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 😎