|
I have done the event Mission Possible for five years--since 8th grade. I have always placed 1st at the regional competition except for two times due to catastrophic failures, which do happen in this event. If you are on this page then you know the rules. Make a Rube Goldberg-like device that has energy transfers in the forms of electrical, chemical, mechanical, heat, and the hardest one to master, electromagnetic. Of course they change the rules slightly every year. They usually always change the way you start the device and the goal, as well as some of the bonus reactions. Most of this page will be dedicated to the most efficient way to employ the electromagnetic spectrum energy transfers. The first two years I built circuits for each electromagnetic energy transfer. Using one of Forrest Mims III electronic books for dummies, I built circuits that would switch a relay if there was a change in the amount of light, measured by a photoresistor. This was fairly inaccurate because you had to adjust a potentiometer very carefully for it to work. Also if someone would walk by and leave a shadow, it would trigger the device. So the third year I decided to apply some of my knowledge of different electronics that I had gained from viewing science fair projects. In seventh grade I saw a senior high project by Taylor Griswold of Trinity Presbyterian in Montgomery that employed something called a Basic Stamp to create a "Dancing Ant" robot. It was a crowd pleaser. A Basic Stamp is a programmable IC that only requires you to learn a high level language. You do not have to program in assembly on this microcontroller. I bought the Basic Stamp 2 OEM version, and it revolutionized my Mission Possible device. You only have to program your Basic Stamp and build a very small amount of circuitry. This is a whole lot less work than the other way I was using. Because the pins on the Basic Stamp cannot sync that much power, I used a switching transistor to switch a relay. The relay then goes to whatever you like--light bulb, motor, or even NiCr wire for those heat reactions. The nice part, is the circuit is very reliable. The only problem is in the past the rules have clearly stated no programmable circuits. This rule was taken out before I started to use the Basic Stamp; they might add it back in the future. The next tip on making a reliable Mission Possible device is to try and get the most points out of the least reactions. You don't want reactions that just carry you on to new reactions and earn no points. Try to make every reaction count for points. The bonus reactions are kind of fun. I like to try and figure out ways to employ the bonus reactions without sacrificing reliability. They like to make you use chemical reactions for bonuses. For example chemical into electromagnetic. In my first two high school Mission Possible devices I would get this bonus reaction by beating up a raver for his glow sticks. I would then cut one of the glow sticks open and pour out the clear liquid into a bottle. Then, I would take out the glass tube containing the second reactant. I would wash it off with Dawn because the reactants seem to be hydrophobic oils. Finally, I would break open the glass tube in another bottle. In the device I would set it up so that the the device would mix the reactants which would create light and trip a photogate. This got to be expensive, and for whatever reason if they accidentally mixed during set up you would be in a predicament. So I chose to simplify in my later Mission Possible devices. Using the Basic Stamp I would set up a photogate (an LED or infrared LED on one end of a bottle and a sensor on the opposite side.) I would put baking soda in the bottle and have vinegar in the test tube above the bottle. When the motor is energized the vinegar pours into the bottle and mixes. The foam blocks the LED and you get bonus points for that reaction. You can use the exact same reaction for chemical to mechanical. Instead this time you put a black ping pong ball in a tube. When the reaction occurs the foam lifts the ping pong ball and blocks the light coming from your source. The Basic Stamp allows you to do many different things. In my latest device I used a digital thermometer IC. This allows you to read the temperature as an actual number in Celsius. I would suggest using Infrared all the time. You won't have to shield your device from light. Remember the best Mission Possible device is the the most reliable one, not the most exotic. Using a Basic Stamp is exotic enough! When I was coming down to get my medal for Mission Possible at the state competition the judge asked, "So are you the kid that used a microprocessor in your device last year? Did you use it again this year?" My team thought it was hilarious and yelled out, "Microprocessor" whenever we won an event for the rest of the awards ceremony! Tip three involves trying to get the most reactions conversions out of a relatively simple reaction. This reaction involves NiCr wire out of an old toaster oven, a rechargeable car battery, some string, and a switch. I first did this reaction in my first Mission Possible device and perfected it in my second. The idea is simple: tie down a switch so that it is open; when the string breaks, the switch is closed and repeats the process. I used a 900mAh 9.6 volt NiCd racing car battery. This is powerful enough to heat up the 6 cm length of NiCr wire so that a match touching it will instantly ignite. To connect the wires to the NiCr wire I used wing nuts around a screw. The screw and wing nut held the NiCr wire tightly to something I have no idea what it is called, but on one end you have a place to stick the wire and crimp it down and the other end you have the place to stick the screw in. Hmmm. Now comes the hard part: setting up the string system. Here is how I did it. Fasten a board to the bottom of your device and screw a real long screw (10cm) about 1 cm into the board. Now tie your string to the screw and loop it past the NiCr wire and match. I like using eye bolts for the looping. Now bring it up to the switch and tie it to your switch (I'll talk about the switch in a second.) To tighten the string until the switch is open tighten the screw. I found it easier for switching if you mounted the switches above the matches with the plungers facing upward. I used some Radio Shack switches that were spring loaded. I would actually have two switches connected to one string. One being closed and one being open when the string is tightened. When the string breaks one switch opens (turning off the current NiCr wire), and the other one closes (energizing the next reaction.) I connected them together by setting up a lever with popsicle sticks. First I would cut two 2 cm popsicle stick lengths and drill a hole at the end of each just large enough for it to fit on the plunger. I would hot glue that on each plunger. You want them to be toward the top of the plunger in the same plane that the switch goes up and down (all in the z-plane.) Now I would connect the two popsicle sticks at the end facing toward you with another stick. If you did it right, if you push down on the part that connects them both, the switches open or close. Since you have them mounted facing upward, just tie the string down to your lever and tighten. It should hold the lever down. If you can't figure out what I just described, try to make up your own system, but using the same idea of switches, NiCr wire, string, and levers (to lessen the amount of tightening.) Remember, we want you thinking as an engineer, on this event. There are many books out there on Basic Stamps. Just do a quick search on Amazon to get you going. Parallax also has some great free online sources. I found their guides on making robots very helpful because they had all the information I needed to know on using photoresistors and infrared emitters and sensors. I don't think I will post any pictures of my Mission Possible device or my source code because I really want this to be a starting guide for your own novel ideas. You won't learn anything if your dad does it or you duplicate someone else's device! To help you along I have included my last two energy transfer lists in Excel format: |