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Instant Container Heating Using PTC Elements and Smart Wireless Control

Instant Container Heating Using PTC Elements and Smart Wireless Control Using Bluetooth and Android Applications

Abstract Page



It is not uncommon to hear people complaining about how much they abhor having cold food for lunch at work. This problem is not localized to a particular geographic area or age, it affects everyone who prefers having hot food at workplace or college. Initially, microwave ovens were built to satisfy this purpose, but, portability and feasibility problems occur. The Smart Lunch box aims at providing hot food to users anytime and anywhere they want. It uses heating elements along with microcontrollers powered by batteries to provide heat even in the absence of a power outlet. The batteries have to be sufficiently charged well before hand, the box can be controlled to set temperatures and timer through a mobile application which simplifies the user interface and also reduces human intervention. The box can also be used as a noodle maker by using hot water. The technical applications are immense. This invention can be of great help to various working sects of the society.


Contents Page



Sl. No. Details Page No.
1 Introduction 1-9
1.1  Overview 1
1.2  Information Technology  
1.3  Embedded Systems 2
1.4  Conventional Heating Methods 3-5
1.4.1   Conduction 3
1.4.2   Convection 4
1.4.3   Radiation 5
1.5  History of Lunch Box 6
1.6  Basic Characteristics of Lunch Box 7-8
1.6.1  Material 7
1.6.2         Storage  
1.6.3         Food Protection  
1.6.4            Temperature Resistance 8
1.6.5            Temperature Insulation  
1.6.6 Mobility  
1.7  Arduino  
1.8  Connectivity and Communication 9
1.9  Android Application  
1.10  WordPress Website  
2 Analysis 10-13
2.1  Existing System 10
2.1.1   Types of Lunch Boxes    Wired Lunch Box 11    Wireless Lunch Box 12
2.1.2   Drawbacks of Existing System  
2.2  Proposed System  
2.2.1   Advantages of Proposed System 13
3 Software and Hardware Specifications 14
4 Modules 15-16
4.1  Module Specifications 15
4.1.1   Hardware Module  
4.1.2   Users Module  
4.1.3   Android Module  
4.1.4   Arduino IDE Module 16
4.1.5   Administrator Module  
5 Design 17-19
5.1  System Architecture 17
5.2 System Flow Chart 18
5.3 Schematic Diagram 19
5.4 Unified Modelling Language 20-25
5.4.1  Definition  
5.5 Building Blocks of UML 21-
5.5.1  Things in the UML 21
5.5.2            Relationships in the UML 22
5.5.3            Diagrams in the UML 23                      Structural Diagrams                      Behavioural Diagrams 24
5.6 Use-Case Diagram 26
5.7 Class Diagram 27
5.8 Activity Diagram 28
5.9 Sequence Diagram 29
6 Code 30-46
6.1              Arduino Code 31
6.2  Android Code 35
7 Screenshots 47-53
8 Testing 54-63
8.1  Types of Testing 54
8.2  Unit Testing 56
8.3  Integration Testing  
8.4            Acceptance Testing 57
8.5  Test Cases  
8.5.1   Smart Lunch Box Website 57
8.5.2   Application Communicating with Lunch  Box 58
9 Conclusion and Scope for Future Enhancements 64
10 References 65-66












  1.            Introduction


  1.       Overview

The Lunch box, alternatively known as a lunch pail or lunch kit is a container used to store and carry food for later consumption. It is capable of protecting the food from the surroundings and delaying the time of the food becoming spoilt. There are several models of lunch boxes in the market nowadays which have a range of uses: boxes that double as bowls and containers; that have movable dividers for different foods; that are dish-washer safe/ microwave safe; stackable containers, collapsing containers and so on. Though the materials keep getting upgrades, the functionality of the box hasn’t had many changes. Lunch Boxes do an average job at keep food warm to begin with. The ideas of portability and introducing new technologies to keep food warm haven’t been explored all too much. Thus came about the need to have a way to heat up food that is portable, easily accessible, decreases human intervention and actually brings warmth of food up to adequate temperatures. The Smart Lunch Box uses PTC heating wireless control through Bluetooth connectivity and an Android application to heat up the containers.


  1.       Information Technology

Information Technology, here, refers to the application of computers to store, study, retrieve, transmit and manipulate data.  ‘Information Technology’ or, ‘IT’ is a generic name given to all improvements that are taking place in our world due to the inter-linked advancement in technology, learning, and information. The term refers to modern technological developments that are taking place because of technology and due to better information. [1] The internet acts as a resource and opens us to the world of information superhighway enabling us to seek the information that we want. We can download programmes and information through a computer and /this makes gathering information any easy process. In this approach, gathering knowledge and information has become, easy, cheap and fast. The IT revolution has altered the very face of business operations and E- commerce is big part of it. Now, IT revolution is sweeping over the world. Although, the IT boom has revolutionised the western world beyond recognition it is still to make much progress in changing lives in India. The boom has, however, definitely affected only the affluent and the urban India. The benefits of IT boom needs to seep down to the ordinary men and women living in our country.


  1.       Embedded Systems


Embedded systems are a part of Information Technology that deal with computer systems that are designed for limited or no human interaction. An embedded device is an object that contains a special-purpose computing system. The system, which is completely enclosed by the object, may or may not be able to connect to the Internet. Embedded systems have extensive applications in consumer, automotive, commercial, industrial and healthcare markets. [2] It’s estimated that by 2015, over 15 billion embedded devices will be connected to the Internet. An embedded system employs a combination of hardware & software (a “computational engine”) to perform a specific function; is part of a larger system that may not be a “computer”; works in a reactive and time-constrained environment. Software is used for providing features and flexibility. Because embedded systems have limited computing resources and strict power requirements, writing software for embedded devices is a very specialized field that requires knowledge of both hardware components and programming.

The use of processing power in small packages has further driven the digital revolution. Embedded systems are a large part of the process of scaling down on the size of the devices and customizing the device to perform only what is required. [3] Embedded systems are used in situations where general-purpose computers, like PCs are too obtrusive, bulky or over-priced for a majority of products. The embedded devices incorporate an embedded system technology that allows the core functionality to be within a small device without having to rely on a PC.  There are also situations when the general-purpose solutions fail to meet certain functional or performance requirements such as size-limitations, reliability, real-time performance, power-consumption, etc. Using embedded systems, we are able to downsize on the physical devices needed to run a specific operation onto one device. The use of processing power in small packages has further driven the digital revolution.

  1.       Conventional Heating Methods


Heat transfer is the physical action of thermal energy being exchanged between two systems by dissipating heat. Flow of heat and temperature are the basic principles of heat transfer. Temperature determines the amount of thermal energy and similarly heat flow represents the movement of thermal energy. [4] On a microscopic scale, the kinetic energy of molecules is the direct relation to thermal energy.

The molecules become thermally agitated in linear motion and vibration as the temperature rises, Regions that contain greater kinetic energy transfer the energy to regions with lower kinetic energy. The conventional methods of warming up food involve a manual control of devices with wired connection to heat up the contents of the device following the principles of conduction, convection or radiation. According to a study of food safety and hygiene, when reheating food, it should be steaming hot all the way through or reach a temperature of 70 ˚ C for more than 2 minutes. [5]

Convection Conduction Radition

Figure1.1:Pictorial Representation of Heating Methods

  1. Conduction


Conduction is the process of transmission of heat through the material of the substance for which the temperature difference is applied. It transfers heat via direct molecular collision. Thermal energy from an area of greater kinetic energy will be transferred to an area with lower kinetic energy. Higher-speed particles will collide with slower particles. The slower-speed particles will increase in kinetic energy as a consequence. This process is the most common form of heat transfer and takes place by via physical contact. The path of travel and cross-section both play an important part in conduction. As the size and length of an object increase, the more energy is required to heat it. And the greater the surface area that’s exposed, the more heat is lost. Smaller objects with smaller cross-sections have negligible heat loss.


Figure1.2:Pictorial Representation of Conduction


  1. Convection

Convection is the transfer of heat due to the movement caused within the fluid due to the tendency of hotter, less dense material to rise and colder, denser material to sink under gravity. When air or fluid is heated and travels away from the source, it carries the thermal energy along with it. This mode of transfer of heat is called convection. The fluid above a hot surface becomes less dense, expands and then rises. The molecules expand upon introduction of thermal energy at the molecular level. As temperature of the fluid mass increases, the volume of the fluid must also increase by same factor. This effect on the fluid causes displacement. As the immediate hot air rises, it pushes denser, colder air down. This sequence of events represents how convection currents are formed.
Figure1.3:Pictorial Representation of Convection

  1. Radiation

Radiation is the transfer of heat in form of electromagnetic waves. Thermal radiation is generated from the emissions that electromagnetic waves generate. The energy is carried away from the emitting object. Radiation occurs through any transparent medium (either fluid or solid) or vacuum. Thermal radiation is the direct result of movements of atoms and molecules in matter. Movement of the charged electrons and protons produces electromagnetic radiation emissions. All materials radiate thermal energy based on their temperature. The hotter an object becomes, the more it will radiate. The sun is a apparent example of heat radiation that transfers heat across the solar system. Object radiate as infrared waves at normal room temperatures. The temperature of an object affects the frequency and wavelength of the radiated waves. With a rise in, the wavelengths within the spectra of the radiation emitted decrease and emit shorter wavelengths with higher-frequency radiation.

Figure1.4:Pictorial Representation of Radiation

  1.       History of Lunch Box


The concept of lunch box has been around for a very long and there isn’t much information about who invented it, but the earliest recorded usage was in the late 19th century. Some of the earliest examples were woven baskets with handles where the meal would be wrapped in a handkerchief. During the same period, the wealthier would have fancy wooden boxes for their food. Afterwards, the metal variety was introduced; when the containers became a marketable product to the youth.  It was one of hundreds of consumer goods produced for the post-war market in 1950’s U.S.A. The industrial revolution led Americans to work in factories, which made it difficult to go home to lunch every day. [6] Thus, raised need for a container to protect and transport a meal. The Thermos, a vacuum flask which enabled hot or cold beverages to remain at optimal temperatures until lunchtime, was introduced in 1904. It was suitable for either hot or cold beverages to remain at optimal temperatures until lunchtime. [7] Over time, lunch boxes were manufactured using various materials. Children’s lunch boxes were made of plastic or vinyl, while the adults had ones made of tin or aluminium- due to the greater need for durability.  The first use of plastics was the lunch box, but it later spread to the entire box. [8] In the 1960s, insulated foam replaces the vacuum boxes. The trend continued to present manufacturing types. Today, lunch boxes are generally made of plastic, with foam insulation and an aluminium/vinyl interior. These are better at retaining their temperature but are less rigid/ protective.

Image result for lunch boxes  for kids old fashioned      Image result for lunch boxes for office


Figure1.5:Lunch box for children and adult

  1.       Basic Characteristics of Lunch Box

Characteristics of a lunch box are important for research and product development to augment the existing systems. Therefore, a continuous study is required in order to an understanding to enhance a creative development.  There are a few characteristics that can be identified in a basic lunch box, which are:

  1. Material

In manufacturing terms, ‘Material’ refers to substances used in fabricating thermal heated, lunch box products. The type of material used to manufacture the product  is important in how effective it is as a product for the user. Research on characteristic of the material should be done first and ensure it is safe to use and does not affect human health.

  1. Storage

Storage space refers to the capacity or volume that a lunch box is capable of holding. The allowance in the containers effects the user’s ultimate decision of using the product or not. There are several studies that state the differences between volumes of food that different people require per meal. [9] A study that compares genders eating habits show that the average female adult consumes less food than the average male adult. Children usually only require half the meal size of that of an adult. [10] As for result, different sizes of lunch box appear in the market, targeted at different demographics.

  1. Food Protection

Food protection characteristic in the lunch box is another feature should be considered. It refers to the capability to cover the food and protect it from dust or water which will spoil the food. This also depends on the materials encasing the containers and the actual substances the containers are composed of. The essential purpose of a lunch box is to separate the food from contact of external surroundings, because the air contains dust or bacterial cultures which will affect the taste and freshness of the food. Spoilage Aerobic; bacteria than needs oxygen to grow is could be a possibility if the food is exposed to air. [11] Some lunch boxes also come with an air seal or leak proof feature to ensure it is fully protected from moisture and air.

  1. Temperature Resistance

Temperature resistance on plastic lunch box is the ability to withstand heat without causing chemical reaction. If the temperature resistance is not high enough it may react and endanger human health when using it. When developing an electric lunchbox, the material’s heat resistance determines the durability and safety; with regard to health, of the product. [12] It is important to test the material’s temperature resistance at various temperatures before deeming it acceptable for holding food.

  1. Thermal Insulation

Thermal insulation refers to the characteristic of the material capable of reducing rate of heat transfer. The transmission of heat could happen in one of three modes: conduction, convection or radiation. Thermal insulation is the method of preventing heat from escaping a container or from entering the container. [13] It can be applied to keep the food warm for longer period of time. Material selection become important as it will affect the rate of heat transfer.

  1. Mobility

Mobility refers to the object capable of being in motion. In other word, it is the ability to bring along when travelling from a distance. Weight of the product should be as light as possible to allow user carry. The size of the product should also be small. When the size is small it allows is easy to be keep and bring along.


  1.       ArduinoIn order to prototype this project, Arduino Pro Mini is used. It is a microcontroller board based on the ATmega328. It has sets of digital input/output (I/O) pins, an on-board resonator, reset button and holes for mount pin headers. This board is meant for applications and installations where space is premium and projects are made as semi-permanent setups. To dump code on the microcontroller, there is an integrated development environment (IDE) called Arduino IDE; that works on most operating systems (OS), for programming on embedded C and deploying the code to Arduino. The IDE contains a text editor for writing code, a text console and a toolbar with buttons for common functions. The software was used to code the Arduino Pro Mini board; for it to communicate with the Android application on the user’s phone.


  1.       Connectivity and Communication

The interior of the lunch box has all the major components which are connected with connector cables and take power from the rechargeable lithium ion batteries. Wireless connectivity between the box and user’s Android application is possible through Bluetooth connectivity. The Arduino Pro Mini is responsible for conveying commands to the mechanical relays, PTC heating elements based on the instructions it receives from the Android application through the Bluetooth HC-05 module.


  1.       Android Application

On the Linux based kernel Operating System (OS), an application is developed to run. Google provides Android Studio to develop, debug, test, deploy Android applications. The Smart Lunch Box application is developed to communicate with the box over a Bluetooth connection to send commands to heat the containers; either to start heating immediately or at set time. to retrieve. The application is coded in Android studio using Java programming language. The Smart Lunch Box application was coded to work in Android phones with APIs 15 and higher.

  1. Analysis


  1.       Existing System


Present products of lunch boxes can be divided into a few categories. Overall, they are classified into two general groups. That is, the conventional lunchboxes which focuses on material but not technology and the lunchboxes which focus on incorporating latest technology into the storage and/or temperature system. Our focus is on the lunchboxes that have undergone modifications based on applied science as opposed to manufactured materials. The present trends in lunch boxes are focused on a variety of factors to make the user experience first-rate. These factors have branched off from the basic of functionality of the lunch box to protect the food. The design, durability and portability of the container are areas that manufacturers are focusing on. A product sold by ‘Foodskin’ is a flexible lunchbox which has elasticised silicon skin, maintains the shape of the food inside; without crushing it. [14] Their target was developing a container which would take up minimum space and keep the food safe at the same time. The development of lunch boxes has expanded to electric lunchboxes. Electric Lunch Boxes started cropping up when people realized that the lunch boxes up till that point weren’t doing a great job keeping the food warm for more than a couple of hours. The new electrically wired lunch boxes allowed the consumers to plug their box into a socket to heat up food at their convenience. These are powered by some type of power source to heat up the food. The sub categories under electric lunchboxes are wired and wireless. There are different approaches to maintain the warmth of the food inside containers; whether it is a wired product or heat-persisting materials.


  1. Types of Lunch Boxes

The types of lunch boxes we have categorized as traditional: different manufacturing processes/materials, wired: different power sources or wireless: controlled from a non-physical location. Our focus is on the lunchboxes that have undergone modifications based on applied science as opposed to manufactured materials. Thus, for this study, the categories of boxes fall under either wired or wireless.

  1.                 Wired Lunch Box


Most electric heated lunch boxes are classified as wired lunch boxes. There isn’t any recorded data of the first inventor of the electric lunch box but there have been attempts at creating them from the late 90s. [15] Some patents have been established in the 2010s for Electrical Lunch Boxes that were meant to be plugged into AC outlets or car cigarette lighter to warm the containers. [16]There are several models of electric lunch boxes that have been coming into the market the past decade.

Prepology Electric Warming Lunch Box is a plug-in lunch box that allows user to steam food at their desk. [17] The user has to pour water into the base, put food in the container and wait for approximately twenty minutes. The box has a disadvantage as the inner cooking container doesn’t seal shut and has been reviewed as being difficult to use. It is trademarked by IC Marks, Inc., based in Wilmington, Delaware.

The Koolatron LBS-01 plugs into a car’s cigarette lighter, targeted at users who want to be able to heat their food on the go. [18] It’s meant to keep foods steam but it is not for cooking foods; despite the brand’s claim. It isn’t durable enough for daily use, doesn’t always heat the food and is not accessible to all users as it only works if plugged into the cigarette lighter in your car. It is manufactured by Koolatron Corporation, based in Canada.

Tayama EBH-01 Electric uses very little power but can still heat your dishes up by using a PTC heating element. Where it makes up for in concept, it lacks in design as it was built poorly. It also takes approximately one to two hours to get to high temperatures. It is manufactured by Tayama Appliance Inc., based in California, USA. [19]

HeatsBox is a multi-sided warming lunch box. It is said to feature a leak-proof design that distributes heat evenly to all the food. It uses a USB C-type charging cable to power the box; even allowing user to heat up box from their laptop. It is compact and the power source is not all to reliable as a laptop as a charging dock will lead to degradation of its battery. The HeatsBox is made by the start-up Faitron, based in Switzerland. [20]

The Yescom Portable Electric Heating Lunch Box/ Food Storage Warmer uses PTC heating and uses a regular power outlet to heat the food. It takes a minimum of forty-five minutes to heat the food. It does not have detachable containers, making maintenance rather difficult. There are also instances of the box leaking even though there is a locking lid. It is manufactured by Yesccom, based in USA. [21]



  1.                 Wireless Lunch Box

Wireless lunch box aren’t as common as the wired variety. There have been very few successful products that have been released as a ‘wireless heating container’. Though, over the years, small start-ups have proposed some ideas of a potential wireless heating container, none have followed through with building the product. The possibility of a lunchbox with an in-built battery operated heater was suggested on various industrial design forums, but the idea was not executed. [22]  There hasn’t been a successful wireless lunchbox in the market till now. In 2016, a Switzerland based company called Hibachi proposed a self-heating lunchbox wireless lunch box. [23] It seemingly doesn’t need an external device to be plugged into a socket to heat the food. Though their proposal is fascinating, they haven’t disclosed further details nor do they have any news presence to support their claims.

  1. Drawbacks of Existing System

The existing systems are focused singularly on protecting the food from the environment, introducing materials that retain heat, collapsible containers or aesthetically pleasing designs. But there isn’t much focus on providing functionality for the lunch box itself to heat up food, wirelessly. Coming to electric lunch boxes, they are almost all of the wired variety. These are not as portable as they are marketed because the user will always be looking for a power outlet to connect the box to. Also, the user still has to manually turn the power switch on and plug the device on. The existing systems are not automated enough.


  1.       Proposed System


Our main aim is to provide an interface to the user where he is able to control the timer for heating the Smart Lunch Box over a wireless Bluetooth connection and refer to a countdown timer that depicts time until food is ready. The proposed system is an attempt at improving the interaction between a user and the physical lunch box: in lessening human intervention and providing an alternate method to ensure food is warm enough.

  1. Advantages of Proposed System


The proposed system uses Positive Temperature Coefficient (PTC) heating technology, Bluetooth connectivity and rechargeable batteries to introduce automation to the process of heating up with a electric lunch box.  PTC heating is a unique technology that eschews traditional resistance and replaces it with ceramic stones/chips. These are safer than normal heating elements. They also last longer and are easier to maintain. Bluetooth connectivity helps to bring wireless control of the lunch box; by using the Android application. The rechargeable batteries allow the box to be charged for multiple rounds of heating the containers without having to ever depend on a power outlet connection to charge the box.























  1.            Software and Hardware Specifications


  1. Software Requirements


  • IDE     : Arduino 1.8.2 IDE
  • Operating  System   : Linux, Windows or any equivalent  OS
  • Android Development   : Android Studio 2.2.2
  • Website for Application  : WordPress Website


  1. Hardware Requirements for Computer
  • RAM    : min 512 MB
  • Processor   : min 1.0 GHz
  • Android Phone   : API 15 or higher


  1.  Hardware Requirements for Kit


  • Lunchbox  : Containers fitted with copper plates and aluminium foil
  • Microcontroller : Arduino Pro Mini
  • Bluetooth Module : Bluetooth HC-05
  • Heating Elements : PTC Heating Elements
  • Mechanical Relays : One-Channel Relay Module
  • Power Supply  : Rechargeable Lithium Ion Batteries (12V)
  • Connectors
  1. Modules


  1.       Module Specifications

There are mainly five modules in our project, they are:

  • User Module
  • Hardware Module
  • Android Module
  • Arduino IDE Module
  • Administrator Module


  1.  Hardware Module


The hardware of the Smart Lunch Box consists of several components fitted into the base of the box. They are the Arduino Pro Mini microcontroller, Rechargeable Lithium Ion batteries, Bluetooth HC-05, Mechanical Relays and PTC Heating Elements; in the containers. The two containers in the box are coated with copper plates and aluminium foil. One on/off switch and two LEDs are fitted to the side exterior surface of the Lunch Box.

  1.  User Module


In this module, Users are required to download the android application onto their Android phones from the ‘SmartLunchBox’ WordPress website. The user manually switches on the Lunch box switch before opening the application on their phone. The application prompts them to allow permission for turning Bluetooth on, if not already done. The application allows the user to either ‘Heat Now’ or ‘Set Lunch Time’ to begin heating their food placed in the containers.

  1.   Android Module


This module is coded entirely in Android Studio to create the Android application that is to be downloaded by the user. It includes functionality for connectivity to the Bluetooth   Module HC-05. The application has two screens: Home and Set Time. The Home screen deals with establishing Bluetooth connectivity. The second screen is where the user can set time to heat lunch box in one of two options: Heat Now; to start heating immediately or ‘Set Lunch Timer’; to set a specific time to have the lunch ready by then. A countdown  at the bottom shows time left for lunch box to be done heating.

  1.  Arduino IDE Module


The IDE version 1.8.2 is designed to be able to run programs on a hardware kits like Arduino Pro Mini and Bluteooth Module. The Arduino code allows the microcontroller to receive commands about heating from the Android application; over Bluetooth connection. The code allows the microcontroller to signal the PTC heating elements to start heating up.  The lighting up of the two LEDs on the box that are connected to the upper and lower containers are also coded in the Arduino IDE.

  1.  Administrator Module


This module is for the administrator; which deals with him controlling the application functionality and monitoring the WordPress website from which user can download the Android application. If changes are made to the Smart Lunch Box application, the administrator updates the new APK file to the WordPress website.









  1.            Design


5.1 System Architecture



Lunch Box with Switch

PTC Heating Element in Container

Mechanical Relay

Arduino Pro Mini


Fig 5.1 Showing the architecture of the Smart Lunch Box system

From the figure, one can infer the flow of command from Smart Lunch Box application to the Arduino Pro Mini microcontroller over a Bluetooth connection. The Arduino then signals the Mechanical Relays to close the circuit; for power to the PTC heating elements inside the containers. During heating, the countdown timer runs in the application; depicting time until food is ready.



  1.       System Flow Chart
  2.       Schematic Diagram




  1.       Unified Modelling Language

Unified Modelling Language (UML) is a standard language for writing software blue prints. The UML is a language for

  • Visualizing,
  •  Specifying,
  •  Constructing
  • Documenting the artefacts of a software intensive system.

The UML is a language which provides vocabulary and the rules for combining words in that vocabulary for the purpose of communication. A modelling language is a language whose vocabulary and the rules focus on the conceptual and physical representation of a system. Modelling produces an understanding of a system. UML is a method for describing the system architecture in detail using the blueprint.

  1. Definition

UML is a general purpose visual modelling language that is used to specify, visualize, construct and document the artefacts of the software system. UML is language that provides vocabulary and rules for communication and function on conceptual and physical representation- it is a modelling language. Specifying means building models that are precise, unambiguous and complete, in particular the UML addresses the specification of all the important analysis design and implementation decisions that must be made in developing and displaying the software intensive system. Visualization is where the UML includes both graphical and textual representation. It makes easy to visualize the system and for better understanding. Constructing is where UML models can be directly connected to a variety of programming languages and it is a sufficiently expensive and free from any ambiguity to permit the direct execution of models.

  1.       Building Blocks of UML

The vocabulary of the UML encompasses three kinds of building blocks:

  • Things
  • Relationships
  • Diagrams

Things are the abstractions that are first-class citizens in a model; relationships unite these things; Diagrams collect interesting collections of things.

5.5.1. Things in the UML

There are four kinds of things in the UML:

  • Structural things
  • Behavioural things
  • Grouping things
  • Annotational things


Structural things are the nouns of UML models. The structural things used in the project design are:

First, a class is a set of objects that share the same attributes, operations, relationships and semantics.












Fig 5.1: Classes

Second, a use case is a description of set of sequence of actions that a system performs which a particular result of value to a particular actor.

Fig 5.2: Use Cases

Third, a node is a physical element that exists at runtime and represents a computational resource, which generally has some memory and often processing capability.

Fig 5.3: Node

Behavioral things are the dynamic parts of UML models. The behavioural thing used is:

An interaction is a behaviour that comprises a set of messages exchanged between a set of objects within a particular context to achieve a specific purpose. An interaction involves a series of other elements, including messages, action sequences (the behaviour invoked by a message and links (the connection between objects).

Fig 5.4: Messages

5.5.2. Relationships in the UML

There are four kinds of relationships in the UML:

  • Dependency
  • Association
  • Generalization
  • Realization

dependency is a semantic relationship between two things in which changing one thing may affect the semantics of the other thing (the dependent thing).

Fig 5.5: Dependencies

An association is a structural relationship in which a set of links are described; a link being a connection among objects. Aggregation is a special kind of association, that represents a structural relationship between a whole and its parts.

Fig 5.6: Association

generalization is a specialization/ generalization relationship in which objects of the specialized element (the child) are substitutable for objects of the generalized element (the parent).

Fig 5.7: Generalization

realization is a semantic relationship between classifiers, where one classifier specifies a contract that another classifier guarantees to carry out.

Fig 5.8: Realization
5.5.3 Diagrams in the UML

A diagram is a graphical representation of set of elements, most often rendered as a connected graph of vertices (things) and arcs (relationships).

There are two types of diagrams; they are:

  • Structural
  • Behavioral Structural Diagrams

The UML‘s four structural diagrams exist to visualize, specify, construct and document the static aspects of the system. One can view the static parts of system using one of the following diagrams. The structural diagrams represent the static aspect of the system. These static aspects represent those parts of a diagram which forms the main structure and therefore stable. These static parts are represents by classes, interfaces, objects, components and nodes. Structural diagrams consist of Class diagram, Object Diagram, Component Diagram, Deployment Diagram.

Use-Case Diagram


A use case is a set of scenarios that describing n interaction between a user and a system. A use case diagram displays the relationship among actors and use cases. The two main components of use case diagram are use cases and actors. An actor represents a user in another system that will interact with the system you are modelling. A use case diagram is an external view of the system that represents some action the user might perform in order to complete a task.


Activity Diagram


Activity diagram describes the flow of control in a system. So it consists of activities and links. The flow can be sequential, concurrent or branched. Activities are the functions of a system. Numbers of activity diagrams are prepared to capture the entire flow in a system. Activity diagrams are used to visualize the flow of controls in a system. This is prepared to have an idea of how the system will work when executed. They can be used to describe business workflow or the operational workflow of any component in a system. Sometimes activity diagrams are used as an alternative to State machine diagrams.


Sequence Diagram

Sequence diagram in UML shows how object interact with each other and the order those interactions occur. It is important to note that they show the interactions for a particular scenario. The processes are represented vertically and interactions are shown as arrows. Behavioural Diagrams

The UML’s five behavioural diagrams are used to visualize, specify, construct, and document the dynamic aspects of a system. The UML’s behavioural diagrams are roughly organized around the major ways which can model the dynamics of a system.  Behavioural diagrams basically capture the dynamic aspect of a system. Dynamic aspect can be further described as the changing/moving parts of a system. Behavioural diagrams consist of Use case diagram, Sequence Diagram, Collaboration Diagram, State Chart Diagram, Activity Diagram.


 Class Diagram


Class diagrams are used to describe the types of objects in a system and their relationships. Class diagram model class structure and contents using design elements such as classes, packages and objects. Class diagrams describe three different perspectives when designing a system, conceptual, specification and, implementation. These perspectives become evident as the diagram is created and help solidify the design. Class diagrams are arguably the most used UML diagram type. It is the main building block of any object-oriented solution. It shows the classes in a system, attributes and operations of each class has three parts, name at the top, attributes in the middle and operations or method at the bottom. In large systems with many classes related classes are grouped together to create class diagrams. Different relationships between diagrams are shown by different types of arrows.

  1.       Use Case Diagram


Fig 5.9 showing the use case diagram for user in the project

The above diagram   is the use case diagram of our system.It shows the set of actions performed by a user. As described earlier, the content in the Ovals are actions performed in the system and those actors are like symbols represent users in system. Those dashed lines from user to action means users are performing those actions respectively.

  1.       Class Diagram






Fig 5.10 showing the use case diagram for user in the project





The above diagram represents class diagram of our system i.e., it shows various classes used in our system and the relationship with one class to other in the system. Each rectangle box represents a class and the upper portion of it represents class name and middle portion represents attributes of the class and the lower represents the functions performed by that class.

  1.       Activity Diagram



Fig 5.11 showing the activity diagram for user in the project

The above diagram represents activity diagram of the system i.e., it represents the flow of activities in our project. Dot at the start represents starting and dot with circle represents ending and an activity is represented as curve sided rectangle. On seeing it we can understand the flow activities that has to be gone from start to end

  1.       Sequence Diagram


Fig 5.12 showing the sequence diagram for user in the project

The above diagram Show sequence diagram for a user. It represents sequence or flow of messages in system. The rectangle boxes at top represent objects that are invoked by the user and the lines dropping from those boxes are life lines which shows existence of the object up to what time. The boxes on the dashed lines are events and the lines connecting them represent messages and their flow.















  1. Code
  1.    Arduino Code

int PTC1=4;

int PTC2=2;

//The relay board runs on active low configuration, so HIGH=LOW and LOW=HIGH

int LED1=7;

int LED2=8;

String inString= “”;

int timeToWait=0;

int inByte;

int k=0;

void setup(){


pinMode(PTC1, OUTPUT);

pinMode(PTC2, OUTPUT);

pinMode(LED1, OUTPUT);

pinMode(LED2, OUTPUT);


digitalWrite(PTC1, HIGH);

digitalWrite(PTC2, HIGH);






















void loop() {


int i=0;

int p=0;

inByte =;

timeToWait = inByte;



inString +=(char)inByte;


if(inByte == 101){

timeToWait = inString.toInt();













for(i=0; i<4; i++){


















































digitalWrite(PTC1, LOW);














  1.       Android Code

Screen 1
package com.example.rohi.smartlunchbox;

import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.content.Intent;

public class Screen1 extends AppCompatActivity implements View.OnClickListener {
Button connect;
protected void onCreate(Bundle savedInstanceState){
connect= (Button)findViewById(;
public void onClick(View v){
Intent i=new Intent(getApplicationContext(), Screen2.class);
Screen 2

package com.example.rohi.smartlunchbox;

import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothSocket;
import android.content.DialogInterface;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.TimePicker;
import android.widget.Toast;

import java.util.Calendar;
import java.util.UUID;
import android.os.CountDownTimer;


public class Screen2 extends AppCompatActivity implements View.OnClickListener {
private static final String TAG = “SmartLunchBox”;
TimePicker timePicker;
Button btnOn,btnSetTime;
private static final int REQUEST_ENABLE_BT = 1;
private BluetoothAdapter btAdapter = null;
private BluetoothSocket btSocket = null;
private OutputStream outStream = null;
CountDownTimer countDownTimer;
TextView textView;
private static final UUID MY_UUID = UUID.fromString(“00001101-0000-1000-8000-00805F9B34FB”);
private static String address = “98:D3:32:10:55:7A”;
protected void onCreate(Bundle savedInstanceState) {
Log.d(TAG,”In onCreate()”);
btnOn = (Button)findViewById(; //heatnow
btnSetTime = (Button)findViewById(;
textView = (TextView)findViewById(;
btAdapter = BluetoothAdapter.getDefaultAdapter();
Button connect;
public void onClick(View v) {
switch (v.getId()) {
countDownTimer = new CountDownTimer(31 * 60 * 1000, 60 * 1000) {
public void onTick(long millisUntilFinished) {
textView.setText(“Minutes Remaining : ” + millisUntilFinished / 60000);
public void onFinish() {
textView.setText(“Heating Completed”);
Toast.makeText(this, “Heating command sent”, Toast.LENGTH_LONG).show();
Calendar cal = Calendar.getInstance();
long lunchHour = timePicker.getCurrentHour();
long lunchMinute = timePicker.getCurrentMinute();
long currentHour = cal.get(Calendar.HOUR_OF_DAY);
long currentMinute = cal.get(Calendar.MINUTE);
long waitHours = abs(lunchHour – currentHour);
final long waitMinutes = abs(lunchMinute – currentMinute) + waitHours * 60;

DialogInterface.OnClickListener dialogClickListener = new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
switch (which) {
case DialogInterface.BUTTON_POSITIVE:
sendData(waitMinutes + “e”);
case DialogInterface.BUTTON_NEGATIVE:
AlertDialog.Builder builder = new AlertDialog.Builder(v.getContext());
builder.setMessage(“Are you sure you want to fix this as Lunch Time?”).setPositiveButton(“Yes”, dialogClickListener)
.setNegativeButton(“No”, dialogClickListener).show();
countDownTimer = new CountDownTimer(waitMinutes * 60 * 1000, 60 * 1000) {
public void onTick(long millisUntilFinished) {
textView.setText(“Minutes Remaining : ” + millisUntilFinished / 60000);

public void onFinish() {
textView.setText(“Heating Completed”);
public void onResume() {
Log.d(TAG, “…In onResume – Attempting client connect…”);
// Set up a pointer to the remote node using it’s address.
BluetoothDevice device = btAdapter.getRemoteDevice(address);
try {
btSocket = device.createRfcommSocketToServiceRecord(MY_UUID);
} catch (IOException e) {
errorExit(“Fatal Error”, “In onResume() and socket create failed: ” + e.getMessage() + “.”);
Log.d(TAG, “…Connecting to Remote…”);
try {
Log.d(TAG, “…Connection established and data link opened…”);
} catch (IOException e) {
try {
} catch (IOException e2) {
errorExit(“Fatal Error”, “In onResume() and unable to close socket during connection failure” + e2.getMessage() + “.”);
// Create a data stream so we can talk to server.
Log.d(TAG, “…Creating Socket…”);
try {
outStream = btSocket.getOutputStream();
} catch (IOException e) {
errorExit(“Fatal Error”, “In onResume() and output stream creation failed:” + e.getMessage() + “.”);
public void onPause() {
Log.d(TAG, “…In onPause()…”);
if (outStream != null) {
try {
} catch (IOException e) {
errorExit(“Fatal Error”, “In onPause() and failed to flush output stream: ” + e.getMessage() + “.”);
try     {
} catch (IOException e2) {
errorExit(“Fatal Error”, “In onPause() and failed to close socket.” + e2.getMessage() + “.”);
private void checkBTState() {
// Check for Bluetooth support and then check to make sure it is turned on

// Emulator doesn’t support Bluetooth and will return null
if(btAdapter==null) {
errorExit(“Fatal Error”, “Bluetooth Not supported. Aborting.”);
} else {
if (btAdapter.isEnabled()) {
Log.d(TAG, “…Bluetooth is enabled…”);
} else {
//Prompt user to turn on Bluetooth
Intent enableBtIntent = new Intent(btAdapter.ACTION_REQUEST_ENABLE);
startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT);
private void errorExit(String title, String message){
Toast msg = Toast.makeText(getBaseContext(),
title + ” – ” + message, Toast.LENGTH_SHORT);;
private void sendData(String message) {
byte[] msgBuffer = message.getBytes();
Log.d(TAG, “…Sending data: ” + message + “…”);
try {
} catch (IOException e) {
String msg = “In onResume() and an exception occurred during write: ” + e.getMessage();
if (address.equals(“00:00:00:00:00:00”))
msg = msg + “. Update your server address from 00:00:00:00:00:00 to the correct address on line 37 in the java code”;
msg = msg +  “. Check that the SPP UUID: ” + MY_UUID.toString() + ” exists on server. ”;
errorExit(“Fatal Error”, msg);

Screen 1 Activity

<?xml version=”1.0″ encoding=”utf-8″?>
<RelativeLayout xmlns_android=””

android_text=”Connect to Box”
android_layout_centerHorizontal=”true” />

android_adjustViewBounds=”false” />

Screen 2 Activity

<?xml version=”1.0″ encoding=”utf-8″?>
< xmlns_android=””

android_text=”Set Lunch Time”
android_layout_marginTop=”420dp” />

android_text=”Heat Now”
android_layout_marginTop=”350dp” />

android_elevation=”4dp” />


app_popupTheme=”@style/AppTheme.PopupOverlay” />




tools_background=”@android:color/white” />




Manifest File 

<?xml version=”1.0″ encoding=”utf-8″?>
<manifest xmlns_android=””

<uses-permission android_name=”android.permission.BLUETOOTH” />
<uses-permission android_name=”android.permission.BLUETOOTH_ADMIN” />

<activity android_name=”com.example.rohi.smartlunchbox.Screen1″
<action android_name=”android.intent.action.MAIN” />

<category android_name=”android.intent.category.LAUNCHER” />

  1. Screenshots


  1. User opens SmartLunchBox website at from their android mobile phone to access the necessary download file.


Note: The website when accessed from a computer, looks as follows.

  1. Link redirects to MediaFire where user downloads link for the APK file.


  1. User downloads the APK file and installs it.

Screenshot_20170426-011340.png              Screenshot_20170426-011343.png

Note: Application does not require any special access.

  1. User opens application after installation is completed and is directed to the SmartLunchBox home screen.

Screenshot_20170426-011447 (1).png                   Screenshot_20170426-011455.png

  1. User manually switches an on/off switch on the side of the Lunch Box.IMG-20170414-WA0012.jpg             WhatsApp Image 2017-04-26 at 12.13.32 PM.jpeg

Note: The blue LED’s light up when the box is turned on.

  1. Upon clicking connect to box, a connection is established with Arduino Pro Mini controller and the application will redirect to the second screen. If the Bluetooth is turned off, a prompt to enable Bluetooth will pop up; user must select ‘Turn On’. After turning Bluetooth on, user will select ‘Connect to Box’ to proceed.


  1. In the second screen, the user has two options to begin heating the lunch box; ‘Heat Now’ or ‘Set Lunch Time’.


  1. On clicking ‘Heat Now’, the android application hints the Arudino pro mini which in turn activates the PTC heat  sensors to start heating the food immediately. This occurs with the help of the entire hardware set up at the bottom of the lunch box.

WhatsApp Image 2017-04-26 at 11.58.28 AM.jpeg

  1. The PTC heat sensors are placed on copper foil ,which acts as a conductor and it is covered with aluminium foil so that the food doesn’t stay in contact with any of the electrical components.

IMG-20170414-WA0009.jpg        IMG-20170414-WA0010.jpg

  1. These PTC sensors are charged via lithium batteries and are connected to it externally as in shown in the figure.


  1. The user can also choose ‘Set Lunch Time’ option, using which the food gets heated by a certain set time.


Note: The Arduino Pro mini waits till the set time and activates the heat sensors 30 minutes prior to the set lunch time to heat the food. By the end of the set time the food gets heated and can be consumed.

  1. Meanwhile, we can also see the ‘Minutes Remaining’ feature on the application which shows the amount of time remaining for the food to get heated.


  1. Once the food is heated, unplug the switch and remove containers to consume the food.
  1. Testing


The purpose of a test is to find errors. Testing is the process of trying to discover every conceivable lack or weakness in a work product. It helps to provide a way to check the functionality of components, sub assemblies, assemblies and a finished product. It is the process of exercising software with the intention of ensuring that the software system meets your requirements and user’s expectations and does not fail in an unacceptable manner. Each type of test responds to specific testing requirement.


  1.       Types of Testing


Unit Testing

Unit testing involves the design of test cases that validate that the internal program logic is functioning properly, and that program inputs produce valid outputs. All decision branches and internal code flow should be validated. It is the testing of individual software units of the application .it is done after the completion of an individual unit before integration. This is a structural testing, that relies on knowledge of its construction and is invasive. Unit tests perform basic tests at component level and test a specific business process, application, and/or system configuration. Unit tests ensure that each unique path of a business process performs accurately to the documented specifications and contains clearly defined inputs and expected results.


Integration Testing
Integration testing is designed to test integrated software components to determine if they actually work as a program. The tests are event driven and are more concerned with the basic result of screens or fields. The integration tests show that although the components were individual satisfaction, as demonstrated by the successful unit test, the combination of components is correct and consistent. The integration tests are specifically oriented to expose the problems that arise from the combination of components.

Functional Testing

Functional tests provide systematic demonstrations that proven functions are available as specified by commercial and technical requirements, system documentation, and user manuals.

Functional tests focus on the following elements:

  • Valid Input               :  we must accept the valid input.
  • Invalid Input             : we must reject the invalid input.
  • Functions                  : exercise the functions.
  • Output                      : exercise the application outputs.
  • Procedures                  : invoke interfacing systems or procedure.

Requirements, key functions or special test cases are the main things that the organization and preparation of functional tests focuses on. In addition, we should consider systematic coverage related to the identification of business process flows; Data fields, predefined processes, and successive processes for testing. Additional tests are identified before the functional test is completed, and the actual value of the ongoing tests is determined.

System Testing

The entire integrated software system should meet the requirements, so system testing ensures that this criterion is achieved. To ensure known and predictable results we should test a configuration. An example of system testing is the configuration-oriented system integration test. System testing relies on descriptions and process flows, with emphasis on pre-driven process linkages and integration points.


White Box Testing


White Box Testing is a test in which the software tester has knowledge of the internal operation, structure and language of the software, or at least its purpose. It is the purpose. It is used to test areas that cannot be reached from a black box level.



Black Box Testing

Black Box Testing is testing the software without any knowledge of the internal operation, structure or language of the module being tested. Black box testing, like most other types of tests, should be written from a definitive source document, such as a specification document or requirements, such as a specification document or requirements. It is a test in which the software under test is treated, like a black box. You cannot “see” in it. The test provides inputs and responds to outputs without regard to how the software works.


  1.       Unit Testing

Usually, unit tests are performed as part of a combined code and a unit testing phase of the software life cycle, although it is not uncommon for coding and unit testing to be performed in two distinct phases.


Test strategy and approach

Field testing will be performed manually and functional tests will be written in detail.

Test objectives

  • Lunch Box should be powered up : LED
  • APK file must function properly
  • Bluetooth Connectivity should be established

Features to be tested

  • Communication established with Lunch Box
  • LED lighting up at appropriate times
  • Heating of containers according to set time
  • Accurate ‘minutes remaining’ displayed
  • All buttons should perform correct operations.
  1.       Integration Testing


Two or more software components integrated into a single platform. This will produce faults caused by interface defects. This is tested incrementally in integrated testing. The components or software applications are checked by integration testing. Components in a software system or – a step above – enterprise-level software applications – interact without error.

Test ResultsAll the test cases mentioned above passed successfully. No defects encountered.

  1.       Acceptance

In user acceptance testing, the user should accept the system completely and it should be according to the user specified. It also ensures that the system meets the functional requirements.

Test ResultsAll the test cases mentioned above passed successfully. No defects encountered.

  1.       Test Cases


  1. Smart Lunch Box Website
S.No Test Case Excepted Result Test Result
1 On entering Smart Lunch Box website link in mobile browser. Smart Lunch Box website opens up to Home Screen. Successful
2 On clicking external Download Link from mobile browser. Redirect to MediaFire download link Successful
3 On clicking MediaFire APK download link from phone APK file downloads onto the Android phone Successful



Fig 8.1 showing the test cases for Smart Lunch Box Website


  1. Application Communicating with Lunch Box
S.No Test Case Excepted Result Test Result
On manually switching on Lunch Box on/off switch Blue LED1 and LED2 light up to indicate turned on Successful
On  Clicking the Connect To Box Button Enable Bluetooth/ Application connects to Lunch Box over Bluetooth connectivity and LEDs light up Successful
On clicking Heat Now Lunch Box starts heating immediately: signalled by LEDs on (alternatively). Successful
On clicking Set Lunch Time Lunch Box waits and heats at set time; signalled by LED on (alternatively). Successful
On  clicking Heat Now/ Set Lunch Time Display Minutes remaining at bottom of Application screen. Successful
On exiting application and opening to check Minutes Remaining Application second screen opens with Minutes Remaining displayed at the bottom of the screen Successful
On Minutes Remaining: 0 Lunch Box finishes heating, LEDs off Successful


Fig 8.2  showing test cases for communicating with the lunch box through Application







8.2 Testing Heating of Various Food Types

The effect of heating varies depending on the type of food in the container, the extent of heating must be understood clearly so that it would not make food unfit to consume. For this testing the following components were used—

  1. Cooked rice 100 grams
  2. Oatmeal 100 grams
  3. Cooked Noodles 100 grams
  4. Thermometer ranging -50˚to 300˚celsius.

Fig 8.3 showing the Experimental Setup
Fig 8.4 showing Thermometer (range: -50 to 300˚C)

Time (min) Cooked Rice (˚c) Oatmeal (˚c) Cooked Noodles (˚c)
0 27.1 29.9 29.3
2.5 38.1 30.7 37.3
5 58.1 32.2 46.5
7.5 68.2 39.3 55
10 68.9 52.5 65.3
12.5 72.1 65.6 71.6
15 73 78.4 81.3
17.5 73.3 81.6 86.5
20 73.4 85.8 87.3
22.5 74.5 86.4 88.1
25 75.1 87.3 88.9
27.5 76.4 88 90.3
30 77.6 88.8 91.4

Fig 8.5 showing table for Experiment Readings

Fig 8.6 showing graph for heating of Cooked Rice

Fig 8.7 showing graph for heating of Oatmeal

Fig 8.8 showing graph for heating of Cooked Noodles


Fig 8.9 showing graph for comparing heating of all three foods


Fig 8.10 showing temperature of rice at 25 minutes of heating

The experiment shows that the temperature increases exponentially within the first  10 minutes for all three foods. Following the 10 minute mark, the rice and noodles slowly heat up. But for the oatmeal, this observation occurs at the 15 minute mark. This difference in temperature rise is dependent on the type of food substance used.  From the ‘Food Comparison’ graph, we can tell that the cooked rice has the most rapid increase in temperature while oatmeal takes longer.
When reheating food, it should be steaming hot all the way through or reach a temperature of 70 ˚C for more than 2 minutes. The tested foods satisfied this condition at times 12.5 minutes for rice and noodles and at 15 minutes for the oatmeal.



  1.   Conclusion and Scope for Future Enhancements

The Smart Lunch Box allows the user to control their wirelessly controlled, heating lunchbox from their phone. This system offers automation of some traditional features; such as being able to send commands to the lunch box without having to physically set timer for heating food. The device will serve as an alternative to using conventional microwaves for the purpose of heating food. This will make life easier for users who want to have hot food on the go. It eliminates the need to have an external power source at the time of heating and therefore, will serve as a quick alternative.
For future additions, we would like to address several areas:

  • Improving the battery capacity for the Lunch Box’s power supply for longer usage time.
  • An addition of a power outlet and/ USB port for alternative options to charge the box in the situation where batteries aren’t charged or based on user preference.
  • A feature to charge the batteries directly from a port on the box without having to remove them each time recharging is needed.
  • An addition for setting temperature as well as timer for Lunch Box such that user can customize the heat settings.
  • Further automate the process such that user can choose either the physical switch or a setting in the application to completely switch the box off.
  • A sleeker design of the lunchbox for materials with higher retaining materials to store food and exterior materials that has higher insulating properties.

References Page

  1.     References
  1. The Rise of Big Business under article History of the United States Industrialization and reform, N.d, Article on The USA Online, Retrieved from   [6]
  2. Sam Arora. 2016, “Does Food Spoil In Vacuum”, retrieved from  para3 [11]
  3. Rico Francois. 2010, Electrical Lunch Box Patent, US 20100275615, under United States Patent Office, retrieved from  claim 19 [16]
  4. Ramachandra Budihal 2010, “Emerging Trends in Embedded Systems and Applications”, retrieved from  [3]
  5. Rachel Johnson. 2006,  “Men and Women: Differences in How Men Eat and How Women Eat”, retrieved from p.1  [9]
  6. N.d., “Future of Embedded and Career Options”, retrieved from para7 [2]
  7.  N.d. “Insulation Materials”, retrieved from para6 [13]
  8. Michael D. Grissom 2004, “Battery powered hot lunch box” under Lunchbox with In-built Battery Operated Heateron CreativityPool website, retrieved from [22]
  9. Mandy Francis. 2014, The Electric Lunch Box, under “The plug-in lunchbox that cooks your food at your desk”, on DailyMail UK,  retrieved from  [17]
  10. Lunch Box. N.d. Wikipedia Article. Retrieved from  p.1 para2  [7]
  11. Lisa Bramen 2009, “The History of the Lunch Box”, Article on Smithonian Magazine Retrieved from  para7   [8]
  12. Kyle Munkittric. 2011, “In Which Technological Era Are We Living”, retrieved from [1]
  13. Katrina Turril 2016, “How big child food portions should be compared to adults’”, retrieved from   [10]
  14. Jo Lakin 2011, “Cooking and Re-heating Food”, retrieved from  para4, [5]
  15. Jen Lowry 2013, “Cheap Metals/Plastics that are heat resistant”, retrieved from [12]
  16. Heating  Lunch Box, N.d. Product Listing, under Thermal Lunchbox, retrieved from  [19]
  17. Google Patents N.d, Heated Electric Lunch Boxes, under Google-listed patents, retrieved from  [15]
  18. Faitron 2016“HeatsBox Makes Post Workout Meals Easy” and “Faitron Funded Closing Seed Round Raising More Than Six Digits” on HeatsBox website, retrieved from  para5 [20]
  19. Daniel Imperiale 2017, Koolatron LBS-01 under “7 Best Electric Heated Lunch Boxes” , retrieved from para1 [18]
  20. Carlos Gonzalez 2015, “What’s the Difference Between Conduction, Convection, and Radiation?” , retrieved from [4]
  21. 2013, “Foodskin Flexible Lunchbox: Save Your Sandwiches” Article on Huffington Post, retrieved from  para3 [14]
  22. “Yescom Portable Electric Heating Lunch Box” under Lunch Boxeson Amazon USA, retrieved from  [21]
  23. “Yescom Portable Electric Heating Lunch Box” under Lunch Boxeson Amazon USA, retrieved from  [23]

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