Interactive GizmoJonathan StockhoZack SandersJohn PrattCSCI 7000 Things That ThinkSpring 2004IntroductionThe idea for this project is taken from the movie Gremlins, which was released in1984. The movie centered on a young man named Billy who received a mogwai forChristmas and named it Gizmo. The mogwai is a little furry creature with big ears. Inorder to take care of a mogwai, Billy had to follow three rules. The first rule was that hecould not expose Gizmo to sunlight. Sunlight would kill him. The second rule stated thatGizmo could not get wet. And finally, under no circumstances should a mogwai ever befed after midnight. Through the course of the movie, it was shown that getting a mogwaiwet would make him reproduce through an asexual method of releasing fur balls from hisback, which then developed into other mogwais. If the creatures were fed after midnightthey would form cocoons and turn into gremlins, which were reptilian-like creatures thatdestroy everything in their paths. We decided to create an automaton using a Gizmoplush doll that would allow us to simulate the breaking of these three rules. A cameraflash causes Gizmo to cover his eyes, spraying him with water causes cotton balls to flyout from him to simulate the spawning, and if he is given food after midnight (the time isshown on a clock display) the platform rotates to reveal a gremlin.Mechanical ElementsFor this project we employed two main mechanical elements: a pulley and a gear.We decided to mount Gizmo on a spinning platform so we could turn it to reveal agremlin if Gizmo is fed after midnight. In order to spin the platform, we decided to setup a gear system. We started off with a lazy Susan, which would act as the base for thespinning platform. After putting a central pillar in for added structural support, weaffixed a gear to pillar. Another gear was connected to a worm-drive motor assemblyattached to the spinning top of the lazy Susan. This gear spins when the motor isactivated, allowing the platform to turn. In order to stop the platform after a half rotation,we employ a switch that is activated by a tab on the upper-platform. Here are somepictures of the base gear system and the stopping mechanism:In order to make Gizmo move, and for the other effects, we use a system ofpulleys. After cutting apart the plush doll we installed a three-pulley system in Gizmo'shead. The central pulley is used to spin the rod connecting the three pulleys. The othertwo are used to pull a piece of fishing line that runs out of Gizmo's eyes to his hands.When a central string is pulled, the outer pulleys wind the fishing line and pull Gizmo'shands to his eyes. The central string is hooked up to another pulley that is driven byworm-drive motor. In order to get Gizmo's hands to retract, we had to use an additionalpulley hooked up to the same motor with the string on it wound in reverse. The stringfrom that pulley is attached to Gizmo's hands from underneath, and pulls them downwhile the central line for pulling up his hands is releasing. Here are pictures of the gearsin Gizmo's head and the pulley system under the top platform: For the final effect we used another pulley system that is activated when a switchon a water bottle is toggled. A worm-drive motor drives this pulley and the string isattached to two pieces of cardboard. These pieces are used to cover tubes that holdsprings and wads of cotton. When the cardboard is released, the springs fire the cottonwads up, simulating the birthing process of a mogwai. The following pictures show thepulley system and the covers for the cotton wads:Computational / Electronic ElementsWhile working on the initial design of this project, we realized that we would notbe able to use the Lego motors that the crickets were designed for. They simply did nothave enough torque, nor were they fast enough to suit our needs. We settled on usingworm-driven motors from Tamiya. The motor running Gizmo's hands runs on a 216:1ratio and the other two run on a 336:1 ratio. The Tamiya motors gave us the torque andspeed we needed for everything to work. Unfortunately for us, the crickets use a 9-voltpower supply while the motors we are using run on 3 volts. In order for the system towork we had to figure out a way to get the motors running using the crickets. The firstidea we had was to simply lower the voltage going into the motors. We used resistors todrop the voltage down to 3 volts. This approach worked at first, but we soon realized thatthe batteries in the crickets all had different voltages and after that after using them a fewtimes the voltage would drop down. The problem was that if the circuit was designed fora 9-volt supply and it was only getting 8 volts, the motor would only receive 2 volts,which wouldn't start it. In order to fix the problem we used relays that could be activatedwith a 9 volt power supply. The relays close a circuit containing 2 double-A batteries,which gives the motor 3 volts. Here is what the circuit looks like with the relays: Once the motors were ready to run, we had to write the code for the crickets towork and add in the sensors for the three rules. The first sensor we installed was a lightsensor. This sensor was placed in Gizmo's head between his eyes. The code for thecricket that moves his hands waits until the light sensor reads a high value (i.e. from acamera flash) and then uses the motor outputs to close the circuit that moves the motorforward. Since we use relays and secondary power supplies, we could not use thecricket's ability to run a motor in two directions. Normally the cricket can change thedirection of current through the motor ports, but in our case it did not matter whatdirection the current was flowing because the only effect the motor ports have is to closea switch. We had to hook up two sets of batteries to the motor to get it moving indifferent directions. To move it forward, we hooked up the positive battery terminal tothe positive motor terminal and the negative battery terminal to the negative motorterminal. To move the motor backwards, the polarities are connected in reverse. Whenmotor A is turned on by the cricket, our motor moves forwards and when motor B isturned on, it moves backwards.We used the same system on the motor that pulls the covers from the cotton balllaunchers. A switch that is connected to a water bottle is read by a cricket whichactivates the relays for that system. We wanted to