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
• Standards
• Project Description
• Parts List
• Schedule of Tasks

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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.
• The only inputs into the system will be the video
  synchronized signal from the camera and the
  intensity of the light read by the sensor.
• The outputs will be the intensity of the light
  from the strobe.
• The recorded image will be analyzed to determine
  the effectiveness of the system.

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Standards
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Block Diagram
Timing signal and 250K clock
Timing Circuitry
DMX Interface
Viewed image
Intensity Adjustment
Synchronized Signal
Power Compensation
Strobe
Video Recorder
Light input
Light
Sensor
Image
Reflected Light
Video input (reflected light)
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Block Diagram
Timing signal and 250K clock
Timing Circuitry
DMX Interface
Viewed image
Intensity Adjustment
Synchronized Signal
Power Compensation
Strobe
Video Recorder
Light input
Light
Sensor
Image
Reflected Light
Video input (reflected light)
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Video Camera

• Sony XC-75 CCD Black and White Video Camera
  Module
• We will have to determine from where in the
  camera we will get the shutter signal
• The input to the camera will be the reflected
  light from the image

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Block Diagram
Timing signal and 250K clock
Timing Circuitry
DMX Interface
Viewed image
Intensity Adjustment
Synchronized Signal
Power Compensation
Strobe
Video Recorder
Light input
Light
Sensor
Image
Reflected Light
Video input (reflected light)
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Timing Circuitry

• Delay Circuitry to insure strobe fires during
  time when shutter is open.
• This delay will be calculated and implemented
  with an RC circuit
• 250 KHz clock signal
• This will be used to shift the bits of data to
  the strobe at the necessary 250 Kbaud rate as
  specified by DMX
• This will be implemented using a 555 timer

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Block Diagram
Timing signal and 250K clock
Timing Circuitry
DMX Interface
Viewed image
Intensity Adjustment
Synchronized Signal
Power Compensation
Strobe
Video Recorder
Light input
Light
Sensor
Image
Reflected Light
Video input (reflected light)
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Sensor

• We will be using a photodiode to sense the light
  output from the strobe
• Circuit design for converting photodiode output
  to useable levels has yet to be explored

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Block Diagram
Timing signal and 250K clock
Timing Circuitry
DMX Interface
Viewed image
Intensity Adjustment
Synchronized Signal
Power Compensation
Strobe
Video Recorder
Light input
Light
Sensor
Image
Reflected Light
Video input (reflected light)
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Power Compensation

• Window Detector
• This will determine the need to increase or
  decrease the intensity of the strobe
• The measured value of intensity from the sensor
  is the input and will be compared to ideal
  intensity levels which will be determined
  experimentally
• The output will be a signal denoting the need to
  increase or decrease the intensity

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Block Diagram
Timing signal and 250K clock
Timing Circuitry
DMX Interface
Viewed image
Intensity Adjustment
Synchronized Signal
Power Compensation
Strobe
Video Recorder
Light input
Light
Sensor
Image
Reflected Light
Video input (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, duration is second,
  and the rate is set by DMX refresh

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Block Diagram
Timing signal and 250K clock
Timing Circuitry
DMX Interface
Viewed image
Intensity Adjustment
Synchronized Signal
Power Compensation
Strobe
Video Recorder
Light input
Light
Sensor
Image
Reflected Light
Video input (reflected light)
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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 using
  250Kbaud timing clock.

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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

Duration Data
Break - 88us
Intensity Data
Mark after break - 8 us
Idle line
Stop Bits for data
Start bit for data
Start code - 44us
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DMX Interface
Power Compensation Output
Duration Presets
Stop Bits
Intensity Counter
Start Bits
64-bit Shift Register
RS-485 Interface
Differential DMX-512 output to strobe
64-bit Counter
250 KBaud clock
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DMX Interface
Power Compensation Output
Duration Presets
Stop Bits
Intensity Counter
Start Bits
64-bit Shift Register
RS-485 Interface
Differential DMX-512 output to strobe
64-bit Counter
250 KBaud clock
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DMX Interface
Power Compensation Output
Duration Presets
Stop Bits
Intensity Counter
Start Bits
64-bit Shift Register
RS-485 Interface
Differential DMX-512 output to strobe
64-bit Counter
250 KBaud clock
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DMX Interface
Power Compensation Output
Duration Presets
Stop Bits
Intensity Counter
Start Bits
64-bit Shift Register
RS-485 Interface
Differential DMX-512 output to strobe
64-bit Counter
250 KBaud clock
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DMX Interface
Power Compensation Output
Duration Presets
Stop Bits
Intensity Counter
Start Bits
64-bit Shift Register
RS-485 Interface
Differential DMX-512 output to strobe
64-bit Counter
250 KBaud clock
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DMX Interface
Power Compensation Output
Duration Presets
Stop Bits
Intensity Counter
Start Bits
64-bit Shift Register
RS-485 Interface
Differential DMX-512 output to strobe
64-bit Counter
250 KBaud clock
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Tradeoffs

• Large shift register and counter would be
  difficult to implement and control.
• Microprocessor is capable of controlling timing
  of data as well as transmission of data.
• Window detector output will interface directly
  with a microprocessor without A/D conversion,
  thus eliminating round off error.
• Software will make the project easy for future
  students to modify or add features.

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Microprocessor

• Interrupt driven timing control of data to follow
  DMX 512 standards
• Will output serial data to RS-485 interface as
  shift register would

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Parts List

• Strobe - Snap Shot DMX/D
• Video Camera - Sony XC-75 (in stock)
• RS-485 Interface - MAX1480C
• Sensor - EGG Vactec PhotoDiode (in stock)
• EMAC Evaluation Board (in stock)
• Sensor amplification-AD823 dual precision, 16MHz,
  operational amplifier. LM741 dual in-line
  operational amplifier. (in stock)

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Schedule of Tasks

• Finish project by Student Expo
• Other than that, were not sure how long things
  will take.