Modul Amali Elektro-Pneumatik_5nov08

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CHAPTER 3 ELECTRO-PNEUMATICS 3.1 Learning Outcome At the end of this module, student will be able to: a) Identify and use the typical electro-pneumatics components. b) Design electro-pneumatic circuits using DCV single solenoid and DCV double solenoids for single and multiple cylinders with various outputs. c) Install and test-run the electro-pneumatic circuits based on the designed cicuit. 3.2 Theory 3.2.1 Definition and Advantages Electro-pneumatic term is defined from words of electro which mean electrical and pneumatic which mean air pressure. The electro-pneumatic equipments and system is an integration of electrical and mechanical components with compressed air source. The electrical controller work with 12 to 24V DC electrical source. Electro-pneumatic controllers have the following advantages over pneumatic control systems: Higher reliability (fewer moving parts subject to wear). Lower planning and commissioning effort, particularly for complex controls. 1

Transcript of Modul Amali Elektro-Pneumatik_5nov08

Page 1: Modul Amali Elektro-Pneumatik_5nov08

CHAPTER 3

ELECTRO-PNEUMATICS

3.1 Learning Outcome

At the end of this module, student will be able to:

a) Identify and use the typical electro-pneumatics components.

b) Design electro-pneumatic circuits using DCV single solenoid and DCV double

solenoids for single and multiple cylinders with various outputs.

c) Install and test-run the electro-pneumatic circuits based on the designed cicuit.

3.2 Theory

3.2.1 Definition and Advantages

Electro-pneumatic term is defined from words of electro which mean electrical and

pneumatic which mean air pressure. The electro-pneumatic equipments and system is

an integration of electrical and mechanical components with compressed air source.

The electrical controller work with 12 to 24V DC electrical source.

Electro-pneumatic controllers have the following advantages over pneumatic control

systems:

Higher reliability (fewer moving parts subject to wear).

Lower planning and commissioning effort, particularly for complex controls.

Lower installation effort, particularly when modern components such as valve

terminals are used.

Simpler exchange of information between several controllers.

Electro-pneumatic controllers have asserted themselves in modern industrial practise

and the application of purely pneumatic control systems is a limited to a few special

applications.

3.2.2 Components

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Both pneumatic and electro-pneumatic controllers have a pneumatic power section. In

an electro-pneumatic control, the signal control section is made up of electrical

components, for example with electrical input buttons, proximity switches, relays, or a

programmable logic controller. The directional control valves form the interface

between the signal control section and the pneumatic power section in the controller

(refer figure 3.1).

Figure 3.1: Signal flow and components of an electro-pneumatic control system

Source : Prede, G. and Scholz, D.

FESTO Electro-Pneumatic Basic Level TP201 Textbook

3.2.2.1 Switch

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Signal flow Electro-pneumatic Components

Commandexecution

Signaloutput

Signal processing

Signalinput

Power components- Cylinder- Swivel cylinder- Pneumatic motors- Optical displays

Final Control Elements- Electropneumatically operated directional control valves

Processing Elements- Relays- Contactors- Programmable logic controllers (PLCs)

Input Elements- Pushbuttons- Control switches- Limit switches- Reed switches- Ind. proximity sensors- Cap. proximity switches- Light barriers- Pressure-actuated switches

Pneumaticpower section

Electrical signal control section

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There are three (3) types of electrical switches used in the design of electro-pneumatic

circuit. They are:

i) Opened contact switch

ii) Closed contact switch

iii) Multiple contact switches.

Figure 3.2(a), 3.2(b) and 3.2(c) shows the three types of contact switches at the

training box.

Figure 3.2(a): Opened contact switches

Figure 3.2(b): Closed contact switches

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Figure 3.2(c): Changeover contact switches consist of opened and

closed contact switches

3.2.2.2 Switching Method for Logic Operations

Six basic switching methods in an electrical circuit consist of single or multiple

switches as shown in the Figure 3.3(a), 3.3(b) and 3.3(c).

Figure 3.3(a): YES gate and NOT gate are the simplest electrical circuits

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Figure 3.3(b): OR Gate and AND Gate uses parallel and serial circuits with

opened contact switches.

Figure 3.3(c): NOR Gate and NAND Gate uses serial and parallel circuits with

closed contact switches.

3.2.2.3 Relay

Relay is an electrical device which contains a coil and a contactor switch. Relay also

can consist of a coil and multiple contactors. Figure 3.4 shows a coil (K) with 4

contactor switches at a training box.

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Figure 3.4: Relay with a coil and multiple contactor switches

Figure 3.5: The current flow in the coil will change the condition of

contactor switch

Figure 3.5 illustrates the changes of contactor switch. Once the current energizes the

coil, the contactor will switch from closed contact to be an opened contact. Inversely,

once the coil is de-energized, the contactor will return to it ordinary condition.

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) Switching more than one outputs simultaneously using relay with a coil with

multiple contactors.

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Figure 3.6(a) and 3.6(b) shows the electrical circuits with a relay and single output

(H1), and multiple outputs (H1, H2, H3, H4).

Figure 3.6(a): The electrical circuits WITHOUT and WITH relay (R1)

Figure 3.6(b): Relay in an electrical circuit is used to switch

4 lamps H1, H2, H3 and H4

3.2.2.4 Solenoid Valve

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Solenoid valve is an electro-mechanical device that built-in with a coil (solenoid) and

a pneumatic/hydraulic directional control valve (DCV). There are three types of built-

in solenoid directional control valve. They are:

3/2 Way DCV single solenoid with spring return

5/2 Way DCV single solenoid with spring return

5/2 Way DCV double solenoid

The 3/2 way DCV single solenoid with spring return is used to control the actuation of

single acting cylinder, while the 5/2 way DCV single solenoid or double solenoid

respectively are used to control the actuation of double acting cylinder.

The 5/2 way DCV single solenoid and double solenoid can be distinguished by a built-

in spring instead of coil. DCV single solenoid or monostable valve consists of a built-

in solenoid at the left hand side and a built-in spring at the right hand side of the valve.

For the case of ‘normally closed DCV’, once the electrical current energizes the

solenoid, the valve is pushed to an ‘Opened’ position. Inversely, when the solenoid is

de-energized, the spring will push the valve back to the ‘Closed’ (original) position.

DCV double solenoid consists of two solenoids at the both sides of the valve. Both

solenoids are energized by electrical current to push the valve to an ‘Opened’ and

‘Closed’ positions. It is also called ‘bistable valve’ or ‘memory valve’.

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Figure 3.7: Electro-pneumatic circuit for actuating a single acting cylinder

Figure 3.7 shows the pneumatic and electrical circuits (electro-pneumatic circuits) for

actuating a single acting cylinder using 3/2 DCV single solenoid with spring return.

Then, Figure 3.8(a) and 3.8(b) shows the pneumatic and electrical circuits for

actuating a double cylinder using 5/2 DCV single solenoid and double solenoids

respectively.

Figure 3.8(a): 5/2 DCV single solenoid is used for actuating a

double acting cylinder

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Figure 3.8(b): 5/2 DCV double solenoid is used for actuating a

double acting cylinder

3.2.2.5 Proximity Sensor

Proximity sensors are commonly used to monitor a process condition in a machine.

For instance, sensor is used to ensure the raw part was placed on a fixture, height of

raw material within control, etc. There are three types of proximity sensors (Figure

3.9), they are:

Inductive sensor – able to detect metal, especially mild steel.

Capacitive sensor – able to detect most parts except low density product.

Optical sensor – able to detect bright surface reflectively except black /

rough surface.

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Figure 3.9: Three types of proximity sensors

Figure 3.10: Proximity sensor (PS) is placed at the beginning of the

actuator movement

3.2.2.6 Electrical Timer

The electrical timer can be classified to two types, they are:

Time delay ON timer

Time delay OFF timer

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Time delay ON timer delays the switching time upon an energizing. Let say a timer is

set to 5 seconds. When the timer coil T1 is energized, the timer will start compute the

time from zero second, thus the switches will change after 5 seconds. On the other

hand, when the timer coil T1 is de-energized, all switches will instantly return to it

original conditions.

Time delay OFF timer delays the switching time upon de-energizing. Let say a timer is

set to 10 seconds. When the timer coil T2 is energized, the timer will instantly change

the switching. Inversely, when the timer coil T2 is de-energized, the timer will start

compute the time until 10 seconds before the switches return to it original conditions.

Figure 3.11 shows the symbols for both types of delay timers.

Figure 3.11: Symbols of time delay ON and time delay OFF timers at a

controller box

Figure 3.12 shows the simple electrical circuit which consist of time delay OFF timer.

Once the switch S1 is pressed, the timer T2 is energized and the contactor K2 will

instantly changed to a closed contact condition. Then, if the switch S1 is released, the

timer will start computer the time to 5 seconds before the contactor K1 return to an

opened contact condition.

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Figure 3.12: Electrical circuit with time delay OFF timer

3.2.2.7 Electrical Counter

An electrical counter can count 1000 numbers from ‘0’ to ‘999’. The count number

can be set when a counter is connected with a switch and a relay for reset. The counter

will start counting upon receive an electrical pulse. The switch will change upon the

counting is finished. The separated signal is needed as a reset to return the switch to it

original condition and reset the counter to ‘0’.

Figure 3.13: Counter, switch and reset relay need to be connected in an electrical circuit design

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3.3 Practice

3.3.1 Practice 1

Fakulti Kejuruteraan Mekanikal dan Pembuatan

AMALAN KEJURUTERAAN MEKANIKAL II (BDA 1811)

Title : Electro-Pneumatic Practice I

Objectives : Upon completing this task, student be able to :

d) Draw a basic electro-pneumatic circuit, install and test run it to

move an actuator.

e) Identify and operate a few types of electro-pneumatic components.

f) Install the serial and parallel electrical circuits for OR/ AND

functions.

Task :

Design the electro-pneumatic control circuit for the following operations :

a) Press switch A to extends a cylinder piston and press switch C to retracts it.

b) Press either switch A or B will extend a cylinder piston. Then, it will be

automatically retracted when touching a limit switch.

c) Press switch A will extends a cylinder piston. It will be retracted if a sensor

detect it end while switch B is pressed.

*Use a 5/2 way DCV double solenoids.

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Name and sketch the related electro-pneumatic symbols :

a)

b)

c)

Sketch the related Pneumatic and Electrical Circuits :

a)

b)

c)

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3.3.2 Practice 2

Fakulti Kejuruteraan Mekanikal dan Pembuatan

AMALAN KEJURUTERAAN MEKANIKAL II (BDA 1811)

Title : Electro-Pneumatic Practice II

Objectives : Upon completing this task, student be able to :

a) Draw, install and test run the memory circuits.

b) Identify and operate a few types of electro-pneumatic components

including relay and its contactors.

Task :

Design an electro-pneumatic control circuits for the following operations :

a) Press switch A to extend a cylinder piston, while it will retract if

switch A is released.

b) Press switch A to extend a cylinder piston, and it will be retracted

once a switch B is pressed.

c) Press switches A and B to extend a cylinder piston. The piston will

be retracted if switch C is pressed or limit switch detect the piston

end. Once a piston move to extend, a green LED will be ON. Then,

a red LED will be ON when the piston reach the maximum extend

position.

* Use 5/2 way DCV single solenoid with spring return.

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Name and sketch the related pneumatic and electrical component symbols :

a)

b)

c)

Sketch the related Pneumatic and Electrical circuits :

a)

b)

c)

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3.3.3 Practice 3

Fakulti Kejuruteraan Mekanikal dan Pembuatan

AMALAN KEJURUTERAAN MEKANIKAL II (BDA 1811)

Title : Electro-Pneumatic Practice III

Objectives : Upon completion this task, student be able to :

a) Draw, install and test run an electro-pneumatic circuits for multiple

cylinders with sequence motion.

Task :

Design an electro-pneumatic control circuits using two pistons for the following

operation :

Press switch A to initiate extend of piston A and switch on a green LED. Fully extend

of piston A will initiate extend of piston B. Piston A will retract to an initial position if

piston B was fully extended. Once piston A was fully retracted, a red LED will be

switching ON while piston B start to retract.

Use two 5/2 way DCV single solenoid with spring return

Use two 5/2 way DCV double solenoid

Write the Sequen Motion :

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Draw the Step Displacement Diagram for this operation :

Name and sketch the related pneumatic and electrical sysmbols :

Sketch the Pneumatic & Electrical circuits :

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3.3.4 Practice Case 4

Fakulti Kejuruteraan Mekanikal dan Pembuatan

AMALAN KEJURUTERAAN MEKANIKAL II (BDA 1811)

Title : Electro-Pneumatic Practice IV

Objective : Upon completing this task, student be able to :

a) Draw, install and test run the electro-pneumatic operation using an

electrical timer dan counter.

Task :

Install and test the following circuits :

a) (i)

Electro-pneumatic circuit with a ‘Time Delay ON’ timer

(ii)

Electro-pneumatic circuit with a ‘Time Delay OFF’ timer

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24V

13 17 S1 T1

14 18

A1 5 seconds

T1 H1 A2

0V

24V

15 17 S1 T1

16 18

A1 5 seconds

T1 H1 A2

0V

24V

17 17 S2 S1 C1

18 18

A1 R1 5 seconds

C1 H1 A2

R2

0V

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b)

Electro-pneumatic circuit with an electrical counter

3.4 References

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Shuttle., (2007). Sistem Kawalan Pneumatik. Shark.

Prede, G., and Scholz, D. (1998). Electro-Pneumatic Basic Level TP201 Textbook.

Ed 12/1998. FESTO Didactic.

Groover, M.P., (2001). Automation, Production System and Computer Integrated

Manufacturing. 2nd edition. Prentice Hall.

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