1. Ryan Roberts April 2, 2013

2. Background The tool I am building will be used by me on my dads stock car team. I have a tool already that I use to measure the circumference of the tires. This tool is a stand with wheels on it that the tire spins on, while the tire is spun a tape measure is run along the surface of the tire to measure the circumference of the tire. The circumference of the tire is a very crucial measurement because this measurement is used to calculate the front and rear stagger of the tires.

3. Stagger Explanation Stagger is the difference between the right side tire and the left side tire. The right side tires are larger then the left side tires by about 2-3”. Stagger is very important because it can determine the handling of the car. Usually we run 2 1/4” stagger in the front and 2 3/8” in the rear. More stagger can cause the car to become loose when cornering and less stagger can cause the car to be tight when cornering so this is a very crucial measurement that is needed. These measurements are needed every time the car goes out for a session and when it comes in from a session because as the tires are run they get hotter and air pressure builds up which changes the size of the tire. So I am measuring these tires multiple times which can be very time consuming and tedious.

4. System Diagram My solution to this problem is a device that automatically measures the tire with a wheel when the tire is spun on the stand and the displays the measurement on a LCD screen.

5. Mechanical Drawing

6. Block Diagram 9V to 5V Power Supply LM2674 9V to 5V Power Supply LM2674 HCS08SH Chip Optical Encoder LCD Display Push Buttons

7. Power Supply LM2674-5 -High Efficiency 90% or greater -Step down buck regulator -Input Voltage 8 – 40V -Tested with 9V input measured 4.945V output. -Basically uses battery voltage half the time and stored energy from the inductor the other half.

8. LM2674-5 Board

9. Optical Encoder

10. Electrical Schematic

11. Code

12. Similar Products Longacre $42.95 Joes $72.94

13. Pricing PartPrice x 1Price x 100 Encoder37.3625.60 Wheel12.82 MCS08SH2.091.16 7660.95.60 Headers X55.194.50 Switches3.402.80 Resistors.12 Capacitors.24 Roller Stand42.95 Total105.1290.79 Total Without Stand62.1747.84

14. Questions