165000503 electro-pneumatic

Introduction to Electro Pneumatics
Contents :-
1. What is Electro-Pneumatics : a definition
2. Electro-Pneumatic Signal Control system
3. Electro-Pneumatics Basic control components
4. Application Example

WikiAnswers.com wrote,
Pneumatics is a method to transfer energy from one point to another
using actuators which are driven by fluids under pressure.
Pneumatics restricts itself to gaseous fluids while hydraulics uses
liquids to transfer the energy.
The transferring of energy in pneumatics such as pumping air into a
pneumatic cylinder must be controlled.
You can control the pressure by manually opening a valve,
automatically by detecting its pressure, or by sending an electrical
signal. The control of pneumatic components by electrical
impulses is known as electro-pneumatics.
1.1 Definition of Electro-Pneumatics

Both pneumatic & electro-pneumatic controllers have
a pneumatic power section. In an electro-pneumatics
control, the signal control section is made up of a
electrical components, such as electrical input
buttons, proximity switches, relays, or a
programmable logic controller (PLC).
Source : Electropneumatics – A basic, G Prede, D Scholz
Question 1 :
What is your definition for Electro-Pneumatics?
_____________________________________
_____________________________________
[3 marks]
1.2 Other Definition of Electro-Pneumatics

Definition :
 Electro-pneumatic term is defined from the words of
electro which means electrical and pneumatic which
means air pressure.
 The electro-pneumatics equipments and system is
an integration of electrical and mechanical
components with compressed air source.
 Electro pneumatic is a pneumatic control system
where air pressure and direction of valve are
controlled by an electrical current.
1.3 Our Definition of Electro-Pneumatics

 Electro pneumatic is integration of two control circuit
1. Pneumatic Circuit
2. Electrical Circuit
1.4 Electro-Pneumatics’ circuit

(a)
Pneumatic circuit

(b)
Electrical circuit

1.5 Combination of Pneumatic circuit and Electrical circuit

2.1 A Background – Basic Control system
Command
Execution
Signal
Output
Signal
Processing
Signal
Input
Power component
Final Control element
Processing element
Input element

2.2 Signal flow and component of an Electro-
Pneumatic control system
Source :
Electropneumatics Basic Level
by G Prede, D Scholz

2.3 Pneumatic power section
Directional control valves form the interface
between the signal control section (electrical) and
the pneumatic power section in an Electro-
pneumatic system.

2.4 Electrical signal control section

1. Lesser wear-off parts. Lesser installation jobs.
i.e., Electrical control valve, Electrical switches
2. Replace tube in pneumatic system to electrical
wire in electro-pneumatic
3. Less parts are used  Reduce working space.
4. Sensor and Controller (such as PLC) can be
included in the system
2.5 Advantages of using Electro-Pneumatics
Push Button
E-260
Electrical signal
input
(switch panel)

Question :
List-up (at least) 2 advantages and 2 disadvantages
of Pneumatic system.
2.3 Assignment 1

Question :
By using suitable pneumatic circuit, show
pneumatic component classification.
Source: 2009 Sem2 DNT241 Final exam question
This year final exam Question(?)
List-up 4 component classifications in Electro-
pneumatic control system and give 2 example for
each component.
3.0 Introduction to Electro-pneumatic control
component

Switches :
There are 3 types of electrical switches used in
design Electro-pneumatic circuit.
1. Normally Open switch
2. Normally Close switch
3. Multiple contact switches
Sensors :
1. Mechanical Position sensor (Limit switch)
2. Proximity sensor
3. Reed switch
3.1 Input Element component

3.2 Switching Contact and type of actuation

3.3.1 Normally Open (N.O) and Normally Close (N.C)
In pneumatic circuit :
For example : 3/2-way Push button (valve)
Normally Open Normally Close
In electrical circuit :
For example : Push button switch
Normally Open Normally Close

3.3.2 Normally Open (N.O) and Normally Close (N.C)

3.4 Mechanical Position sensor
(Pneumatic)
3/2-way N.C valve with roller (Limit switch)
(Electro-Pneumatic)
Mechanical Position sensor (Limit switch)

 Proximity sensor contain a transistor which
conducts and switches (trigger ON) when something
comes near to the sensors.
 Some of the proximity sensor only work with steel
material components － Inductive proximity sensor
3.5 Proximity sensor

Question :
1. Name the switch type used for START and STOP button.
2. What is the different between A1 and A2 in Electrical circuit?
3.5.1 Proximity sensor – Symbol and Sample Circuit
Proximity Sensor

 Reed switch is one of the sensor which is operated
by the magnetic field.
 Usually fit directly onto cylinder with clips.
 The piston of the cylinder has a magnet built into it
and when the piston comes close to the reed
switch, the contact is close (ON).
3.6 Reed switch

 Relay is an electrically actuated switch, contains a coil
and a contactor switch or multiples contactors.
 When power is applied to relay coil, the core
magnetizes, drawing the contact assembly in.
 This will change the state of all the contacts in the relay
(i.e., N.O contact becomes closed or N.C contact
becomes open).
 Relay uses small amount of power to control switching
(advantage). The voltage applied to the coil doesn’t
have to be the same as that in control circuit.
 Relay is used to allow low voltage control systems to
switch large current/ high voltage
(function / advantage)
3.7 Processing element - Relay

3.7.1 Sample circuit
Coil
When Toggle switch 1S3 is pressed, power is applied to
Relay (K1) coil which result to the all contactors in relay
change their state (open  close or close  open).
Solenoid valve 1Y1 activate to ON
E-140
Contactor

3.7.2 N.O and N.C wire connection
Normally Close (N.C)
Example : Pin 21  22
Normally Open (N.O)
Example : Pin 41  44

3.7.3 Animation (Relay OFF)
Source : UniKL Electro-Pneumatic Lecture Note, 2008

3.7.4 Animation (Relay ON)

3.7.5 More about Relays
 Relay has a few functions as a safety device:
1. The high voltage output (i.e. 240V) can be switched ON
through a contactor using relay with low voltage (i.e.
24V) supplied to a coil.
2. The high current output can be switched ON through a
contactor using relay with low current supplied to a coil.
3. Functioned as Safety control circuit for emergency
power cut-off (EMERGENCY START and STOP button)
to the whole circuit.
Use in automation process  Switching more than one
outputs simultaneously using relay with a coil and multiple
contactors.
To control ON and OFF of various outputs sequences using
several Relay.

 Solenoid valve is an electro-mechanical device that
built-in with a coil (solenoid) and a pneumatic
Directional control valve.
 Solenoid actuated Directional control valve (DCV)
convert electrical signals to pneumatic signals.
 They are used to start, to stop and/or to change
the direction of air flow.
 There 3 main types of solenoid valve.
1. 3/2-way Solenoid valve with spring return
2. 5/2-way Solenoid valve with spring return
3. 5/2-way Double solenoid valve
3.8 Final control element – Solenoid DCV

5/2-way Solenoid valve with
spring return
3/2-way Solenoid valve with
spring return
3.8.1 Solenoid DCV
5/2-way Double solenoid valve

3.8.2 Symbol and sample circuit
(Pneumatic)
Pilot actuated 5/2-way Directional control valve
(Electro-Pneumatic)
Solenoid actuated 5/2-way Directional control valve
Pneumatic Power Component --- cylinder
Final Control element --- Solenoid valve

3.8.3 Symbol in Electrical circuit
When Pushbutton switch (SW1) is pressed, power is
applied to Solenoid S1 which then change the electrical
signal to pneumatic signal and allow air flow to cylinder
A (single acting with spring return) for rod to extend.
Solenoid

3.8.4 Sample Circuit connection
Red cable is connection
from 24V line.
Blue cable is connection to
GND (0 V).

3.8.5 Solenoid - Structure
Source : UTeM Chapter 4 --- ElectroPneumatic

4.0 Supply / Power component
In Electro-Pneumatic system, the supply or power
source component is divided into two, based on the
system component.
1. Pneumatic － Compressor
2. Electrical －AC / DC power supply
Symbol for 24V DC
IEC Standard JIC Standard

4.1 Self-Latching concept
Self-latching will enable the automation system to run in automatic
mode after the START button is pressed and the system repeats until
STOP button is pressed.
The advantage of having self-latching in the system is that it can be
used as power switching and emergency button.
START
STOP
Self-latching
circuit

4.2 Electro-Pneumatic Application
In this section, we will learn some of the actual
application for Electro-pneumatic system.
1. Single-acting cylinder (with spring return)
2. Double-acting cylinder (1 unit)
3. Double-acting cylinder (2 units)
Based on the system / operation given, the students
should capable to :
a) Understand the system’s operation and draw /
sketch Displacement-step diagram
b) Design Pneumatic circuit and Electrical circuit for
the system.

4.3 Application 1
Using a sorting device, parts are to be transferred from conveyor
belt. By pressing the pushbutton switch, the piston rod of a single-
acting cylinder pushes the part off the conveyor belt. When the
pushbutton is released, the piston rod returns to the retracted end
position.

4.3.1 Pneumatic circuit and Electrical circuit
Question :
Complete the missing part in Electrical circuit.
Pneumatic circuit Electrical circuit
?

4.4 Application 2
Wooden planks are to be pushed along from a gravity feed magazine
to a clamping device. By pressing a pushbutton switch one plank is
pushed by the slide out of the gravity feed magazine. After the slide
has reached the forward end position it is returned to its start
position.

4.4.1 Pneumatic circuit
Question :
Please design complete Electrical circuit to control above pneumatic
circuit.

4.5 Application 3
Using a transfer station blocks are to be transferred from a magazine to a
processing station.
The blocks are pushed out of the magazine by cylinder A and transferred to
the processing station by cylinder B. The piston rod of cylinder A may only
return when the piston rod of cylinder B has reached the retracted end
position. The magazine is monitored by means of limit switches. If there
are no more blocks in the magazine, it is not possible to start the cycle.
This is indicated by means of push button to act as a sensor. The control is
to be operated in single cycle.
Cylinder A
Cylinder B

4.5.1 Displacement-step Diagram
1. The blocks are pushed out of the magazine by cylinder A and
transferred to the processing station by cylinder B.
2. The piston rod of cylinder A may only return when the piston rod of
cylinder B has reached the retracted end position.
3. The magazine is monitored by means of limit switches. If there are no
more blocks in the magazine, it is not possible to start the cycle. This is
indicated by means of push button to act as a sensor, named as
‘Part_detect’ sensor.
4. The control is to be operated in single cycle.
Abbreviation notation : A+  B+  B-  A-
Displacement-step Diagram :

4.6 Other components in Electro-Pneumatic
1. AND / OR Logic
2. Timer ON / Timer OFF.
3. Pressure Switch.
4. Counter
5. LED
Etc…

We should be :
1. Understand what has been called as Electro-
Pneumatics and can simply describe it.
2. Understand the 5 main components in Electro-
pneumatic control system
3. Understand the name and symbol of each
component and how its working in the electrical
circuit (function).
4. Understand on how to design Pneumatic and
Electrical circuit based on the given applications.
5. Can demonstrate the theories learning in class to
practical.
5.0 What has been learned in this session?

Application 1
6.0 Answer
Application 2

Pneumatic circuit
6.1 Application 3
Electrical circuit

Pneumatic circuit
6.2 Include Self-latching circuit
Electrical circuit

165000503 electro-pneumatic

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