Year: 2017

Photochromic Eggs: Not For Breakfast

April 18, 2017 by 17 Comments

Photochromic paint is pretty nifty – under exposure to light of the right wavelength, it’ll change colour. This gives it all kinds of applications for temporary displays.  [Jiri Zemanek] decided to apply photochromic paint to an egg, utilising it to create stroboscopic patterns with the help of a laser.

Patterns for the egg are generated in MATLAB. A Discovery STM32 board acts as a controller, looking after the laser scanner and a stepper motor which rotates the egg. A phototransistor is used to sync the position of the laser and the egg as it rotates.

The photochromic paint used in this project is activated by UV light. To energize the paint, [Jiri] harvested a violet laser from a Blu-ray player, fitting it to a scanning assembly from a laser printer. Instead of scanning the laser across an imaging drum, it is instead scanned vertically on a rotating egg. Patterns can then be drawn on the egg, which fade over time as the paint gives up its stored energy.

[Jiri] exploits this by writing a variety of patterns onto the egg, which then animate in a manner similar to a zoetrope – when visualised under strobing light, the patterns appear to move. There are also a few holiday messages shown for Easter, making the egg all the more appropriate as a billboard.

If you like the idea of drawing on eggs but are put off by their non-uniform geometry, check out the Egg-bot. Video below the break.

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Hackaday Prize Entry: GoKart Tank

April 18, 2017 by 26 Comments

There is probably something in all of us that yearns to drive a tank, just once. Most of us will probably never fulfill it, in fact, unless we work in farming or construction we’re unlikely to even drive a skid-steer vehicle of any type. But that doesn’t mean we can’t have a go at building one ourselves, as [samern] is doing with his Hackaday Prize entry.

The GoKart Tank has a chequered history, as a build that started as an internal combustion go-kart, became a half-track, and eventually the fully tracked electric vehicle we see today. It has a wooden frame, two 1KW electric scooter motors, and tracks made from IntraLox modular plastic industrial conveyor belt parts. This last choice is particularly interesting because even though it isn’t designed for use as a track it is designed for heavy-duty service and could offer a component source for other tracked vehicle projects.

What you see is a working tracked vehicle, but it is not without problems. The electric motors are only powerful enough to move a child, so there are plans to return it to internal combustion power. We can, however, see it working, as you can watch the video of it we’ve put below the break.

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Networking: Pin The Tail On The Headless Raspberry Pi

April 18, 2017 by 69 Comments

Eager to get deeper into robotics after dipping my toe in the water with my BB-8 droid, I purchased a Raspberry Pi 3 Model B. The first step was to connect to it. But while it has built-in 802.11n wireless, I at first didn’t have a wireless access point, though I eventually did get one. That meant I went through different ways of finding it and connecting to it with my desktop computer. Surely there are others seeking to do the same so let’s take a look at the secret incantations used to connect a Pi to a computer directly, and indirectly.

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Up, Up, Up: $2k More Seed Funding For Projects That Matter

April 18, 2017 by 5 Comments

Getting a project off the ground often means an up-front investment in parts. Hackaday is upping our efforts to smooth out that obstacle for those who want to Build Something That Matters. Seed funding for the 2017 Hackaday Prize is simple, enter your design plans, share it far and wide so that a lot of people will show their admiration with a ‘like’ on the project page. You get a dollar for each like to help jump-start the build phase.

This year has started off like a rocket. Last week we passed the $4000 seed funding limit even though there’s still two weeks left in the Design Your Concept round. We’re raising the pot to a total of $6000. That means there’s more up for grabs. Enter your project now. If you’ve already done that, polish up your presentation and show it around to your friends and on social media. You’ll get a dollar for every like up to $200 max, or until we undoubtedly reach the new limit once again. Don’t delay, it’s time to Build Something that Matters!

The HackadayPrize2017 is Sponsored by:

Electronifying A Horror Fraught Hydraulic Press

April 18, 2017 by 38 Comments

[Josh] is replacing the springs in his car’s suspension. He wanted to know the travel rates of these springs, but apparently, this is a closely guarded trade secret in the industry. One company did manage to publish the spring rates, but they weren’t believable. Instead of taking this company’s word, [Josh] built a spring tester.

The theory behind a spring tester is pretty simple: apply a force to a spring, measure it, then measure how much the spring has traveled. Or compress a spring an inch or so, measure the force, and compress it some more. Either gets you the same data.

This spring tester is built around a Harbor Freight hydraulic press. Yes, the spring is completely captured and won’t fly out of the jig if you look at it wrong. The bottom of the press contains a few load cells, fed into an ATmega8, which displays a value on an LCD. For the displacement measurement, a ruler taped to the side of the press will suffice, but [Josh] used a Mitutoyo linear scale.

What were the results of these tests? You shouldn’t buy coils from Bilstein if these results are correct. The rates for these springs were off by 70%. Other springs fared better and won’t bind when going over bigger bumps. That’s great work, and an excellent application of Horror Fraught gear.

The Surface Area To Volume Ratio Or Why Elephants Have Big Ears

April 18, 2017 by 48 Comments

There are very few things that are so far reaching across many different disciplines, ranging from biology to engineering, as is the relation of the surface area to the volume of a body. This is not a law, as Newton’s second one, or a theory as Darwin’s evolution theory. But it has consequences in a diverse set of situations. It explains why cells are the size they are, why some animals have a strange morphology, why flour explodes while wheat grains don’t and many other phenomena that we will explore in this article.

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Making Tension Based Furniture

April 18, 2017 by 21 Comments

[Robby Cuthbert,] an artist and designer based out of Fort Collins, Colorado is creating stable cable tables that are simultaneously a feat of engineering and a work of art.

[Cuthbert’s] tables are held together by 1/16″ stainless steel cables that exert oppositional tensions that result in a structurally stable and visually appealing coffee table. In his video, [Cuthbert] leads us through his process for creating his tables, step by step. [Cuthbert] starts by cutting out bamboo legs on his CNC mill. He then drills holes in each leg for cables and mounts each leg on his custom table jig. Then, he attaches the stainless steel cabling taking care to alternate tension direction. The cables are threaded through holes in the legs and affixed with copper crimps. After many cables, he has a mechanical structure that can support his weight that also looks fantastic. All in all, [Cuthbert’s] art is a wonderful example of the intersection of art and engineering.

If we’ve whet your appetite, fear not, we have featured many tension based art/engineering hacks before. You might be interested in these computer-designed portraits or, if the thought of knitting by hand gives you the heebie-jeebies, the Autograph, a string art printer might be more your style.

Video after the break.

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