To take these images you do require some perseverance and be prepared to invent and experiment to get the timing and setup just right.
There are a few ways to do this but this is how I did mine.
1 Build a photo gate trigger system.
2 Build a blow gun and some darts.
3 Construct a housing to enclose the Photo Gate
4 Spend time and have fun :)
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Step 1: The Photogate Trigger
The images show the two kits, the boxed unit is the HiViz MT2, the breadboard is the simpler breadboard type that is fine if you just want to take a few shots and have no big plans to do a lot of different experiments.
I built the MT2 the greater versatility and solid plugs and an enclosed circuit board suit me better when I'm messing with water, though you can take shots of balloons with talc powder inside that gives an interesting image.
Step 2: The Blow Pipe and Darts.
As you can see from the image I used Velcro to attach my MT2 to the tripod, it keeps it from being dragged about when moving cables and ensures a steady connection for the cable that is between the camera and the trigger output on the MT2 unit.
The construction of the darts and blowpipe depend on what you have laying about. I had a 2 foot piece of 1/2" plastic tube, its about 3/8" on the inside but its not to important, the dart does not require to be a snug fit mine is fairly loose.
Trim your pipe of any sharp edges and make sure its clean enough to be put in your mouth.
The darts are constructed from a plastic headed noticeboard pin and a short piece of jumbo plastic straw, my first used paper for a body but even coated with varnish their life span was very short. I pushed the body of the dart against the head of the pin to flair the straw a little then simply used super glue to glue the head to the body. During setup I found that the infra red of the Photo gate sensor passed through the straw body, so I put a strip of insulating tape along it, it now blocked the light, you could paint it I suppose but the insulating tape was quick and easy.
To ensure the dart was seen by the photo diodes every time, you can see how I used a bit of coat hanger wire to form a square with an open side a little bigger than the blowpipe diameter. I also wrapped black tape over the photodiodes as they appear to be affected by daylight to a degree, this makes the action more reliable. Now the main reason for doing it this way is to allow you to focus your attention on hitting the balloon, the dart will always be in line this way. Once you have your photodiodes taped to the wire frame lay the wire frame onto the blowpipe and fix in place with Zip ties, I used four it holds them firmly enough and you can still make fine adjustments if required, you could superglue the lot after that if you like.
Step 3: Hanging the Balloons.
I used small water balloons, I tied a string between washing line poles but I'm sure you can rig something. To make it quick and easy fitting the balloons I used an inch of solder, bend it tightly under the knot and form a hook with the other end, its quick and easy to hang them up and you can use the same bit time and time again..
Please think about where the dart will go after it either hits the balloon or misses and overshoots the target.
I will add more images if more clarity is required.
You can see more of my images on Flickr
I have no commercial interest with HiViz , I love the product and the after sales support is second to NONE so I'm recommending the product on my personal experience and hope you get the same joy I have in using the kits.
Step 4: Improved Design
The original photo gate with wire frame design was made to test the idea and get some initial images, it worked well enough. One problem was ambient light would hit the diodes and make it less sensitive so here is my improved design.
The sizes are whatever suits your tube and what you have at hand, I've since decided that it may be more ambient light proof if you don't cut the notch. The blow pipe tube would be inserted to the same depth as in this design, this would help the photo diodes be completely enclosed in the housing.
Select a block of wood a little thicker than your tube, drill a hole the entire length.
cut a notch the just wider than the diameter of the tube, so the darts don't catch on exit.
Drill two holes for the photo diodes , these have to be well aligned so drill from one side all the way through the other side if you can.
Glue the tube into the hole flush with the bottom off the diode notch, slip the diodes in their holes, try not to let them go all the way to end so that they are shielded from daylight, like a lens hood. using a black sharpie darken the little box that the photo diodes point into to stop reflected light and help make the action more reliable.
carefully use black tape to hold all the wires in place and smarten the unit up.
I've included a shot of the parts I used for the dart, a press tack and length of jumbo plastic straw.
Step 5: Water Drops
If you want to catch water drops you require a way to time the drops accurately I use a kit called Astrosplash.
by varying the lighting and fluid used the endless combination of shapes and colours will be created.