A few years back there was an article in the Portuguese Elector magazine where they described a system for tracking the Sun by using 3 LDRs each one inside a pipe which served to limit the sun incidence to right above the LDR. The LDRs and pipes were attached to the array and moved with it. The principle was that you want the Sun to be always more on the middle LDR, if one of the others was getting more sun then you move the array in that direction. Never tried it but it seemed feasible at the time... Now I think that first you have to find the Sun and you probably need 5 LDR's to do the two axis, you will have to find the right length of pipe to use and you probably need to determine end stops for the travel of the arrays. Is cheap so it's probably worth a try. Best regards Luis -----Original Message----- From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of Bob Axtell Sent: 21 August 2006 17:14 To: Microcontroller discussion list - Public. Subject: Re: [EE] Solar Array Tracking Good info, thanks! Probably more money than he'd want to spend. However, we will allow an RS232 connection to sync the internal PIC time-of-day, and to determine when to move to the dawn position. Yes, the horizon to horizon could be automatic, then simply advise the user than there is an error in direction, so he can press buttons to move it manually. --Bob M. Adam Davis wrote: > There's lots of ways to do this. Assuming you want full tracking > (azimuth, elevation), and assuming the location is fixed, then I'd use > a simple RTC and sun camera. The sun camera would be attached to the > solar array iteself (moves with the array so you don't have to > calibrate the motors). > > Since you know the time and location, you can point to the sun. The > elevation only needs to be adjusted perhaps once a week if you want > nearly perfect tracking, but even once a month or four times a year is > about as good. Most trackers only do azimuth (horizon to horizon) and > are user adjustable for elevation since 4 times a year is within a few > percent of total energy output. > > The sun camera is used to determine the location of the sun on clear > days, and can be used to set the RTC as well as the array. It's not > needed if the motors are calibrated (ie, a known home position, like a > printer does) and you know the time is exact (GPS receiver). > > You could use the phototransistors instead of a sun cam, and probably > get pretty good resolution. It would certainly take less processing > if you went digital, and going digital gives you an easy way to reset > the array at the end of the day. > > If you used a GPS receiver, a magnetic field detector, and had good > motors you could conceivably correctly track the sun on a moving > platform. > > -Adam > > On 8/21/06, Bob Axtell wrote: > >> To my delight, I have been given a shot at designing a solar tracking >> system, >> the arrays running at 24V. The arrays are very large, 14' sq and 18' sq. The >> user is UNCONNECTED from the AC mains, running his entire business >> from inverters attached to the system. >> >> Anybody have ideas? I know about (1) not allowing the moon to be tracked, >> (2) end the day by moving the array to immediately catch the dawn sun >> when it comes up, to minimize movement, and (3) the funny 4-diode array >> to determine where the sun is.. >> >> --Bob >> >> -- >> http://www.piclist.com PIC/SX FAQ & list archive >> View/change your membership options at >> http://mailman.mit.edu/mailman/listinfo/piclist >> >> -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist