Senior Design Project at USM

1. Visual Sideline Assistant Presented by: Matt Johnson and David Smith Electronics Engineering Technology

2. Abstract The Visual Sideline Assistant (VSA) was designed to enable sideline sports personnel to visually communicate desired information to the team’s players with a two-character alphanumeric code. The display face consists of two seven-segment digits which have user-adjustable brightness. The system is portable which is made possible by a 24 Volt battery pack, but can also be powered by a standard 120 VAC source. The battery pack is maintained using a “smart” charging circuit.

3. System Block Diagram

4. Overview Block Diagram Circuit Level Theory of Operation Technical Specifications Conclusions

5. Theory of Operation Lead-Acid Battery Charging Circuit Charges two 12 V lead-acid batteries placed in series. Cycle charging voltage (13.9 Vdc per battery) Utilizes the LM311 voltage comparator which is modified with a Schmitt trigger for the purpose of hysteresis range.

6. 24V Battery Charging Circuit

7. Theory of Operation (cont.) 24 VDC Battery Pack Comprised of two 12 V 34 AH sealed lead-acid batteries Charged and maintained by designed charging circuitry Primary power source of the display system At 2.5 A of load current, the batteries will be considered fully discharged in approximately 13.6 hrs. The weight of 24.5 lbs per battery will provide weight for a stable display base

9. Piezo speaker beeps with 1 kHz 45 msec tone for audible feedback of a keypress.

10. Keypad with numbers 0-9, *, #, A, B, C, D

11. * is used as the clear key to blank the display

13. Theory of Operation (cont.) Digit Driver Circuit BASIC STAMP 2 Microcontroller TTL logic levels 16 Addressable I/O ports TPIC6595 8-bit Shift Registers 250 mA outputs @ 8 Additional Flip-Flops and strobing feature for no delay of bit shifting Cascadable due to SDO pin Programming BASIC language Main commands used: SEROUT, SHIFTOUT, PULSOUT Look-up tables to translate keypresses into ASCII

14. Digit Driver Schematic

15. Logic Table

16. Segment Self-Test during Start-up

17. Theory of Operation (cont.) 24 VDC Regulation Regulates 30 VDC power supply to provide 24 VDC for main display power Allows display to be powered from a standard 120 VAC source

18. 24 VDC Regulation

19. Theory of Operation (cont.) Active Dimming Circuit Utilizes LM338 variable voltage regulator Capable of handling a bulk current of 5 Amps 10 KΩ (10 turn) potentiometer for adjusting output voltage

20. Dimming Circuit

21. Working Proto-Board Mock-Up

22. Working Proto-Board Mock-Up

23. Enclosure Design Each digit is 30” tall Control panel with PCBs Bed-liner coated upper cabinet Rear View Hollow 2” square steel tubing 30V @ 8A Power Supply Charging Circuit 24”x 12” x 8” Carbon/Steel NEMA Enclosure 12V Batt. 12V Batt. Voltage Regulation Circuit 13” x 5” HD Pneumatic Tires 10” Pneumatic Swivel Casters

24. Specifications Max. power consumption ~ 60W Size Heightmax = 108” Width = 38” Depth = 32” Weight ~ 225 lb. Dimming Level = 50 mA – 100 mA per segment (Vo = 20V – 24V)

25. Testing Results and Data 5 Hour Battery Load Test

28. Thank You

29. Battery Charging Circuit Demonstration