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

Electrical Engineer Responsibilities: 1.Keep batteries charged. 2.Work with Mechanical Engineer to attach the battery, motors, and sensors to the model and the Cortex. 3.Work with the Computer Engineer to complete Motor and Sensor Setup. 4.Complete the Motor and Sensor Schematic on Automation Through Programming Summary.

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.

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.

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.

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.

Motors Attach Motors to the model and Cortex Motors transform electrical energy into mechanical energy, which creates rotary motion.

Motors Two methods to connect 2-wire motor to Cortex Motor ports 1 and 10 Motor port 2-9 using Motor Controller 29 2-Wire Wire 393 Controller 29 Motor Ports

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.

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

Attach Sensors to the model and Cortex Sensors Bumper Switch Limit Switch Potentiometer Line Tracker

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:

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:

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.

Line Tracker 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. 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.

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

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.

ROBOTC - Programming Work with the Computer Engineer to complete Motor and Sensor Setup Configure and name each motor and sensor connected to the robot.

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.

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.

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.

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.

Resources Carnegie Mellon Robotics Academy (2011). VEX Cortex Video Trainer. Retrieved from obotc_cortex/index.html obotc_cortex/index.html