This
Project comprises of a Hardware mechanical model which is controlled by the
electronic circuits to assist a blind person. I.e., This mechanical model is
attached with the walking stick of the blind person. The model will move automatically. This model
helps the blind person to reach the destination quickly. The model has a
wireless link to a nearby computer system through which it can identify the
shortest path. When the source and destination is selected the unit will send
the data to the computer. The computer
will calculate the shortest path using Dijkstra’s shortest path algorithm and
transfers the route to the unit. The
unit will then tell the user to move in which direction. The movement of the
user in ensured using a RFID proximity cards and a reader. The reader will be
placed on the unit and on encountering of cards (Cards placed at each point)
will tell the user has to take right or left or straight through voice output. An APR 9600 voice storage and retrival IC is
used for this purpose. The unit will
give alarm signal when it finds a Obstacle. This project is divided into
modules for better understanding of the circuit.

The modules
included in this project are

Pic
Embedded Microcontroller PIC 16F877

Battery for Power Supply

RFID
Card Reader with cards

APR 9600 Voice Recording and Playback IC

Wireless RF Receiver unit

Wireless RF Transmitter unit

Software Driver in Hitech ‘C’ Language.

__Pic Embedded Microcontroller (PIC 16F877):__
This is the heart of the device
which is responsible for sensing the obstacles and producing voice Output.

__RFID Card Reader with Cards__
A RFID Card reader is
fixed on the unit. Cards will be placed
on the path at regular intervals. When
the unit encounters a card, it can sense the point at which the unit is present
through the unique code present in the card.

## APR 9600 Voice Recording and Play Back IC

**This IC is a Single Chip Voice Recording and Playback IC. A Prerecorded Voice is Stored into the IC. It can be played again by the controller by sending a control signal to the IC.**

__RF Wireless Transmitter and Receiver:__
A
Wireless RF module is used to establish a wireless link between the unit the
PC. The frequency range is 433.92 and 315 MHZ.

__Dijkstra's algorithm__
Conceived by Dutch computer scientist Edsger
Dijkstra in 1959, is a graph search algorithm that solves the
single-source shortest path problem for a graph with nonnegative edge path costs, producing a shortest path tree. This algorithm is often
used in routing.
An equivalent algorithm was developed by Edward F.
Moore in 1957

For a given source vertex (node) in the graph, the algorithm
finds the path with lowest cost (i.e. the shortest path) between that vertex
and every other vertex. It can also be used for finding costs of shortest paths
from a single vertex to a single destination vertex by stopping the algorithm once
the shortest path to the destination vertex has been determined. For example,
if the vertices of the graph represent cities and edge path costs represent
driving distances between pairs of cities connected by a direct road,
Dijkstra's algorithm can be used to find the shortest route between one city
and all other cities. As a result, the shortest path first is widely used in
network routing protocols, most notably IS-IS and OSPF (Open Shortest Path
First).

## Algorithm

Let the node we are starting be called an

**initial node**. Let a**distance of a node Y**be the distance from the**initial node**to it. Dijkstra's algorithm will assign some initial distance values and will try to improve them step-by-step.
1. Assign to
every node a distance value. Set it to zero for our initial node and to
infinity for all other nodes.

2. Mark all
nodes as unvisited. Set initial node as current.

3. For current
node, consider all its unvisited neighbours and calculate their distance (from
the initial node). For example, if current node (A) has distance of 6, and an
edge connecting it with another node (B) is 2, the distance to B through A will
be 6+2=8. If this distance is less than the previously recorded distance
(infinity in the beginning, zero for the initial node), overwrite the distance.

4. When we are
done considering all neighbours of the current node, mark it as visited. A
visited node will not be checked ever again; its distance recorded now is final
and minimal.

5. Set the
unvisited node with the smallest distance (from the initial node) as the next
"current node" and continue from step 3.

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