MANGOSUTHU UNIVERSITY OF TECHNOLOGY
DEPARTMENT OF ELECTRICAL ENGINEERING
Process Instrumentation II
2021 First Semester Assignment
Due date: 14/07/2021
Submit Electronic copies via class reps
Figure 1 shows a bottle-filling operation system. There is a motor, M, in the system. The motor
drives the conveyor system to transport the bottle to the right position. When the bottle arrives
at the right position, the motor should be switched off to make the bottle to stop so that the
liquid can be filled into the bottle. There is a photo-sensor (BPPS) that detects whether the
bottle is filled or not. Design a PLC control system as given below for the bottle-filling
operation illustrated in Fig. 1. The system consists of the following physical entities:
-
Start and stop pushbuttons (to start and stop the whole system),
Photo-sensor
-
Figure 1. Bottle filling system
Proximity switch (to detect if the bottle arrives at the right position;
Level limit switch (to detect the level of the liquid in the tank system which delivers the
liquid to fill the bottle);
Input valve switch (to control the amount of liquid into the tank);
Output valve switch (to control the filling process);
-
Photo-sensor (to detect if a bottle is filled);
Motor switch;
Output valve switch.
Let:
PB1 for start pushbutton, (PB1=1) for the start pushbutton is pressed
PB2 for stop pushbutton, (PB2=1) for the stop pushbutton is pressed
LLS for the level limit switch, (LLS=1) for the level of the liquid over the desired
(LLS=0) for the level of the liquid below the desired
BPPS for the proximity switch, (BPPS=1) for a bottle to arrive in position
(BPPS=0) for a bottle not to arrive in position
PS for the photo-sensor, (PS=1) for the bottle filled
(PS=0) for the bottle unfilled
S1 for input valve,
(S1=1) for the input valve is on
(S1=0) for the input valve is off
S2 for output valve,
(S2=1) for the output valve is on
(S2=0) for the output valve is off
M for motor switch
(M=1) for the motor is on
(M=0) for the motor is off
The basic control problem can be described in the following:
(1) The process is turned on by pressing the start pushbutton button switch
(2) The process is turned off by pressing the stop pushbutton switch, where off also means
that conveyor motor is off.
(3) When the process is running:
- When the LLS=0, the input valve must be energized;
- After a bottle arrives in position, the output valve must be energized;
- After a bottle is filled, the output valve must be de-energized;
- The conveyor is on when a bottle is not in position and is off when a bottle is in
position and is being filled; and
- The filling of bottles is then required over and over again.
Please do the following:
(a)
(b)
(c)
(d)
(e)
State all outputs;
Name all inputs; and
Develop a PLC implementation (ladder diagram-LAD).
Develop a PLC implementation (Statement List-STL).
Develop a PLC implementation (Function Block Diagram-FBD).
All the best!!!!!!!
Eng. James Rwafa
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