【正文】 into contact with the support structure. The panels used for sensing and powering rotation were placed on the plane of the platform. Mirrors were placed perpendicular to and in between the panels to shade one and amplify the other in order to produce a difference to power the motor. The sensing panels were placed outside the platform area to maintain the largest area possible for collecting panels. A third sensing panel was mounted nearly vertical and facing east to aid rotation back towards the sun in the morning. This panel was attached to the frame under the platform, so that during most of the day, it?s shaded with minimal effects on sensed rotation. Minimizing the torques on the motor was a main concern in order to minimize the motor power needed. The platform designed for the placement of the collecting solar panels was placed under the rotational shaft so that the panels would be aligned with it the rotational axis. Since the main panels prise the majority of the weight putting these in the plane of the rotational axis reduces torque on the shaft. The sensing panels were placed symmetrically about the axis of rotation in order to prevent additional torque on the motor. The third panel was attached to the frame instead of the platform or rotational shaft so as to also avoid any torque. Materials Materials selection for most of the frame was simple because it had already been constructed. The mirrors used for the amplification and shading of the sensing panels were also already purchased and available for use. Additional parts for attachment of the panels and mirrors to the frame were taken from the scrap pieces available in the machine shop. In our selection of sensing panels, size and power needed to be balanced effectively. The panels were to be as small as possible in order to add minimal stress and weight to the frame but also needed to be powerful enough to power the rotation of the platform. Therefore, the most powerful of the intermediate sized panels available were selected. The panels purchased also appeared to be the most reliable of our options. Drive Mechanism After designing a prototype and testing it, the motor purchased and used by the previous solar tracker group was slipping. It was removed, and the installation of a gear system with another simple motor was suggested and attempted. Professor Knight supplied some gears as well as some belts and pulleys. One end of the shaft was lathed so that one of the pulleys could be set on it, and spacers were bought so that a 6V motor we had available could power another pulley. These pulleys were to be connected by a belt. This motor demonstrated insufficient strength to turn the rotational shaft. The original motor, once detached, was taken apart and examined. Itappeared to be working again so a new pulley was purchased to fit it and was attached in the place of the 6V motor. 5. Detailed Design Frame The frame was designed from one inch square aluminum tubing, and a five foot long, two inch square tube for the axle. It is constructed with a rigid base and triangular prismatic frame with side supporting bars that provide stability. The end of the axle is attached to a system of pulleys which are driven by the motor. It is easily transported by removing the sides of the base and folding the structure. Sensor Our sensing panels are bolted to the bottom of the main solar panel frame and braced underneath with half inch Lbrackets. The mirrors are attached to the inside of the sensing panels and braced by Lbrackets as well. The whole structure attaches easily to the main panel frame which is attached to the main axle using four 2inch Ubolts. A third panel is bolted to the structure to return the main panels direction towards the horizon of sunrise. How the Sensor Works Our sensor creates movement of the motor by shading one of the panels and amplifying the other when the system is not directly facing the sun. The two sensing panels are mounted parallel to the main panels symmetrically about the center axle with two mirrors in between them. The shading on one of the panels creates high impedance, while the amplified panel powers the motor. This happens until the panels receive the same amount of sunlight and balance each other out (. when the sensing panels and main panels are facing the sun.). We initially attempted using a series configuration to take advantage of the voltage difference when one of the panels was shaded (Appendix C). This difference, however, was not large enough to drive the motor. We subsequently attempted a parallel configuration which would take advantage of the impedance of the shaded panel (Appendix C) and provide the current needed to drive the motor. Once the sensing mechanism has rotated from sunrise to sunset, the third panel, which is usually shaded, uses sunlight from the sunrise of the next day to power the motor to return the panels towards the direction of the sun. 6. Prototype Testing Initial testing was done using just the sensing ponent and a 6V motor. The panels were tilted by hand to create shading and amplification. A series configuration of the sensing panels was initiall