Tutorial 3 Grafcet

BENE3113 INDUSTRIAL CONTROL TUTORIAL 3: GRAFCET Question

1.

With four input elements (START, STOP, FORM and FAIL) and three output elements (MOTOR, EJECT and CYCLE), write the ladd er diagram for the below mentioned sequence. All input elements to the PLC are NO momentary pushbuttons. a. When the program starts, all outputs are to be OFF  b. When START is pressed, MOTOR should switch ON. MOTOR should stay on even after START is released. MOTOR is switched OFF b y pressing STOP. c. If FORM is pressed and MOTOR is ON, CYCLE switches switches ON. CYCLE stays on only during the time that t hat FORM is being pressed. CYCLE cannot operate if MOTOR is OFF. d. If FAIL is pressed and MOTOR is OFF, EJECT will switch ON. Even after FAIL is released, EJECT will stay sta y ON. EJECT automatically switches OFF when MOTOR is again switched ON. EJECT cannot operate while MOTOR is ON. i) Design the inputs and outputs assignment like the table below. ii) Design the wiring diagram as the w iring diagram example below.

iii) iv)

Design the GRAFCET. Design the PLC instructions/ladder diagram

2.

i) Design the inputs and outputs assignment list from the GRAFCET above.

Input Device

Input Operand/Data

PB

0.00

SW1

0.01

LS1

0.02

LS2

0.03

IR_1

2.00

Out ut Device

Output Operand/Data

Light1

1.00

Light2

1.01

Motor1

1.05

Control Device

Control Operand/Data

Interlock

IL

Interlock clear

ILC

ii) Design the PLC instructions/ladder diagram

3.

The action sequence of the automatic washing machine is given below. A start pushbutton will start the operation. Sequence

1

Action Fill the tub

Remarks LS1 low water level sensor, LS2 high water level sensor 

V1 water supply valve 2

Wash

Timer 1 for 15 minutes

M1 for washing motor 3

Drain

LS1 low water level sensor, LS2 high water level sensor 

V2 water drain valve 4

Spin

Timer 2 for 2 minutes

M2 for Spin motor

i)

Design the inputs and outputs assignment table.

Input Device

Input Operand/Data

Start Pushbutton

PB

0.00

Low water level sensor

LS1

0.02

High water level sensor

LS2

0.03 Output Device

ii)

Output Operand/Data

Water supply valve

V1

1.00

Water drain valve

V2

1.01

Washing motor

M1

1.05

Spin motor

M2

1.06

Control Device

Control Operand/Data

Timer 1

TIM

0001 # 1200

Timer 2

TIM

0002 #9000

Design the wiring diagram

0

1

2

3

4

5

6

7

8

9

10 11 12 13 14 15 comm

Outputs PLC In uts

0

1

2

iii) Design the GRAFCET

3

4

5

6

7

8

9 10 11 12 13 14 15 comm

iv) Design the PLC instructions/ladder diagram

Additional instructions 4. A PLC type OMRON CJ1GCPU42H is used as the controller for part of stamping machine. The description of operation and the I/O assignment tabl e are shown as below: Literal Description

Symbolic Description

The operator put the box at the platform and presses

If PB = 1 and b2 =1,

the start pushbutton. Detecting sense signal from sensor b1

-when b1  = 1, B-

Waiting for the next start button

Input Device

Input Operand/Data

PB

I1

 b1

I2

 b2

I3 Output Device

Output Operand/Data

B+

O1

B-

O2

B+

B b2

B+

Stamping

 b1

Sensor

Box

PB Start  pushbutton i) ii) iii) iv)

Prepare the GRAFCET diagram for the sequence of this system. Develop the PLC Ladder Diagram for latching equation. Develop the PLC Ladder Diagram for power circuit Develop the PLC Ladder Diagram for transitions firing equations