Method
Description of Overall Method
The main purpose of our experiment is to observe popcorn popping and to determine whether the size of the kernel has any relationship to the size of the popcorn piece produced, as well as determine the jump off velocity of a popping kernel. We are looking not only for difference in size, but also in shape. Differences in kernel size and shape will be compared to differences in the amount of “fluff” in the popcorn, the amount of kernel showing on the popcorn, and the general size of the popcorn. It goes without saying that this requires excellent, multiple-exposure photographs of popping popcorn, another goal of our experiment.
In order to determine the relationship between kernels and popcorn, we are going to rely on a large sampling of different sized kernels to try and determine whether there is a statistical relationship between the two. However, there may well be no relationship or we aren’t able to determine it without precise measurements of the kernels/popcorn.
The process of popping popcorn is relatively simple—it requires only a heat source, oil, and a kernel. For our experiment, our heat source is a hot plate. On the hot plate there is the bottom of a frying pan with a washer placed in the middle of it. The frying pan bottom is to prevent oil from directly touching the hot plate. The washer is in the center, so that we have a centralized place to put the oil and the kernel without the oil spreading out. The hard part is getting the right amount of oil. If too much oil is added, then it takes a long time for the kernel to pop; however, not adding enough oil does not make the kernel pop faster. Instead, not enough oil causes a “dud-like” effect. The kernel will burn and split a little bit. This results in a half-popped kernel with no white fluff. There is no actual pop if there isn’t enough oil.
Equipment:
-Metrologic Laser -Fan
-LED Photogate Sensor -3 Vivitar-283 Flash Units
-Hotplate -Washer
-Frying pan bottom -Popcorn Kernels
-Apple II Plus -Vegetable Oil
-Interface Box -Tripod
-Nikon D50 w/ zoom lens
Description of Equipment Setup
Our equipment setup consists of three basic parts, the photogate/hotplate component, the computer component, and the flash/camera component. The first component consists of a hotplate, which is sitting in the center of a table on the right side of the room. On the hotplate is a washer, which we fill with oil to cook the kernels in. To the right of the hotplate, there is a Metrologic Laser on top of a stack of mouse pads. These mouse pads raise the laser so that the beam crosses the hotplate just above the washer. On the left side of the hotplate, there is a light sensor mounted on a ring stand so that it is directly in the path of the laser beam. The light sensor is connected via wires to our second component, the computer, which is on a table on the left side of the room. We used an Apple II Plus along with an interface box to automate our flashes. The light sensor is connected to the interface box, as are the three Vivitar-283 flash units. The computer uses a Intervalometer program to automate the whole triggering process, which sets off the flash units. The third component of our setup, the flashes and camera, are located directly in front of the hotplate. The camera, a Nikon D50 with 28-200 mm zoom lens, is situated on a tripod on the floor directly in front of the hotplate to raise it directly in line with the washer on the hotplate. The three flash units are positioned on the table slightly to the left of the camera’s position. One of the flash units is clamped to the table, and the other two are on a box just to the left of the first flash.
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Description of Triggering, Timing, and Imaging Methods
Our method of taking pictures involves some informed guessing and a precise computer setup. First, the laser and the computer are turned on. We open up the program Multiplexer Flasher, and change the settings to match what we have found using guess-and-check to be the best times. The guess-and-check process involved taking multiple sets of photos, adjusting the flash delay each time until we found a reasonably successful setting. The initial delay is set to 0.02 ms, with the delay between flashes set to 25 ms. After the program is set up, we turn on the flashes, and use the flash test function to test the timing system and make sure all is in working order. Then, with the room lights on, we place a drop of oil into the washer along with a kernel and let it sit for 10 seconds, then flip it using a nail. Right after the kernel has been flipped, the lights are shut off and the timing system is enabled using the 4 key. Immediately, one group member starts taking pictures, with the shutter speed set at 2 seconds, and continues until the popcorn kernel pops which is usually within 15 seconds. Sometimes the kernel does not pop, or the smoke sets off the photogate, in which case a second group member quickly enables the timing system again using the 4 key and the process continues. After the kernel pops, the lights are turned back on, blank pictures deleted and data recorded.
Appendix: High Speed Video
We also took videos using the MotionScope 8000s High Speed Video Camera. We used light fixtures to illuminate the hotplate, then set the camera to record. The MotionScope 8000s takes 2 second video clips, and unless it is stopped it will continue to record over the previous video. So we let the camera record until the kernel popped, then quickly stopped the recording, ensuring we got the video. Once we had a clip we liked, we then recorded it onto tape using an everyday camcorder that was wired to the MotionScope 8000s. The two videos we took are included on the video page.
