Tacking Against The Sun: Flying A Batteryless Solar RC Plane Is Almost Like Sailing

October 7, 2019 by Danie Conradie 28 Comments

Flying on the power of the sun is definitely not a new idea, but it usually involves a battery between the solar panels and the propulsion system. [ukanduit] decided to lose the battery completely and control the speed of the motor with the output of the solar panels. This leads to some interesting flying characteristics, almost akin to sailing.

When a load tries to draw more current than a solar panel can provide, its output falls dramatically, so [ukanduit] had to take this into account. Using a ATTiny85, he built a MPPT (Maximum Power Point Tracker) unit that connects between the RC receiver and the motor speed controller. It monitors the output of the panels and modulates the speed of the motor accordingly, while ensuring that there is always enough power to run the servos and receiver. The airframe (named the Solar Bear) is a small lightweight flying wing, with a balsa and carbon fibre frame covered with clear film, with the solar cells housed inside the wing. Since the thrust of the motor is directly proportional to how much sunlight hits the top of wings, it requires the pilot to “tack” against the sun and use momentum to quickly get through turns before orienting into the sun again.

If you want to build your own controller, the schematics and software is up on RC Groups. Check out the Solar Bear in action, flown here by [AJWoods].

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Is Solar Right For You? Find Out!

September 7, 2019 by Bryan Cockfield 22 Comments

Solar panels are revolutionizing the electric power industry, but not everyone is a good candidate for rooftop solar. Obviously people in extreme northern or sothern latitudes aren’t going to be making a ton of energy during the winter compared to people living closer to the equator, for example, but there are other factors at play that are more specific to each individual house. To find out if any one in particular will benefit from solar panels, [Jake] and [Ryan]’s solar intensity sensor will help you find out.

The long-term intensity tracker is equipped with a small solar panel and a data recording device, properly contained in a waterproof enclosure, and is intended to be placed in the exact location that a potential solar installation will be. Once it has finished gathering data, it will help determine if it makes economical sense to install panels given that the roof slope might not be ideal, landscaping may be in the way, or you live in a climate where it rains a lot in the summer during peak production times.

As we move into the future of cheap, reliable solar panels, projects like this will become more and more valuable. If you’re not convinced yet that photovoltaics are the way of the future, though, there are other ways of harnessing that free solar power.

Solar-Harvesting Blinkenlights

September 3, 2019 by Bryan Cockfield 15 Comments

A few years ago a fad ripped through the makersphere where people would build cheap, solar powered LED blinkers, glue a magnet to them, and throw them on anything metal. It was an interesting time, but luckily did not last for too long. With some effort and craftsmanship, though, the solar throwie idea can be turned into something more elegant, though, such as this solar harvesting blinking gadget.

Like its predecessors, the device itself behaves simply, although this one is equipped with a small supercapacitor which can run the device for 8 hours without sun. It has a small solar panel which can charge the capacitor in five minutes, and from there the LEDs inside simply blink. The quality shows in the final packaging, as [Jasper] has taken to encasing them in epoxy shapes such as pyramids, for a nice paperweight or tchotchke. It is also noteworthy because of Jasper’s test device; since he is mass producing them he needed something to test each board for functionality before encasing them in the epoxy, and he built a small pen tester specifically for them too.

While the build is pretty straightforward, anyone looking to enclose a simple circuit in epoxy without bubbles or other problems might want to check this one out. It would also be a good platform for building other throwie-like projects on top of. In the past they didn’t just blink lights but also did things like run small Linux servers.

Soak Up The Sun With This 3D Printed Solar Harvester

July 9, 2019 by Tom Nardi 31 Comments

At first glance, adding solar power to your project might seem easy. Get a photovoltaic panel, point it towards the big ball of burning gas in the sky, and off you go. But in reality, there’s a bit more to it than that. Especially when you’re trying to do something on a small scale. Without a rooftop full of panels pumping out power, you’ve got to take what you can get.

If you’re looking to power small electronic devices such as sensors with a single solar panel, [Vadim Panov] has put together a very concise write-up and video on building a low-cost solar harvester. It combines a relatively small photovoltaic panel, a charging circuit, and a battery for energy storage into a easily mountable package. He’s provided all the details necessary to create your own version, all you have to do now is come up with the application for it.

As far as the electronics go, this project is about as straightforward as it gets. The three watt panel is connected up to a simplistic charging circuit, which in turn feeds into a single 18650 cell. You might be wondering why a charge controller is even necessary in such a simple set up. One problem is that the output voltage of the panel is higher than that of the battery. You also need a blocking diode that will prevent the battery from discharging into the cell during the night or in cloudy conditions.

While the electronics might seem elementary to some readers, we think the 3D printed case alone is worth taking a look at. Not only has [Vadim] come up with a design that perfectly encloses the fragile solar panel and associated electronics, but in the video after the break, he also explains how the entire thing can be made waterproof with an epoxy coating. As 3D prints can have a tendency to be porous, this technique is definitely something you should file away mentally if you’ve been thinking of deploying a printed enclosure outdoors.

Whether you’re looking to power environmental sensors for as near a century as is technically possible or a portable OpenWRT router for mobile anonymity, these small solar panels hold a lot of promise if you know how to work around their limitations.

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Keeping Birds At Bay With An Automated Spinning Owl

May 30, 2019 by Tom Nardi 3 Comments

There’s nothing wrong with building something just to build it, but there’s something especially satisfying about being able to solve a real-world problem with a piece of gear you’ve designed and fabricated. When all the traditional methods to keep birds from roosting on his mother’s property failed, [MNMakerMan] decided to come up with a more persuasive option: a solar powered spinning owl complete with expandable batons.

We imagine the owl isn’t strictly necessary when you’re whacking the birds with a metal bar to begin with, but it does add a nice touch. Perhaps it will even serve to deter some of the less adventurous birds before they get within clobbering distance, which is probably in their best interest. [MNMakerMan] says the rotation speed of the bars seems low enough that he doesn’t think it will do the birds any physical harm, but it’s still got to be fairly unpleasant.

At first glance you might think that this contraption simply spins when the small 10 watt photovoltaic panel next to it catches the sun, but there’s actually a bit more to it than that. Sure he probably could just have it spin constantly whenever the sun is up, but instead [MNMakerMan] is using a ATtiny85 to control the 11 RPM geared DC motor with a IRF540 MOSFET. By adding a DS3231 RTC module into the mix, he’s able to not only accurately control when the spinner begins and ends its bird-busting shift, but implement timed patterns rather than running it the whole time. All of which can of course be fine-tuned by adjusting a couple variables and reflashing the chip.

We’ve seen plenty of automated systems for keeping cats away, and of course squirrels are a common target for such builds as well, but devices to deter birds are considerably less common among these pages. So it would seem that, at least for now, [MNMakerMan] has the market cornered on solar bird smashing gadgets. We’re sure Mom’s very proud.

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Give Your Solar Garden Lights A Color Changing LED Upgrade

April 24, 2019 by Roger Cheng 14 Comments

White LEDs were the technological breakthrough that changed the world of lighting, now they are everywhere. There’s no better sign of their cost-effective ubiquity than the dollar store solar garden light: a complete unit integrating a white LED with its solar cell and battery storage. Not content with boring white lights on the ground, [Emily] decided to switch up their colors with a mix of single-color LEDs and dynamic color-changing LEDs, then hung them up high as colorful solar ornaments.

The heart of these solar devices is a YX8018 chip (or one of its competitors.) While the sun is shining, solar power is directed to charge up the battery. Once the solar cell stops producing power, presumably because the sun has gone down, the chip starts acting as a boost converter (“Joule thief”) pushing a single cell battery voltage up high enough to drive its white LED. Changing that LED over to a single color LED is pretty straightforward, but a color changing LED adds a bit of challenge. The boost converter deliver power in pulses that are too fast for human eyes to pick up but the time between power pulses is long enough to cause a color-changing circuit to reset itself and never get beyond its boot-up color.

The hack to keep a color-changing LED’s cycle going is to add a capacitor to retain some charge between pulses, and a diode to prevent that charge from draining back into the rest of the circuit. A ping-pong ball serves as light diffuser, and the whole thing is hung up using a 3D-printed sheath which adds its own splash of color.

Solar garden lights are great basis for a cheap and easy introduction to electronics hacking. We’ve seen them turn into LED throwies, into a usable flashlight, or even to power an ATTiny microcontroller.

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Dollar Store Garden Lights As ATtiny Power Supplies

April 20, 2019 by Jenny List 19 Comments

Solar garden lights are just another part of the great trash pile of our age, electronics so cheap as to be disposable. Most of you probably have a set lurking somewhere at home, their batteries maybe exhausted. Internally though they are surprisingly interesting devices. A solar cell, a little boost converter chip, and a little NiCd battery alongside the LED. These are components with potential, as [Randy Elwin] noted with a mind to his ATtiny85 projects.

The YX805A chip he references in his write-up is one of several similar chips that function in effect as joule thieves, extending the available charge in the battery to keep the LED active as long as possible when their solar panel is generating nothing, and turning it off in daylight when the panel can charge. Their problem is that they are designed as joule thieves rather than regulators, so using them as a microcontroller PSU without modification can result in overvoltage.

His solution is to use the device’s solar panel input as a feedback pin from his ATtiny, allowing the microcontroller to keep an eye on its supply voltage and enable or disable the converter as necessary while it keeps running from the reservoir capacitor. Meanwhile the solar panel now charges the NiCd cell through a single diode. It’s not perfect and maybe needs a clamp or something, he notes that there is a condition in which the supply can peak at 8 volts, a level which would kill an ATtiny. But still, we like simple hacks on dollar store parts, so it’s definitely worth further investigation.

This isn’t the first garden light hack we’ve shown you, there was this flashlight, and some LED hacks.

Solar light picture: Leon Brooks [Public domain].