In and Out Line Monitoring System for Volleyball Kelley White Advisor: Professor Buma

What problem will this project solve? A line judge determines if a ball lands in or outside the court There is a need to ensure good calls and a fair game for players and coaches Develop a system that can determine if a ball lands on the line

Specifications The prototype will be a 6 foot portion of the end line Thin line to ensure safety for players Battery powered and rechargeable (able to last a 10 hour tournament day) LED light indicating ball contact Simple installation with overlying tape over existing line Cost effective

Block Diagram Input from sensor microcontroller Indicator (LED)

Sensors 9 force sensitive resistors (FSR’s) that are 2 feet long each and have ¼” sensing section Each sensing section will be 2 feet long and contain 3 FSR’s

The Design Most important specification factor is safety The height of the line from the gym floor will be no larger than 0.5 mm thick Negligible to players 0.5 mm 2” wide tape 3 FSR’s wires 2” wide double sided tape

Testing ΔT=0.026 sec ΔT=0.258 sec Running Ball Bounce

Testing Scenario ΔT (seconds) Bounce 0.026 Hard Hit 0.038 Soft bounce 0.014 Step 0.516 Run 0.258 Two Foot Jump 0.612

Microprocessor Arduino Uno R3- receives voltage signal from one or multiple two foot sections Output LED light at the Arduino for ball contact and no light for foot contact Describe photo

Detect an input voltage pulse Algorithm Detect an input voltage pulse Start Clock Pulse ends stop clock Duration less than 100ms? NO YES Light off Light on

Final Testing: Part One Accuracy of the Arduino paired with the sensors will ultimately determine how well the system works Using four different scenarios, 10 trials each: walk, two foot jump, bounce, and hard hit Mean percent error of 4.14% for all scenarios combined Scenario Mean Percent Error Standard Deviation Walk 2.17% 1.73% Two Foot Jump 3.77% 1.90% Bounce 4.01% 2.13% Hard Hit 6.62% 2.84%

Final Testing: Part Two No light LIGHT

Conclusion Goal Success? Safety Maybe Power/battery Cost effective Easy installation No Accuracy/ Does it work? Yes!

Future Work: 1. Expanding to the whole court 180 foot perimeter 90 two foot sensing sections Analog/digital MUX

Future Work: 2. Ensure Accuracy Need to test all types of contacts An impact that barely touches the end sensor A high velocity ball that rolls over the sensor(s) Any false positives from body contact on the line

Future Work: 3. Recovery time An FSR’s resistance changes every time there is an impacting force With continuous force on the same sensor, the resistance of the sensor may not go back to its “normal” resistance before the next impact This can cause the system to miss a ball contact on the line

Questions?

Appendix Budget: Stage: Part: Purpose: Price Force Sensitive Resistors (9) FSR 408 Needed to send signal to microprocessor $161.55 Microprocessor Arduino Uno R3 Converts input to output $39.38 Op amps (3)LM358 Part of circuit * Resistors (3)820K ohm   Battery 9V lithium ion battery Power for circuit $3.81 Wires Soft flex wire Thin, durable wire to connect components $11.69 Tape 3” wide tape Tape for transportation $15.70 2” wide Tape for overlaying line for prototype $6.58 Battery holder 9V enclosed battery holder with on/off switch Encloses power for circuit and Arduino $2.95 Indicator LED Provides output for ball contact Encloser Arduino Uno and Ethernet shield transparent acrylic case Holds Arduino, solder board and battery pack $6.95 Cable Sleeving Smart Power Supply Cable Sleeving Kit Holds all of the wires together $9.95 TOTAL $258.56 The * indicates the component will be covered by the ECE department.

Thickness: Basic scotch tape: 0.058 mm Wires: 0.2546 mm FSR’s: 0.40 mm Max total thickness: 0.40+0.058= 0.458 mm *will be negligible to players

Resistor Data Parallel v. series RM= 820K One FSR is hit, resistance will have more of a change in parallel than in series. Therefore it is more accurate to have them is parallel. All FSR’s are hit, overall resistance in lower in parallel and series. Less of a drastic difference here. RM= 820K Highest resistance suggested is 100K, but this is only for small forces Tested with 100K, 500K, and 820K and the 820K gave the clearest output signal +9V FSRs LM358 Vout 820K

FSR’s .5” diameter $6.95 1.75”x1.5” $7.95 .16” diameter $5.95

Arduino Uno v. Arduino Mega Specifications: 1. Pins: Need at least 4 digital pins 2. Memory rate: Unneeded. Processing real time data to make the output decision. Not storing any outputs/inputs. 3. Sampling rate: 10 samples a second worked well for differentiating force, 100 samples a second worked very well with the scope, 50 samples a second would ensure enough accuracy 4. Small enough current draw to ensure 10 hour running time on a 9V battery Arduino Type Price Number of Digital Pins Memory Sampling Rate Current Draw Arduino Mega 2560 45.95 54 256KB 16MHz 500mA Arduino Uno R3 24.95 14 32KB 50mA

Power The system needs to work for a full 10 hour day tournament Current draw: Microprocessor: 50mA LED: 3mA Op amp: 45nA FSR’s: 0.11mA (each) Total consumption: 54.035mA Battery Capacity/current draw= number of hours Battery Capacity=540.35 mAH **Need lithium ion 9V battery with 620 mAH