1. Synchronized Strobe for Video Camera Jeff Baskett & Jason Zubo Project Advisor: Dr. Irwin

2. Contents of Presentation Project Summary Strobe Light Microprocessor DMX Interface Video Camera Hardware Results Problems Encountered Unfinished Work

3. Project Summary We are designing a circuit to control a DMX512 strobe that will be synchronized with the shutter on a video camera. Based on the shutter speed of the camera, we plan to fire a strobe during each frame to freeze high-speed motion preventing any blurring effects. This project is for the mechanical engineering department to aid in research involving fast moving fluids.

4. Block Diagram Reflected Light Viewed Image Sync Pulse Circuitry Video Recorder Sensor Power Compensation Strobe Rs-485 Interface Microprocessor Image

5. Block Diagram Reflected Light Viewed Image Sync Pulse Circuitry Video Recorder Sensor Power Compensation Strobe Rs-485 Interface Microprocessor Image

6. Strobe Snapshot DMX/D –Requires differential input of DMX512 signal –Will operate in DMX mode where intensity is the first byte of data received, the duration will be preset and the rate will be determined by the refresh rate.

7. Standards

8. Block Diagram Reflected Light Viewed Image Sync Pulse Circuitry Video Recorder Sensor Power Compensation Strobe Rs-485 Interface Microprocessor Image

9. Microprocessor (DMX Interface) Increment or decrement strobe intensity based on output from power compensation circuitry. Use preset duration value (found experimentally) to maximize strobe effectiveness. Output appropriate DMX signals to strobe at 250Kbaud.

10. Microprocessor (DMX Interface) The rate is determined by DMX refresh –The strobe will fire at the end of a packet of data Sample packet of data (RS-485 levels) Break - 88us Mark after break - 8 us Start code - 44us Start bit for data Stop Bits for data Idle line Intensity Data Duration Data

11. Software Flowchart

12. Microprocessor Timing circuitry and DMX interface will be implemented in software. Serial data will be designed to meet DMX-512 standards. UART will output serial data to RS-485 interface. Output (TTL levels) must be inverted (RS-485 levels). Additional data packets were sent due to DMX addressing problems.

13. UART UART will output data at an extended rate of 250 Kbits/sec. Data will be accompanied by one start bit and two stop bits UART implementation requires Mod515.inc header file

14. DMX Output

15. Block Diagram Reflected Light Viewed Image Sync Pulse Circuitry Video Recorder Sensor Power Compensation Strobe Rs-485 Interface Microprocessor Image

16. RS-485 Circuit

17. Block Diagram Reflected Light Viewed Image Sync Pulse Circuitry Video Recorder Sensor Power Compensation Strobe Rs-485 Interface Microprocessor Image

18. Video Camera Sony XC-75 CCD Black and White Video Camera Module –On loan from ME department –Sync output was not functional - embedded in video signal

19. Block Diagram Reflected Light Viewed Image Sync Pulse Circuitry Video Recorder Sensor Power Compensation Strobe Rs-485 Interface Microprocessor Image

20. Sync Pulse Circuitry Converts Video signal into sync signal Uses Precision Rectifier, inverter and Schmitt Trigger

21. Sync Pulse Circuitry Video SignalSync Pulse Sync Pulse is used to trigger software interrupt to output Dmx data to fire strobe

22. Block Diagram Reflected Light Viewed Image Sync Pulse Circuitry Video Recorder Sensor Power Compensation Strobe Rs-485 Interface Microprocessor Image

23. Sensor We are using a photodiode with a current to voltage converter to sense the light output from the strobe

24. Sensor Circuit Added a low pass filter to clean up output of the photodiode circuit

25. Block Diagram Reflected Light Viewed Image Sync Pulse Circuitry Video Recorder Sensor Power Compensation Strobe Rs-485 Interface Microprocessor Image

26. Power Compensation Window Detector –This determines the need to increase or decrease the intensity of the strobe –The measured value of intensity from the sensor is the input and is compared to ideal intensity levels which were determined experimentally –The output is a signal denoting the need to increase or decrease the intensity

27. Window Detector

28. Results System is functional minus power compensation We are able to view stop-motion effects We performed several experiments to show functionality

29. Experiments Performed with and without synchronized video strobe –Light Bulb breaking –Spinning Wheel –Spinning Football –Spinning Frisbee –Golf Swing

30. Light Bulb - Room Light

31. Light Bulb - With SVS

32. Water Drop - Room Light

33. Water Drop - With SVS

34. Spinning Football - Room Light

35. Spinning Football - With SVS

36. Spinning Frisbee - Room Light

37. Spinning Frisbee - With SVS

38. Golf Swing - Room Light

39. Golf Swing - With SVS

40. Problems Encountered UART troubles DMX Inversion Number of DMX data packets to send Expo troubles Inconsistency of Strobe

41. Strobe Inconsistency Strobe was designed for theatre and stage show usage - not for precision Delay between receiving data and firing varies by about 15 ms

42. Work in Progress Purchase more precise strobe Integrate Window Detector into system Eliminate EMAC board - Place software on to a programmable chip

43. Questions?