Journal of Science and Technology

ISSN: 2456-5660 Volume 8, Issue 07 (July -2023)

www.jst.org.in DOI:https://doi.org/10.46243/jst.2023.v8.i07.pp01 - 07

Scalable and Robust IoT-Based Liquid Level Monitoring/Control

System for Home and Industrial Automation

Prasanth P. P.1 | Athul Thomas1 | James Kurian1

1Department of Electronics, Cochin University of Science and Technology

Cochin-682 022,

To Cite this Article

Athul Thomas1, James Kurian , Scalable and Robust IoT-Based Liquid Level Monitoring/Control System for Home
and Industrial Automation ” Journal of Science and Technology, Vol. 08, Issue 07,-July 2023, pp01-07

Article Info
Received: 22-06-2023 Revised: 25-06-2023 Accepted: 02-07-2023 Published: 08-07-2023

ABSTRACT

In this study, a dependable liquid level monitoring and control system for automated home or industrial
settings is presented. The system uses state of the art Internet of Things (IoT) technology to accomplish its
goals. The suggested system, which consists of a minimum of four interconnected functional units, utilises
Wi-Fi connectivity to establish communication between the parts. These nodes can efficiently share data by
using the simple MQTT protocol, which enables scalability by allowing the installation of additional nodes to
manage various tank and reservoir levels. In the suggested approach, the Sensor node simultaneously
subscribes to several topics pertaining to user settings and measurement frequency while publishing
measurements to the server. By subscribing to these topics, the Actuator Control node may control pumps or
valves appropriately and communicate their current states. The User Interface node publishes changes to
user configuration and subscribes to all topics from other nodes. All firmware codes were created using the
C++ libraries and programming structures in the Arduino development environment. An Android application
that has been specially created can serve as the system's graphical user interface, allowing users to interact
with it via a variety of portable devices.
KEYWORDS: Internet of Things, MQTT, Arduino, Home automation

INTRODUCTION
Liquid level management is a common requirement in many industrial environments. For automatic
liquid level monitoring and control, it is desirable to have a reliable system which adds less complexity to
the existing factory automation set up. In conventional level monitoring/controlling systems [1-3], their
installation and maintenance are tedious and laborious. It is mainly due to the fact that the
instrumentation demands a tangled cabling for the interconnection of the system. This includes the
sensing, processing and control units, that relies in different sections of the factory floor. The presented
work focuses on a feasibility study of implementing state of the art IoT (Internet of Things) technology for
the remote monitoring and controlling [4-7] of liquid level in an industrial or home automation scenario.
The next section discusses the main objectives of the system that were considered during the designing
process. It follows an overview of different units of the level controller and discusses the hardware of each
node. A detailed explanation of the communication protocol and the software and app development were

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provided in the software section. The final section concludes the work and unveils the future scopes and
modifications.

Figure 1 Shows the block diagram representation of different nodes of the proposed liquid level monitoring
and control system

I. OBJECTIVES
The main objective of this study is to develop and implement a liquid level monitoring and control system,
and to extend its features using the capabilities of IoT technology. Recent advancements in wireless
technology and Chip manufacturing offers Wi-Fi enabled low power microcontroller units. These units are
handy to control peripherals like sensors; relays etc. and allow them to communicate over a wireless
network. Some of the target requirements of the system architecture includes:
Distributed Wireless Computing Nodes: Here the elementary units of the system, such as sensors,
actuators, user interface etc. were implemented in fully independent, self-contained hardware modules.
This feature improves the modularity of the system so that any number of nodes can be added (as a part of
system upgradation) or removed (during maintenance) from the architecture without disturbing its overall
functionality.
Client Server Architecture: Here, as the name indicates, the whole system is divided in to a group of clients
and a main server. Clients are intended to do a specific dedicated operation like sensing, actuator
controlling, etc., where there is less requirement for processing power, memory and I/O operations.
Processes such as network management and plant operations log, can be moved to the server node with
better computational resources. This approach also helps to improve the cost effectiveness of the system by
using low cost processors for the client modules.
Scalability: As discussed before, the architecture of the system should be dynamic so that any
elementary module can be inserted or removed in the system. This feature will free the developer from
changing the entire firmware or configuration each time, when a new node is added.

II. SYSTEM HARDWARE

Proposed hardware model for the liquid level monitoring and control system has been divided into four
functional nodes, as depicted in Figure 1.

i Level Sensing
ii Actuator Control
iii User Interface
iv Server

Raspberry pi 2 has been used as the server to control the network. The remaining nodes were controlled
by ESP8266-12F Wi-Fi module. Low-power, highly-integrated ESP8266-12F modules enables the
implementation of wireless network. Client nodes were programmed in the station mode (STA). The
ultra-compact power supply module HLK-PM01 facilitates 5v dc output from the main supply and ensures
proper isolation. Following subsections explains each of the nodes in detail.

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Level Sensing
The Level Sensing node includes an economic ultrasonic sensor HC-SR04 along with an ESP-12F Wi-Fi
module programmed in the station mode (STA). Compared to traditional level sensors like electrodes or
float switches, non-contact ultrasonic sensors offer high degree of accuracy and reliability. The HC-SR04
module comprise ultrasonic sound transmitter, detector and control circuit. The transmitter sends out
sonic bursts which will travel at the speed of sound and the echo from liquid is received by detector. By
estimating the time of flight using a microcontroller, the level of liquid can be determined. The sensor
module can provide 2cm to 400cm [8] of measurement range with a resolution of up to 3mm. The hardware
is mounted on top of the container with ultrasonic module facing towards the liquid.
Besides the Wi-Fi functionalities ESP8266 integrates an enhanced version of Tensilica L106
microcontroller. The controller offers enough I/O modules and A-D converters to interface sensors or other
peripherals. The Trigger, Echo pins from the Ultrasonic module HC-SR04 is connected to the
programmable I/O pins of the ESP8266 module. The L106 controller estimates distance towards obstacle
by analysing the delay between trigger and echo pulses. Measured levels will be scaled and calibrated
according to the container dimensions. Depending on the user configuration, this value may be processed
further before getting transmitted to the server. Figure 2 shows the Level Sensing node.

Figure 2. Shows the photograph of Level Sensing node with ultrasonic sensor and other programming and
interfacing circuits

Actuator Control
The Actuator Control node integrates an appropriate power driving system for the pump/valve control.
ESP8266 Wi-Fi module receives commands from the server through Wi-Fi and act accordingly by driving
the relevant actuator. Figure 3 shows the Actuator Control node.

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 Figure 3. Shows the photograph of Actuator Control node with four relays and connectors with driving
circuits for valves/pumps

As shown in the figure, the Actuator Control node has four 5V relays with a rating of 10A. These four
channels can be either configured as independent mono switches or as a pair of dual switches. This feature
enables the node to drive different models of valves and motors.

User Interface
In an industrial system, there should be some provision for human machine interaction. The level control
system has several parameters such as maximum and minimum level, flow rate, manual on/off, current
liquid level, etc., for monitoring and controlling. This can be made possible through the following ways.
User can interact with the level controller system in the following ways. The server provides a terminal
where the control parameters can be adjusted and current system status can be observed. A custom
developed GUI app can communicate with the server and display the information on a portable mobile
device. A dedicated hardware with OLED and push buttons with a microcontroller will serve as a User

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Interface node that provides an aid for user interaction for controlling or monitoring the system
parameters.

Server Unit
The Server Unit (MQTT broker), handles and relays communications between all the other units. This
work uses Raspberry Pi with a Linux operating system as the MQTT broker [9].
The Level Sensing Unit is linked to both the User Interface Unit and to a process control routine running
in the Actuator Control Unit via local Wi-Fi network. The measured liquid level is wirelessly transmitted to
the process control to adjust the control actuators. The level data is also shared with the User Interface unit
for monitoring the instantaneous liquid level. The communication between the sensor unit, control unit
and the user interface unit has been implemented using Message Queuing Telemetry Transport (MQTT)
protocol, that is explained in the software section below.

III. SYSTEM SOFTWARE

The most important part of the software development was to find a suitable IoT protocol on which the
entire system communications can be relied. In the proposed system the Message Queuing Telemetry
Transport (MQTT) protocol has been used.
All the firmware codes for the client nodes were developed in the Arduino development environment and
there by uses the C++ libraries and programming structures. An android application has also been
developed to be used as a convenient mobile interface through which the user can interact with the system
from various mobile devices.

MQTT Protocol
Message Queue Telemetry Transport is a lightweight connectivity protocol based on the TCP/IP stack
which uses the publish/subscribe method for transportation of data [10-12]. It is open-ended and supports
a high level of scaling, which makes it an ideal platform for development of Internet of Things (IoT)
solutions. It is a message-based protocol that uses publisher-subscriber pattern. The key component in
MQTT is the MQTT broker. The main task of MQTT broker is dispatching messages to the clients
(“subscribers”). Broker receives messages from publisher and dispatches these messages to the
subscribers. While it dispatches messages, the MQTT broker uses the topic to filter the clients that will
receive the message. The topic is a string and it is possible to combine the topics creating topic levels.
Figure 4 shows an overview of the MQTT protocol.

Figure 4. Shows the working of the system with MQTT protocol for updating liquid level

Client Firmware

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 The open source Arduino Integrated Development Environment (IDE) has been used for the firmware
development of all client boards. Several libraries were used for the programming and driver development.
Some of them have been modified to meet the requirements discussed in the objectives.

Android App Development

For the android app development MIT App Inventor has been utilized [13-16]. It is an open source web
application, developed by MIT Media Lab and MIT Computer Science and Artificial Intelligence Lab, to
create software for the Android operating system. It uses an easy graphical interface that allows users to
drag and drop visual objects to create an application that can run on Android devices. Figure 5 depicts a
screenshot of the Android app.

Figure 5 Shows the screenshot of the level controller application with the current level and pump status

Server Implementation
The Raspberry Pi board with a Linux OS acts as the server (MQTT Broker) for the entire system. The
MQTT protocol has been implemented in the server with Eclipse Mosquitto. Eclipse Mosquitto provides a
lightweight server implementation of the MQTT protocol that is suitable for the low power embedded
computers. The current implementation has the capability to accept the connections from up to 1000
clients. It also has an option to enable a bridge that allows it to connect to other MQTT servers, including
other Mosquitto instances. This allows networks of MQTT servers to be constructed, passing MQTT
messages from any location in the network to any other, depending on the configuration of the bridge.

Figure 6. Shows the working of the system with MQTT protocol for updating liquid level

Cloud Connection
Communicating sensor readings, switch states etc with the internet is the key point in any IoT enabled
system. The proposed level controller uses Adafruit Cloud as the remote server (Figure 6). The cloud

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facilitates a secured environment where the received sensor data can be analysed and based on that the
control valves can be adjusted [9]. Server running in Raspberry Pi will talk with Adafruit cloud over the
internet. Adafruit dashboard has feeds corresponding to “sensor level”, “switch state” etc. The local server
can publish its readings or subscribe to switch states through these feeds. Any device which has access to
the Adafruit IoT dashboard can view or modify the system once authenticated with the API key.

III. CONCLUSION
Implementation of an IoT based liquid level monitoring/controlling system is discussed. The MQTT
protocol has been successfully integrated in the firmware design that enables an easy interfacing and
installation of hardware nodes without any major modification of the existing factory management setup.
The same implementation can also be used in home automation with several added features such as
optional manual override, water consumption rate.

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