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PICList Thread
'Sun Tracking'
1998\12\24@211821 by Brian Gracia

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Hi All,

I am trying to design a project to track the sun.  Has anyone ever tried to
do this.  Any help would be greatful.

Brian

1998\12\24@230042 by Osama ALASSIRY

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I have some friends' graduation report (A sun tracker, used with a solar cell, ... only a hardcopy)
major observations:
* Continuous tracking not necessary (very small gain in power), they put the 16c71 to sleep and woke it up every 30minutes (using a 555, AFAIR)
* They used a PIC (an improvemnt over an older PC-Based project)

Here's a few ASCII Drawings

+--------------+
|*1ssssssssss2*|
|  ssssssssss  |
|  ssssssssss  |
|  ssssssssss  |
|*3ssssssssss4*|
+--------------+

s=solar cell
*=sensor

sensor  amp   +---+
*-------|>----| 1 |    +------+
*-------|>----| 6 |----+Motor |----MOTOR#1
*-------|>----| c |    |      |
*-------|>----| 7 |----+Driver|----MOTOR#2
              | 1 |    +------+
              +---+

They used a simple algorithm:
ON WAKE UP:
turned power on for everything
if Sensor1+Sensor2>Sensor3+Sensor4 then move up else move down
if Sensor1+Sensor3>Sensor2+Sensor4 then move left else move right
repeat until Differences very small (optimal position)
turned power off from most of the board
SLEEP for 30 minutes

At 02:12 25/12/98 , you wrote:
>Hi All,
>
>I am trying to design a project to track the sun. Has anyone ever tried to
>do this. Any help would be greatful.
>
>Brian
>

_____________________________________________________
Osama ALASSIRY  osama@qatar.net.qa osama@alassiry.com
                              http://www.alassiry.com

1998\12\25@023940 by Eric Borcherding

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Brian,

Yes I have done a sun tracker for PV arrays  What do you have in mind.
Will there be a PIC controller?   Basically one can make a quadrature
encoder (a plus sign with some depth for shading) using low sensitivity
phototransisters of CDS cells with shading over them.   There is also
a need to have the home location of the tracker - like overnight have
it return for catching morning sun.    The method I used was to use two
steppers motors and a PC running on a Dig Analog I/O card with
Borland C.    It would be possible to push this into a PIC like a 16C76
type.  Keep in touch...

Eric

1998\12\25@103359 by WIL REEDER

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Merry Christmas all!
I have an interest in this as well ... for a solar panel tracker.  James
Cameron is on this list and has interest and ideas on this subject. I would
like to drive the panel mount with a 12vdc trailer jack as they are robust,
available and reasonably priced. This means an 'H' drive circuit and a
12c508 with a couple of photo transistors would make the decisions. I am
told the best setup is to have both sensors shaded when the panel is aimed
and maybe a startup/low light sensor would be a hot idea. If this is
anywhere close to what you want to do, let me know, I'll work along with
you.


Wil Reeder
spam_OUTteachtechTakeThisOuTspambc.sympatico.ca
Vancouver,Canada
----------
> From: Brian Gracia <.....brian_graciaKILLspamspam@spam@HOTMAIL.COM>
> To: PICLISTspamKILLspamMITVMA.MIT.EDU
> Subject: Sun Tracking
> Date: Thursday, December 24, 1998 6:12 PM
>
> Hi All,
>
> I am trying to design a project to track the sun.  Has anyone ever tried
to
> do this.  Any help would be greatful.
>
> Brian

1998\12\25@134904 by Morgan Olsson

picon face
At 20:12 1998-12-24 -0600, you wrote:
>Hi All,
>
>I am trying to design a project to track the sun.  Has anyone ever tried to
>do this.  Any help would be greatful.
>
>Brian

Hi Brian and all

I am thinking to build a solar heat collector the coming year, dual-axis
rotating against sun.

As the position of the sun is *very* predictable...

I have decided to use just time for positioning, to avoid any problems with
contamination of sensor, like fies shit, autumn leaves, partial snow cover,
or degradation of the sensor (the collectors and environmental casing is
designed for 30 yrs, so i don«t want a lousy sensor to shit it up)

The position feedback sensors are probably much cheaper than a suitable
optical sensor arrangement, and also make more use, like make it stand
correct at sunrise or after a half day dark clouds, without any additional
logic.  

For the turn-around it is just to follow the clock: n revolutions of motor
per minute, and an index at 12 a.m to calibrate zero twice a day.

For the height using a sine with frequency of the day, amplitude modulated
with  a constant + sine with frequency of the year.

Time is fetched from logging system.

Update every hour might give unmeasurably less power tna continuous, but i
think i will settle for every five minutes or so, keeping a more constant
temperature in the motors, making them always slightly warmer than outside,
thus keeping them dry iven if small leak in casing, as there always will be
in 30 yrs time...


Good luck
/Morgan
       Morgan Olsson                   ph  +46(0)414 70741
       MORGANS REGLERTEKNIK            fax +46(0)414 70331
       H€LLEKS           (in A-Z letters: "HALLEKAS")
       SE-277 35 KIVIK, SWEDEN               .....mrtKILLspamspam.....iname.com
___________________________________________________________

1998\12\28@103622 by lilel

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I'm also interest in this idea.

The prospect of fixing the sensors so they are both DARK is one I
haven't thought of.

Does anyone use somethind besides CDS cells, say phototransistors?  I
would think a small phototransistor would be easy to aim in a drilled
hole.

-- Lawrence Lile

=> Median Filter Source Code
=> AutoCad blocks for electrical drafting
=> Brownout tester plans
=> Amateurish pictures of my family

at:  http://home1.gte.net/llile/index.htm

1998\12\28@104010 by lilel

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Morgan Olsson  sez

> As the position of the sun is *very* predictable...
>
> I have decided to use just time for positioning, to avoid any
> problems with contamination of sensor,

That's a good idea.  I would suspect that a very accurate timekeeper,
not just a crystal, would be needed.  Either a watch crystal or one
of those timekeeping devices from Dallas.  If you had more that a few
minute's error per month you would accumulate large position errors.

How far from the equator are all you solar tracker makers?  At higher
lattitudes the winter to summer variation in dawn times is
signifigant.  Perhaps, though, you are only interested in heat in the
winter.  In that case calibrating it for winter Dawn times is enough.



-- Lawrence Lile

=> Median Filter Source Code
=> AutoCad blocks for electrical drafting
=> Brownout tester plans
=> Amateurish pictures of my family

at:  http://home1.gte.net/llile/index.htm

1998\12\29@002304 by steve

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> > As the position of the sun is *very* predictable...

> That's a good idea.  I would suspect that a very accurate timekeeper,
> not just a crystal, would be needed.  Either a watch crystal or one
> of those timekeeping devices from Dallas.  If you had more that a few
> minute's error per month you would accumulate large position errors.

You're possibly overlooking the obvious. Why try and maintain a long
term clock for a short term requirement ?
A single light sensor will let you detect when the world changes from
dark to light and back to dark again. You'd only need half a dozen
bytes to make a long counter and measure the length of the day. Since
today is going to be very close to the length of yesterday and you
can see the sun rise, you have all the information you need to
predict where the sun is.
You could even use a median filter. :-)

Steve.

======================================================
Steve Baldwin                Electronic Product Design
TLA Microsystems Ltd         Microcontroller Specialists
PO Box 15-680, New Lynn      http://www.tla.co.nz
Auckland, New Zealand        ph  +64 9 820-2221
email: EraseMEstevebspam_OUTspamTakeThisOuTtla.co.nz      fax +64 9 820-1929
======================================================

1998\12\29@014156 by James Cameron

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WIL REEDER wrote:
> I have an interest in this as well ... for a solar panel tracker.
> James Cameron is on this list and has interest and ideas on this
> subject.

True, but I haven't actually got a current need for it yet; perhaps in
another four or five months when our road is in place.

On the other hand, with as much solar panel area as I will need (for
7kw/h per day) pointing them is not trivial.  I may just buy some more.

I like the idea of sleeping for thirty minutes between checks to cut
down the power consumption of the controller.

--
James Cameron                                      (cameronspamspam_OUTstl.dec.com)

OpenVMS, Linux, Firewalls, Software Engineering, CGI, HTTP, X, C, FORTH,
COBOL, BASIC, DCL, csh, bash, ksh, sh, Electronics, Microcontrollers,
Disability Engineering, Netrek, Bicycles, Pedant, Farming, Home Control,
Remote Area Power, Greek Scholar, Tenor Vocalist, Church Sound, Husband.

"Specialisation is for insects." -- Robert Heinlein.

1998\12\29@024527 by Tjaart van der Walt

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James Cameron wrote:
>
> WIL REEDER wrote:
> > I have an interest in this as well ... for a solar panel tracker.
> > James Cameron is on this list and has interest and ideas on this
> > subject.
>
> True, but I haven't actually got a current need for it yet; perhaps in
> another four or five months when our road is in place.
>
> On the other hand, with as much solar panel area as I will need (for
> 7kw/h per day) pointing them is not trivial.  I may just buy some more.
>
> I like the idea of sleeping for thirty minutes between checks to cut
> down the power consumption of the controller.

You don't need a controller at all. Use two photosensitive
devices seperated by a sheet of opaque material. Use their
outputs to drive two comparators. The comparators are used
to keep the panel in a 'window' where the motors will not
be driven. You can drive the H bridge directly from the
comparators. If you use FET type opamps, there is no way
you can do better (current consumption wise) with a controller.

--
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1998\12\29@073355 by luberth

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part 0 1038 bytes
ive seen a sun tracker for a solar panel
in a book i have

it was made with fischer technic a german plastic construction toy
frequently used toy at universitys for prototyping

the program was made in basic
it was controlled by a schneider, sinclair zxspectrum, commodore 6*/8*
acorn or msx way back in 1985

later fischer technik developed an ibm interface
the have made more interesting things
like robotic arms plotter/scanner/digitiser etc.

i think if you do a web search on fischer technic
you wil find pages about this subject
maybe there is even a news group fischer technic

the booklet i have is dutch
robot besturing met uw homecomputer (translated robot control with your
home computer)
publisher Elektuur ISBN90-70160 (first press date 1986)

hope this helped a bit

attached image suntrack.gif

greeting's luberth


http://home.wxs.nl/~luberth

home build qbasic plotter engraver vinyl-cutter pcb-driller
http://home.wxs.nl/~luberth/plotter/plotter.htm

Attachment converted: wonderland:SUNTRACK.GIF (GIFf/JVWR) (00023476)

1998\12\29@125113 by Peter L. Peres

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On Tue, 29 Dec 1998, James Cameron wrote:

> WIL REEDER wrote:
> > I have an interest in this as well ... for a solar panel tracker.
> > James Cameron is on this list and has interest and ideas on this
> > subject.
>
> True, but I haven't actually got a current need for it yet; perhaps in
> another four or five months when our road is in place.
>
> On the other hand, with as much solar panel area as I will need (for
> 7kw/h per day) pointing them is not trivial.  I may just buy some more.
>
> I like the idea of sleeping for thirty minutes between checks to cut
> down the power consumption of the controller.

You mean, sleeping a PIC which draws some 10 mA with all sense amps etc,
on a 7kW installation ? ;)

Are you far away from civilized places ? I.e. in the wilderness ? If so,
you might want to know that there is a PICless panel pointing system that
relies on the differential pressure in two freon-filled chambers exposed
to the sun. The chambers are shaded equally when pointing into the sun and
deliver pressure for action cylinders to move the panel(s). This also
works in az/el (4 vessels, 4 actuators on a swashplate or gymbals). By
choosing the pressures right when there is not enough sun/heat, the panel
'parks' face down and rolls into the expected next sunrise by gravity (the
base plate is inclined towards that side). The face down position also
reduces rain etc mudding the mirrors (actually they get washed because
slanted).

There is no need for maintenance, someone simply walks around with a freon
bottle and fills the two (four) circuits for each panel up from time to
time. By differential filling small alignment errors can be fixed.

I've read about this system a long time ago, in a solar/environment
magazine that predates the 'greens' ;)

hope this helps, although OT,

Peter

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