1. Electrical Engineer Responsibilities
Connect VEX and ROBOTC
Electrical Engineer Responsibilities
Automation and Robotics VEX
© 2011 Project Lead The Way, Inc.

2. Electrical Engineer Responsibilities: Keep batteries charged.
Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
Electrical Engineer
Responsibilities:
Keep batteries charged.
Work with Mechanical Engineer to attach the battery, motors, and sensors to the model and the Cortex.
Work with the Computer Engineer to complete Motor and Sensor Setup.
Complete the Motor and Sensor Schematic on Automation Through Programming Summary.

3. Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
Cortex
The VEX® Cortex microcontroller coordinates the flow of information and power on the robot.
All electronic system components must interface the microcontroller.
The microcontroller is the brain of every VEX® robot.

4. Power Keep batteries charged
Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
Power
Keep batteries charged
Every robot needs a power source to operate.
A 7.2V NiCd rechargeable battery will be used.
Attach a battery strap to your model.
Battery life and batteries in general are well explained in the VEX Inventors Guide (Power). Page 4.9 describes how to revive batteries that appear weak due to voltage drop.

5. Power Keep batteries charged
Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
Power
Keep batteries charged
When your team is ready to test, obtain a battery from your teacher.
Attach the battery to the model using the strap.
Plug into the Cortex.

6. Power Keep batteries charged
Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
Power
Keep batteries charged
At the end of class, use the VEX® charger to prepare the battery for the next class.
Only charge batteries using the safe mode.

7. Motors Attach Motors to the model and Cortex
Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
Motors
Attach Motors to the model and Cortex
Motors transform electrical energy into mechanical energy, which creates rotary motion.
Use motors to power the robot’s drive wheels. The wheels need to make continuous full rotations, which is exactly the kind of motion provided by the motors. Rotation for forward motion is shown.

8. Motors Two methods to connect 2-wire motor to Cortex
Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
Motors
Two methods to connect 2-wire motor to Cortex
Motor ports 1 and 10
Motor port 2-9 using Motor Controller 29
Motor Ports
2-Wire 269
Controller 29
2-Wire 393

9. Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
Motors
Connect one end of the VEX Motor Controller to the 2-wire Motor. Carefully align the black and red wires.
Use the supplied wire ties to secure both ends. Include excess wire to prevent the 2-wire Motor and Motor Controller wires from separating.

10. Claw Notice the motor used to open and close the claw.
How many motors are needed for this project?

11. Sensors Attach Sensors to the model and Cortex Bumper Switch
Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
Sensors
Attach Sensors to the model and Cortex
Bumper Switch
Potentiometer
Sensors are used so the robot can sense its environment and the robot can adjust its own behaviors based on that knowledge. A sensor will generally tell the robot about one very simple thing in the environment, and the robot’s program will interpret that information to determine how it should react. The Bumper Switch sensor, for instance, will tell the robot whether it is in contact with a physical object. Depending on how the sensor is set up, this can tell the robot a lot of different things. If the sensor is mounted on the front bumper, the robot could use this information to tell whether it has run into an obstacle, like a wall inside a maze.
By making good use of sensors to detect the important aspects of its environment, a robot can make things much easier for its human operator. A robot can even operate completely independent of human control, autonomously.
Limit Switch
Line Tracker

12. Bumper Switch Sensor Signal: Digital
Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
Bumper Switch Sensor
Signal: Digital
Sensor Values: 1 = pressed, 0 = released
Description: The bumper sensor is a physical switch. It tells the robot whether the bumper on the front of the sensor is being pushed in.
Type: SPST switch (“Single Pole, Single Throw”) configured for Normally Open behavior
Signal Behavior:
Signal Behavior: When the switch is not being pushed in, the sensor maintains a digital HIGH signal on its sensor port. This High signal is coming from the Microcontroller. When an external force (like a collision or being pressed up against a wall) pushes the switch in, it changes its signal to a digital LOW until the switch is released. An unpressed switch is indistinguishable from an open port.

13. Limit Switch Sensor Signal: Digital
Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
Limit Switch Sensor
Signal: Digital
Sensor Values: 1 = pressed, 0 = released
Description: The limit switch sensor is a physical switch indicating whether the arm is pushed.
Type: SPDT microswitch, configured for SPST Normally Open behavior.
Signal Behavior:
Signal Behavior: When the switch is not being pushed in, the sensor maintains a digital HIGH signal on its sensor port. This High signal is coming from the Microcontroller. When an external force (like a collision or being pressed up against a wall) pushes the switch in, it changes its signal to a digital LOW until the switch is released. An unpressed switch is indistinguishable from an open port.

14. Line Tracker Signal: Analog Sensor Values: Range from 0-4095
Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
Line Tracker
Signal: Analog
Sensor Values: Range from
Description: A line follower uses an infrared light sensor and an infrared LED. It illuminates a surface with infrared light, and then the sensor senses the reflected radiation. The intensity determines the surface reflectivity. Light colored surfaces reflect more light than dark surfaces. The sensor detects a dark line on a pale surface, or a pale line on a dark surface.

15. Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
Line Tracker
A line follower is an analog sensor, meaning that its output covers a range of values (in this case, from zero to five volts) rather than being only high (five volts)
or low (zero volts), as is the case for a digital sensor.
You can use the line trackers to help your robot navigate along a marked path. A typical application uses three line follower sensors, such that the middle sensor is over the line your robot is following.
This range of output from zero to five volts is sent to the microcontroller, which reads it as a range
of integer values from 0 to For this particular sensor, sensor output will be low (around 0) when the infrared light bounces back to the detector – in other words, when the surface is pale or highly reflective – and high (around 4095) when the light is absorbed and does not bounce back.
We can then set a threshold value in our code to act as a trigger for behaviors. From this basic premise, we can build more complicated behaviors.
For example, if you have three line sensors on the front of your robot [hint: use the mounting bar included in your kit!], then you can program your robot to follow a white line on a black surface.
LineFollower_Middle should always see white, and the other two — LineFollower_Left
and LineFollower_Right — should always see black. If LineFollower_Left starts seeing
white, then your robot needs to steer back to the left. If LineFollower_Right starts
seeing white, then your robot needs to steer back to the right.

16. Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
Line Tracker
Use the line trackers to find the boundary between two high-contrast surfaces.
The optimal range for the line tracker to read a value is ¼ in.
In this elevator model, the line tracker sensor is used to determine if the elevator is at the correct floor.
Line Tracker
Paper – ¼ in from sensor

17. Potentiometer Signal: Analog Sensor Values: Range from 0-4095
Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
Potentiometer
Signal: Analog
Sensor Values: Range from
Description: The Potentiometer is used to measure the angular position of the axle or shaft passed through its center. The center of the sensor can rotate roughly 265 degrees and outputs values ranging from to the VEX® Microcontroller.
Mounted Potentiometer
CAUTION!
When mounting the potentiometer on the robot, be sure that the range of motion of the rotating shaft does not exceed that of the sensor. Failure to do so may result in damage to your robot and the Potentiometer.

18. ROBOTC - Programming Work with the Computer Engineer to complete
Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
ROBOTC - Programming
Work with the Computer Engineer to complete
Motor and Sensor Setup
Configure and name each motor and sensor connected to the robot.

19. Motor Setup Type a name to describe the motor location.
Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
Motor Setup
Type a name to describe the motor location.
Remember Ports 1 and 10 can be used for 2 – wire motors. You can also use a Motor Controller 29 to plug into ports 2-9.
Check Reversed if you want the motor to turn in the opposite direction.
Gateway VEX® kits do not contain servo motors, so students should never choose Servo Style Motor.

20. Analog Sensor Setup Type a name to describe the sensor.
Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
Analog Sensor Setup
Type a name to describe the sensor.
Choose the type of sensor – the only analog sensors for Gateway are Line Follower and Potentiometer.

21. Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
Digital Sensor Setup
LEDs can be plugged in to Digital Ports The type is VEX® LED.
Type a name to describe the digital sensor location or purpose. Both the limit and bumper switches are Touch Type.

22. Motor and Sensor Schematic
Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
Motor and Sensor Schematic
Complete the Motor and Sensor Schematic on Automation Through Programming Summary
This information should match the motor and sensors setup done in ROBOTC.

23. Resources
Carnegie Mellon Robotics Academy (2011). VEX Cortex Video Trainer. Retrieved from