The photos in this gallery are images of balloons being popped by a BB/Pellet gun. In most of the images there is a small amount of corn starch in the balloon. That's the white stuff you can see inside the balloons.

I am using a controller I built from an Arduino microcontroller to control the shots.

I attached a "ballistic sensor" to the front of the gun barrel. It has 2 photo detectors on it at exactly 2 inches apart. When the Arduino detects the projectile passing through the first photo detector, it starts a timer, and when it passes through the second detector, it figures out how many nanoseconds the projectile took to cross the distance. It calculates the speed of the projectile, then use the distance from the second sensor to the target to calculate the delay before firing the flash. It fires the flash at the calculated time, hopefully catching the balloon in the middle of popping.

I designed and built a trigger switch and attached it to the trigger of the gun.

The trigger switch is a strip of thin flexible plastic (like from a blister-pack package) folded in half into a slight V shape, with copper foil tape taped to the the inside. When you squeeze the V together, the 2 pieces of foil touch, closing a switch. I soldered a piece of wire to each piece of foil, and hot-glued the assembly to the trigger of my BB gun. Now as you begin to squeeze the trigger it closes the switch, grounding a pin to the Arduino. The Arduino then opens the camera shutter, turns off the lights, and starts waiting for the projectile to pass through the photo sensors.

It takes a significant amount of time (around 50 MS (milliseconds) for the camera shutter to open, so the system starts opening the shutter as you pull the trigger. If you wait until the ballistic sensor detects the projectile then you don't have enough time to open the shutter.

I bought some 12 volt LED landscape lights and have 1 pointing at my work area and one pointing at the target. When the arduino detects the trigger being pressed, it turns off the LED lights just before opening the camera shutter. The light from LEDs stops almost instantly when the power is removed, so the room is dark by the time the camera shutter is open.

I find the patterns in the cornstarch fascinating. My theory is that the torn edges of the balloon flap as they split apart, making waves in the cornstarch. What I really want is an ultra-high-speed video of the whole process, with a frame every couple of microseconds....