Ch

1
Ch2Robotics With The Boe Bot

• Boe-Bot Servo Test

2
Prepare Power Supply

• Put 9V battery in your kit box!!
• Find 6 V battery pack and add 4 AA batteries
• Set Jumper position to V in

3
Connect Continuous Servo Motors and Battery Pack

• Connect Servos to headers 12 and 13
• Connect battery back as shown

4
Continuous rotation Servo Control

• The pulse width defines the direction and speed
  of the servo motor.
• 850 Maximum speed counterclockwise
• 750 Stopped
• 650 Maximum speed clockwise
• Pulses are still separated by 20ms
• Use the servo center programs on the next slide
  to ensure servo is stopped at 750.

5
Centering Servos-Run programs below and adjust
servo with parallax screw driver
6
Testing individual Servos(Subsystem Test)

• Servo full speed (50 60 RPM)
• 1.3 ms or 650 2us (clockwise)
• 1.7 ms or 8502us (counterclockwise)
• Run Program
• Now change pin argument to 13 instead of 12
• Make both rotate full speed clockwise at same
  time.

• 4 Now make both servos rotate counterclockwise
  at full speed at the same time

7
Controlling Robot Direction

• Run program to right
• Imagine Servos as wheels on opposite sides of
  your robot
• Think about why this would make the robot go
  forward
• Now modify so Robot would move backward

Try holding servos back to back when doing this!
8
Adjusting speed and direction

• Fill out the description column in table 2write
  some code and test your thoughts
• The behavior column will be filled out when the
  boe-bot is fully assembled

9
Controlling Servo Run Time

• One time through loop
• 1.7 ms
• 20 ms
• 1.3 ms (code overhead)
• ______________
• 23 ms X 100 2.3 sec
• RUN VERIFY WITH STOP WATCH

Use reset to begin timing
10
Servo Run Time Contd

• The code to the right should make the servo run
  twice as long
• Do the math
• Verify with stop watch

11
Run time of both servos moving robot forward at
top speed

• P13 servo 8502us
• P12 servo 6502us
• Pause
• Code Overhead

• 1.7 ms
• 1.3 ms
• 20 ms
• 1.6 ms
• _______
• 24.6 ms

12
Run time Calculations

• RUN TIME (Pulses) (.0246sec)
• How many pulses required to run robot full speed
  for 3 seconds?
• 3 sec (Pulses) (.0246sec)
• Pulses 122
• Enter code to rightthis should make both servos
  go in opposite directions for 3 seconds then
  reverse for 3 seconds...RUN VERIFY WITH
  STOPWATCH
• USE RESET TO START TIMING!

RESULTING CODE