Finding The Sun And Moon The New Old-Fashioned Way

The ability to build a robot to take care of a tedious task for you is power indeed. For a few centuries, the task of helping determine one’s location fell to the sextant. Now, you can offload that task to this auto-sextant, courtesy of [Raz85].

To be clear, this robo-sextant doesn’t give you your exact location, but it does find and display the bearing and altitude of the most luminous object around and display them on the LCD — so, the sun and moon. A pair of cheap servos handle the horizontal and vertical movement, an Arduino Uno acts as the brains and nervous system, and a photoresistor acts as the all-seeing eye. Clever use of some cardboard allow [Raz85] to keep the photoresistor isolated from most all light except what the sextant is currently pointed at. Servos have a limited field of movement, so you might need to adjust [Raz85]’s code accordingly if you’re rebuilding this one yourself.

After taking three minutes to make its rounds of the sky, the Uno records the servos’ positions when fixed on the sun or moon, translating that data into usable coordinates. Don’t forget the best part, it runs on batteries making it convenient for all your wave-faring excursions!

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The Most Powerful Diesel Engine

Ever. Literally.

A gearhead friend of ours sent along a link to a YouTube video (also embedded below) promising the world’s most powerful engine. Now, we’ll be the first to warn you that it’s just an advertisement, and for something that you’re probably not going to rush out and buy: the Wärtsilä 14RT marine engine.

A tiny bit of math: 96 cm cylinder diameter times 250 cm piston stroke = 1,809,557 CC. And it generates around 107,000 HP. That’s a fair bit, but it runs at a techno-music pace: 120 BPM RPM. With twelve cylinders, we’d love to hear this thing run. Two-strokes make such a wonderful racket! Wonder if they’ve tried to red-line it? It’s a good thing we don’t work at Wärtsilä.

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Hacklet 98 – Underwater ROVs

A few motors, propellers, a camera, maybe a wire tether, and some waterproof electronics. Throw it all together and baby you’ve got an underwater Remotely Operated Vehicle (ROV) cooking! It all sounds simple on the surface, but underwater ROVs are a tough challenge. We’ve all seen deep-sea ROVs searching the wreck of the Titanic, or working to stop the flow of oil below the Deepwater Horizon. Plenty of hackers, makers, and engineers have been inspired to build their own underwater ROVs. This week on the Hacklet, we’re spotlighting at some of the best ROV projects on!

borgcubeWe start with [Tim Wilkinson] and BorgCube ROV. [Tim] has jumped into the world of underwater ROVs with both feet. BorgCube is designed to operate in the unforgiving salt waters of the Pacific Ocean. This ROV can see in stereo, as [Tim] plans to use a head mounted VR display like the Oculus Rift to control it. [Tim] wanted to use a Raspberry Pi as the brains of this robot. Since the Pi Compute module can handle two cameras, it was a natural fit. The electronic speed controls are all low-cost Hobby King R/C car units. [Tim] created a custom circuit board to hold all 12 ESCs. This modular design allows individual controllers to be swapped out if one meets an untimely doom. BorgCube is just getting wet, but with 37 project logs and counting, we’re sure [Tim] will keep us posted on all the latest action!


lunaNext up is [MrCullDog] with Luna I ROV. Inspired by a professional underwater ROV, [MrCullDog] decided to build a deep diving unmanned vehicle of his very own. Like BorgCube above, many of Luna I’s motors and drive components come from radio controlled hobby electronics. [MrCullDog] is bringing some 3D printed parts into the mix as well. He’s already shown off some incredibly well modeled and printed thruster mounts and ducts. The brains of this robot will be an Arduino. Control is via wired Ethernet tether. [MrCullDog] is just getting started on this project, so click the follow button to see updates in your Feed.

cavepearlNext up is [Edward Mallon] with The Cave Pearl Project. Not every underwater system needs motors – or even a human watching over it. The Cave Pearl Project is a series of long duration underwater data loggers which measure sea conditions like temperature and water flow. [Edward’s] goal is to have a device which can run for a year on just three AA batteries. An Arduino Pro Mini captures data from the sensors, time stamps it, and stores it to a micro SD card. If the PVC pipe enclosure keeps everything dry, the data will be waiting for [Edward] to collect months later. [Edward] isn’t just testing in a swimming pool, he’s been refining his designs in open water for a couple of years now.


If you want to see more under (and above) water projects, check out our updated waterborne projects list! If I missed your project, don’t be shy! Just drop me a message on That’s it for this week’s Hacklet. As always, see you next week. Same hack time, same hack channel, bringing you the best of!

Hacklet 71 – Waterborne projects

Water: Life on earth wouldn’t exist without it. 71 percent of the Earth is covered by water. That only leaves 29 percent for us humans to live – and not all of that land is inhabitable. Water is so important that most human settlements start near water of some sort. Water to drink, or water to move goods. With all this water in oceans, lakes, and rivers, it is no surprise that hackers, makers, and engineers alike build some incredible projects that work on and under the water.

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Retrotechtacular: Fire Control Computers in Navy Ships

Here is a two-part Navy training film from 1953 that describes the inner workings of mechanical fire control computers. It covers seven mechanisms: shafts, gears, cams, differentials, component solvers, integrators, and multipliers, and does so in the well-executed fashion typical of the era.

Fire control systems depend on many factors that occur simultaneously, not the least of which are own ship’s speed and course, distance to a target, bearing, the target’s speed and course if not stationary, initial shell velocity, and wind speed and direction.

The mechanisms are introduced with a rack and pinion demonstration in two dimensions. Principally speaking, a shaft carries a value based on revolutions. From this, a system can be geared at different ratios.

Cams take this idea further, transferring a regular motion such as rotation to an irregular motion. They do so using a working surface as input and a follower as output. We are shown how cams change rotary motion to linear motion. While the simplest example is limited to a single revolution, additional revolutions can be obtained by extending the working surface. This is usually done with a ball in a groove.

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Retrotechtacular: Breaking Atoms to Break the Ice


This documentary from 1959 gives a satisfyingly thorough look inside a nuclear powered icebreaking ship called Lenin. This actually set a couple of world’s-firsts: it was the first nuclear powered surface vessel and the first civilian vessel to be powered thusly.

The ship was built to clear shipping paths to the northern ports of Russia. Testing of both ice and models of the ship design point to the ability to break ice layers that are two meters thick. This requires a lot of power as ice-breakers generally use their hull shape and gravity to break the ice by driving up onto it to bend the ice to the breaking point. The Lenin achieved this power using its nuclear reactor to heat steam which drove electric generators. The energy produced drove three screws to power the vessel.

Of course this was back in the day when control panels were substantial, which you can get a peek at starting half-way through the twenty-minute film. This includes a demonstration of the ship’s network of radiation sensors which alert the control room, and sound a local alarm when they are triggered. During it’s 30-year operational life the vessel had a couple of accidents stemming from refueling operations. You can find more on that over at the Wikipedia page, but stick with us after the jump to see the vintage reel.

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Stopping a hackerspace from rusting away


The illutron hackerspace in Copenhagen makes their home on a barge sitting in port. Not only is this awesome, but the members of the hackerspace also worry about corrosion to their beloved fablab. In an effort to ally some fears about rust slowly eating through the hull, [Dzl] has rigged up a cathodic protection system for their hull, essentially preserving their barge at the expense of a few old steel rails.

Cathodic protection systems are able to protect the steel of a ship’s hull by offering up a sacrificial anode made of aluminum or zinc. This can be done by either attaching a sacrificial anode directly to the hull, or with a more complex system that connects both the cathode (the ship) and the anode (an engine block) to a DC power source.

[Dzl] is converting mains voltage down to 12 VDC, then further lowering the voltage with an Arduino-controlled buck converter. The control panel allows for adjustments in the voltage, as well as a nice uptime meter to make sure it’s running.

The results are fairly impressive; in the above pic, the right piece of steel was electrically connected to the barge’s hull, while the left piece was free to rust in the North Sea. That’s only two days worth of corrosion there.