Thanks for the advice. That was what i was thinking. Generating the
values beforehand. Hehe. Anyway my table is going to be huge. As our
project involves a concentrator and a MJC so the light rays kinda
need to be perpendicular to the concentrator for maximum efficency.
So would have to update regularly during the period from 11-1pm where
the sun shifts alot.
What a huge project that my prof assigned to my group >.<
Minghui
--- In oopic@yahoogroups.com, Brian Lloyd <brian-wb6rqn@...> wrote:
>
>
> On Apr 4, 2008, at 2:21 AM, minghui1984 wrote:
>
> > Hehe actually that was one of the consideration but our prof
wants it
> > done by calculation though the light sensor provides a better
> > solution since when it is raining the motor would not move.
>
> A combination of the two provides backup in case of a sensor or
clock
> failure. Heck, you can use the light sensor to time-calibrate your
RTC
> if you like by using your light sensor array as a sun-dial. :-)
You
> can detect sunrise and sunset and use that to determine a rough cut
on
> day-of-year and time-of-day. (Celestial navigation is your friend.)
>
> First, I strongly recommend that you cheat. That is, do your heavy
> math calculation on something that is happy doing heavy math
> calculation, e.g. your PC. Have it produce a table you then store
in
> the ooPIC's flash. This will be an hour-angle value for the
position
> of the sun. You will need to calculate this table for different
times
> during the year but you will find that around the June and
December
> solstices, things don't change very much for quite some time
(other
> than sunrise and sunset times) so you will need fewer rows in your
> table around that time of year. Near the equinoxae you will need
your
> table rows to be closer together in calendar time. All in all you
can
> probably get away with twenty rows.
>
> (Or are you positioning in both X and Y in order to deal with
changes
> in declination with the seasons?)
>
> The earth rotates 15 degrees per hour. A positioning error of up to
15
> degrees is not going to make a difference as the Cosine of 15
degrees
> is .97. So repoint your panel every hour. That makes your table
pretty
> small, i.e. 20x14 or so. (How many hours in the longest day? 24 if
you
> are above the arctic/antarctic circles.)
>
> > Servo
> > Control was also one of the consideration. But oh well... the
> > presentation is in 2 week's time. >.< but definitely much to learn
> > about programming a robot. Hopefully i can do much more next time.
>
> Process control is my favorite form of programming as your code
> actually does something (and you don't have to deal with someone
> else's aborted idea of a UI). There isn't a lot of rocket science
> involved and code that does real things can be developed pretty
quickly.
>
> >
> >
> > Minghui
> >
> >
> > --- In oopic@yahoogroups.com, Brian Lloyd <brian-wb6rqn@> wrote:
> >>
> >>
> >> On Apr 1, 2008, at 4:37 AM, minghui1984 wrote:
> >>
> >>> Thanks all for the replies. More stuff learnt with every post. I
> > just
> >>> realised that oopic does not support double or float numbers?
hmm
> >>> this is because my application deals with controlling a stepper
> > motor
> >>> to move a solar tracker, not quite the usual applications that
ppl
> >>> use the oopic for. So i didn't realised when i ordered, how
would
> > i
> >>> store a values from the calculations and calculate inverse. One
> > more
> >>> problem is i realised that only single step movement is possible
> > for
> >>> the stepper function. >.<
> >>>
> >>> Guess i have to make do, the oopic simple interfacing allows me
> > to do
> >>> the prototype that demostrates my solar tracking. Hmm perhaps i
> > would
> >>> list it as future improvement.
> >>
> >> Why not just change from open-loop (time-of-day) to closed loop
> >> tracking? When the sun goes down drive your tracker back to its
> >> easternmost position. When the sun comes up, use a pair of light
> >> sensors separated by a vertical baffle (parallel to the polar
axis
> > on
> >> your tracker) with a light sensor on either side. If the panel is
> > not
> >> facing the sun, the baffle will shade one sensor or the other.
Use
> >> that do drive your tracking motor one way or the other until both
> >> sensors see the same light level. Now you won't need to know the
> > time
> >> of day and your tracker will work just fine based on sun
position.
> >>
> >> Here is a bit of a diagram. Use a fixed-width font to view:
> >>
> >>
> >> SSS
> >>
> >> |
> >> |
> >> |
> >> s | s
> >> -------
> >> P
> >>
> >>
> >> SSS = sun
> >> s = light sensor
> >> P = polar axis (coming out of the screen toward you)
> >>
> >>
> >> --
> >>
> >> Brian Lloyd Granite Bay Montessori
> >> brian AT gbmontessori DOT com 9330 Sierra College Blvd.
> >> +1.916.367.2131 (voice) Roseville, CA 95661, USA
> >>
http://www.gbmontessori.com
> >>
> >> I fly because it releases my mind from the tyranny of petty
> > things . . .
> >> — Antoine de Saint-Exupéry
> >>
> >> PGP key ID: 12095C52A32A1B6C
> >> PGP key fingerprint: 3B1D BA11 4913 3254 B6E0 CC09 1209 5C52
A32A
> > 1B6C
> >>
> >
> >
> >
> > ------------------------------------
> >
> > Yahoo! Groups Links
> >
> >
> >
> >
>
> --
>
> Brian Lloyd Granite Bay Montessori
> brian AT gbmontessori DOT com 9330 Sierra College Blvd.
> +1.916.367.2131 (voice) Roseville, CA 95661, USA
>
http://www.gbmontessori.com
>
> I fly because it releases my mind from the tyranny of petty
things . . .
> — Antoine de Saint-Exupéry
>
> PGP key ID: 12095C52A32A1B6C
> PGP key fingerprint: 3B1D BA11 4913 3254 B6E0 CC09 1209 5C52 A32A
1B6C
>
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