nota pneumatic and hydraulic system

INSTALLATION OF PNEUMATIC CIRCUIT

3.2.2 Example 2 : The logic AND function (Press machine)

The piston rod of the cylinder is to advance only if a workpiece is inserted
in the workpiece retainer, a guard has been lowered and the operator
presses the pushbutton valve. Upon the release of the pushbutton or if
the guard is no longer in its lower position, the cylinder is to retract to the
initial position.

42

53
1

2
11

2
11

1 S1 2 2 2
1S2 1S3
13 3 3
1 1

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INSTALLATION OF PNEUMATIC CIRCUIT

3.2.3 Example 3 : The logic OR function (Basic circuit)

A double acting cylinder is to advance if one of two pushbuttons is
operated. If the pushbutton is then released, the cylinder is to retract.

Example circuit 1 Example circuit 2

1S3

42

53 42
1 53

1

2 2
11 1

2 2 1 1 S2 2 2
13 13 1S3
1 S1 2 13
13
13

BPLK 7/24 DMV 1152/3152/4152/5152

INSTALLATION OF PNEUMATIC CIRCUIT

Example circuit 3

1S3 1S4

42
53

1

2
11

2
11

1 S1 2 1 S2 2 2 3 2
1S3 1S4
13 1
31 13

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INSTALLATION OF PNEUMATIC CIRCUIT

3.2.4 Example 4 : The logic OR function

A double acting cylinder is used to transfer parts from a magazine. If
either a pushbutton or a foot pedal is operated, the cylinder is to advance.
Once the cylinder is fully advanced, it is to retract to the initial position. A
3/2 way roller lever valve is to be used to detect the full extension of the
cylinder.

1S3

2 42
11 53

1

2 2 2
13 13 1S3

13

BPLK 9/24 DMV 1152/3152/4152/5152

INSTALLATION OF PNEUMATIC CIRCUIT

3.3 SPEED CONTROL OF CYLINDERS

3.3.1 Example 1 : Memory circuit and speed control of a cylinder

The piston rod of a double acting cylinder is to advance when a 3/2 way
pushbutton valve is actuated manually. The cylinder is to remain
advanced until a second valve is actuated. The signal of the second valve
can only take effect after the first valve has been released. The cylinder is
to then return to the initial position. The cylinder is to remain in the initial
position until a new start signal as given. The speed of the cylinder is to
be adjustable in both directions.

42

53
1

22

13 13

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INSTALLATION OF PNEUMATIC CIRCUIT

3.3.2 Example 2 : Memory circuit and speed control of a cylinder

A double acting cylinder is to be used o transfer parts from a magazine.
The cylinder is to advance fully when a pushbutton is operated and then
retract automatically. Full extension is confirmed by a roller lever valve.
The cylinder is continued forward even if the pushbutton is released
before full extension is reached. The speed of the cylinder is to be
adjustable in both directions of motion.

1S2

42

2 53 2
13 1
1S2

1 3

BPLK 11/24 DMV 1152/3152/4152/5152

INSTALLATION OF PNEUMATIC CIRCUIT

3.3.3 Example 3 : The quick exhaust valve

The combined actuation of a manually actuated valve 1S1 and 1S2 to
advances a forming tool on an edge-folding device. The forming tool is
driven by a double acting cylinder. For rapid forward travel, the circuit
utilizes a quick exhaust valve. The retracting speed is to be adjustable. If
either of two valve are released, the tool returns to its initial position.

2
1

3

42

53
1

1 2
2 1

2

13 13

BPLK 12/24 DMV 1152/3152/4152/5152

INSTALLATION OF PNEUMATIC CIRCUIT

3.4 PRESSURE DEPENDENT CONTROL

3.4.1 Example 1 : Pressure dependent control

A plastic component is embossed using a die driven by a double acting
cylinder. The die is to advance and emboss the plastic when a
pushbutton is operated. The return of the die is to be effected when a
preset pressure is reached. The embossing pressure is to be adjustable.

42 2
53
3
1 1

2
13

12

BPLK 13/24 DMV 1152/3152/4152/5152

INSTALLATION OF PNEUMATIC CIRCUIT

3.4.2 Example 2 : Pressure dependent control; embossing of plastic
components.

A plastic component is embossed using a die powered by a double acting
cylinder. The return of the die is to be effected when the cylinder rod has
fully extended to the embossing position and the preset pressure is
reached. A roller lever valve is to be used to confirm full extension. The
signal for retracting must only be generated when the piston rod has
reached the embossing position. The pressure in the piston chamber is
indicated by a pressure gauge.

1S2

42
53

1

2

2 3
13 12 1

2
1S2

13

BPLK 14/24 DMV 1152/3152/4152/5152

INSTALLATION OF PNEUMATIC CIRCUIT

3.5 TIME DEPENDENT CONTROL

3.5.1 Example 1 : The time delay valve

A double acting cylinder is used to press together glued components.
Upon operation of a pushbutton, the clamping cylinder extends.
Once the fully advanced position is reached, the cylinder is to remain for
a time of T = 6 seconds and then immediately retract to the initial position.
The cylinder retraction is to be adjustable. A new start cycle in only
possible after the cylinder has fully retracted.

A0 A1

2 42 2
11 53
3
1 1
2
12 A1
13
2 2
13 A0

13

BPLK 15/24 DMV 1152/3152/4152/5152

INSTALLATION OF PNEUMATIC CIRCUIT

3.5.2 Example 2 : The time delay valve

A double acting cylinder is used to press together glued components.
Upon operation of a pushbutton, the clamping cylinder slowly advances.
Once the fully extended position is reached, the cylinder is to remain for a
time of T = 6 seconds and then immediately retract to the initial position.
A new start cycle is only possible after the cylinder has fully retracted and
after a delay of 5 seconds. During this delay the finished part is manually
removed and replaced with new parts for gluing. The retracting speed
should be fast, but adjustable.

1S1 1S2

42 12 2

53 2 3
1 1
3
2 1
11

12

2 2 2
13
13 1 3
1S1 1S2

BPLK 16/24 DMV 1152/3152/4152/5152

INSTALLATION OF PNEUMATIC CIRCUIT

3.6 MULTIPLE CYLINDER CONTROL

In the case of multiple cylinder circuits, a clear definition of the problem is
important. The representation of the desired motion of all actuators is described
using the displacement-step diagram. The special conditions for the start of the
sequence must also be defined.
If the motion diagram and auxiliary conditions have been clearly defined, drawing
of the circuit diagram can commence.
In order for a circuit to operate, it is essential to avoid overlapping signals. By an
overlapping signal, we understand signals applied simultaneously at the two
control ports of a double pilot valve. The following valves can be used to
eliminate signal overlap; roller lever valve with idle return or toggle lever valves,
time delay valves, reversing valves or sequencers.
To provide a better understanding of the methods, some examples are given for
the use of the roller lever valves with idle return and reversing valves.

BPLK 17/24 DMV 1152/3152/4152/5152

INSTALLATION OF PNEUMATIC CIRCUIT

3.6.1 Basic sequence

3.6.1.1 Example 1 : Co-ordinated motion

Two cylinders are used to transfer parts from a magazine onto a
chute. When a pushbutton is pressed, the first cylinder extends,
pushing the part from the magazine and positions it in preparation
for transfer by the second cylinder onto the out feed chute. Once
the part is transferred, the first cylinder retracts, followed by the
second.

a1 b1 a0 A
B
A+ B+ A- B-

St b0

Displacement-step diagram

1 2 3 4 5=1
a1 A-
A A+

a0 B+ B-
b1
B

b0

BPLK 18/24 DMV 1152/3152/4152/5152

INSTALLATION OF PNEUMATIC CIRCUIT a1 b1

Circuit diagram A+ B+

St b

A0 A1

42

2 53 A1
1
B0 3
1 2
B1

13

Start

2

13

BPLK 19/24 DMV

a0

A- B-

b0

B0 B1

42

53
1

2 2 3
13
A0
1

V 1152/3152/4152/5152

INSTALLATION OF PNEUMATIC CIRCUIT

3.6.2 Cascade System

3.6.2.2 Example 1 : Reversing valves

Using a transfer station, parts are to be transfer from a vertical
magazine onto a chute. The parts are pushed out of the magazine
by cylinder A and then transfer into a chute by cylinder B. The
piston rod of cylinder A may only retract once cylinder B is in initial
position. Limit switches and magnetic switches are used to
confirm cylinder positions.

A
B

Displacement-step diagram

1 2 3 4 5=1
1
A

0
1
B

0

BPLK 20/24 DMV 1152/3152/4152/5152

INSTALLATION OF PNEUMATIC CIRCUIT

Circuit diagram

A+ B+ B- A-

A0 A1 B0 B1

42 42

53 3 53
1 1

2 2
B0 A1

1 13

Start 2 42 2
13
53
1
B1

1 3
2 3

A0
1

BPLK 21/24 DMV 1152/3152/4152/5152

INSTALLATION OF PNEUMATIC CIRCUIT

3.6.2.3 Example 2 : Reversing valves

Using a transfer station, parts are to be transfer from a vertical
magazine onto a chute. The parts are pushed out of the magazine
by cylinder A and then transfer into a chute by cylinder B. The
piston rod of cylinder B may only extend once cylinder A is in
initial position. Limit switches and magnetic switches are used to
confirm cylinder positions.

Displacement-step diagram

1 2 3 4 5=1
1
A

0
1
B

0

BPLK 22/24 DMV 1152/3152/4152/5152

INSTALLATION OF PNEUMATIC CIRCUIT

Circuit Diagram

A+ A- B+ B-

A0 A1 B0 B1

42 42
53
53
1 1

Start 2 2 3

13 A0
1
1
2
3

2 42 2

B0 53 A1
1 1 13
2
42
B1
53 13
1

3

BPLK 23/24 DMV 1152/3152/4152/5152

INSTALLATION OF PNEUMATIC CIRCUIT

SUMMARY

In this chapter we have studied to :
1.

REFERENCES

1. Fundamentals Of Pneumatic Control Engineering Text Book, Festo Didactic, 1989
2. Electro-Pneumatics Basic Level TP 201 Text Book, Festo, 1998
3. FluidSim Pneumatic Software Version 4.0

BPLK 24/24 DMV 1152/3152/4152/5152

COMPONENTS SYMBOLS AND DESCRIPTIONS-ELECTRO-PNEUMATICS

CHAPTER 5: COMPONENTS SYMBOLS AND
DECRIPTIONS-ELECTRO-PNEUMATICS

INTRODUCTION

LEARNING OBJECTIVES

BPLK 1/16 DMV 1152/3152/4152/5152

COMPONENTS SYMBOLS AND DESCRIPTIONS-ELECTRO-PNEUMATICS

5.1 INTRODUCTION COMPONENTS SYMBOLS AND
DESCRIPTIONS

5.1.1 Pneumatic circuit diagram

The pneumatic circuit diagram of a control system shows how the various
pneumatic components are connected to each other and how they
interact. The graphical symbols representing the components are
arranged so as to obtain a clear circuit diagram in which there is as little
crossing of lines as possible. A pneumatic circuit diagram therefore does
not reveal the actual spatial arrangement of the components.

In a pneumatic circuit diagram the components are represented by
graphical (circuit) symbols, which are standardized according to DIN/ISO
1219-1. It must be possible to recognize the following characteristics from
a graphical symbol :
 Type of actuation
 Number of ports and their designations
 Number of switching positions
The symbols shown on the following pages are only those for
components which are used frequently in electro-pneumatic control
systems.

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COMPONENTS SYMBOLS AND DESCRIPTIONS-ELECTRO-PNEUMATICS

Graphical symbols for the power supply section

i. Supply
- Compressor with constant displacement
volume

- Accumulator, air reservoir

- Pressure source

ii. Maintenance

- Filter Filtration of dirt
particles

- Water separator, manually actuated

- Water separator, automatic

- Lubricator Metered quantities of oil
are added to the air flow

- Pressure Adjustable with relief port

regulating valve 3

iii. Combined symbols

- Service unit Consisting of water
separator, compressed
air filter, pressure
regulating valve,
pressure gauge
and lubricator

Simplified representation
of air service unit

Simplified representation
of a service unit without
lubricator

BPLK 3/16 DMV 1152/3152/4152/5152

COMPONENTS SYMBOLS AND DESCRIPTIONS-ELECTRO-PNEUMATICS

Graphical symbols of valves

i. Switching position are represented by squares

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

iii. Lines indicate flow paths, arrows indicate flow
Direction

iv. Closed ports are represented by two lines drawn
at right angles to each other

v. Connecting lines for supply air and exhaust air
are drawn on the outside of a square

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COMPONENTS SYMBOLS AND DESCRIPTIONS-ELECTRO-PNEUMATICS

Graphical symbols for directional control valves

Number of ports 2
Number of switching positions
i. 2/2 – way valve in flow direction 1
2
ii. 3/2 – way valve in closed position
13
iii. 3/2 – way valve in flow direction 2

iv. 4/2 – way valve 13
Flow from 1 – 2 and from 4 – 3 42

v. 5/2 – way valve 13
Flow from 1 – 2 and from 4 – 5 42

vi. 5/2 – way valve 53
Closed in mid position 1

42

53
1

BPLK 5/16 DMV 1152/3152/4152/5152

COMPONENTS SYMBOLS AND DESCRIPTIONS-ELECTRO-PNEUMATICS

Types of actuation for electro-pneumatic directional control valve
i. Manual operation
- General

- By pushbutton

ii. Mechanical resetting
- By spring

- Spring centered

iii. Electrical actuation
- By one solenoid

- By two solenoids

iv. Combined actuation
- Pilot actuated valve,
double solenoid,
manual override

v. Pneumatic actuation
- Single pilot actuation

- Double pilot actuation

BPLK 6/16 DMV 1152/3152/4152/5152

COMPONENTS SYMBOLS AND DESCRIPTIONS-ELECTRO-PNEUMATICS

Graphical symbols for non return valves, flow control valves and quick exhaust valve
i. Non return valve
ii. Non return valve, spring loaded
iii. Flow control valve, adjustable
iv. One way flow control valve, adjustable

v. Quick exhaust valve

3

BPLK 7/16 DMV 1152/3152/4152/5152

COMPONENTS SYMBOLS AND DESCRIPTIONS-ELECTRO-PNEUMATICS

Graphical symbols for pressure control valves 1
i. Adjustable pressure regulating valve
without relief port 2

ii. Adjustable pressure regulating valve 3
with relief valve 1

iii. Pressure sequence valve with external 2
supply line
1
iv. Pressure relief valve 12

v. Pressure sequence valve – combination 2
1

2

2

3
12 1

BPLK 8/16 DMV 1152/3152/4152/5152

COMPONENTS SYMBOLS AND DESCRIPTIONS-ELECTRO-PNEUMATICS

Graphical symbols for pneumatic power components

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COMPONENTS SYMBOLS AND DESCRIPTIONS-ELECTRO-PNEUMATICS

5.2 ELECTRICAL SYMBOLS

Electrical symbols : Basic functions

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COMPONENTS SYMBOLS AND DESCRIPTIONS-ELECTRO-PNEUMATICS

Graphical symbols for contacts : basic functions and delayed actuation

BPLK 11/16 DMV 1152/3152/4152/5152

COMPONENTS SYMBOLS AND DESCRIPTIONS-ELECTRO-PNEUMATICS

Graphical symbols for manually operated switching devices

BPLK 12/16 DMV 1152/3152/4152/5152

COMPONENTS SYMBOLS AND DESCRIPTIONS-ELECTRO-PNEUMATICS

Graphical symbols for electromechanical drives

BPLK 13/16 DMV 1152/3152/4152/5152

COMPONENTS SYMBOLS AND DESCRIPTIONS-ELECTRO-PNEUMATICS

Graphical symbols for relays and contactors

BPLK 14/16 DMV 1152/3152/4152/5152

COMPONENTS SYMBOLS AND DESCRIPTIONS-ELECTRO-PNEUMATICS

Graphical symbols for sensors

BPLK 15/16 DMV 1152/3152/4152/5152

COMPONENTS SYMBOLS AND DESCRIPTIONS-ELECTRO-PNEUMATICS

SUMMARY

In this chapter we have studied to :
1.

REFERENCES

1. Fundamentals Of Pneumatic Control Engineering Text Book, Festo Didactic, 1989
2. Electro-Pneumatics Basic Level TP 201 Text Book, Festo, 1998
3. FluidSim Pneumatic Software Version 4.0

BPLK 16/16 DMV 1152/3152/4152/5152

ELECTRICAL COMPONENTS AND CIRCUIT DEVELOPMENT

CHAPTER 6: ELECTRICAL COMPONENTS AND
CIRCUIT DEVELOPMENT

INTRODUCTION

LEARNING OBJECTIVES

BPLK 1/22 DMV 1152/3152/4152/5152

ELECTRICAL COMPONENTS AND CIRCUIT DEVELOPMENT

6.1 SWITCHES

Switch is a electrical device having two states: on, or closed; and off, or open.
Ideally a switch offers a zero impedance to a current when it is closed, and it
offers infinite impedance when open. Mechanical switches, which operate by
moving contacts together and apart, are often classified by the number of
connections they can make or break at once and the number of closed positions
in which they can be placed.

6.2 SWITCHES SELECTION

6.2.1 Pushbutton and control switches

Switches are installed in circuits to apply a current to a load or to interrupt
the circuit. These switches are divided into pushbuttons and control
switches.
 Control switches are mechanically detended in the selected position.

The switch position remains unchanged until a new switch position is
selected. Example: Light switches in the home.
 Push button switches only maintain the selected position as long as
the switch is actuated (pressed). Example: Bell push.

6.2.1.1 Normally open contact (switch).

In the case of a normally open contact, the circuit is open if the
switch is in its initial position (not actuated). The circuit is closed
by pressing the pushbutton – current flows to the load. When the
plunger is released, the spring returns the switch to its initial
position, interrupting the circuit.

BPLK 2/22 DMV 1152/3152/4152/5152

ELECTRICAL COMPONENTS AND CIRCUIT DEVELOPMENT

Figure 6.1 Normally open contact (switch)
6.2.1.2 Normally closed contact (switch)

In this case, the circuit is closed when the switch is in its initial
position. The circuit interrupted by pressing the pushbutton.

BPLK Figure 6.2 Normally closed contact (switch)

3/22 DMV 1152/3152/4152/5152

ELECTRICAL COMPONENTS AND CIRCUIT DEVELOPMENT

6.2.1.3 Changeover contact (switch)

The changeover contact combines the functions of the normally
open and normally closed contacts in one device. Changeover
contacts are used to close one circuit and open another in one
switching operation. The circuits are momentarily during
changeover.

Figure 6.3 Changeover contact (switch)

6.3 SWITCH CONTACT IDENTIFICATION

6.3.1 Sensors for measuring displacement and pressure

Sensors have the task of measuring information and passing this on to
the signal processing part in a form that can easily be processed. In
electro-pneumatic controllers, sensors are primarily used for the following
purposes:
 To detect the advanced and retracted end position of the piston rod in

cylinder drives.
 To detect the presence and position of workpieces.
 To measure and monitor pressure.

BPLK 4/22 DMV 1152/3152/4152/5152

ELECTRICAL COMPONENTS AND CIRCUIT DEVELOPMENT

6.3.2 Limit switches

A limit switch is actuated when a machine part or workpiece is in a certain
position. Normally, actuation is effected by a cam. Limit switches are
normally changeover contacts. They can then be connected as required,
(normally open contact, normally closed contact or changeover contact)

Figure 6.4 Mechanical limit switch: Construction and connection possibilities

6.3.3 Proximity switch

In contrast to limit switches, proximity switches operated contactlessly
(non-contact switching) and without an external mechanical actuating
force. As a result, proximity switches have a long service life and high
switching reliability. The following types of proximity switch are
differentiated:
 Reed switch
 Inductive proximity switch
 Capacitive proximity switch
 Optical proximity switch

BPLK 5/22 DMV 1152/3152/4152/5152

ELECTRICAL COMPONENTS AND CIRCUIT DEVELOPMENT

6.3.3.2 Electronic sensor

Inductive, optical and capacitive proximity switches are electronic
sensors. They normally have three electrical contacts.
 Contact for supply voltage
 Contact for ground
 Contact for output signal

In these sensors, no movable contact is switched. Instead, the
output is either electrically connected to the supply voltage or to
ground (= output voltage 0V)

There are two types of electronic sensor with regard to the polarity
of the output voltage.
 In positive switching sensors, the output voltage is zero if no

part is detected in the proximity. The approach of a workpiece
or machine part leads to switchover of the output, applying the
supply voltage.
 In negative switching sensors, the supply voltage is applied to
the output if no part is detected in the proximity. The approach
of a workpiece or machine part leads to switchover of the
output, switching the output voltage to 0V.

BPLK 6/22 DMV 1152/3152/4152/5152

ELECTRICAL COMPONENTS AND CIRCUIT DEVELOPMENT

6.3.3.3 Inductive proximity sensor

An inductive proximity sensor consist of an electrical oscillator (1),
a flip-flop (2) and an amplifier (3). When a voltage is applied, the
oscillator generates high-frequency alternating magnetic field that
is emitted from the front of the sensor. If an electrical circuit is
introduced into this field, the oscillator is attenuated. The
downstream circuitry, consisting of a flip-flop and an amplifier,
evaluates the behaviour of the oscillator and actuates the output.
Inductive proximity sensors can be used for the detection of all
good electrical conductors (materials). In addition to metals, these
include, for example, graphite.

Figure 6.5 Inductive proximity sensor

BPLK 7/22 DMV 1152/3152/4152/5152

ELECTRICAL COMPONENTS AND CIRCUIT DEVELOPMENT

6.3.3.4 Capacitive proximity sensor

A capacitive proximity sensor consists of a capacitor and an
electrical resistance that together form an RC oscillator, and a
circuit for evaluation of the frequency. An electrostatic field is
generated between the anode and the cathode of the capacitor. A
stray field forms at the front of the sensor. If an object is
introduced into this stray field, the capacitance of the changes.
The oscillator is attenuated. The circuitry switches the output.
Capacitive proximity sensors not only react to highly conductive
materials (such as metals) but also to insulators high dielectric
strength (such as plastics, glass, ceramics, fluids and wood).

BPLK Figure 6.6 Capacitive proximity sensor

8/22 DMV 1152/3152/4152/5152

ELECTRICAL COMPONENTS AND CIRCUIT DEVELOPMENT

6.3.3.5 Optical proximity sensor

Optical proximity sensors use optical and electronic means for
object detection. Red or infrared light is used. Semiconductor
light-emitting diodes (LEDs) are particularly reliable sources of red
or infrared light. They are small and rugged, have a long service
life and can be simply modulated. Photodiodes or phototransistors
are used as a receiver. Red light has the advantage that the light
beam can be seen during adjustment of the optical axes of the
proximity switch. Polymer optical fibres can also be used because
of their low attenuation of light of this wave-length.
Three different types of optical proximity switch are differentiated:
 One-way light barrier
 Reflective light barrier
 Diffuse reflective optical sensor

6.3.3.5.1 One-way light barrier

The one-way light barrier has spatially separate
transmitter and receiver units. The parts are
mounted in such a way that the transmitter beam is
directed at the receiver. The output is switched if
the beam is interrupted.

BPLK Figure 6.7 One-way light barrier

9/22 DMV 1152/3152/4152/5152

ELECTRICAL COMPONENTS AND CIRCUIT DEVELOPMENT

6.3.3.5.2 Reflective light barrier

In the reflective light barrier, the transmitter and
receiver are mounted together in one housing. The
reflector is mounted in such a way that the light
beam transmitted by the transmitter is practically
completely reflected to the receiver. The output is
switched if the beam is interrupted.

Figure 6.8 Reflective light barrier

BPLK 10/22 DMV 1152/3152/4152/5152

ELECTRICAL COMPONENTS AND CIRCUIT DEVELOPMENT

6.3.3.5.3 Diffuse reflective optical sensor

In the diffuse reflective optical sensor, the
transmitter and receiver are mounted together in
one unit. If the hits a reflective object, it is
redirected to the receiver and causes the output of
the sensor to switch. Because of the functional
principle, the diffuse reflective optical sensor can
only be used if the material or machine part to be
detected is highly reflective (for example polished
metal surfaces, bright paint).

Figure 6.9 Diffuse reflective optical sensor

BPLK 11/22 DMV 1152/3152/4152/5152

ELECTRICAL COMPONENTS AND CIRCUIT DEVELOPMENT

6.4 SWITCH ACTUATION METHOD

6.4.1 Direct control of a single acting cylinder

The electrical circuit diagram for direct control of a single acting cylinder is
shown in figure 6.10(b). When the pushbutton is pressed, current flows
through the solenoid coil y1 of the 3/2 way valve. The solenoid is
energized, the valve switches to the actuated position and the piston rod
advances.
Releasing the pushbutton results in interruption of the flows of current.
The solenoid is de-energized, the directional control valve switches to the
normal position and the piston rod is retracted.

6.4.2 Indirect control of a single acting cylinder

If the pushbutton is pressed in an indirect control system (figure 6.10(c)),
current flows through the relay coil. Contact K1 of the relay closes, the
directional control valve switches. The piston rod advances.
When the pushbutton is released, the flow of current through the relay coil
is interrupted. The relay is de-energized, and the directional control valve
switches to the normal position. The piston rod is retracted.

+24V 1 +24V

a) b) c) 3 3

2 3
Y1
S1 S1 K1
13
4 44

Y1 K1 A1
0V 0V Y1

A2

Figure 6.10 a) Pneumatic circuit diagram
b) Electrical circuit diagram for direct control
c) Electrical circuit diagram for indirect

control

BPLK 12/22 DMV 1152/3152/4152/5152

ELECTRICAL COMPONENTS AND CIRCUIT DEVELOPMENT

6.4.3 Control of a double acting cylinder

The piston rod of double acting cylinder is to advance when pushbutton
S1 is pressed and retracted when the pushbutton is released.

a) b)

42 42
Y1
Y1
13 53
1
c) +24V 1
d) +24V
3
33
S1 S1 K1

4 44

Y1 K1 A1
0V 0V Y1

A2

Figure 6.11 Circuit diagram for control of double acting cylinder
a) Pneumatic circuit diagram with 4/2 way valve
b) Pneumatic circuit diagram with 5/2 way valve
c) Electrical circuit diagram with direct control
d) Electrical circuit diagram with indirect control

BPLK 13/22 DMV 1152/3152/4152/5152

ELECTRICAL COMPONENTS AND CIRCUIT DEVELOPMENT

6.5 THE SWITCH AS A BUILDING BLOCK

6.5.1 Signal storage

In the circuits that we have looked at so far, the piston rod only advances
as long as the input pushbutton is actuated. If the pushbutton is released
during the advancing movement, the piston rod is retracted without
having reached the forward end position.

In practice it is usually necessary for the piston rod to be fully advanced
even if the pushbutton is pressed only briefly. To achieve this, the
directional control valve must remain in the actuated position when the
pushbutton is released; in other words, actuation of the pushbutton must
be stored.

6.5.2 Signal storage with double solenoid valve

A double solenoid valve maintains its switching position even when the
associated solenoid coil is no longer energized. It is used as a storage
element.

BPLK 14/22 DMV 1152/3152/4152/5152