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LED Indicator for Heart Rate Monitoring System in

Sport ApplicationN.H.Mahmood

1#, N.Uyop

1, N. Zulkarnain

1, F.K.Che Harun

1, M.F.Kamarudin

2, A.Linoby

3

1Faculty of Electrical Engineering, Universiti Teknologi Malaysia (UTM), Malaysia

2INSTEDT, Bangunan Kejora, Jalan Dato Onn, 81930 Bandar Penawar, Johor, Malaysia3Universiti Teknologi MARA (UiTM) Pahang, 26400 Bandar Tun Abdul Razak Jengka, Pahang, Malaysia

#nasrul@fke.utm.my

Abstract This paper presents a current invention formonitoring the athletes heart rate during training or exercise

session. A bracelet with different color code of Light Emitting

Diode (LED) is designed as a wrist heart rate monitor. This

color-coding makes the heart rate easier to monitor and enabling

the user to know their heart rate range at a certain moment. Our

works investigate the used of Zigbee and ANT+ as a transmissionmedium from transmitter (chest strap) to receiver (bracelet).

Different colors signify different ranges of heart rate.

Preliminary result demonstrated that it is very helpful for

athletes and coaches to monitor the fitness level of athletes and

regulate their exercise training regime in a more effective and

safer manner.

Keywords Light Emitting Diode(LED), Electrocardiogram,

wireless heart rate, heart rate monitor, Zigbee, ANT+

I. INTRODUCTIONNowadays, the use of a heart rate monitor is very common

and not merely use at the hospital as a patient monitor.Generally, heart rate monitor was used by a person who caresabout their heart to ensure that they have a normal heart rate.

The early detection of the abnormal heart rate can help to

prevent from the serious disease. In the sport field, the heart

rate monitor is needed to determine the range of heart rate.

This range of heart rate should be compatible with the

exercise done by an athlete to get an optimum exercise and toprevent from serious injury.

Such digital display of target heart rate did not provide for

ease of reading the display under the most conditions of use,

particularly when the user is exercising vigorously [1,4].

Hence, this paper proposed an innovation to respond to this

problem by providing an easily viewed target heart ratemonitor which displayed a uniform color homogenously

across the entire surface of the monitor, enabling a user to tell

at a brief glance, whether they are exercising at a suitable

intensity. The proposed innovation will be programmed to

automatically suggest user with the optimum heart rate zones

in accordance to their exercise goal, without having toperform any entangled calculation. The work will only be

focused for sport training application and inspired by [2]. This

prototyping can monitor appropriate heart rate exercise

training zone while performing an exercise by sending

feedback to a user via specific color (LED). The Zigbee and

ANT+ wireless protocol are chosen as a transmission medium

because each of wireless protocol has their own advantages.

Zigbee communication protocol is applied in this paper as it

provides a small volume, high expansion, low power

consumption, stylization and two-way transmission [3].

Meanwhile, the ANT+ is the most suitable communicationprotocol due to ultra low power consumption compared to

Bluetooth [5].

II. METHODOLOGY AND PROTOTYPE DESIGNIn this section, the application of Zigbee and ANT+ as a

communication protocol tool are described. Both application

are conducted separately or in other words, there are two

different experiments which are the application using Zigbee,

and the other one using ANT+ as communication protocolbetween transmitter and receiver. Figure 1 shows the whole

steps of the work for designing the prototype that

communicates with ZigBee.

Fig. 1 Zigbee wireless network connected to the microchip.

The work starts by gathering all the data and informationneeded from the pulse oximeter. The PIC16F1827

microcontroller is used due to the small power has a surface

ZigBee

Battery

ADC

Microcontroller

Multicolor LED

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amount microcontroller and serial port interface (SPI). The

data that have been processed by microcontroller will bedisplayed through an LED indicator on the bracelet as well as

on computer screen. This LED indicator is able to show the

different colors that indicate the range of heart rate. The data

from the microcontroller is also sent to the computer via

ZigBee wireless network connected to the microchip

MRF24J40.

Instead of using Zigbee, another communication protocolthat has been chosen is ANT+. It used to control and program

the heart rate data that had been received from ANT+, the

microcontroller is used. Initially, microcontroller will

calculate the heart rate maximum (HRmax) and determine

target heart rate zone desired by user. This HRmax obtained

by inserting the user age and gender information. The formula

use to calculate the HRmax is presented in equation (1) and (2)

respectively for male and female[2].

Male : HRmax= 206.9 - (0.67 x age) (1)

Female : HRmax= 212.9 - (0.67 x age) (2)

Then, equation (3) is used to calculate the target heart rate

(THR) zone.

THR = HRmax x % intensity (3)

The complete block diagram of heart rate monitoring

system design from chest strap to bracelet is shown in Figure

2. The chest strap (transmitter) will detects the voltage

different on the skin during every heart beat. The nRF24L01

which is act as wireless protocol will communicate with chest.

Finally, the data is processed by microcontroller and the result

is displayed through the LED strip. The color of LED strip

will indicates the target heart rate zone desired by user. The

LED strip chosen is a RGB LED with a serial peripheral

interface (SPI) controlled. It is the 5V multicolor strips and iscontrolled by an HL1606 chips.

Fig. 2 Block diagram of heart rate monitoring system

III.RESULTS AND DISCUSSIONSCurrently, the prototype of color coded heart rate

monitoring system is successfully designed for both

applications using Zigbee and ANT+. For Zigbee application,

the pulse oximeter is used to measure the heart beat and tracks

heart beats per minute continuously. Figure 3 shows the

conceptual drawing of the bracelet. This design of bracelet has

used the cloth material for more ergonomic design.

Fig. 3 The conceptual drawing of the bracelet

Conductive thread was used to connect the electronic devices

with the multicolor LEDs. A board consists of ZigBee and the

microcontroller module is placed in the middle of the bracelet.

The prototype design of a bracelet is shown in Figure 4 with

multicolor LED shows the different colors that signify therange of the heart rate. The range of heart rate [2] can be

classified into five zones as described details in Table I.

Fig. 4 Bracelet Prototype design

Table I is also used as a reference for ANT+ application.

Instead of using multicolor LED with conductive thread as

described earlier, the LED strip is also capable to showdifferent colors that indicate the range of certain target heart

rate. The design of LED strip is shown in Table II.

Chest strap

nRF24L01

MicrocontrollerLED strip

Zigbee Module with

Microcontroller module

MulticolorLED

Conductivethread Cloth material

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TABLEIDESCRIPTION FOR TARGET HEART RATE ZONE

Target

zone

Intensity

(%)

Exercise training

recommended

Zone1:

Very light

50-60% For recovery and cool-down

exercises throughout the

training season.

Zone2:

Light

60-70% Everybody for long training

sessions during base trainingperiods and for recovery

exercises during competition

season.

Zone3:

Moderate

70-80% Runners progressing towards

events or looking for

performance gains,

particularly for half and full

marathon training.

Zone4:

High

80-90% Experienced runners for all

year round training in

varying length. Becomes

more important during precompetition season.

Zone5:Maximum

90-100% Very experienced and fitrunners. Short intervals only,

usually in final preparation

for short running events.

TABLEII

DIFFERENT COLOR OF LED STRIP BASED ON HEART RATE ZONE

Blue Yellow Green Purple Red

Zone1 Zone2 Zone3 Zone4 Zone5

From Table II, it shows that the color coded is very helpful for

training purposes. For example, if a coach wants to knowwhether their athletes are fit or not, it simply can be detected

by looking at the Red color of the LED indicator. This

invention gives the coach easier to evaluate athletes fitness

instead of manually calculate the heart beat of their athletes.The prototype of this portable heart rate monitoring system is

worn as a wrist is shown in Figure 5. Future works should be

focused on reducing the size for more reliable for the athletes

or any users.

Fig. 5 Example of device worn upon wrist

IV.CONCLUSIONSThe portable color coded heart rate monitoring system is

design to be noninvasive, lightweight and easily worn so thatthe athlete feel comfortable and will not impeded their

activities. This device also gives an advantage to coach to

easily get the information about athlete heart rate condition by

only monitoring the LED indicator on bracelet wearing byathletes. Future works will be focused on reducing the size ofLED strips/bracelet to be worn as a wrist band and improving

both of the data communication (Zigbee and ANT+) between

the transmitter and receiver.

ACKNOWLEDGEMENT

The authors would like to sincerely thank to Ministry of

Higher Education Malaysia (Sport Section) for the support

and Universiti Teknologi Malaysia (UTM) for the facilities

and equipment provided for this research.

REFERENCES

[1] Daoming Z. and Branko C. Monitoring Physiological

signals during running exersice, Proc. of 23rd

Annual

EMBS Int. Conference, 2001. pp. 3332-3335.

[2] A.Linoby, Color-coded Heart Rate monitoring bracelets

(COBRA) to guide specific exercise training intensity.,

RMI-UiTM (Patent), 2009. pp. 1-12.

[3] N. Watthanawisuth, et al., "Wireless wearable pulse

oximeter for health monitoring using ZigBee wireless

sensor network," ECTI-CON, 2010, pp. 575-579.

[4] Edwards C., Healthcaress hi-tech lifelines, Journal ofEngineering & technology, 2008. Volume 3/14. pp.36-39.

[5] Chen, Z., Hu, C.,Liao J, Liu S., Protocol architecture for

wireless body area network based on nRF24L01, IEEE

International Conference on Automation and Logistics,

2008. pp. 3050-3054.

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