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

2. 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

3. 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

4. Block Diagram
Input from sensor
microcontroller
Indicator (LED)

5. 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

6. 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

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

8. 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

9. 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

10. 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

11. 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%

12. Final Testing: Part Two
No light
LIGHT

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

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

15. 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

16. 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

17. Questions?

18. 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.

19. Thickness:
Basic scotch tape: mm
Wires: mm
FSR’s: 0.40 mm
Max total thickness: = mm
*will be negligible to players

20. 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

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

22. 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

23. 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: mA
Battery Capacity/current draw= number of hours
Battery Capacity= mAH
**Need lithium ion 9V battery with 620 mAH