Computer-Controlled Light Tracker
Cheyenne Rahimi (Analy High School), and Akash Desai (Maria Carrillo High School), Mostafa Sadraii (SSU Junior), Steve Anderson (SSU Staff)
The Computer-Controlled Light Tracker project consisted of three distinct parts, mechanical design, electronic driver, and computer programming. This was a challenging project for two talented high school students, Cheyenne Rahimi and Akash Desai, who spent most of their summer of junior year working on the project. In addition to the faculty mentors, a junior SSU engineering student and the department technician provided support. The project started with several lecture sessions so the students gained some knowledge about electronics and different materials, in particular semiconducting materials. A small solar panel was used as the light collector and also sensor.
The mechanical structure consisted of a metal base which supported the panel attached to two rotational mechanisms utilizing stepper motors. The system is capable of azimuth as well as latitude rotation enabling it to track a moving source of light in three dimensions. The motor shafts were fitted with appropriately sized pulleys which were connected to pulleys fixed to the shafts with driving belts. The geared stepper motors were selected to provide a 1-2 rpm rotational speed for tracking the light at slow rates. A relay mechanism delivered power from a 1,200 mAhr Ni-MH battery, which is capable of providing power to the system for relatively long periods of time.
The voltage output of the solar panel was fed into a National Instruments DAQ card, which was read by LabVIEW after analog to digital signal conversion. A threshold voltage was chosen by the students to indicate the lower limit of light intensity. The team wrote a LabVIEW program that would start one of the motors once the voltage output of the solar panel dropped below the threshold level. The motor would turn in an arbitrary direction and would continue moving in that direction if the sensor sensed an increase in the light intensity. The motor would reverse its direction if the sensor sensed a drop in the light intensity. The motor would stop once it reaches an optimum position and the computer would send a trigger signal to the second motor to start its rotation. Similar to the first motor, the second motor would stop when it reaches its optimum position.
The system is programmed so the computer would continuously monitor the light level received by the sensor. The electronics behind the reversing mechanism of the motors was facilitated by several relays that acted as digital logic gates for delivering power to the motors to rotate in clockwise or counterclockwise directions as needed. The light tracker system was successfully demonstrated at the SHIP event in which the students described the project to the University and Sonoma County School District administrators, faculty, and staff. The students were also given an opportunity to present the project to the Board of Directors of Sonoma County Office of Education (SCOE) and were awarded a certificate of accomplishment by the Board. The students will also receive a stipend of $1,000 each for their successful summer internship efforts from SCOE. This project will be used for demonstration in the SSU electrical engineering courses and the goal is to involve the electrical engineering students to fine tune and improve the light tracker system at SSU.