Wheels

Purpose

Learning:	how to control servo motors
Making Roomba:	drive forward and stop

Sandbox

Try these things:

Set your robot plow-down on a table so wheels don’t touch the ground (shown here).
Set the power switch to different positions (0, 1, 2).
Press and release the reset (RST) button (shown here).
Look at the back of the motors and find the “set screws” under the pieces of tape. (shown here in yellow)
Press reset to get the wheels spinning. While they’re spinning, gently turn the screws.

Write in your sprint notes…

what do the screws do?

Walkthrough

Part 1: Getting Started

Part 2: Turning the Wheels

First, we need to make sure our wheels stay still when we tell them to. Follow the Servo Centering Program instructions to calibrate your wheels.
Once your wheels are centered, try the Speed & Direction Program to learn how to make your wheels move at different speeds and directions.

Take a picture…

(or a video?) of your robot driving, then check the box in your sprint notes.

Note: Hang on to this picture. You’ll use this again soon in the assessment.

Exercises

1. Dance Move

Approaching

Make your robot do a “spin move”:

Spin clockwise for 1 second
Stop for 1 second
Spin counterclockwise for 1 second
Stop for 1 second

Hint: To spin, make one wheel go forward and one backward at the same time.

Write in your sprint notes…

the servo values that make the robot spin.

2. Stop and Go

Proficient

Create a program that:

Drives forward for 2 seconds
Stops completely for 1 second
Drives backward for 2 seconds
Stops completely

Hint: To drive forward, set one wheel to a positive number, and the other to a negative number.

Write in your sprint notes…

the servo values that make the robot drive forward.

3. Speed Control

Distinguished

Create a program that makes your robot drive forward:

Start very slowly
Speed up to medium speed after 2 seconds
Speed up to fast after another 2 seconds
Stop

Write in your sprint notes…

the servo values you used.