The Sfa Rover Project

The SFA Rover Project

Documentation for the parts and updates to the rules can be found on the course home page. http://www.physics.sfasu.edu/astro/courses/phy262.html

Background Each year students in the electronics course build small vehicles as part of a class project. The goal of this project is to learn how to make the best use of a battery and DC motor in to order cover 50 feet. In years past, DC motors were used to turn wheels that were in contact with the floor. In the spring of 2002, we used cooling fans from the inside of old PC computers to propel the vehicle forward. In 2003 the project will be improved upon again. Instead of an individual project, this is now a team project. New high torque motors will now be used. In addition to this the vehicles will be required to autonomously detect and avoid obstacles. There are web pages linked on the course home page that document the vehicles built during previous semesters and the prototype for the 2003 vehicles called the "The SFA Rover".

Construction Concepts and Goals 1. Construct a vehicle powered only by a standard 9 Volt battery and the motors provided. No other stored energy supplies - including springs or gravitational potential energy - may be used. 2. The components provided will be used in the semesters that follow. Please take care of the parts provided. Do not cut the wires on the motors or other parts provided. 3. The course will be 50-feet long. The race will begin near the Physics Resource Center (PRC) and end near the mirror on the third floor of the science building. You should scout out that area and take note of any obstacles in that area (including chairs and doorstops). 4. The team must release the vehicle from rest. The team cannot touch the vehicle during the race unless instructed to do so. 5. Each team will have 10 minutes to run the course. Each vehicle will run the course separately. Multiple attempts will be allowed if time is available. 6. During the course each team vehicle must demonstrate that it can avoid obstacles on the left and on the right. The vehicles will have two buttons mounted on the front (left and right). For example, if the vehicle hits the right wall, then the vehicle must stop, back up, turn left, and then continue the course. 7. Questions about the construction of the vehicle or the rules will be answered during office hours or by email.

Scoring D = Distance traveled in feet in 10 minutes (the maximum distance is 50-feet) R = 15 if the vehicle successfully demonstrates avoiding an obstacle on the right and 0 if it is not demonstrated L = 15 if the vehicle successfully demonstrates avoiding an obstacle on the left and 0 if it is not demonstrated T = -10 each time the vehicle is touched by a team member during the course

Grade = T + L + R + D × 70/(50ft)

Bonus: For each extra left or right obstacle avoided, 2 points of extra credit will be earned for each member of the team. A maximum of 20 extra points can be earned in this manner.

Vehicle Parts Each team can add any additional parts to the list below provided that the rules above are still followed.

1. Breadboard and Wires o These are the standard parts that we have in the lab. 2. 9-Volt Battery o You can replace this battery on the day of the vehicles run the course. 3. Vehicle Chassis and Bolts o The chassis (pronounce as 'cha-sE or 'sha-sE) is the supporting frame of a structure (as of an automobile or television). o You can replace the chassis or modify it if you ask your instructor. 4. 1 Caster o A caster is a wheel mounted in a swivel frame that is commonly used for the support and movement of furniture, trucks, and portable equipment. o This will be one of three wheels on the vehicle. 5. 2 DC Motors with Wheels o The motors have 90 degree output shafts and a 224:1 gearbox and were purchased from Solarbotics. o This motor offers 50 in·oz of torque, rotating 360 degrees every 1.6 seconds (38 rpm - just a hair slower than a servo), at 5V, drawing 600mA at stall (free running at 52mA). 6. H-Bridge Chip o An H-Bridge is a circuit that is constructed from transistors that allows you to change the direction of rotation of motors or stop the motors. o The H-Bridge chip provided is a 754410 chip from Acroname that is great for controlling small motors at roughly 1A peak current. o The 754410 is a single chip with 2 H-Bridges in it that can handle up to 1A per channel. o The pin assignments can be found on the PDF Data Sheet provided. 7. PIC Microcontroller: 16F84A or 16F819 o What is a microcontroller? A microcontroller as a single chip computer. o The Programmable Integrated Circuit (PIC) Microcontrollers that we will use have 18 pins and are made by Microchip. o The pin assignments can be found on the 16F84A PDF Data Sheet or the 16F819 PDF Data Sheet. o As part of a PHY475 project at SFA, Randy Innerarity created Getting Started With The PIC Microcontroller, a document that can be found on the course home page. o The assembly program written by Randy Innerarity for his SFA Rover will be used for each PIC Microcontroller. Teams can modify the program for their robot after the initial tests. 8. Voltage Regulator 7805 o Voltage regulators are needed to reduce the 9-Volts provided by the battery to 5-Volts. o These are Fairchild LM7805C regulators. o The pin assignments can be found on the PDF Data Sheet provided. 9. Two Buttons o These buttons should be mounted on the front of the vehicle to detect obstacles to the left or right. o These should be wired to the PIC Microcontroller.

SFA Rover Circuit Diagram

The SFA Rovers will run the course starting at lab time on the last lab of the semester.