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AUTOMATIC BMI CALCULATOR

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International Journal of Management, Technology And Engineering ISSN NO : 2249-7455

AUTOMATIC BMI CALCULATOR

Mr.T.CHANDRASEKHAR 1, Ms.KOVVURI.SURYA BHAVANI2,

Mr.M.MAHENDRA3.
1
HEAD OF THE DEPARTMENT ,GIET Engineering College ,RJY
2
3nd Year ECE , GIET Engineering ,College ,RJY
3
3nd Year ECE , GIET Engineering ,College ,RJY

Abstract
The aim of the project was to design a microcontroller based automated Body
Mass Index (BMI)calculator with LCD display, which calculates the body mass index
using the two basic parameters that are weight and height. The hardware of the
project consists of a weighing mechanism i.e. weighing machine, which is used to
calculate the body weight of a person, and a height sensing mechanism i.e. Ultra sonic
sensor, which is use to calculate the height of a person. The weight of the person is
calculated in Kilograms and the height in centimeters in accordance of the BMI
standard formula. The microcontroller based automated Body Mass Index calculator
is a useful device when it comes to controlling your weight and maintaining a healthy
life style. The calculated weight of the person through weighing machine, converts
the mechanical force into electrical signals that can be easily obtain after processing
through microcontroller. While the height of the person is calculated by the
Ultrasonic . All this data is manipulated through microcontroller and then
theresultBMI is displayed on theLCD displayanda feed back message is displayed
related to health status indicating the daily Protein Intake and Energy consumed in
kilocalories per day.

INTRODUCTION
In this generation, there are many existing technologies that help to
distinguish healthy from unhealthy persons. Many software developers created an
application that monitors man’s proper weight according to height. These include BMI
calculators that exist on application stores that can be downloaded through internet.
This software requires height and weight to measure the body fat. It provides correct

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information of the body that you can track on a consistent basis. It determines exactly
what size you should be for your specific build

Before 1980, doctors generally used weight-for-height tables, one for men and
one for women that included ranges of body weights for each inch of height. These
tables were limited because they were based on weight alone, rather than body
composition. BMI become an international standard for obesity measurement in the
1980s. The public learned about BMI in the late 1990s, when the government
launched an initiative to encourage healthy eating and exercise [1].

The body mass index (BMI) is a measure of relative weight based on an

individual's mass and height. In the nineteenth century, a Belgian statistician named
Adolphe Quetelet came up with the Quetelet Index of Obesity, which measured
obesity by dividing a person's weight (in kilograms) by the square of his or her height
(in inches) [2].

While the formula previously called the Quetelet Index for BMI dates to the
beginning of the 19th century, the new term "body mass index" for the ratio and its
popularity date to a paper published in the July edition of 1972 in the Journal of
Chronic Diseases by Ancel Keys, which found the BMI to be the best proxy for body
fat percentage among ratios of weight and height [3].

BMI provides a simple numeric measure of a person's thickness or thinness,

allowing health professionals to discuss overweight and underweight problems more
objectively with their patients

Nowadays, Body Mass Index (BMI) is calculated manually through measuring

tape and weighing scale. There are charts and graphs that show the ratio of proper
weight according to height measurement to determine whether a person has too
much body fat. This takes time and effort to calculate the body fat. The calculation of
BMI occurs in hospitals and use by health professionals to determine healthy weights
and risky weights. It is also used by schools to diagnose students in their various
weight classification (Underweight, Normal, Overweight, and Obese) when
conducting feeding programs. Some universities utilized this calculation in physical
examination and medical purposes. Also, fitness gyms used BMI calculations to
evaluate their clients and help them reach their proper weight. Pediatricians employ
BMI percentile screening for health monitoring including children, teenage and adult,
those working in a hospital or medical school, and those with fewer patients on public
insurance. Parents often wondered if their children are overweight, underweight or
just right. Using body mass index calculator can figure out if the child is in an

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appropriate weight for his or her height [4]. Dinsdale [5] stated that BMI provides a
good indicator for levels of body fat, and it is known that having a BMI that is either
too low or too high is associated with an increased risk of ill health in life

The proponents developed a system that detects height and weight of a

person that passed through the device and calculates their various weight
classifications.This classification includes Underweight or those human whose body
weight is considered too low to be healthy, Normal, And Overweight or person who
has some excess body fat relative to bone structure and height and Obese or those
individuals who has a lot of excess body fats. Through this system, the result will be
given in just few seconds. The purpose of conducting this study and the intention of
the proponents to pursue the designed project is to automate the BMI calculators in
the hospitals to lessen the jobs of the nurses and to make a faster response to the
patients; in the school feeding program and survey to save time and to make it easier
for the staffs to determine which students are included in the program and needed
health assistance. And for the fitness gyms, to help out the clients to easily check
their health status. The study also helped in surveying the health status of a certain
community. The advantages of this technology are easy to use in practice,
noninvasive, associated with no harm, accurate and consistent measurement,
reliable equipment, fast calculation if many persons are in queue, inexpensive, easy
maintenance, and less effort in doing the activity. It obtains information faster than
doing it manually. The system will be a useful tool for quickly assessing weight
classification. While it does not directly measure body fat, it is more accurate at
approximating degree of body fatness than weight alone [6]. It can last for a long
period of time.

Lustig [7] stated that the childhood obesity epidemic has taken the globe by
storm, and it has slowly made its way into the lifestyles of Filipinos. Obesity rates in
the U.S. are reaching disturbing proportions, and the Philippines is beginning to
follow suit. This study helped the proponents on calculating BMI health status
suitable for the Filipinos.

O`Brien [8] stated that the weighing scales should be calibrated monthly using
the 80kg calibration weights. Any calibration drifts should be recorded in the
calibration record book. Subsequent subject weights should be adjusted according to
the calibration drift. A calibration record should be maintained in the calibration
record book. Height measurements should be taken and adjusted according to the
calibration drift. This study helped the proponents in calibrating the exact weight
measurement. Bray and Gray [9] stated one current school of thought is to let nature takes its
course with regard to body weight.

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People who are obese (BMI of 30 or above) almost always have a large
amount of body fat in relation to their height. There are exceptions, of course and it
varies depending on body fat. Big athletes with lots of muscle might have a BMI over
30, but may still have a healthy body composition. They would not be considered
obese from the perspective of health risk [11].

The proposed design used a sensor amplifier that is related to the project
which is entitled Temperature Sensor Amplifier. The entire system constructs and
tests an amplifier circuit that increased the output voltage of a temperature sensor.
This project determined how changing external component values effects the output
of the circuit. The proponents gathered data from this project to apply it to the load
cell which uses an amplifier to amplify the voltage signal [12].

Strain gauges are sensors which are used in variety of physical

measurements. They change resistance when they are stretched or compressed.
Because of this property, strain gauges often are bonded to a solid surface and used
for measuring acceleration, pressure, tension and force [13].

The system will be a great help in various hospital instances; first, in the
hospitals, in the admission department for faster health care and services and when
admitting pregnant women. Checking BMI is very important because pregnant
woman with high BMI has higher risk of disease. Second is when identifying
malnutrition of patients in acute hospitals. Also, it helps hospitals for faster recording
of the BMI. It shows the number of the patients of the hospitals who need more
nutrients in body and to those who need to gain weight. The system also will help
schools and universities when having feeding program for faster distinguishing of
unhealthy students. Some subjects also need BMI calculator like Physical Education,
Medical diagnosis and etc.

Another help of the design is in fitness gyms.

Body builders, fitness enthusiasts, and weight lifters need to check the
participants’ BMI for their target weight according to their height. The importance of
having this device is its inexpensiveness. It saves a lot of money. The other tests for
obesity estimation or fat assessment like bioelectrical impedance and isotope
dilution are expensive and require highly trained professionals. BMI calculation
system stands out to be easily affordable by everyone [14].

Another importance of the project is it is also a good predictor of serious

ailments like cardiovascular diseases. High BMI indicates high levels of cholesterols
and triglycerides. High BMI also poses potential risks of breast cancer, colon

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cancer, endometrial cancer and respiratory problems. It's a rough indicator of current
health status and disease risk, based upon weight and degree of obesity.

To the future researchers, the design served as a reference for them in making
their own design. This system served as a guide to those persons who are health
conscious and have health problems. Through this, in a certain community,
monitoring of health status will be easy. It will also be possible to decrease the
number of underweight and obese person in that area so that there will be no excuse
to be unhealthy.

OBJECTIVES OF THE STUDY

To design and develop an Automated BMI calculation that will display the BMI
through height and weight measurement of a person. There are specific objectives
that this project aimed to analyze the manual calculation of BMI and automating it; to
design a circuit that will combine all the functions of the weight sensor and proximity
sensors and microcontroller; to develop software embedded in the microcontroller;
and to test, implement and evaluate the proposed design.

HARDWARE AND SOFTWARE DESIGN

This section presents the requirements analysis and specification, hardware
and software design of the system.

Design Process

The proponents chose embedded system design process model because it has
the step by step process which the proponents need and work on. The process has
requirement analysis wherein the design must first meet its requirement before
flowing through specifications, going through system architecture which has three
processes, the software design in which the design must need application, compiler
and especially the operating system, interface design which has software and
hardware drivers and the hardware design that is composed of architecture, compiler
and synthesis which are lastly connected into the integration and testing.

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Figure 1: Embedded Systems Design Process

Requirements Specification
The system design’s functionality is useful for clinics and schools in which they
are maintaining their student’s health. It is also economic friendly for it is not
releasing smoke and it does not damage environment. The proponents’ system design
energy consumption is just up to 12V for the sensor amplifier it does not consume
large amount of power. If it were to be manufactured, it would be inexpensive
because it doesn’t require many materials. The table 1 shows the requirements of the
design project. It includes also the engineering requirement which involve its accuracy
and speed of the system.

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Table 1: Marketing Requirement

Engineering Justification

Requirements

1. The Accuracy The proponents

of the test it by

BMI system trial and error

calculation will with the
be between system can
96% and 99% achieve a 96%
up to

99% of
accuracy.

2. The time to The system

read the needs to

height and provide

weight of the convenient use
subject and by just
calculate its entering into
BMI the system
hardware.
measure should
not exceed to
60 seconds.

3. The system The outputs of

should the

automatically calculated BMI

store it in the should be
system imposed in the
database. system
database where
it is saved and
can be viewed
upon

the user login.

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Requirements:
(1) System should provide clear and accurate outputs; (2) System should be able to
read automatically; (3) System should be able to fit for obese and underweight; (4) System
should be easy to use.

Hardware Requirements
In the designed system, in order to meet the objectives and functions of the proposed
system, the team considered using the following hardware tools:

Ultrasonic Proximity sensor for Height measurement, Load cells for Weight
measurement, ARDUINO ATMEGA328 and Sensor Amplifier and ZigBee transmitter and
Receiver

Software Requirements
The minimum software requirements of the Automated BMI Calculation Prototype
are: Arduino Integrated Development Environment.

Hardware Design
Figure 2 shows how the components are connected in transferring data. The
ultrasonic proximity sensor is used to measure the height of a person and weight sensor i.e
Load cells is used to measure the weight and, The measured height information is
transmitted through a wireless link called ZIGBEE transmission operating at 2.4 GHz to the
microcontroller Arduino Uno. Figure 2: System Block Diagram

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The micro-based BMI system is composed of five modules, consisting of ultrasonic

proximity sensor, sensor amplifier, load cell, ZIGBEE

transmitter and receiver and Arduino microcontrollers. Load cell reads the weight
of the test subject sending its collected data into sensor amplifier to amplify the voltage to
be transmitted into the microcontroller while the ultrasonic

proximity reads and collects the data height information coming from analog and sends the
gathered data to the another microcontroller in which will display the BMI status.

The functionality of the first microcontroller controls the proximity sensor that sends
5V output into the proximity sensor and collects the data coming from the proximity sensor.
The Rx of microcontroller transmits data to the other module and the Tx for receiving data
from the proximity. The microcontroller manipulates the data coming from proximity sensor
that will be computed as height measurement.

Internal Load cells for Weighing

A load cell is a transducer that is used to convert a force into electrical signal. The
most common use of this sensor is in weighing machine. Every weighing machine which
shows weight has a loadcell as sensing element. This conversion is indirect and happens in
two stages. Through a mechanical arrangement, the force being sensed deforms a strain
gauge. The strain gauge measures the deformation (strain) as an electrical signal, because
the strain changes the effective electrical resistance of the wire. A load cell usually consists of
four strain gauges in a Wheatstone bridge configuration. The electrical signal output is
typically in the order of a few millivolts and requires amplification by an instrumentation
amplifier before it can be used. The output of the transducer is plugged into an algorithm to

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calculate the force applied to the transducer. Load cells are used in several types of
measuring instruments such as weighing scales, universal testing machines.

Wireless communication protocol

Zigbee communication is specially built for control and sensor networks on IEEE
802.15.4 standard for wireless personal area networks (WPANs), and it is the product from
Zigbee alliance. This communication standard defines physical and Media Access Control
(MAC) layers to handle many devices at low-data rates. These Zigbee’s WPANs operate at 868
MHz, 902-928MHz and 2.4 GHz frequencies. The date rate of 250 kbps is best suited for
periodic as well as intermediate two way transmission of data between sensors and
controllers.

Zigbee protocol architecture consists of a

stack of various layers where IEEE 802.15.4 is defined by physical and MAC layers while this
protocol is completed by accumulating Zigbee’s own network and application layers.

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Physical Layer: This layer does modulation and demodulation operations up on transmitting
and receiving signals respectively. This layer’s frequency, date rate and number of channels
are given below.

MAC Layer: This layer is responsible for reliable transmission of data by accessing different
networks with the carrier sense multiple access collision avoidance (CSMA). This also
transmits the beacon frames for synchronizing communication

Network Layer: This layer takes care of all network related operations such as network
setup, end device connection and disconnection to network, routing, device configurations,
etc.

Application Support Sub-Layer: This layer enables the services necessary for Zigbee device
object and application objects to interface with the network layers for data managing
services. This layer is responsible for matching two devices according to their services and
needs.

Application Framework: It provides two types of data services as key value pair and generic
message services. Generic message is a developer defined structure, whereas the key value
pair is used for getting attributes within the application objects. ZDO provides an interface
between application objects and APS layer in Zigbee devices. It is responsible for detecting,
initiating and binding other devices to the network.

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Heart of Our Design Arduino

Arduino/Genuino Uno is a microcontroller board based on the ATmega328P. It has 14

digital input/output pins (of which 6 can be used as PWM

Zigbee module and Ultrasonic sensor Interfaced with Arduino Uno for height calculations
outputs), 6 analog inputs, a 16 MHz quartz crystal, a USB connection, a power jack, an ICSP
header and a reset button. It contains everything needed to support the microcontroller;
simply connect it to a computer with a USB cable or power it with a AC- to-DC adapter or
battery to get started.

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Weight sensor Load cells interfaced with Arduino uno for weight calculations

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LCD displaying the The Weight and height and programmable BMI

parameters

CONCLUSION
The technology nowadays converted manual into automatic process, which becomes
more efficient in everyday usage. The proponents used this as an advantage in monitoring
the health status of patients or students. The purpose of this project is to calculate the
weight and height measurement and display its BMI measurement automatically and save
the BMI measurement in the system’s database. The proponents developed an embedded
system which composed of two microcontrollers Arduino Uno and Arduino NANO; holding
the ultrasonic proximity sensor for the measurement of height and loading cell for the
measurement of the weight of the test subject. The proponents have combined this function
by gathering the data coming from each module to come up with the needed result. The
proponents have analyzed, automated the BMI and designed the circuit that combined all the
functions of the weight and proximity sensors and developed the software embedded in the
microcontroller. The proponents conducted different series of testing. This includes unit
testing, integration testing and acceptance testing. In general, the proponents developed the
device to provide and maintain the health status of the test subjects and to encourage
person to have a proper diet for their health. The proponents analyzed the manual BMI
calculation and automated it. The proponents designed a circuit that combined the functions
of the ultrasonic proximity sensor and weight sensor in one system and developed software
embedded in two microcontrollers which control and manipulate the whole system of the
design project.

The proponents recommended that their system design project is to be used in clinics
and institutes that needs BMI measurements for an easy calculation of their patient’s BMI;
the height stand must be folded or extendable for portable usage; and the platform in height
stand for safety purposes should be attached.

REFERENCES
[1] Rajeswari P. (2014). Glimpse on body mass index. Volume 3, Issue 4, 2014.Retrieved from
“International journal of medical and applied science”. Website: www.earthjournals.org

[2] Sun, J (2007). The History of BMI, url:

http://www.epsport.idv.tw/blog/blog/show.asp?rep no =1744&nickname=JungleSun

[3] Body Mass Index, url: https://en.wikipedia.org/wiki/Body_mass_index

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[4] Dinsdale B. (2011). A simple guide in classifying body mass index in children.Changing
Lifestyle, 2nd ed. Pg. 169-170.

[5] Body Mass Index: Advantages and

url: http://www.livestrong.com/article/40808-body- mass-index-advantages

[6] Lustig J. (2011). Wellness and Fitness of a child, wellness and fitness, 3rd edition, page 165-
167

[7] O`Brien, (1995), ABC of Hypertension, BMJ Publishing group, London, 1-34Measuring
obesity- classification and description of anthropometric data, WHO report-consultation on
the epidemiology of obesity. Warsaw 21-23 Oct 1987

[8]Bray J. & Gray S. (1988). Gain weight.Western Journal of Medicine, Vol. 2, No. 1, May 1998

[9]Harper F.(2012) BMI calculator with LCD display, Version 2, No.3, October 2012

[10] Clark S. (2014) Nutrient Prices and Other Socio-Economic and Health Determinants of the
Body Mass Index of Canadians, Vol. 20, No. 3, August 2014

[11]Fall E. (2013) Temperature Sensor Amplifier Project, Volume 3, No. 7, September 2013

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