Rover Runs Slow And Steady On Solar Power

March 15, 2020 by Danie Conradie 11 Comments

The solar panel technology we have available today doesn’t really lend itself to practical everyday transport. But when speed isn’t a concern, it can make for some very interesting autonomous rovers. One example of this is [Daniel Riley] aka [rctestflight]’s solar powered rover, which he built to live autonomously at his flight testing field, crawling around whenever it has gathered enough juice from the sun.

[Daniel] has thing for autonomous craft of all types, with quite a few aircraft and boats to his name. This rover is built around a welded steel frame, with each wheel driven by a brushless geared motors via a chain. While it’s technically a skid steer, the electronic speed controls are from a quadcopter and can’t reverse, so it doesn’t turn quite on the spot.

With the rigid steel frame, any small bump in the ground would cause one wheel to lose traction. To fix this, the frame was cut in two and a pivot added in the center, allowing all four wheels to always remain on the ground. Another problem is that the wheels would sometimes dig themselves into the soft wet ground, so this, [Daniel] attached a 3D printed “hump” to each drive wheel, which helps them to climb out of any soft spots. For the next version of this rover, [Daniel] plans to use cheap DC geared motors from a Barbie jeep. They’re a bit too fast though, so he’ll be adding 3D printed cycloidal reduction gearboxes. We’re definitely looking forward to seeing here this project goes from here.

There have been a number of projects to test solar powered robots for agricultural use. We really like the idea, with its potential for long duration missions. Imagine something like this roaming the Black Rock playa in the US, the Makgadikgadi Pan in Botswana, or even the Sahara Desert, while gathering environmental data and making awesome time-lapse videos.

Solar Panel Keeps Car Battery Topped Off Through OBD-II Port

March 10, 2020 by Dan Maloney 47 Comments

Up until the 1980s or so, a mechanic could check for shorts in a car’s electrical system by looking for sparks while removing the battery terminal with everything turned off in the car. That stopped being possible when cars started getting always-on devices, and as [Kerry Wong] learned, these phantom loads can leave one stranded with a dead battery at the airport after returning from a long trip.

[Kerry]’s solution is simple: a solar trickle charger. Such devices are readily available commercially, of course, and generally consist of a small photovoltaic array that sits on the dashboard and a plug for the lighter socket. But as [Kerry] points out in the video below, most newer model cars no longer have lighter sockets that are wired to work without the ignition being on. So he chose to connect his solar panel directly to the OBD-II port, the spec for which calls for an always-on, fused circuit connected directly to the positive terminal of the vehicle battery. He had to hack together an adapter for the panel’s lighter plug, the insides of which are more than a little scary, and for good measure, he added a Schottky diode to prevent battery discharge through the panel. Even the weak winter sun provides 150 mA or so of trickle charge, and [Kerry] can rest assured his ride will be ready at the end of his trip.

We used to seeing [Kerry] tear down test gear and analyze unusual devices, along with the odd post mortem on nearly catastrophic failures. We’re glad nothing burst into flames with this one.

Continue reading “Solar Panel Keeps Car Battery Topped Off Through OBD-II Port” →

Laser Etches Solar Absorbing Material

February 6, 2020 by Al Williams 19 Comments

Having a laser cutter these days isn’t a big deal. But [Chunlei Guo], a professor at the University of Rochester, has a powerful femto-second pulse laser and used it to create what might be the perfect solar absorber. You can see a video about the work, below.

It stands to reason that white materials reflect most light and therefore absorb less energy than black materials — this is part of what makes a radiometer work. Tungsten, in particular, is a good metal for absorbing solar power, but this new laser treatment — which builds nanostructures on the surface of the metal — increases efficiency by 130% compared to untreated tungsten.

Continue reading “Laser Etches Solar Absorbing Material” →

Teardown And Analysis Of A Cheap Solar Lamp

January 26, 2020 by Jenny List 57 Comments

If you walk the aisles of a dollar store one constant that you will see worldwide is the Chinese solar lamp. Your dollar gets you a white LED behind plastic, mounted on a spike to stick into the ground, and with a solar cell on top. It charges in the sunlight during the day and then lights the LED for a few hours at nightfall. They are in gardens everywhere, and no doubt landfill sites are full of them because they do not last very long. [Giovanni Bernardo] had one that stopped working, so he subjected it to a teardown to find out what was up, and what made it tick (Italian, Google Translate link).

As expected, the culprit proved to be a leaking and corroded 1.2 volt NiMh cell, and its replacement with an AA cell brought the lamp back to life. But the interesting part of this tale comes from his teardown and analysis of the lamp’s components. It’s centered around a YX8016 battery charger and power management chip. The device has an amazing economy of design with only four components including the solar cell and the LED. The final component is a small inductor that forms part of the boost converter to keep the LED lit as the battery voltage falls. The chip switches at 580kHz, and produces a 3.2 volt supply.

If this is a subject that interests you, don’t forget to take a look at the power harvesting challenge we ran a while back.

Modular Solar-Powered IoT Sensors

January 19, 2020 by Danie Conradie 1 Comment

Bringing a product to market is not easy, if it were everyone would be doing it, and succeeding. The team at Pycno is in the process of launching their second product, a modular solar powered IoT unit called Pulse. It’s always interesting to get an inside look when a company is so open during the development process, and see how they deal with challenges.

Pycno’s first product was a solar powered sensor suite for crops. This time round they are keeping the solar part, but creating a modular system that can accept wired or wireless connections (2G/3G/4G, WiFi, LoRa, GPS and Bluetooth 5) or modules that slide into the bottom of the unit. They plan to open source the module design to allow other to design custom modules, which is a smart move since interoperability can be a big driving factor behind adoption. The ease of plugging in sensors is a very handy feature, since most non-Hackaday users would probably prefer to not open up expensive units to swap out sensors. The custom solar panel itself is pretty interesting, since it features an integrated OLED display. It consists of a PCB with the cutout for the display, with solar cells soldered on before the whole is laminated to protect the cells.

Making a product so completely modular also has some pitfalls, since it can be really tricky to market something able to do anything for anybody. However, we wish them the best of luck with their Kickstarter (video after the break) and look forward to seeing how the ecosystem develops.

When a large community develops around a modular ecosystem, it can truly grow beyond the originator’s wildest dreams. Just look at Arduino and Raspberry Pi. We’re also currently running a contest involving boards for the Feather form factor if you want to get in on the act. Continue reading “Modular Solar-Powered IoT Sensors” →

Building A Low-Tech Website For Energy Efficiency

January 10, 2020 by Sharon Lin 38 Comments

In an age of flashy jQuery scripts and bulky JavaScript front-end frameworks, loading a “lite” website is like a breath of fresh air. When most of us think of lightweight sites, though, our mind goes to old-style pure HTML and CSS sites or the intentionally barebones websites of developers and academics. Low-tech Magazine, an intentionally low-tech and solar-powered website, manages to incorporate both modern web aesthetics and low-tech efficiency in one go.

Rather than hosting the site on data centers – even those running on renewable power sources – they have a self-hosted site that is run on solar power, causing the site to occasionally go off-line. Their model contrasts with the cloud computing model, which allows more energy efficiency at the user-side while increasing energy expense at data centers. Each page on the blog declares the page size, with an average page weight of 0.77 MB, less than half of the average page size of the top 500,000 most popular blogs in June 2018.

Some of the major choices that have limited the size of the website include building a static site as opposed to a dynamic site, “dithering” images, sparing a logo, staying with default typefaces, and eliminating all third-party tracking, advertising services, and cookies. Their GitHub repository details the front-end decisions including using unicode characters for the site’s logo rather than embedding an SVG. While the latter may be scalable and lightweight in format it requires distribution to the end-user, which can involve a zipped package with eps, ai, png, and jpeg files in order to ensure the user is able to load the image.

As for the image dithering, the technique allows the website to maintain its characteristic appearance while still minimizing image quality and size. Luckily for Low-tech Magazine, the theme of the magazine allows for black and white images, suitable for dithering. Image sprites are also helpful for minimizing server requests by combining multiple small images into one. Storage-wise, the combined image will take up less memory and only load once.

There are also a few extraneous features that emphasize the website’s infrastructure. The background color indicates the capacity of the solar-charged battery for the website’s server, while other stats about the server’s location (time, sky conditions, forecast) also help with making the website availability in the near future more visible. Who knows, with the greater conscience on environmental impact, this may be a new trend in web design.

ESP32 Makes Great MPPT Controller In Low-Cost Solar Installation

November 4, 2019 by Dan Maloney 34 Comments

Solar power projects have become, in general, a matter of selecting components like panels and batteries, hooking them together with industry-standard connectors, and sitting back to watch the free electricity flow. As such, solar projects have become a bit boring, so it’s not often we see one that attracts our attention the way this dirt-cheap open-source solar project does.

The backstory on [Tim O’Brien]’s DIY off-grid PV system starts with his desire to charge his eWheel, which amounts to a battery-powered standing unicycle. They look like a fun option for getting around an urban environment if you have the requisite degree of coordination, which we clearly lack. But charging something like that or an eBike is a great use case for solar, especially since [Tim] happened upon a 450W PV panel on the cheap. Sadly, the panel was a commercial unit, and compatible off-the-shelf MPPT, or maximum power-point tracking, controllers are expensive.

His solution was to build his own controller using a cheap DC-DC converter that just so happens to have serial remote control. An ESP32 monitors the panel voltage and controls the buck converter to run whatever he wants. When he’s not charging his eWheel, the system runs his laptop and router. As a bonus, the ESP32 talks to IoT services like Adafruit.io and Thingspeak, allowing him to track MPPT data without shipping it off to parts unknown.

While we appreciate a DIY MPPT controller and like [Tim]’s build, we feel like the documentation needs a bit of fleshing out. With solar installations, the devil is in the details, and not addressing seemingly mundane issues like cable routing and connector installation can lead to disaster.