Tag: hobby projects

Solar Tracker prototype – mount for solar panels

I’ve been working out how to mount the solar panels onto the rising and falling tube. Not being very mechanically minded, it’s been a bit of a struggle – hot glue to the rescue!

Rather than work directly with the acrylic tube on my (partially) working prototype, I found another plastic tube that fits nicely on top of it and am working with that.

Here’s a side view showing details of how I’ve constructed it.

photo showing the side view of the main and sun-follower solar panels' mounting assembly
side view of the main and sun-follower solar panels’ mounting assembly

I’ve still to get another angle bracket for the other side so you’ll see it’s missing in this top view of the assembly:

photo showing the top view of the assembly showing how the sun-follower solar panel is angled
top view of the assembly showing how the sun-follower solar panel is angled

Here’s the plan….

With the sun-follower solar panel angled as shown, when the sun moves far enough across the sky so that it’s no longer in the shade of the main solar panel, power will be delivered to the motor.

As the motor rotates, it lifts and turns the central tube. This will put the sun-follower solar panel back in the shade of the main solar panel, which is now pointing directly at the sun. So the motor no longer gets power and rotation stops until the sun moves far enough across the sky again.

Recap

When dusk arrives, the main solar panel stops producing power. When this happens, the battery charging circuit switches off and the battery gets connected to the output.

Whatever else the output may be connected to (string of garden LEDs etc) it will start supplying power to the motor. This will rotate the whole mechanism until the tube reaches the bottom of its travel and so resets the solar panel to the dawn position.

At the same time, as it reaches the bottom of its travel a normally closed reed switch is opened by a strategically placed magnet, turning off power to the motor.

sketch showing how the motor is powered at dusk until the opening of the reed switch stops it.
how the motor is powered at dusk until the opening of the reed switch stops it.

Note that I’ve called the sun-follower solar panel “secondary solar panels” in the sketch.

Solar tracker project – motor arrived

The motor I ordered has arrived and I’ve incorporated it into the prototype. Here’s how it now looks. Very Heath-Robinson! 🤪

motor operating the lift-and-twist mechanism

There’s still a few problems to solve. Mainly that the motor draws too much current for common and cheap hobby 6V solar panels.

After making the video I poured some water into the milk container to see what it did to the current drawn by the motor. It drew 250mA for only a combined weight to lift of around 500g. Without the water it’s about 100g, needing around 200mA.

Don’t quote me on those figures, they’re very rough and ready.

I’ve emailed the supplier of the motor for options, mentioning the following:

  • The solar panel I have to use can’t deliver the required load current unless it’s really bright sunshine. Besides, at 6V the 12 rpm is too fast.
  • I think a worm drive would work if I could get the final output shaft to rotate at 1rpm or less. Or maybe a pinion and timing belt???
  • Ideally I’d like something that would draw only 100ma under load so maybe an alternative motor would be better (with a worm drive / pinion-timing belt as well)???

Let’s see what they say.

That’s all until the next update 😎

Proof of Concept Solar Panel Sun Tracker

There are all sorts of commercially available sun trackers for solar panels but they are use sophisticated engineering / electronics.

Until now, there’s been nothing out there for the hobbyist. Have a look at this proof of concept video:

proof of concept Solar Panel Sun Tracker video

Details on driving the motor

Thanks to my good friend Bart, NightHawkInLight and NASA for one part of the solution…

The above video shows how to power the motor during the day for tracking the sun.

However, when the day draws to a close and the main solar panel is receiving no light, there’s still one thing left to do…

Resetting things ready for the following day

We have to drive the motor to rotate the plate another 180° to allow the inner tube to return to the starting position, resetting the solar panel so it points in the direction it was in at the start of the day.

That part is easy with the aid of a diode, reed switch and a magnet.

The Solar Lithium Ion Battery Charger module already has the capability to deliver power (from the battery) when darkness falls, so we use this power to drive the motor some more.

To stop the motor at the right time is where the diode, reed switch and magnet come into play:

sketch showing how the magnet and reed switch work in conjunction with the motor to return the inner tube to the bottom when dusk falls
sketch showing how the magnet and reed switch work in conjunction with the motor to return the inner tube to the bottom when dusk falls

When dusk falls, dark-activated power from the battery comes on. This drives the motor via the closed reed switch and the diode.

When the inner tube has returned to the bottom, the magnet activates the reed switch, opening it and cutting power to the motor. This leaves the inner tube at the bottom, with the main solar panel pointing in the direction it started at the beginning of the day.

When daylight arrives again, the secondary solar panels will once more start driving the motor as dictated by the sun’s position. The diode is there to protect the battery from any reverse voltage spikes generated by the motor.

I haven’t checked the exact operation of the secondary solar panels and motor yet, so another reed switch may be needed to prevent the dark activated power from leaking through them when the inner tube is being lowered by the motor.

That’s it for now. I’d love to hear your comments – especially if you spot any flaws!