Transcript Synchronized Strobe for Video Camera

Synchronized Strobe for Video
Camera
Jeff Baskett & Jason Zubo
Project Advisor: Dr. Irwin
Contents of Presentation
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Project Summary
Strobe Light
Microprocessor
DMX Interface
Video Camera
Hardware
Results
Problems Encountered
Unfinished Work
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.
Block Diagram
Sync Pulse
Circuitry
Rs-485
Interface
Microprocessor
Power
Compensation
Viewed
Image
Strobe
Image
Sensor
Video
Recorder
Reflected Light
Block Diagram
Sync Pulse
Circuitry
Rs-485
Interface
Microprocessor
Power
Compensation
Viewed
Image
Strobe
Image
Sensor
Video
Recorder
Reflected Light
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.
Standards
Block Diagram
Sync Pulse
Circuitry
Rs-485
Interface
Microprocessor
Power
Compensation
Viewed
Image
Strobe
Image
Sensor
Video
Recorder
Reflected Light
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.
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
Intensity
Data
Duration
Data
Idle line
Start bit for data
Stop Bits
for data
Software Flowchart
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.
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
DMX Output
Block Diagram
Sync Pulse
Circuitry
Rs-485
Interface
Microprocessor
Power
Compensation
Viewed
Image
Strobe
Image
Sensor
Video
Recorder
Reflected Light
RS-485 Circuit
Block Diagram
Sync Pulse
Circuitry
Rs-485
Interface
Microprocessor
Power
Compensation
Viewed
Image
Strobe
Image
Sensor
Video
Recorder
Reflected Light
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
Block Diagram
Sync Pulse
Circuitry
Rs-485
Interface
Microprocessor
Power
Compensation
Viewed
Image
Strobe
Image
Sensor
Video
Recorder
Reflected Light
Sync Pulse Circuitry
• Converts Video signal into sync signal
• Uses Precision Rectifier, inverter and
Schmitt Trigger
Sync Pulse Circuitry
• Sync Pulse is used to trigger software
interrupt to output Dmx data to fire
strobe
Video Signal
Sync Pulse
Block Diagram
Sync Pulse
Circuitry
Rs-485
Interface
Microprocessor
Power
Compensation
Viewed
Image
Strobe
Image
Sensor
Video
Recorder
Reflected Light
Sensor
• We are using a photodiode with a
current to voltage converter to sense
the light output from the strobe
Sensor Circuit
• Added a low pass filter to clean up
output of the photodiode circuit
Block Diagram
Sync Pulse
Circuitry
Rs-485
Interface
Microprocessor
Strobe
Power
Compensation
Viewed
Image
Image
Sensor
Video
Recorder
Reflected Light
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
Window Detector
Results
• System is functional minus power
compensation
• We are able to view stop-motion
effects
• We performed several experiments to
show functionality
Experiments
• Performed with and without
synchronized video strobe
– Light Bulb breaking
– Spinning Wheel
– Spinning Football
– Spinning Frisbee
– Golf Swing
Light Bulb - Room Light
Light Bulb - With SVS
Water Drop - Room Light
Water Drop - With SVS
Spinning Football - Room Light
Spinning Football - With SVS
Spinning Frisbee - Room Light
Spinning Frisbee - With SVS
Golf Swing - Room Light
Golf Swing - With SVS
Problems
Encountered
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UART troubles
DMX Inversion
Number of DMX data packets to send
Expo troubles
Inconsistency of Strobe
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
Work in
Progress
• Purchase more precise strobe
• Integrate Window Detector into system
• Eliminate EMAC board - Place
software on to a programmable chip
Questions?