Brian Sweeney
Tim Collier
NCSSM class of 2003 With Dr. Loren Winters
Setup and Procedure
Our first successful sets of photos came from a few similar photographic setups. These setups were based on the use of a device to trigger the reaction inside a latex balloon. Our first challenge was to devise a way of mixing the desired ratios of gasses consistently. We chose to construct our ratios on the basis of volume and used a water tank to determine our ratios.
This system used a gas tank (1) of hydrogen or oxygen to put gas in balloons via a gas assembly (2) where the volume could be measured in the water tank (4). The gas could then be pushed into the main balloon assembly (5) via the T-clamp joint (3). The main balloon assembly could then be detatched from the clamp assembly and taken to the photo lab to conduct the combustion experiment.
The Photographic Setup
The photo lab consisted of many different elements that contributed differently to the way our photos turned out. In the photo lab, we used the detatchable mixing balloon assembly of the chemistry setup.
The balloon assembly had an integratted triggering assembly composed of a filament between two alligator clips. That triggering assembly was integrated into a series circuit with a 12 volt power supply and a pushbutton switch. When the circuit was closed, the filament heats up, and the balloon combusts. Eventually, the filament wore out and the replacement created had too much of a delay and too much unreliability, so we used the push button ignitor from a gas grill to trigger a spark from a small length of wire in the one of the alligator clips to the other inside of the balloon to ignite the gas. Eventually the 12 volt power supply was replaced by a solid state induction coil.
You can view the evolution of the photographic setup below. Each one gave us different types of results depending on what we were looking for. Our photo's were taken with a Nikon D1 model Camera with a Nikon 105mm lens and a Sigma SB-28DX 200mm lens.
This is our initial setup. The photograph was taken with a shutter speed of one second during which a switch is closed to activate the explosion. This setup allowed us to capture photos of the exploding balloon but did not allow us good enough timing to see the balloon shrink.
We eventually added a high speed video camera and remote triggering to make the process easier. With this setup, one person was able to detonate the explosion and trigger the camera while the other person would run the high speed video camera. The video camera was added to help us with our timing, revealing to us whether we took a picture too early or too late. Some of our videos are accessible through the photo gallery.
Our next setup included a computer setup independent of our triggering process that would trigger a series of Vivitar 283 flashes. This setup was designed to capture multiple images of the balloon over the course of one exposure. We used an Apple II computer, which was chosen because of its reliable clock speed making it ideal for running timing programs. We ran a program on the computer called Intervalometer 2 that would trigger our flashes at intervals specified by the user. This process was rather unreliable as we were still using long shutter speeds and manual triggering.
Our final and most complex lab setup from our initial experiments automated the experimental process entirely. Just by triggering the camera, we were able to trigger the entire detonation process with a photosensor that would trigger an input/ output interface box upon recieving a light signal from the camera's flash. Using an input/output interface box, we were able to trigger the explosion as soon as light was detected from the camera's flash. Three other flashes were wired to the I/O box via an optoisolater, a device that protected the flash circuitry from the high voltage in the primary triggering circuit. The Apple computer was still used to manage the different timings and we modified the program Intervalometer 2 into a program called Hydrogen Balloon that incorporated more timings to help us capture images at shorter shutter speeds. This was the setup that allowed us to capture our images of the balloon shrinking as well as some other interesting expansion photos. Images from the various setups can be viewed in the photo gallery.
All photos on this site are copyrighted by Brian Sweeney
and Tim Collier, 2002.
To inquire about picture use please contact Loren Winters at winters@ncssm.edu