Obstacle Sensing Walking Stick for Visually Impaired Persons : Block Diagram
From the block diagram given above you can see that this project has four major parts.
The Power Bank
Finding 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 Finders
These 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.
This 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.
A 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.
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