Blind stick
This project is designed to guide a visually impaired person to
walk and avoid bumping into obstacles. Low cost ultrasonic
rangefinders along with a microcontroller is used to measure the
distance to obstacles and if they are close enough provide a
feedback to the user in form of beeps or vibrations. The project is
made on a small single layer PCB. The sensors are not mounted on
the PCB but they are mounted on front of the stick and connected to
the main board using wires. All the parts of project PCB is shown
in the image below.
Using the stick is simple, just plug the power bank to the USB
plug (refer the image above) and switch on board using the On/Off
Switch. The power indicator LED should glow. The system is now
ready.
For testing purpose keep all the three sensors on flat surface
such as ultrasonic beam emitted by them is horizontal. Make sure
their are no obstacles in front of any sensor up-to a distance of 1
meter. Slowly come close to the center sensor until the buzzer
starts beeping. For obstacles found by the center sensor their are
two quick beeps. Try to remember this beep patten. Now move slowly
towards the right sensor also make sure their is no obstacle in
front of the front sensor. For obstacles sensed by right sensor it
will give three quick beeps. Similarly for left sensor it will give
single beep.
From the block diagram given above you can see that this project
has four major parts.The Power BankFinding a good power source for
this project was a challenge, the power supply should have to be
mobile, so that we cannot use power adapters. Also it had to be
rechargeable so that it is economical for day long use to. And last
but not the least! It had to be low cost. So we picked up a
rechargeable 5v power bank used to charge mobile phones or tablets.
Due to mass production and high demand as a mobile accessory these
are dirt cheap! A common 2700mAH power bank with USB type socket is
shown below.
These can be charged in 2hours using a 5v charger. The charger
is plugged into the wall socket and 5v output from the charger is
given to the power bank and allowed to charge for 2 hours. The
power bank must be detached from the project while
charging.Ultrasonic Range FindersThese are used to measure the
distance to the obstacle. They emit sound waves with their
frequency lying in the ultrasonic spectrum (more than 20Kz) and
thus inaudible to human ears. These sound waves goes to the
obstacle and bounces back to the detectors. We use a common HC-SR04
rangefinder module for this purpose.
PIC MicrocontrollerThis is the heart of the project. It reads
distance to obstacle using the sensor and also commands the buzzer.
There are several member in the PIC MCU family, but we have chosen
PIC16F877A because it is very popular, easily available and is
recommended in the academic course of many universities of
Bharat.
BuzzerA small 10mm diameter 5 volt buzzer is used to alert the
user about the obstacles. It beeps once for a obstacle in left,
twice for a obstacle in front and thrice for an obstacle in right.
You can also connect a vibrator motor in parallel with the buzzer.
This will provide a vibrational feedback along with audio
beeps.
Bill of Materials (BOM)S.NoReferenceValuePartQuantity
01R1, R34K71/4 Watt Resistor2
02R2, R4330 ohms1/4 Watt Resistor2
03C1, C222pFCeramic Disc Capacitor2
04C3, C40.1uFCeramic Disc Capacitor2
05Q1BC548Transistor1
06D1-5mm Round LED GREEN1
07D2-5mm Round LED RED1
08U1-PIC16F877A Microcontroller (PRE PROGRAMMED WITH
FIRMWARE)1
09J1-USB Type A Plug1
10J2-2 Pin Relimate Connecter1
11J3-6 Pin Relimate Connecter1
12SW1-Toggle Switch1
13X120MHzCrystal Oscillator1
14X55vBuzzer 10mm Diameter1
15--Vibrator Motor (Optional)1
16X2,X3,X4-HC-SR04 Ultrasonic Rangefinder Module3
17--5v Rechargeable Power Bank1
18--Charger for Power Bank with Cable1
Top legend layer
Bottom copper layer
Prototype of PCB
For sensing distance to obstacles, an HC-SR04 sensor module has
been used. It has an ultrasonic transducer which generates the
ultra sonic waves, an ultra sonic receiver and control circuitry
built on a small PCB.
Front View of HC-SR04
Back View of HC-SR04For interfacing with microcontroller it
provides two lines namely TRIGGER and ECHO. The trigger pin is an
input pin, the MCU sends a 10uS high pulse on this line to tell the
HC-SR04 to start a taking a measurement.
As soon as the HC-SR04 receives this pulse it sends out
ultrasonic waves and waits for it to goto the obstacle and come
back to the sensor. The sensor then emits a pulse on the ECHO line
whose width is equal to this time. By simple calculation we can
find the distance to obstacle.
Three such such sensors are used in this project to find
obstacle in front, left and right of the user.
/******************************************************************************
A smart walking stick made for visually impaired persons. Three
ultrasonicrange finder (HC-SR04) are used to sense any obstacles
that are in front,left and right of the person. When obstacles are
sensed, an audio warningis given.
Written By Avinash GuptaContact [email protected]
For more interesting microcontroller tutorials and projects.
Please visithttp://www.extremeelectronics.co.in
NOTICE:PROGRAM SAMPLE PROVIDED FOR SELF LEARNING PURPOSE ONLY!NO
PART OF THIS WORK SHOULD BE USED IN ANY COMMERCIAL PROJECTS OR IN
ANYTEACHING INSTITUTES FOR TEACHING THEIR STUDENTSNO PART OF THIS
WORK SHOULD BE PUBLISHED IN ANY FORM LIKE PRINTED OR
ELECTRONICMEDIA
COPYRIGHT (C) 2008-2015 EXTREME ELECTRONICS,
INDIA******************************************************************************/#include
#include
// CONFIG#pragma config FOSC = HS // Oscillator Selection bits
(HS oscillator)#pragma config WDTE = OFF // Watchdog Timer Enable
bit (WDT disabled)#pragma config PWRTE = OFF // Power-up Timer
Enable bit (PWRT disabled)#pragma config BOREN = OFF // Brown-out
Reset Enable bit (BOR enabled)#pragma config LVP = ON //
Low-Voltage (Single-Supply) In-Circuit Serial Programming Enable
bit (RB3/PGM pin has PGM function; low-voltage programming
enabled)#pragma config CPD = OFF // Data EEPROM Memory Code
Protection bit (Data EEPROM code protection off)#pragma config WRT
= OFF // Flash Program Memory Write Enable bits (Write protection
off; all program memory may be written to by EECON control)#pragma
config CP = OFF // Flash Program Memory Code Protection bit (Code
protection off)
/********************************************************************
Configuration Area.UltraSonic (US) sensor connection.
in this example it is connected to as follows
Sensor | MCU_____________Trig | PC0Echo | PC1
********************************************************************/
#define US_PORT PORTA#define US_TRIS TRISA
#define US_TRIG_POS 0
#define US_ERROR -1#define US_NO_OBSTACLE -2
#define THRESHOLD_DISTANCE 60 //CM
void HCSR04Init(){ //Set trigger port as output
US_TRIS&=~(1
