Two parallel light sensors each mounted at the end of a tube. An analog comparator driving a motor. The voltage on each sensor is compared and the motor turns in one direction or the other until the voltage from each sensor is the same.

looks really cool, wanna make it one by my onw… :)
it’d b fun for prototyping

Attach the panels to a Sunflower. Easiest way to track the sun.

http://en.wikipedia.org/wiki/Sunflower#Heliotropism

Addendum : it already exists, BTW. They use dilating liquids instead of metal rods but the idea is similar : http://www.emarineinc.com/products/mounts/tracker.html

From “The Colony”: John C. works to build a device that incorporates two solenoids and a small motor into a solar tracking device, allowing the solar panels to follow the sun during the day, and return to starting positions at night. (http://www.google.com/search?ie=UTF-8&oe=UTF-8&sourceid=navclient&gfns=1&q=%22the+colony%22+solar+tracker&aq=h)

Not only did it work, it worked with scavenged parts. Arduino, please. Why do people insist on overcomplicating things?

Fail. what jeff said.

The discovery channel had a reality show “The Colony” During the show the group created a 1KW solar array out of spare parts left in a warehouse near the LA river.

Like others here mentioned, I would use a simple circuit using two light sensors to drive an analog control circuit for a dc motor. The light sensors would, of course, be the LEDs on two Arduino boards. I would use Arduino boards for structural members as well as casing for the motors and the rest of the project. The circuit would be powered by a generator/sterling engine pair (again, predominantly build from arduino boards). The hot side of the sterling engine would burn Arduino boards for fuel.

Just had to get that in there to poke a little fun at the ArduiNO Trolls.

Two small solar panels placed perpendicular on the side (or on the axis) of the main one.

Both small panels are linked to a DC motor and act both as energy providers and sensors.

The tracker turns to that side of the small photovoltaic module being exposed to the Sun…

Easy, simple… and patented …

Used here on a 4MW tracking solar plant:
http://www.solar-solar.com/Attachments/PICT151.JPG

I realize there are more efficient ways of doing things, but it’s come to a point where arduino projects are put under instant scrutiny here. The arduino is a great platform for hobbyists. It has made the hobby more accessible to others. That means more creative thinking in the pool.

Why not just use the differential output in voltage from the panels themselves?

To cause the analog-driven panel to return to home base when it’s dark, a few extra logic gates could be added. When the voltage output from both the LDRs drops below a threshold (ie. twilight or complete darkness) the motor would run until the panel reaches its east-facing origin.

Do you guys realize that an ATMega168 is around $4 on Digikey? Sometimes the savings in time one gets with a familiar platform are worth that extra dollar for a one-off project. Keep in mind that at a basic engineering wage, even an extra minute of time is around 40 cents…

“Do you guys realize that an ATMega168 is around $4 on Digikey?” how much cost the pc to program it ? ;)
Anyway, it is stupid to add light sensors to solar cells !!! he could simply use the output of the panel and maiximise it. There is no problem to know if it must turn left or right, the sun always moves the same way and at the same speed.

@Dan: like, a switch? The arduino solution would need one too.

Microcontrollers are adequate if the task is complex but of more or less practical value (adding Twitter “just because we can” is a no-no). Consider some “learning” abilities. You turn the rig on for the first time (or push the calibration button), it finds the sun by itself and begins tracking. After a few hours of (almost) steady sun it already knows rough latitude and has estimated sunrise position. After a few days both latitude and season are determined, so automatic positioning is possible even without seeing the sun. And it constantly adjusts itself. The result: not a single ray missed, fool-proof setup, some “resurrection” abilities if left remotely. Might even have practical application. And lots of tinkering, math, even some astronomy — for developers. They actually like those things, you know :)

Some ideas for hardware:

1) output of the panel itself — rough tracking;

2) a single light sensor in a deep blend, 0.5° FOV — fine tracking;

3) “zero” sensors on both azimuth and elevation axes, position is irrelevant — merely to avoid total disorientation;

4) “revolution” sensors on both azimuth and elevation motors — for absolute positioning and to use any motor instead of a stepper.

LOL, I guess I should first read the post about overkill eh? :)

@ jeff-o how about a couple of matchbox cars?

Folks…
Our tracker solution on The Colony was pretty caveman. it took 5 components. I used one CdS cell scavenged from an old radio shack ‘snap circuits’ kit as the bottom leg of a voltage divider. The top leg was a 50K pot removed from a 1950′s era military signal generator. The mid point of that divider drove the base of an NPN darlington pair made from transistors pulled from some old 12v florescent lamp drivers I found. The collector of the darlington drove a DPDT Bosch autorelay I pulled out of a trans am carcass that was upside down in the yard of the Colony. I mounted the CdS cell between two blinders to set the capture apperature for the sun. Then I adjusted the pot so that the darlington was on unless the sun was directly on the CdS cell. I mounted this whole contraption on one of the solar arrays.

When the relay was energized, I used the NO contacts to energize a large DC gear motor with an 80:1 reduction. Mike had coupled that to an additional 20:1 reducer that drove a linkage that turned the panels. the linkage was designed to make the panels move back and forth as the motor turned 360 degrees..

So.. when the rig was turned on, the motor would energize and pan the panels from east to west until the sun was directly between the blinders.. then the motor would stop. When the sun advanced, the motor would energize again and turn to catch up. If a cloud blocked the sun.. the arrays would pan all the way west.. then reverse until they caught the sun again.. (At least when all the linkages stayed tight :-)
I acually built two of the circuits I described above.. The second one had no blinders and was used to turn off the whole apparatus when the ambient light level fell below a set point. This turned the whole rig off at night or on cloudy days so it didn’t drive us crazy trying to track in the dark.
As I said.. pretty caeveman.. but it provided us with reliable power for most of our stay in the post apocolypse.
Cristopher and JBay.. I appreciate you watching the show.. It was an *awesome* experience !
-john C

I don’t see why all of these solutions rely so much on the idea of needing to track the sun it self. Pratical Solar has the right idea. Their implementation is a little bulky in that it requires a computer for a brain but the idea is solid …

The sun follows a predictable cycle through the sky, use a compass to mount your panels, input gps coordinates into a system and have it spit out a path you can program into a rom chip. In the end it would mean more circuits but the results should be 100% accurate and maximize your solar output … assuming you get the math right!

-N

I sketched out a rough design for a completely non computer based system, and built a prototype out of balsa and yoghurt pots!

The sun is predictable, seasons vary but the design allows for this.

Solar panels connect on 3d hinges (cv joints, ball and socket?) at the base and rotate on a support at a distance from the centre point (base of panel at 90 degrees from centre, so panel never touches centre), and an off-centre post holds the top again with 3d hinges.

The off centre post, is mounted slightly back from the centre point, in alignment with the lunch time panel position.

You power using clockwork mech, or a percentage of the solar energy collected to an electric motor. You don’t want someone on this all day moving it.

Rotating the base changes the azimuth and causes the off-centre pole to rotate in two dimensions (base of this pole fixed in position) which angles the panels to track the angle of the sun (northern hemisphere) east vertical, lunch overhead, night western vertical. (change power device rotation for southern hemisphere)

The distance from the centre point to the base of the panels is your seasonal variation.

The height of the panel to top of off-centre support pole is your latitude.

Simple and appropriate. Can be built by artisan crafts people, uses simple ‘waste’ tech, and its only the panels and the charge controller which cost money.

The rotational speed of the motor is down geared to maintain a match with the speed of the sun.

If you want, you can even use additional tech to get the motor to return the unit to the starting position or this could be done manually. It could be that when the motor achieves a full 180, a reverse gear is activated to return the panels back to the start, this could mean a full half rotation would take 12 hours. Maybe winding up the clockwork mech would bring it back to the starting position. It cannot go 360 degree full rotation.

Seasonal alignment could be the sun shining through a long thin hole through part of the panel structure onto a board or some such, and aligning the middle of the light to a dot printed on the board.

Don’t forget. If you use a computer you need to control 2 axes with finite adjustment, and high torque levels, and the frame to support it all. This makes the frame do the work, and an alternator could be hacked to power it.

No need for bearings, just use 2 neodymium magnets opposed to each other. One on the rotating unit, one on the base, around the drive pole.

I couldn’t agree more, well done.

This is the most ingenious by far. Simple yet cheep at the most. No hacking or programing required.
http://www.greenwatts.info/index.php?page=sun-switch

The problem with solar trackers is that they add to the initial investment needed for a already expensive equipment.