path remembering robot project


i want to start working on a "path remembering robot" project(1st project).

the idea is to know and save how much revolutions each wheel(2 wheels) had made from start to finish and speed of turning..

therefore i need to know more about wheel encoders, since im new to this stuff(first time to use it) - could you tell me which types i'll need, what is their output and how to analyze the output to know the distance/speed..

finally, is there another suggestions on how to remember a path and store it??

thanks your help will be very appreciated.

Hi For an encoder you can simply use two semi circles, 1 white in color and the other one black. place a photo transistor to make the counts. You can either place them besides your wheel or if you have a gear setup for ur motors, you can place them there.

May be this link will help you. download the pdf and read the steps. you will find your answer there

therefore i need to know more about wheel encoders

Wheel encoders alone may not be sufficient. They will allow you to count how many turns a shaft has made, over some period of time.

Replaying that data is not trivial, but it can be done. Unfortunately, there is no guarantee that replaying the motion (especially in reverse) will result in the same absolute movement of the robot. Wheel slippage is a big factor on some surfaces. Wet grass, waxed floors, carpet, etc. will cause differing amounts of slippage. Hard rubber tires will slip more than soft rubber tires. No two tires are the same size, either.

FWIW: There a two types of encoders - absolute (provides non-volatile absolute position) and relative (just counts revolutions and degrees).

Previous post on wheel encoders for your study.