The Lamb-Cam A presentation of Shawn Lamb’s thesis work
Motivation • Go to ASU P&A homepage >> Students >> Grad students >> Shawn Lamb >> Curriculum Vitae (Unpublished Papers) >>“High Concentrating Photovoltaics: Past, Present, and Future” • Pictured is a MegaWatt power farm connected to Arizona Public Service Company’s electrical grid. Each array is an Amonix 25 Kilowatt Gallium Arsenide Mega-module with 250 to 1 Fresnel Lens concentrating.
First Model • Relative position tracking • Stepper motors • Basic Stamp II Microcontroller • Alt / Az tracking • Lookup Table Ephemeris • Wooden frame • Webcam for position confirm
Current Model • Absolute encoding • Alt / Az tracking • CMOS imager used for autoguiding • Full year backup ephemeris • DC motors • Steel frame • Able to drive heavy load.
The Cam Module • Uses CMU-cam from Carnegie Melon’s Robotics Institute • Basic Stamp Microcontroller • Analog out signal • In-circuit reprogramming
CMU-cam • Low Cost < $120 • Well developed with lots of support and code available • Color Blob tracking • Outputs middle mass of color object tracked • 80 x 143 pixel resolution • CMOS imaging implies fast sample rate (up to 17 fps)
CMU-cam • Autonomous unit – works independent of Basic Stamp II • Ubicom’s SX Microcontroller on board • Omnivision’s OV6620 color CMOS imaging chip • I2C interface, TTL or RS232 ports
CMU-cam Tracking • Webcam image of the sun w/o filter • Image of the sun through neutral density solar filter • What the CMU cam sees as the middle mass
The Basic Stamp II • Radio Shack sells BS2 kit for ~ $75 • Powered by 9V battery or external power source • E2PROM based microcontroller • 16 I/O pins • I2C serial interface with peripherals • In circuit debugging • PBASIC language
Motor Driver Module • Uses two SN754410 Quad Half-H drivers • TTL or CMOS input from microcontroller • Drives up to 1A at from 4.5V to 36V • Separate +5V Logic and + 15V driving power sources • Built in Heat sink with cooling fan • CAT5 cable interface with cam module
Position Encoding • Absolute position encoding • Two potentiometers built into frame • Separate 5V reference source • Two 10-bit TLC1549 ADC with serial interface were used on Stamp board • ½ degree resolution • Feedback motion control
Motors • Brevel Motors Inc. 36V DC 780/953075 • Fly wheels used for gearing (~ 19 deg / rev) • Bi-directional and variable speed
Ephemeris • JPL’s HORIZONS System • Alt and Az – 80 at each hour from 9am to 5pm • Inputs needed: Observer’s Lat/Long, UT, Time step, Range, Target Body • Must work data with Excel (no negatives or decimal values) • Can store up to two years worth of data in Xicor X25640 8K x 8 bit EEPROM • Clock chip used for time / date keeping
Paddle Module • Direct ALT / AZ control via pushbuttons • PALCE22V10 gate array logic • PIC12F675 microcontroller with multichannel 10-bit ADC read the encoder value in real-time • MAX6958 7-seg driver takes BCD value from PIC and displays on three digit numerical LCDs • 9V Battery powered • CAT5 cable interface with Motor Driver Module
Applications • Large-Scale Concentrators
Applications • Micro-concentrators
Planned Improvements • PIC microcontroller • Mount on CAP roof • Long-term data • Self powered • Cheaper • Rebuild mount? • Analog video out • LCD text screen • Weather proofing
Acknowledgements • Thanks to Dr. Tom Rokoske my thesis advisor • Dr. Brian Raichle for teaching me about solar panels, concentrators, and renewable energy. • Dr. Sid Clements and Dr. Adrian Daw for teaching me so much about electronics in such a short amount of time. • ASU departments of Physics & Astronomy as well as Appropriate Technology for their support, facilities, equipment, and personal. • Dr. Ergun Oguz (Turkey) for helping me maturate the idea of a low cost CMOS solar tracker with applications in HCPV and other concentrating technology. • The other graduate students who have helped me in this adventure.