Robot876 by Jonathan Parsons

Hi, I am from South Africa and I love robotics . I am seventeen years old and this is my second
robot

My goal was to make an autonomous mobile platform which can traverse an area using dead-reckoning or
infrared obstacle avoidance backed up by bump switches. This platform had to give a user friendly
interface with the help of hyper-terminal and had to be easily configurable through hyper-terminal.

MICROCONTROLLER BOARD 
The microcontroller is the heart of any little robot. It takes the readings from all the sensors
processes it and decides on the course of action. Initially I started off with a motorola
mc68hc908gp32. It was a very powerful processor but I found that it seemed to be very susceptible
to noise. Anyhow I did not need the processing power that this microcontroller offered . It had a
maiximum internal bus speed of 8Mhz and 32 Kilobytes of program space . 

I then changed the robot`s microcontroller to a pic16f876/20p which was made by microchip . It ran
at a maximum of 5Mhz internally and had 8Kb of program space with 14 interrupt sources. I found that
noise did not easily interfere with this microcontroller. This microcontrolller came in a 28 pin
shrink package with many peripherals which are needed by this robot such as PWM , Analog to digital
converter and a serial port . 

SENSORS :
wheel encoders 
infra red avoidance
bump switches
light level sensors

CHASSIS :
perspex disc

MOTORS:
hacked servo motors with encoders

FUNCTIONS:
This little robot can:
1 Avoid obstacles (infra red avoidance and micro switches)
2 Seek for light
3 Run a pre-programmed route

PROBLEMS:
The main problem I had was getting the encoders to work properly.
Firstly the light interferred with it, secondly it was hard to align the 
wheel encoder discs so they would not skip pulses. Therefore i went for internal encoders.

TIME AND COST :
Time about 6 months
Cost about r400 but had alot of the parts lying around

FOR MORE INFO:
THE ROBOT 876 SITE 
http://users.iafrica.com/m/mw/mwjparso/robot876.htm
MY HOMEPAGE WHICH LINKS TO ROBOT876 SITE
http://users.iafrica.com/m/mw/mwjparso/homepage.htm









Email: mwjparso@iafrica.com


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