Star Track: A Lesson in Positional Astronomy With Lasers

[gocivici] threatened us with a tutorial on positional astronomy when we started reading his tutorial on a Arduino Powered Star Pointer and he delivered. We’d pick him to help us take the One Ring to Mordor; we’d never get lost and his threat-delivery-rate makes him less likely to pull a Boromir.

As we mentioned he starts off with a really succinct and well written tutorial on celestial coordinates that antiquity would have killed to have. If we were writing a bit of code to do our own positional astronomy system, this is the tab we’d have open. Incidentally, that’s exactly what he encourages those who have followed the tutorial to do.

The star pointer itself is a high powered green laser pointer (battery powered), 3D printed parts, and an amalgam of fourteen dollars of Chinese tech cruft. The project uses two Arduino clones to process serial commands and manage two 28byj-48 stepper motors. The 2nd Arduino clone was purely to supplement the digital pins of the first; we paused a bit at that, but then we realized that import arduinos have gotten so cheap they probably are more affordable than an I2C breakout board or stepper driver these days. The body was designed with a mixture of Tinkercad and something we’d not heard of, OpenJsCAD.

Once it’s all assembled and tested the only thing left to do is go outside with your contraption. After making sure that you’ve followed all the local regulations for not pointing lasers at airplanes, point the laser at the north star. After that you can plug in any star coordinate and the laser will swing towards it and track its location in the sky. Pretty cool.

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Dual Axis Solar Tracker with Online Energy Monitor

[Bruce Helsen] built this dual axis solar tracker as one of his final projects for school.

As can be experimentally verified in a very short timeframe, the sun moves across the sky. This is a particularly troublesome behavior for solar panels, which work best when the sun shines directly on them. Engineers soon realized that abstracting the sun away only works in physics class, and moved to the second best idea of tracking sun by moving the panel. Surprisingly, for larger installations the cost of adding tracking (and its maintenance) isn’t worth the gains, but for smaller, and especially urban, installations like [Bruce]’s it can still help.

[Bruce]’s build can be entirely sourced from eBay. The light direction is sensed via a very clever homemade directional light sensor. A 3D printer extruded cross profile sits inside an industrial lamp housing. The assembly divides the sky into four quadrants with a light-dependent resistor for each. By measuring the differences, the panel can point in the optimal direction.

The panel’s two axis are controlled with two cheap linear actuators. The brains are an Arduino glued to a large amount of solar support electronics and the online energy monitor component is covered by an ESP8266.

The construction works quite well. If you’d like to build one yourself the entire BOM, drawings, and code are provided on the instructables page.


Perovskite Solar: Coming Soon?

Making solar cells out of silicon is difficult. There’s plenty of manufacturing steps, many of them at very high temperatures, and you need a high vacuum and a clean room. However, perovskite solar cells–cells made with hybrid organic-inorganic materials in a perovskite crystal structure–are relatively easy to make using wet chemistry involving solvents or vapor deposition.

In theory, silicon solar cells could be 30% efficient, but in reality, 25% seems to be a practical limit with commercial cells typically topping out at 20%. Perovskite cells are nearly that high now, and could be higher by stacking thin layers, each sensitive to different wavelengths of light.

A recent development at the Lawrence Berkeley National Laboratory may lead to even more efficient perovskite cells. Researchers found that certain crystal structures had a much higher efficiency than other structures. The problem now is figuring out how to produce the crystals to increase the prevalence of that structure.

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Open Source Solar

What’s the size of a standard euro-palette, goes together in 15 minutes, and can charge 120 mobile phones at one time? At least one correct answer is Sunzilla, the open source solar power generator. The device does use some proprietary components, but the entire design is open source. It contains solar panels, of course, as well as storage capacity and an inverter.

You can see a video about the project below. The design is modular so you can pick and choose what you want. It also is portable, stackable, and easy to transport. The team claims they generate 900W of solar power and can store 4 kWh. Because of the storage device, the peak power out is 1600W and the output is 230V 50Hz AC.

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A Toasty Warm Pool Without The Propane Bills

So, you’ve got the deck, you’ve got the pool and the lounger, you’ve got the summer, and you’ve got the piña colada. All set, you might say.

Sounds idilyic, but sadly we aren’t all lucky enough to live in a tropical climate. So while sipping the cocktail on the lounger you’d be warm enough the chances are that taking a dip would leave you feeling as though you’d just jumped into the Arctic Ocean. Not a problem, just turn on the pool heater. At this point you discover just how much it costs to heat a large body of water kept outdoors and open to the atmosphere. You become the kind of valued customer your liquid propane dealer sends a Christmas card to, you are reduced to living on a diet of budget ramen, and your children wear shoes with holes in them.

[ClanMan] had almost the problems outlined above, at least as far as the uncomfortable propane bills. His solution was a surprisingly simple one, he built himself a solar water heater from inexpensive PVC pipe.

It might not be immediately apparent to the uninitiated, but the key to making an efficient solar collector from such a basic material lies in careful selection of the bores of the various sections of pipe being used. The hot water feed from the propane heater had quite a narrow bore with a fast flow rate, but because [ClanMan] needed his water to linger in the collector and pick up as much solar heat as possible, he chose a much wider bore to feed it to ensure a much slower flow. The collector itself was made from multiple parallel lengths of much narrower pipe, to preserve the slow net flow across their combined cross-section while ensuring the maximum surface area contact between hot pipe and water.

The resulting heat helped take the temperature of his pool from 75 to 80 Farenheit. This may not sound like much, but was enough to make a noticeable difference.

We’ve featured quite a few solar heat projects before here at Hackaday. Best title has to go to the Hippie-Redneck Solar-Heated Kiddo Swimmin’ Pool And Hot Tub, but we’ve also featured a very tidy coiled solar collector. All this swimming is hungry work though, so how about a solar cooker made from a satellite dish?

OzQube-1: A Tiny Australian Satellite

Over the last couple of decades we have become used to the possibility of launching a satellite into orbit no longer being the exclusive preserve of superpowers. Since the first CubeSats were launched over a decade ago a myriad others have followed, and scarcely a week passes without news of another interesting project in this area.

OzQube-1 is just such a satellite, designed for imaging of the Southern Hemisphere, and it’s the brainchild of Australian [Stuart McAndrew]. He’s posted significant details of its design: it’s a PocketQube, at 50mm cubed, an eighth the volume of a CubeSat, and its main instrument is a 2 megapixel camera with a 25mm lens. Images will be transmitted to earth as slow-scan digital video via the 70cm amateur band, the dipole antenna being made from a springy tape measure which will unfurl upon launch. Attitude control is passive, coming from a magnet aligned to ensure the camera will be pointing Earthwards as it passes over the Southern Hemisphere. The project has a little way to go yet, but working prototypes have been completed and it has a Gofundme campaign under way to help raise the money for a launch.

There are plenty of Cubesat and other small satellite builds to be found on the web, here at Hackaday we’ve covered a significant number of them. Many of them are the fruits of well-funded university departments or other entities with deep pockets, but this one comes from a lone builder from Western Australia. We like that, and we wish OzQube-1 every success!

Networked Solar Birdhouses Deep in the Woods

[Oitzu] in Germany wrote in to let us know about a series of short but very informative blog posts in which he describes building a series of solar-powered, networked birdhouses with the purpose of spying on the life that goes on within them. He made just one at first, then expanded to a small network of them. They work wonderfully, and [Oitzu]’s documentation will be a big help to anyone looking to implement any of the same elements – which include a Raspberry Pi in one unit as a main gateway, multiple remote units in other birdhouses taking pictures and sending those to the Pi over an nRF24L01+ based radio network, and having the Pi manage uploading those images using access to the mobile network. All with solar power.

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