This document summarizes the design, development, and cost analysis of four different liquid flow controllers used in food industries: float switch, bistable multivibrator with reed switch, limit switch, and programmable logic controller (PLC). It was found that the bistable multivibrator circuit using an IC 555 chip and reed switch was the most cost-effective solution and provided reliable automatic control of liquid pumps without user interaction. The document describes the components, circuit designs, and costs for each of the four liquid flow controller methods.

1. International Journal For Research & Development in Technology
Volume: 2, Issue: 6, Dec -2014 ISSN (Online):- 2349-3585
31 Copyright 2014- IJRDT www.ijrdt.org
Design, Development and Cost analysis of
various liquid flow controllers in food
Industries
R.Keerthana Priya1
, G.Sujatha2
, T.Sivakumar3
, D. Baskaran4
1
Final year B. Tech (FT) student, 2
Assistant Professor,
3
Dean, Faculty of Food Sciences, 4
HOD, Food Engineering
College of Food and Dairy Technology, Koduvalli, Chennai-52
Abstract— This paper deals with the design and
implementation of different types of liquid flow controllers.
In food industries, normally in water tanks, liquid storage
silos, oil seeds extraction tanks, flow controller is essential.
The usage of flow control is very common in many process-
based industries. Control of water or liquid level in food
process tank is essential in any process control system. The
approximate cost of the developed set up is compared with
other methods. Four methods like IC 555 with reed switch,
Float switch, Limit Switch, Programmable logic controller
(PLC) were used to control the water level and their
development cost was compared. It was found that the cost
incurred in IC 555 in bistable multivibrator mode with reed
switch was less and the design was also found to be reliable.
The main advantage of this water level controller circuit is
that it automatically controls the water pump without any
user interaction.
Index Terms—water level controller, IC 555, Bistable multi
vibrator, Float switch, Reed switch, Programmable logic
controller.
INTRODUCTION
The studies were carried out in the dairy plant service tank,
bulk milk cooler and balance tank in College of Food and
Dairy Technology, TamilNadu Veterinary and Animal
Sciences University, Redhills, Chennai-52.People generally
switch on the pump when their taps go dry and switch off the
pump the overhead tank starts overflowing. This results in the
unnecessary wastage and sometimes non-availability of
water/liquid in the case of emergency. For a control of an ON-
OFF controller are active only when process variable crosses
the set point in the positive or negative direction. When the
process variable is greater than set point the controller is OFF
and when process variable is less than set point the controller is
ON. The designs that is used make the system automatic, i.e. it
switches ON the pump when the water level in the overhead
tank goes low and switches it OFF as soon as the water level
reaches a pre-determined level. It also prevents „dry run‟ of the
pump in case the level in the tank goes below the suction level.
Water Level Controller employs a simple mechanism to detect
and maintain the water level in a tank or any other container by
switching it on/off the motor automatically when needed. Here
the project is done in water tank but it can be applied to any
liquid flow.
MATERIALS AND METHODS
The following four methods were designed to control liquid
flow.
1. Float Switch
2. Bistable Multivibrator with reed switch
3. Limit Switch
4. Programmable Logic Control
FLOAT SWITCH
The device is connected to an electrical pump through an
electrical cable, is used for the auto control of Bulk milk cooler
in Dairy Plant of 500 liter capacity. The float switch contains
spring loaded plate, when water level is lower the contact
Normally Open (NO) is closed and makes the motor to run.
When water level is high, NO is open, hence no current flows.
An electrical cable is used to connect the electrical pump
which is fixed inside the tank. The length of the cable section
between the fixation point of the device and the device body
determines the water level. Electrical pump stops when the
water level in the water tank pool drops to a certain level and
starts to emptying water again when the water level increases.
Specifications
Rated Current: AC 125V/250V
Max Current: 16A
Frequency: 50-60 Hz
Max Operating Temperature: 50ᵒC
Fig 1 Float attached to the tank Fig.2 Float rise
Cost analysis
Float Switch with connecting wire – Rs .550

2. International Journal For Research & Development in Technology
Paper Title:- Design, Development and Cost analysis of various liquid flow controllers in food Industries (Vol.2, Issue-6)
ISSN(O):- 2349-3585
32 Copyright 2014- IJRDT www.ijrdt.org
BISTABLE MULTIVIBRATOR WITH REED SWITCH
The tank is 300 liter capacity with a height 0.77m height and
0.70m diameter. The tank is attached with boiler in the dairy
plant. Here the automation is done using Bistable multivibrator
Circuit with Reed switch (magnetic Switch). In a reed switch,
the inner two reeds acts as magnetic flux conductors when
exposed to external magnetic field like magnet. When a magnet
is brought near the switch, two contacts are closed because the
magnetic force exceeds the spring force on the reeds, which
generates positive polarity on the reeds, thus the current flows
through it and vice-versa [2]. It is constructed using PVC pipe,
Float, Printed circuit Board, IC 555, Capacitor 0.1µF, Push
Button, Capacitor 100µF, LED, Reed Switch, Resistor, Relay,
Buzzer, Diode, Transformer, Magnet, Connecting wires and
EL 4N35 324.IC 555 is configured in Bistable Multivibrator
mode, the reed switch are placed at a distance of 19cm attached
over the hollow pipe which is fitted in the tank lid. The magnet
attached with another pipe of small diameter than the above
and float is attached at the Bottom. This is made to move inside
the Larger Pipe, when level raises the float moves and makes
contact with Reed Switch.
The Circuit get closed when magnet comes close proximity
with upper or lower Reed Switch, thereby causes the motor to
switch ON and OFF.[2]
Fig.3 Float attached to tank Fig.4 Float arrangement
Fig.5 Circuit diagram for Bistable multivibrator
As the name indicates, the bistable multivibrator has two stable
states. Outwardly, the output looks the same as that of the
astable multivibrator. The biggest difference between the two
circuits is that the astable may or may not be triggered, but the
bistable requires a trigger to operate. When the bistable
receives a trigger of the proper amplitude and polarity, it
changes states. It remains in that state until another trigger is
received. At that time, it will change states again. Because the
bistable has two stable states, it is ideally suited for several
applications in electronics. The closest mechanical analogy to a
bistable multivibrator is a toggle switch. Momentary pressure
in the form of a trigger pulse causes the output of the bistable
to change states. That means the output changes from high to
low, or low to high. In electronics, a toggle is a latch that
maintains a condition once pressure or a signal is received. As
the output stays at one state until another trigger pulse is
received, the circuit remembers. That means the circuit can
function as a memory storage device. Each time a trigger is
applied to a bistable, it changes states. Apply trigger no.1 and
the circuit changes states. Trigger no. 2 causes the circuit to
return to its original state. The bistable multivibrator divides
the frequency of the input signal in half. The major uses for the
bistable multivibrator are as a memory storage device, timing
circuit, frequency divider, and an electronic toggle switch.
Fig. 6 PCB with IC 555 Circuits
Table 1 Cost Analysis
S.NO Particulars Numbers Cost in
Rs(approx)
1 Printed Circuit
Board
1 40
2 Resistors 8 5
3 Push Button 2 2
4 IC 555 with
Base
1 15
5 EL 4 N 35 324
with Base
2 20
6 Buzzer and
wire
1 35
7 Reed Switch 2 20
8 Capacitor 1 5
9 Filter 1 10
10 Light Emitting
Diode
1 1
11 Relay 1 15

3. International Journal For Research & Development in Technology
Paper Title:- Design, Development and Cost analysis of various liquid flow controllers in food Industries (Vol.2, Issue-6)
ISSN(O):- 2349-3585
33 Copyright 2014- IJRDT www.ijrdt.org
12 Transformer 1 65
13 Float 1 15
14 Connecting
wires
As
Required
30
Total 278
LIMIT SWITCH
A mechanically operated limit switch is used which relies on a
lever or arm to be displaced mechanically, which activates a
microswitch in the body of the device to open or close an
electrical contact. A standard industrial limit switch is an
electromechanical device that contains an actuator linked to a
series of contacts. When an object meets the actuator, the limit
switch triggers the contacts to either form or break an electrical
connection. Limit switches are commonly employed in a wide
range of applications and under a variety of operating
conditions due to their ease of installation, relatively
straightforward design, ruggedness, and reliability. Here the
milk level is controlled using limit switch in the balance tank in
the pasteurizer unit. The two limit switches are used with relay
for automation. The materials used are limit switch, float,
double pole double throw relay and connecting wires. The two
limit switches are attached on the metal frame with relay
attached to it. The whole set up is fitted with float for
indicating level of liquid over the balance tank. The circuit
diagram below indicates the working of liquid level controller.
Fig. 7 Circuit Diagram for Limit Switch Controller
Fig. 8 Limit Switch and relay Attached to frame
Table 2 Cost analysis
S.No Particulars Numbers Cost in
Rs
1 Float 1 50
2 Limit
Switch
2 500
3 Relay with
base
1 370
4 Frame and
fitting aids
As
Required
75
5 Connecting
Wires
As
Required
30
Total 1025
PROGRAMMABLE LOGIC CONTROLLER
Programmable Logic Controller (PLC) is a digital computer
for automation of process such as control of instruments in
industries. It uses a programmable memory to store instructions
and specific functions that include ON/OFF control, timing,
counting, sequencing, arithmetic, and data handling[4]. The
basic parts include processor, input/output devices, memory
unit, programming panel and power supply. The PLC is also
used for implementing functions such as logic, sequencing,
timing, counting and arithmetic to control through digital or
analog input/output modules various types of machine
processes [1].
The PLC Ladder program designed is given below.
PLC Specifications
Make - ABB model: AC500 eco series
Number of IOs : -Incorporated Binary Inputs: 8PNP and
NPN
Normal value: 24V DC
Filtering STD time: 5ms
- No. Of outputs
Current: 2A
Voltage: max.24 V DC
No .Of Extension : 6

4. International Journal For Research & Development in Technology
Paper Title:- Design, Development and Cost analysis of various liquid flow controllers in food Industries (Vol.2, Issue-6)
ISSN(O):- 2349-3585
34 Copyright 2014- IJRDT www.ijrdt.org
Fig. 9 Water Level Controller Using PLC
Ladder diagram interpretation for Water level controller:
Step 1: Initially the tank is empty.
Step 2 : The internal relay is turned on as the water level
raises. Step 3 : After 2nd step the water level raises above
the low level sensor and becomes open.
Step 4 : After 3rd step the water level raises above the high
level sensor and it also become open.
Step 5: And therefore no true logic path and therefore the
motor turned off
Step 6: After 5th step the water level falls below the high
level sensor and it will become true again.
Cost analysis
Miniature set up with PLC – Rs 10,000 (Approx)
RESULTS AND DISCUSSIONS
The above four methods were designed, developed, tested and
implemented in the liquid flow tanks and their cost
comparisons for different methods were analyzed. These
methods can be implemented to any liquid flow tanks by
varying its height. It is efficient to use low cost automation
method when compared to other methods .The below graph
shows various methods developed in X-axis and production
cost (Rs) in Y-axis. It is found that IC 555 in bistable
multivibrator mode with reed switches (one for ON and the
other for OFF) is a low cost method when compared to float,
limit switches and programmable logic controllers for flow
control in any food industry.
REFERENCES
[1] K. Gowri shankar (2008),“ Control of boiler operation
using PLC-SCADA” ,Proceedings of the International Multi
Conference of Engineers and Computer Scientists, volume II.
[2] S. M. Khaled Reza et.al.,(2010) Microcontroller Based
Automated Water Level Sensing And Controlling: Design And
Implementation Issue, Proceedings of the World Congress on
Engineering and Computer Science 2010 Vol I.San Francisco,
USA
[3] Ulya sabeel and Nidhi Chandra (2013),” An ingenious
wireless Home Security System and Protocol based upon
Multi-hop 802.15.4 Standard, Magnetic Contact and PIR
sensor”,I.J .Modern education and computer
sciences,(Published Online).
[4] V Mathavi, Dhivya. N, G Sujatha and R Chandrakala.
“Static application panels (sap) controlled by plc”.
International journal of applied information systems 5(6):1-7,
April 2013
0
2000
4000
6000
8000
10000
12000
Float
Switch
Reed
Switch
Limit
Switch
PLC
Cost Comparison
Production Cost
in Rs