Project: Simple High Speed Photography

Discussion in 'The Completed Projects Collection' started by FPSOutback, Dec 31, 2015.

  1. FPSOutback

    Thread Starter New Member

    Dec 27, 2015
    2
    5
    Simple High Speed Photography

    High speed photography makes use of a very fast flash triggered at the right time to freeze motion, in this project I will design a simple circuit that will detect the vibration of a bullet hitting an object and trigger a camera flash in order to photograph the bullet in flight.



    Needed

    Piezo transducer
    NPN 2N2222 transistor
    1kΩ resistor
    47kΩ resistor
    100kΩ potentiometer
    Yongnuo YN560II camera flash (other flashes may require different resistor values)
    Camera with manual controls (I use a Sony NEX 5n)
    .22LR firearm or air rifle/cannon (higher velocity rounds will give excessive blur)
    Targets to shoot!

    Schematic

    This simple circuit uses a piezo transducer to convert the vibrations from bullet impact into an electrical current, this current then closes a transistor completing the 4.12 volt circuit from the flash, thus firing it. This circuit was found to be too insensitive to detect the very first initial vibrations from bullet impact and thus the flash fired too slowly to capture the bullet in frame, however it did capture the object breaking apart from bullet impact. Next we will look at improving the sensitivity.

    Image1.jpg

    In order to add variable sensitivity to the circuit current was tapped from the flash itself, this was routed into the base of the transistor through a 47kΩ resistor and a 100kΩ potentiometer. Please note that the transistor was also flipped around so the collector and emitter wires have swapped places, this allowed the use of lower resistance values in the tap. With a small amount of current routed into the base of the transistor some current is now passing through the collector and emitter wires, but not quite enough for the flash to fire, any added current from vibration of the piezo transducer will now tip the transistor over the edge and allow enough current through for the flash to fire. This can be dialled right up to be sensitive to sound.

    Image4.jpg

    Construction

    No board was used in the construction, rather the wires were just soldered together. A socket was used to easily connect the flash through either its pc port or hot shoe adaptor.

    Image3.jpg

    To keep everything clean it was mounted in polycarbonate sheet, this isn't required but prevented damage to the circuit from flying debris and an easy cleanup.

    Image5.jpg

    In Use

    The polycarbonate plate will now detect when the bullet hits any object placed on top. To use the camera was set to have a 10 second timer followed by a 2 second exposure, this 2 seconds provides the window if time to take the shot at the object, the sensor detects the vibration and fires the flash exposing that brief flash duration to the camera capturing a picture of the bullet impact.

    Image4o.jpg

    A drink can with a subsonic .22LR bullet just exiting.

    Image7.jpg

    An apple after being hit with a high velocity .22LR

    Image6.jpg

    The sensor was dialled up to be sound sensitive to capture the bullet just impacting a piece of chalk.

    Image8.jpg
     
  2. FPSOutback

    Thread Starter New Member

    Dec 27, 2015
    2
    5
    This was meant for the completed projects collection, can someone please move it?
     
  3. dannyf

    Well-Known Member

    Sep 13, 2015
    1,828
    365
    With small changes, you can add the ability to change the delay between the vibration is sensed and the flash is triggered -> this can be done either digitally or in analog. This will allow the same fixture to photography the bullets in different spot.
     
  4. magicChristian

    New Member

    Nov 20, 2016
    6
    0
    one idea which may be worth to try it out:
    If you use a high power LED (or some of) and some electronic you could get a sharper image. A flash will have a time of around 1 msec if not cut because exposure control. With LED´s you easily may get down to 100µs. And you could have 5 exposure sparks in a short delay. Very interesting would be to trigger before the target ist hit. You could use a weak paper mounted in some distance earlier to trigger. Better would be an optical trigger unit, but i feel its difficult to achieve.
     
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