Smart Wrist Band for Obstacle Detection
Juliana Shetara1, Sharmin Mazumder2, Shatabdi Acharjee3, Sharith Dhar4 Dept. of Electrical and Electronic Engineering
Premier University, Chittagong, Bangladesh
[email protected]1, [email protected]2, [email protected]3, [email protected]4,
Abstract-Without human guidance, it is challenging for blind person to continue his/her regular life without any disturbance.
Most famous and traditional guidance tool for blind person is walking cane or white cane. This paper is proposed to design an IR based smart wearable guidance system for blind personnel or vision impaired person to avoid collision or any kind of accidental issues. The proposed system is a smart wrist band that has built-in transmitter and receiver based on infrared technology. The smart belt is able to detect obstacle from a distance and a vibration motor will notify the blind person with a vibration about the obstacle. The vibration technology has been used to give a more comfortable notification if the blind person has any more disabilities like deafness.
Index Terms—Safety guard, Blind person, IR sensor, Control system, OP- amp
I. INTRODUCTION
The human eye is the organ of the sight that enables people to perform daily tasks and to learn about the world that surrounds them. Eyes are responsible for 80 percent of the information that human brain receives and thus makes it by far the most vital of sensory inputs. The condition of poor visual perception is called blindness. Around 285 million people worldwide are visually challenged [1]. Among them, 246 million have low vision and 39 million are blind [1]. Data over the last 20 years shows that there has been significant progress in preventing and curing visual impairment around the world. However individuals who are visually impaired or blind often travel to unknown areas and intersections so it is necessary to regularly confirming information using non visual techniques or tools. Hence traffic safety is very important for visually challenged people. In this paper a system has been proposed using IR transmitter and receiver section that will notify the concerned people with a vibration alarm. Thus is will help the blind people to avoid the obstacle without any human guidance and avoiding any accidental issues.
II. LITERATURE REVIEW
Visually defied people can only walk in fixed routes that are significant in their lives. This situation has resulted in many difficulties in their normal routine work, lives, activities and so on. The successful and widely used travel aid for most of the blind people is the long cane. It is used to detect obstacles on the ground, uneven surfaces,
holes, steps, and puddles. However its range of detection is very limited and it is only used to detect object which is near to the user. Moreover, the white cane is not capable of giving a safe street crossing environment in a busy road.
NAVBELT is another device that is a combination of earphone guidance and belt wearing box of electronics. Even though NAVBELT produce a 120 degree view of obstacles around or ahead the user still it has some major problems.
The problem with the method is one need a considerable attention and effort to decode the audio cues and the slow response time the subject cannot travel faster [3].
The other electronic device that has been used till date in order to help the blind person normally use audio alarm to notify if there is any obstacle present [4]. The main drawbacks concern with this electronic aid is to pick up the audio alarm in a noisy or busy street.
III. SYSTEM OVERVIEW
A short overview of the components used in the device is given below:
A. General Structure
This section represents the framework how the components are connected to the wrist band. The equipments are one IR receiver and transmitter, one vibrator, on differential amplifier and voltage follower for each wrist band. The user have to use two wrist bands, one for left hand and one for right hand, so that the total surrounding of the person will cover. For power supply each band has a battery and for switching purpose an “ON-OFF”
switch. As the sensors are mounted on the wrist lower height obstacles can also be detected.
Figure 1 shows the general overview of the system International Conference on Materials, Electronics & Information Engineering, ICMEIE-2015
05-06 June, 2015, Faculty of Engineering, University of Rajshahi, Bangladesh www.ru.ac.bd/icmeie2015/proceedings/
ISBN 978-984-33-8940--4
Fig. 1. Overview of the System
B. Infrared transmitter and receiver
Infrared technology offers important advantages as a form of wireless communication. Nowadays, almost all audio and video equipment can be controlled using an infrared remote control. At the receiving end, a receiver detects the light pulses, which are processed to retrieve/decode the information they obtain. Infrared (IR) light is electromagnetic radiation with longer wavelengths than those of visible light, extending from the nominal red edge of the visible spectrum at 700nm to 1 mm. This range of wavelengths corresponds to a frequency range of approximately 430 THz down to 300 GHz, [5] and includes most of the thermal radiation emitted by objects near room temperature. Infrared light is emitted or absorbed by molecules when they change their rotational- vibration movements. An infrared emitter, or IR emitter, is a source of light energy in the infrared spectrum. It is a light emitting diode (LED) that is used in order to transmit infrared signals. When the 600 Hz infrared light from the LED is reflected by an object, the receiver modules will be triggered.
After receiving the signal from the IR Receiver obstacle detection is done. An infrared data receiver (usually called a transceiver, since it can send and receive) is a dated inter- device communication standard that allowed line-of-sight wireless communication between equipped devices. It sends out pulses of light in the infrared spectrum that are read by another device. These pulses constitute a stream of digital information.
C. Op-Amp
Op-amp is called operational amplifier because we can perform mathematical operation by it. Here the op-amp used as a subtractor. The signal from the receiver is E1 which is fed to the non-inverting input. The reference signal E2 is in the inverting input. We will use superposition to analyze this circuit. First we remove E2 and replace it by ground E1 sees a non-inverting amplifier with a gain (Rf+Ri)/Ri. Thus E1 alone drives Vo to (gain×E1). Next we reconnect E2 and replace E1
by a ground E2 sees an inverting amplifier with a gain (-Rf/Ri) [5]. When both E1 and E2 are connected Vo is given by
V0= (Rf+Ri)/RiE1- (Rf/Ri)E2
Fig. 2. Operation of Op- Amp
D. Voltage Follower
The circuit is called a voltage follower, but it is also referred to as a source follower, unity gain amplifier, buffer amplifier isolation amplifier [5]. It is special case of the non-inverting amplifier. The input voltage Ei is applied directly to the (+) input. Since the voltage between (+) and (-) pins of the op-amp can be considered 0,
Vo= Ei
So, the output voltage equals the input voltage in both magnitude and sign therefore as the name of the circuit implies, the output voltage follows the input or source voltage. The voltage gain is 1 (or unity), as shown by, A= Vo/Ei= 1
Fig. 3. Voltage Follower
E. Vibration Motor
A vibrator is a mechanical device to generate vibrations. The vibration is often generated by an electric motor with an unbalanced mass on its driveshaft. There are many different types of vibrator. Some are components of larger products such as cell phones, pagers, small vibration motor has a Typical Operating current of 70~100 mA. Vibrators are used in this device to get discrete notifications. In crowded streets, it’s sometimes impossible to recognize the alert sound in case there is an obstacle in front of the personnel. That is why a vibrator is basically used here.
International Conference on Materials, Electronics & Information Engineering, ICMEIE-2015 05-06 June, 2015, Faculty of Engineering, University of Rajshahi, Bangladesh
www.ru.ac.bd/icmeie2015/proceedings/
ISBN 978-984-33-8940--4
IV. WORKING PRINCIPLE
The main problem of the blind person is that they cannot detect the direction and height of the obstacle. To overcome this problem our device will be a great help. The user will use two bands so, if the vibrator in left wrist is vibrating than the obstacle is in left side and if the right wrist is vibrating then the obstacle is in right side. If the user feels a vibration in both hand than the obstacle is in front. To detect the height of the object the users have to use their instincts, like if the object is on the floor at the height of the wrist then the vibration will increase continuously as one approach to the object. If the object is at a sufficient distance and which height is lower than the wrist than moving toward the object will decrease or stop the vibration because the object will be gone out of the IR field. For the moving obstacle the same theory can be used. If there is a continuous wall in front of the user it can be easily detected by moving the hand along the obstacle. By remembering this theory our user can use this device even in a totally unknown place.
A. Block Diagram
Fig. 4. Block Diagram of Detecting Obstacle
Block diagram (Figure 4) shows, when the device is ‘ON’, a beam of infrared light is transmitted by the IR transmitter. If any obstacle obstructs the light beam then a portion of the light will reflect back to the device. The closer the obstacle the more we will get reflected light. This reflected light is then fed to the receiver. The receiver module consists of a photodiode and a resistor. The receiver voltage is send to the voltage follower. It is used so that the received signal doesn’t get changed. The signal is then fed to the non – inverting input of the differential amplifier (+input). The inverter input is connected to a potentiometer and a 9v source. By varying the pot we can change the reference voltage. We increased the gain 2 times by connecting Ri= 10kΩ and Rf= 10KΩ resistor. The output of the differential amplifier will be Vo= 2E1-E2
Where E1= receiver voltage, E2= reference voltage
If the received signal is higher than the reference signal than a positive pulse is found at the output of the differential amplifier. This pulse activates the vibrator and it starts vibrating.
B. Procedural Flow
The device offers a series of flow for various operations.
Below is a summarized flow chart of the device.
Fig. 5. Flow Chart of the System
V. BENEFITS OVER CONVENTIONAL SYSTEM
The device is lighter and easier to carry compared to the devices available in the market. Because of the light weighted components used for constructing the device, it has a better portability to user. Instruments used in this device are much cheaper than others that have been used in conventional system. In conventional system, the indication is given by the device through sound. In a heavy traffic or in a noisy place it is difficult to hear the sound with other ongoing sounds. As this device will alert through vibrations, it is much easier to sense even though the road is noisy.
VI. EXPERIMENTAL RESULTS
We had taken the output voltage for some distance at 5cm intervals. To evaluate the performance of the device we have placed some obstacle in front of the device. The data taken from the experiment shows that the output voltage of IR distance sensor is decreasing when the distance between object and IR distance sensor is increasing which in turn decrease the input voltage of the vibrato. The minimum voltage required for International Conference on Materials, Electronics & Information Engineering, ICMEIE-2015
05-06 June, 2015, Faculty of Engineering, University of Rajshahi, Bangladesh www.ru.ac.bd/icmeie2015/proceedings/
ISBN 978-984-33-8940--4
the vibrator to operate is 1.5v A graphical representation of distance and output voltage of differential amplifier is given in figure (6). If we increase the reference voltage our range of sensing will decrease. Thus we can control our range of operation by varying the reference voltage. The experimental data is given in the table below:
TABLE I. EXPERIMENTAL RESULTS
S. No Distance(cm) Output Voltage(v)
1. 5 3.2
2. 10 3.0
3. 15 2.8
4. 20 2.5
5. 25 2.3
6. 30 2.1
7. 35 1.8
8. 40 1.7
9. 45 1.5
5 10 15 20 25 30 35 40 45 50
1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3 3.2
Distance(cm)
Output Voltage(V)
Distance Vs Output Voltage
Fig. 6. Graph Between Distance and Output Voltage
Now the same experiment is carried out by decreasing the reference voltage to a low level and the experimental data are given in the table II.
TABLE II. EXPERIMENTAL RESULTS
S.No. Distance(cm) Voltage(V)
1. 10 4.3
2. 15 4.1
3. 20 3.8
4. 25 3.7
5. 30 3.5
6. 35 3.2
7. 40 2.8
8. 45 2.5
9. 50 2.2
10. 55 1.8
11. 60 1.7
12. 65 1.5
VII. CONCLUSIONS
The result of the experiment is very promising and users have accomplished great success in using this device. In conclusion, the objective of this project is successfully achieved because the sensing device for the visually challenged using infrared distance sensor is successfully created to detect the object position and height within a specific distance range which can help them in mobility. We can use this sensing device as a wrist belt or we can also use it in the ankle when blind people want to climb in the staircase. In robotics it can also be used in the obstacle detection system. This system can be efficiently used in any other circuit where obstacle detection is needed.
ACKNOWLEDGMENT
There are many people who have helped us directly or indirectly in the successful completion of our project. We would like to take this opportunity to thank one and all.
First of all we would like to express our deep sense of gratitude towards our colleagues for always being available whenever we required any guidance as well as for motivating us throughout the project work.
We would like to thank all our friends for their help and constructive criticism during our project period. Finally, we are very much indebted to our parents for their moral support and encouragement to achieve higher goals. We have no words to express our gratitude and still we are very thankful to our parents who have shown us this world and for every support they gave us.
REFERENCES
[1] World Health Organization (2011) Lighthouse International home page [online] available:
http:://www.lighthouse.org/research/statistics-on-vision- impairment/prevalence-of-vision-impairment/
[2] Sharaga Shoval, Iwan Ulrich, Johann Borenstein (2003) , “The NavBelt: a computerized Travel Aid for the Blind”
in IEEE Robotics and Automation Magazine Vol: 10 No.1, March 2003
[3] Saneesh C T, Deepashree A V, Gagana Divya, Trupti Agarwal “Safety Guard for Blind using 8051”
[4] Infrared http://en.wikipedia.org/wiki/Infrared
[5] Robert F. Coughlin and Frederick F. Driscoll, Operational Amplifiers and Linear Integrated Circuit (6th Edition)
International Conference on Materials, Electronics & Information Engineering, ICMEIE-2015 05-06 June, 2015, Faculty of Engineering, University of Rajshahi, Bangladesh
www.ru.ac.bd/icmeie2015/proceedings/
ISBN 978-984-33-8940--4
