams


Switching Symbols for Solenoid Coils and Relays

Electro-magneticallyactuated on both sides

Electro-magneticallyactuated,with pilot control

Contactor or relay with3 normally open contactsand 1 normally closed contact

Electro-magneticallyactuated on one side,with spring return

Representation inelectrical circuitdiagrams

K1

Y1

23

The Relay

In practice, the construction of a relay can be very different, but the function is

nevertheless the same in principle:

� When a voltage is applied to the relay coil through contacts A1 and A2, an

electric current flows through the windings. A magnetic field is built up and pulls

the armature against the core of the coil.

� Switch contact 1 is connected with switch contact 4.

� After removing the voltage, the armature is brought back into its initial position

by a spring.

� Switching contact 1 is connected with switching contact 2.

A relay can have multiple switching contacts which can be actuated simultaneously.

There are the following types, for example:

� Polarised relay

� Current impulse relay

� Time relay

� Thermal relay

124A1 A2

A1

A2

221412 24

11 21

Coil core

Insulation

Contact

Return spring

Relay coil

Armature


The Relay

Coil core

Insulation

Contact

Return spring

Relay coil

Armature

124A1 A2

A1

A2

221412 24

11 21

24

Magnetic Proximity Switches (Reed Switches)

Reed switches are actuated through a magnetic field. In industrial applications, most

reed switches are used with LED displays.

The illustration shows a three-wire reed switch. It has three connections:

� One connection for the positive power supply

� One connection for the negative power supply

� One signal or switch output

The reed switch is attached directly to the body of a cylinder. It is actuated by a

magnetic ring on the cylinder piston.

When the magnetic ring moves past the reed switch, the switching contacts are

closed as a result of the magnetic field and thus provide an output signal.

Identifying letters in electrical circuit diagrams: B (B1, B2, ...)

BN

BK

BU

+24V

0V


Magnetic Proximity Sensors (Reed Switches)

BN

BK

BU

+24V

0V

25

Electrical Output Devices

Supply acoustic signals:

� For example, horns, sirens

� Identifying letters in electrical circuit diagrams: H (H1, H2, ...)

Supply optical signals:

� For example, lamps, LEDs

� Identifying letters in electrical circuit diagrams: H (H1, H2, ...)

Do work:

� For example, electric motors

� Identifying letters in electrical circuit diagrams: M (M1, M2, ...)

M

Signalling device

Motors

Audible indicator:

Illuminatingindicators:

Horn

DC motor

Lamp Light emitting diode (LED)

Siren Bell

Signalling device

Motors


Electrical Output Devices

Audible indicator:

Illuminatingindicators:

Horn

DC motor

Lamp Light emitting diode (LED)

Siren Bell

M

26

The AND Logic Function

The AND logic function consists of at least two switching elements connected in

series:

� The AND logic function can have two or more inputs. A combination of switches

and sensors may be involved.

� The function is represented through a logic symbol with two inputs and one

output.

� Both input signals must be present to switch the output.

&

+24V

0V

S2

H1

S1

1

Output(lamp H1)Input 2

(S2)

Input 1(S1)


The AND Logic Function

OutputInput 2

Input 1&

+24V1

0V

S2

H1

S1

27

The OR Logic Function

The OR logic function consists of at least two switching elements connected in

parallel:

� The OR logic function can have two or more inputs. A combination of switches

and sensors may be involved.

� The function is represented through a logic symbol with two inputs and one

output.

� Only one input signal needs to be present to switch the output.

�1

+24V

0V

H1

S1 S2

1 2

Output(lamp H1)Input 2

(S2)

Input 1(S1)


The OR Logic Function

OutputInput 2

Input 1�1

+24V

0V

H1

S1 S2

1 2

28

Control Chain

The structure of the control chain supports:

� The allocation of components with comparable functions to a group of elements.

� The avoidance of lines crossing each other in pneumatic and electrical circuit

diagrams.

� The preparation of clearly structured and uniformly designed circuit diagrams.

The principle of the control chain should be understood as being only a guideline.

The signal flow of the control system defines the structure of the control chain:

� In the pneumatic circuit diagram, the signal flow is represented from bottom to

top.

� In the electrical circuit diagram, the signal flow is represented from top to

bottom.

+24V

Signalinput

Sig

na

l fl

ow

Sig

na

l fl

ow

Signalprocessing

Signaloutput

0V

S1

S2

K1K1

1Y1

2

1 2

4

5

2

1Y1

31

1A

1V1


Control Chain

+24V

Signal input

Signal processing

Signal output

0V

S1

S2

K1K1

1Y1

2

1 2

4

5

2

1Y1

31

1A

1V1

29

Direct Actuation of a Single-Acting Cylinder

After actuating S1, current flows through the coil 1Y1, which switches the valve 1.1.

Compressed air flows from port 1 to port 2, and the piston rod advances.

If S1 is no longer actuated, there is no current through coil 1Y1. Valve 1.1 switches

back into the initial position.

The cylinder is vented through port 3 of valve 1.1, and the piston rod retracts.

1Y1

2

1Y1

1A

1V1

+24V

0V

S1

1

1 3


Direct Actuation of a Single-Acting Cylinder

1Y1

2

1Y1

1A

1V1

+24V

0V

S1

1

1 3

30

Indirect Actuation of a Double-Acting Cylinder

The use of indirect actuation depends upon:

� The force which is required for the actuation of the positioner

� The complexity of the circuit

� The switching power of the contacts

� Whether or not the system is remote controlled

K1 1Y1

1A

+24V

0V

S1 K1

1 2

4

5

2

1Y1

3

13

A1

A2

13

14 14

1

1V1


Indirect Actuation of a Double-Acting Cylinder

1Y1

1A+24V

0V

S1

1 2

4

5

2

1Y1

3

13

14

1

1V1

31

Electrical Memory Circuit – Dominant Set

A relay can be held in the switched condition if a holding current path is switched in

parallel to the ON pushbutton through an internal normally-open contact in the

relay.

An OFF pushbutton must be built into the memory circuit. The installed position of

the OFF pushbutton determines the function of the memory circuit.

A memory circuit in which a pushbutton (S2, normally-closed) is connected in series

with a relay holding contact (normally-open) is a dominating set memory circuit.

In this dominating set memory circuit, the pushbutton S1 dominates the pushbutton

S2.

If S1 and S2 are pressed simultaneously, current flows through the relay coil K1.

+24V

0V

S1

S2

K1 K1

2

3

1 2 3

13 23

14 24

K1 H1

© TP 201, Transparency 31

Electrical Memory Circuit – Dominant Set

+24V

0V

S1

S2

K1 K1

K1 H1

23

1 2 3

13 23

14 24

32

Electrical Memory Circuit – Dominant Reset

A relay can be held in the switched condition if a holding current path is switched in

parallel to the ON pushbutton to the relay coil through an internal normally-open

contact in the relay.

An OFF pushbutton must be built into the memory circuit. The installed position of

the OFF pushbutton determines the function of the memory circuit.

A memory circuit in which a pushbutton (S1, normally-open) and a relay holding

contact (normally-open) are connected in parallel and then in series with a

pushbutton (S2, normally-closed) is a dominating reset memory circuit.

In this dominating reset memory circuit, the pushbutton S2 dominates the

pushbutton S1.

If S1 and S2 are pressed simultaneously, no current flows through the relay coil K1.

+24V

0V

S1

S2

K1 K1

2

3

1 2 3

13 23

14 24

K1 H1

© TP 201, Transparency 32

Electrical Memory Circuit – Dominant Reset

+24V

0V

S1

S2

K1 K1

23

1 2 3

13 23

14 24

K1 H1

33

Electropneumatic Memory Circuit with Double Solenoid Valve

Double solenoid valves are also called bistable valves or memory valves:

� The valve illustrated is actuated by two solenoid coils.

� The valve retains the switched position brought about through energising one of

the coils, even when the signal to switch the valve is cancelled.

� The switched position is reversed only when a signal is applied to the opposite

coil or a manual override is operated.

� To reverse the switched position, a signal only needs to be applied to one coil.

1A 1S2

4

5

2

1Y1 1Y2

31

1V1

1Y1 1Y2

+24V

0V

S1

1 32 4

1S2 K1 K2

K1 K2

3 4


Electropneumatic Memory Circuit with Double Solenoid Valve

1A 1S2

4

5

2

1Y1 1Y2

31

1V1

1Y1 1Y2

+24V

0V

S1

1 32 4

1S2 K1 K2

K1 K2

3 4

34

Stroke-Dependent Control

Limit switches with roller lever actuation are frequently used to check the position of

pneumatic actuators in simple circuits.

The use of limit sensors in a control depends upon the required accuracy of the

sensor.

Decisive factors are:

� The reliability

� The safety

� The complexity of the circuit

1A 1S21S1

4

5

2

1Y1 1Y2

31

1V1

1Y1 1Y2

+24V

0V

S1

1S1

1 32 4

1S2 K1 K2

K1 K2

3 4


Stroke-Dependent Control

1A 1S21S1

4

5

2

1Y1 1Y2

31

1V1

1Y1 1Y2

+24V

0V

S1

1S1

1 32 4

1S2 K1 K2

K1 K2

3 4

35

Pressure-Dependent Control

A pneumatic-electric signal converter measures the air pressure in the supply line of

cylinder 1A and compares it with a preset value.

As soon as this value is reached, the signal converter generates an electrical signal.

1A

4

5

2

p

1Y1

1B1

1Y2

31

1V1

1Y1 1Y2

+24V

0V

S1

1 6 7

K1 K2

K3

K1

5 6 6

1B2

1B2 1B1

p

2 43 5

K2 K3


Pressure-Dependent Control

1A

4

5

2

p

1Y1

1B1

1Y2

31

1V1

1Y1 1Y2

+24V

0V

S1

1 6 7

K1 K2

K3

K1

5 6 6

1B2

1B2 1B1

p

2 43 5

K2 K3

36

The Electropneumatic Circuit Diagram

The pneumatic and electrical parts of an electropneumatic circuit diagram are

prepared separately, but their contents are closely related.

In the pneumatic part, signal flow is presented from bottom to top.

In the electrical part, signal flow is presented from top to bottom.

In the electrical circuit diagram, the current paths are numbered consecutively from

left to right.

The common circuit diagram elements form the interfaces between the pneumatic

and the electrical circuits. In this case, they are the coils 1Y1 and 2Y1, as well as the

limit sensors 1B1, 1B2, 2S1 and 2S2.

44

55

22

2Y11Y1

3311

2A1A

2V11V1

2S21B21B1

2S1

1Y1 2Y1

+24V

0V

Start 2S1

K6 K5

1B1 1B2

1 3 5 6 8 10 12 13117 92 4

2S2K3 K4 K5 K3 K4K2

K1

K3 K4 K5

K1 K2 K3 K4 K5 K6

5 7 6

7

12

8

9

13

10

11

13 5


The Electropneumatic Circuit Diagram

44

55

22

2Y11Y1

3311

2A1A

2V11V1

2S21B21B1

2S1

1Y1 2Y1

+24V

0V

Start 2S1

K6 K5

1B1 1B2

1 3 5 6 8 10 12 13117 92 4

2S2K3 K4 K5 K3 K4K2

K1

K3 K4 K5

K1 K2 K3 K4 K5 K6

5 7 67

12

89

13

1011

13 5

37

Circuit Diagram Structure

The electropneumatic circuit diagram consists of two parts:

� Pneumatic

� Electrical

� The arrangement of the components follows the signal flow accordingly from

bottom to top.

� Cylinders and valves are drawn horizontally.

� The outward travel motion of cylinders should be from left to right.

� The arrangement of the components follows the signal flow accordingly from top

to bottom.

� The electrical circuit diagram can be subdivided into a control part and a power

part.

1A

1V2

0Z

1S2

4

5

2

1Y1 1Y2

31

1V1

1Y1 1Y2

+24V

Control section Power section

0V

S1

K2

1 32 4

1S2 K1 K2

K1 K2

3 4

Pneumatic

Electrical


Circuit Diagram Structure

1A

1V2

0Z

1S2

4

5

2

1Y1 1Y2

31

1V1

1Y1 1Y2

+24V

0V

S1

K2

1 32 4

1S2 K1 K2

K1 K2

3 4

38

Displacement-Step Diagram

In a displacement-step diagram, the motion sequences of an actuator in a control

system are presented graphically:

� Movements of the cylinder within a step are represented by a line moving

diagonally upwards (advancing) or downwards (retracting).

� Horizontal lines represent the position of the cylinder in the advanced or

retracted end position.

� If the movements of several actuators are to be represented, they are arranged

under each other for every individual step.

� This arrangement clarifies the relationship between the movements of the

individual actuators in every step.

1

0

1

0

1

Step

2 3 4 5=1

1A

2A


Displacement-Step Diagram

1

0

1

0

1

Step

2 3 4 5=1

1A

2A

39


The terminal connection diagram shows the physical implementation of the current

circuit.

The identifications used in the circuit diagram are used in the terminal connection

diagram.

The terminal points and the cables are numbered. This facilitates the setting-up of

the controller as well as troubleshooting and maintenance.

X1-1 X1-2

3 1

11 11

21

4 2

14 14

24

X1-3 X1-4

X1-9 X1-12 X1-14

X1

X1 14

15

14

20

13

19

12

18

11

17

10

16

9

8

7

6

5

4

3

2

1

1Y1

K1 114

3

+24V

K2 21

X1 110V

K1 A2

K2 A2

X1 17

1B1 X1 1+

1B1

1S2

K1

K2

A1

24

1B1

1S2

X1

X1

5

8

1Y1

X1 2S1

X1 31

S1

K2 112

9

12X1

4

5

2

1Y1

31

1A

1V1

1S21B1

1Y1

+24V

0V

S1 1S21B1

1 3 4 52

K1 K2

K2

K1 K2

3 4

5

X1-11

X1-16

X1-10

A1 A1

A2 A2

X1-5 X1-8X1-6 X1-7

X1-13 X1-15

X1-17

Connection

code

Component

code

Co

mp

on

en

tco

de

Connection

code

Term

ina

l n

o.

X1

Jum

pe

r

Targ

et

Targ

et

Machine Control cabinet



X1-1 X1-2

3 1

11 11

21

4 2

14 14

24

X1-3 X1-4

X1-9 X1-12 X1-14

Co

nn

ect

ion

cod

e

X1

X1 14

15

14

20

13

19

12

18

11

17

10

16

9

8

7

6

5

4

3

2

1

1Y1

K1 114

-

3

+24V

Co

mp

on

en

tco

de

Co

mp

on

en

tco

de

Co

nn

ect

ion

cod

e

Term

ina

ln

o.

X1

Jum

pe

r

Targ

et

Targ

et

K2 21

X1 110V

K1 A2

K2 A2

X1 17

1B1 X1 1+

1B1

1S2

K1

K2

A1

24

1B1

1S2

X1

X1

5

8

1Y1

X1 2S1

X1 31

S1

K2 112

9

12X1

Machine Control cabinet

4

5

2

1Y1

31

1A

1V1

1S21B1

1Y1

+24V

0V

S1 1S21B1

1 3 4 52

K1 K2

K2

K1 K2

3 45

X1-11

X1-16

X1-10

A1 A1

A2 A2

X1-5 X1-8X1-6 X1-7

X1-13 X1-15

X1-17

40

Checklist for the Terminal Connection Diagram

In the preparation of a terminal connection diagram, the structure of the control

should be checked once again:

� Is every current path connected to the positive +24V bus bar through a terminal?

� Is every current path connected to the negative 0 V bus bar through a terminal?

� Are all external components, such as switches, sensors and valve coils connected

with one terminal per connection to the current circuit?

� Are all connections to the +24 V and 0 V shown in the terminal connection

diagram?

� Are all external components included in the terminal connection diagram

provided with their connection identifications?

� Check all current paths systematically and complete the terminal connection

diagram.

� Note that not all connections – such as the relay contacts, for example – must be

included in the terminal connection diagram.

Enter all external components with thedesignation of the connection in theterminal connection diagram.

Systematically check all current pathsand complete the wiring diagram.

Not all of the connections have to beentered in the wiring diagram(e.g. relay connections are exempt).

Note:

� �

�

�

�

Each current path must be connectedto the positive +24 V rail via a terminal.

Each current path must be connectedto the negative 0 V rail via a terminal.

External components, such as switches,sensors and solenoids are eachconnected via one terminal per unit.

Identify the connection point for +24 Vand 0 V in the wiring diagram.


Checklist for the Terminal Connection Diagram

Each current path must be connectedto the positive +24 V rail via a terminal.

Each current path must be connectedto the negative 0 V rail via a terminal.

External components, such as switches,sensors and solenoids are eachconnected via one terminal per unit.

Identify the connection point for +24 Vand 0 V in the wiring diagram.

Enter all external components with thedesignation of the connection in theterminal connection diagram.

Systematically check all current pathsand complete the wiring diagram.

Not all of the connections have to beentered in the wiring diagram(e.g. relay connections are exempt).

Note:

� �

�

�

�

�

�

41

Protective Circuits for Inductive Loads

If the current flowing to an inductive load, for example, a solenoid coil, is

interrupted, the magnetic field collapses.

A high induction voltage can be generated which can have the following effects:

� Damage to the coil insulation

� Burning of contacts

This can be avoided through protective circuits using diodes.

I1

I = 01

I = IM 1

IM

I = 0D

I = ID M

+24V +24V

0V 0V


Protective Circuits for Inductive Loads

I1 I = 01

I = IM 1 IMI = 0D I = ID M

+24V +24V0V 0V

42

Alterable Controls

Relay-controlled systems are hard wired. The relay control can be replaced in whole

or in part by a programmable controller.

The structure of a system that is controlled via a programmable logic controller (PLC)

is similar to that of a relay-controlled system. Both systems can be subdivided as

follows:

� Signal input

� Signal processing

� Signal output

The signal processing part is the part that can be hard wired or freely programmable.

Switch

Inputs

Signalinput

Signaloutput

Signal processing

Relays Contacts

Outputs

Program:

WHEN

THENOTHERWISE

WHEN

THENOTHERWISE

E0.1

E0.2

A0.1

A0.1

E0.3

E0.4

A0.2

A0.2

RESET

RESET

AND

SET

AND

SET

Processor

S1

S2

S3

S4

K1

K2

K3

K4

H1

H2

K1 K2

K3 K4

+ +

S1

S2

S3

S4

E1

E2

E3

E4

H1

H2

A1

A2

+ +


Alterable Controls

S1

Switch

Inputs

Signalinput

Signaloutput

Signal processing

Relays Contacts

Outputs

S2

S3

S4

K1

K2

K3

K4

H1

H2

K1 K2

K3 K4

+ - + -

S1Program:

WHEN

THENOTHERWISE

WHEN

THENOTHERWISE

E0.1E0.2

A0.1A0.1

E0.3E0.4

A0.2A0.2

RESET

RESET

AND

SET

AND

SET

S2

S3

S4

E1

E2

E3

E4Processor

H1

H2

A1

A2

+ -+ -

Documents

Fundamentals of Electropneumatics