Servo - December 2013

their robot controller with another Power Point show, which illustrated the following four tests:

1. Make sure all the solders looked good. This meant solders formed shiny cones that did not overflow their pads.

2. Use the DMM to verify there was no continuity between the power and ground terminals of the battery holders.

3. Use the DMM to check that proper voltage existed between the power and ground pins of the PICAXE IC socket. The proper voltage was stated as being between 4. 75 and 5. 25 volts.

4. After inserting the PICAXE-08M2, program it with a simple debug program to test that two-way communication existed between the PICAXE and laptop.

Before assembling the robot body, we gave students two programming assignments. First, they programmed their robot controller to increment a variable. This showed them how to program their robot controller count to 255. The second assignment was to make an LED blink. They then adjusted the length of the PAUSE command and observed its affect on the LED’s rate of blinking.

Making a Robot body and navigating Using dead Reckoning

After creating their first programs, students began building their robot body. Again, we lead them through the construction with a Power Point presentation. After constructing the robot body, students mounted their robot controller to it. To drive the robot, we showed class members how HIGH and LOW commands controlled the spinning of the robot’s wheels. Since the robot had two driven wheels and tail dragger, students learned to make their robot travel forward, backwards, turn left, turn right, and stop by controlling which direction each wheel turned. We did not teach our students to use pulse width modulation as a means to control the speed of each wheel.

After demonstrating that they could program their

38 SERVO 12.2013

A student's first solder. One of the mentors is stabilizing his PCB.

skills taUght

We determined that our families needed eight skills to complete a robot. There wasn’t enough time for them to become experts in all eight skills, considering the limited amount of class time available. Our goal, therefore, became to make them somewhat familiar with the following eight skills.