Synchronized Strobe for Video Camera

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Synchronized Strobe for Video Camera

• Jeff Baskett Jason Zubo
• Project Advisor Dr. Irwin

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Contents of Presentation

• Project Summary
• Strobe Light
• Microprocessor
• DMX Interface
• Video Camera
• Hardware
• Results
• Problems Encountered
• Unfinished Work

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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.

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

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

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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)

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Software Flowchart
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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.

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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

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DMX Output
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Block Diagram
Sync Pulse Circuitry
Rs-485 Interface
Microprocessor
Power Compensation
Strobe
Viewed Image
Image
Sensor
Video Recorder
Reflected Light
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RS-485 Circuit
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Block Diagram
Sync Pulse Circuitry
Rs-485 Interface
Microprocessor
Power Compensation
Strobe
Viewed Image
Image
Sensor
Video Recorder
Reflected Light
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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

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

• Converts Video signal into sync signal
• Uses Precision Rectifier, inverter and Schmitt
  Trigger

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Sync Pulse Circuitry

• Sync Pulse is used to trigger software interrupt
  to output Dmx data to fire strobe

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

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

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Sensor Circuit

• Added a low pass filter to clean up output of the
  photodiode circuit

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

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Window Detector
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Results

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

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Experiments

• Performed with and without synchronized video
  strobe
• Light Bulb breaking
• Spinning Wheel
• Spinning Football
• Spinning Frisbee
• Golf Swing

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Light Bulb - Room Light
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Light Bulb - With SVS
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Water Drop - Room Light
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Water Drop - With SVS
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Spinning Football - Room Light
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Spinning Football - With SVS
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Spinning Frisbee - Room Light
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Spinning Frisbee - With SVS
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Golf Swing - Room Light
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Golf Swing - With SVS
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Problems Encountered

• UART troubles
• DMX Inversion
• Number of DMX data packets to send
• Expo troubles
• Inconsistency of Strobe

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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

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Work in Progress

• Purchase more precise strobe
• Integrate Window Detector into system
• Eliminate EMAC board - Place software on to a
  programmable chip

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Questions?