June 24, 2019

Solar Tracker

This project is going to be a dual axis solar tracking system for a small 20″ x 14″ solar panel.  Ever since I used a solar setup on my Garden Fountain project I’ve wanted to try a making a sun tracking system. I though about trying to do it with a Raspberry Pi or Arduino setup but never got around to looking into the logistics of that so that idea was put on the back burner for awhile.  I recent came across this video on YouTube that shows a setup that just uses mini solar panels and shadows to achieve the tracking and it seemed relatively simple to do.

I’m going to use that method (mixed with a few other ideas I’ve also seen) and combine the four smaller solar panels with two geared motors to scale up the design a bit.  So far I have the basic overall design figured out.  The mechanics of the design consists of 3D printed parts, PVC pipe, two geared motors, four small solar panels, and a few relays.

Starting with the base… the design incorporates a bearing into the main base piece and this forms the rotation axis for the main solar panel. The bearing will be made up of three 3D printed parts and airsoft BB’s for the balls.

The overall frame work also consists of 3D printed joiner parts and 1/2″ PVC pipe for the bracing.

To control both axis I will be using two geared motors.

The rotation axis motor is attached with a motor mount to the frame base (top half of the bearing = grey piece) while the motor shaft connects to the bearing cap (blue piece) which is fixed to the main base. (bottom blue piece) This causes the whole assembly (motor and all) to rotate around the base piece as the motor turns.

The axis that controls the angle of the main solar panel is controlled by the other motor that attaches through the side frame directly to the solar panel mount. (blue piece)

For the non-motor side upper brace I cut two internal races for the BB’s to add a bearing for the pivot shaft.  It’s a little overkill for this application but it’s just something I wanted to try so this seemed like a good time to do so.

The main solar panel then mounts to the solar panel mount and everything else will be attached to the actual frame of the main solar panel.

The mini solar cell setups on the outer frame of the main solar panel will power relays that control the motors.  There will be two cells for each motor with one cell controlling each direction of the motor. As opposed to the panels in that video I will be angling mine and adding an additional shade. The angle and extended shade should provide more precise control of the system and allow for any adjustments that may need to be made.

On to the bits and pieces…. The main solar panel is a 20 Watt 12 Volt Polycrystalline Solar Panel that I bought for my garden fountain project.

The motors I will be using are two Uxcell DC 12V 6RPM Worm Gear Motors.

For the mini solar panels I will be using 5V 70mA Poly Cell Panels also from Uxcell.

Lastly the relays I’m running are EP2R-B3G1 6V “H” Bridge Relays. These are unique in the fact that they are basically two relays in one small package. I use these a lot on my Rov’s becuase they make for an easy forward/reverse setup. They use to be really cheap ($1) but are harder for find these days so the price has jumped considerably.  (The same setup can be made with two duel post duel throw relays though. I’ll get more into that later in the build.)

The way this setup will work (in theory) is if the sun is directly hitting both of the two mini solar panels that control one motor, both of the relays coils will be energized. The good thing about these relays is if both coils are energized at the same time there is no short but no power is directed to the motor.

When the sun moves enough to where one of the mini solar panels is covered by the shade this will turn off one of the relays coils and in response the motor will have power in one direction and turn the entire setup back toward the sun.  As soon as the shaded mini solar panel is back in the sun it will turn the motor off.  There will eventually be a fifth panel on the back side to get the setup to return to the other direction when the sun comes up on the opposite horizon the next morning. (in theory anyway.)

To test out one axis of the setup for the mini solar panels I printed up a quick mount for them and glued a piece of cardboard to it for a shade. The mount is attached to a smaller geared motor for testing.

The relays were taped to the back side. (there are two relays shown but only wired here) and I can just hold the motor to test the setup out.

Here is a quick GIF of it in action.  When the center line of the shade pointing at the sun is manually rotated away from the sun it automatically reorientates itself.  It’s not perfectly accurate but it should work well enough.  Now that everything seems like it should work out it’s on to actually building the full scale setup.

I started by printing all of the pieces for the main base/bearing. These parts were printing in a mix of PETG and PLA.

The next setup was to add the Airsoft BB’s in the bottom portion of the bearing.

The the main frame mount is placed on top and more BB’s are added for the top half of the bearing.

The bearing cap is then secured with (3) 4-40 x 5/8″ flat head screws completing the bearing base.

It’s going to work out quite well I think.

The motor mount was printed in two pieces just for ease of printing. I made the cap to enclosed everything to keep any creepy crawlies out of the inside of the mount.

The motor mounts with (4) 3mm flat head screws.

The motor mount face just clips in place…

… then the motor shaft is inserted into the bearing cap and the mount is then attached to the top bearing piece with (4) 6-32 x 1/4″ button head screws. Next it’s onto the frame.

The frame pieces have been printed and are ready for assembly.

After cutting all of the PVC pipe piece to the correct lengths the frame is mocked up onto the bearing base.

The cross tubes are held in place with (4) 6-32″ set screws.

The motor was mounted to the side frame motor mount with (4) M3 x 25mm socket cap screws.

The side frames are just slid on the cross tubes but may be glued (or screwed) in place later on.

Each panel mounts was printed in two piece then the shaft piece was super glued in place.

The motor side panel mount then just slides onto the motor shaft.

The shaft on the other side has to be inserted up to the first race then the BB’s have to be installed and then this process is continued for the second race also. A screw and cap (not shown) will eventually be fixed to the end of the shaft to keep it in place.

The frame of the main solar panel was then drilled and tapped to accept 4-40 screws for the panel mounts and mini solar panel setups.

The solar panel then just slides up into the mounts and is secured in place with (2) 4-40 x 1/4″ flat head screws.

The mini solar panel holders also mount around the frame with 4-40 x 1/4″ button head screws.

The small solar panels a just stuck to the mount with some double sided tape for now.

The relays were also taped onto the main solar panel and main power for the motors (12 volt source) is wired to both relays.

Wires are then soldered to the one of small solar panels that controls the rotation motor…

… which is then feed to one of the relays coils.

The other small solar panel connects to the other relays coil (green wires) and then the motor feed (red and black wires) are also connected to the relays contact points.

Wrapping the wires around something round and applying heat with a heat gun forms a nice spiral in the wire…

… which gives it some relief flexibility when the solar panel pivots around the axis.

Here everything has been wired and is ready to test.

I had some issues with the first tests and thought that with the small solar panels being angled they were not getting enough sun to trip the relay consistently enough so I went back and made some mounts that positioned them parallel with the main panel.  This seemed to work better at first but I still had issues with one of the axis so I think one of the relays is bad. I’m going to swap it out and see if that helps.

To be continued…..

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