Smelting Solar Style

November 7, 2022 by Al Williams 32 Comments

If you attended the 2022 Supercon, you might have heard the story about the SMD soldering challenge table nearly catching on fire. A magnifying lamp caught the sun just right and burned a neat trench into another lamp’s plastic base. While disaster was averted, [Jelle Seegers] does this on purpose using a huge 5-meter lens to smelt metal.

The Design Academy Eindhoven student is participating in Dutch Design Week and built the machine which is able to manually track the sun to maximize the amount of solar energy applied to the metal.

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The Origin Of The Fresnel Lens

June 7, 2022 by Al Williams 15 Comments

If you are a Hackaday reader, you probably know what a Fresnel lens is. You find them in everything from overhead projectors to VR headsets. While it seems commonplace now, the Fresnel lens was an important invention for its day because it revolutionized maritime navigation and, according to a post over at IEEE Spectrum, that was the driving force behind its invention. In fact, the lens has been called “the invention that saved a million ships“.

The problem stems from issues in navigation. Navigating by the sun and the stars is fine, but not workable when you have heavy cloud cover, or other reasons you can’t see them. A lighthouse often marked an important point that you either wanted to navigate towards or, sometimes, away from. Sure, today, we have GPS, but for a long time, a lighthouse was your best bet.

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Fast Fresnel Hack Embiggens The Smallest Of Heads

November 20, 2019 by Dan Maloney 17 Comments

Aside from frightening small children, we have absolutely no idea why anyone would need a face-magnifying headpiece. But the video below gives us a chuckle every time we see it, and we figure a good laugh that incorporates a quick optics hack is worth a look.

When he’s not playing geek in a box, [Curious Marc]’s videos usually have more of a retrocomputing theme, like his recent conversion of a vintage terminal to a character set from a made-up language, or helping to revive an Apollo Guidance Computer. Given gems like those, we were surprised to learn that [Marc]’s background is physics – optics, to be precise – and that he studied at École Polytechnique, the same school famed physicist Augustin-Jean Fresnel attended. Which fits right into this build since it features one of those large, plastic Fresnel lenses. After a fascinating detour into the history of Fresnel’s namesake lens, [Marc] proceeds with the build.

It’s simplicity itself – a box big enough to wear on the head with one end replaced by the Fresnel lens. A strip of LEDs – warm white, please, lest the wearer takes on a deathly pall – lines the edge of the box just behind the lens. If you want to get fancy, maybe attaching a hard-hat suspension piece would make it more wearable, but even as is it’s just a hoot to see someone with a magnified and distorted head walking around. One probably should be careful not to look at the sun while wearing this, however, for reasons that become apparent beginning at the 3:24 mark of the video.

Thanks to [Marc] for perhaps the oddest YouTube face-reveal yet, and for a great idea for a quick cosplay hack.

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Antique Lighthouse Lens Via CNC

May 11, 2018 by Bryan Cockfield 22 Comments

Before the invention of the high-powered LED, and even really before the widespread adoption of electric lights in general, lighthouses still had the obligation of warning ships of dangers while guiding them into various safe harbors. They did this with gas lights and impressive glass lenses known as Fresnel lenses which helped point all available light in the correct direction while reducing weight and material that would otherwise be used in a conventional lens.

Now, a company in Florida is using acrylic in reproductions of antique Fresnel lenses. At first glance, it seems like acrylic might not be the best substitute for glass, but the company is able to achieve extreme precision using a CNC machine and then polishing and baking the acrylic which makes it transparent and excellent for use in lighthouse lenses like this. The reproduction lenses are built out of brass, and the lens elements are glued in place with a special adhesive. It’s a convincing replication worthy of use in any lighthouse.

Be sure to check out the video below to see how these lenses are built, and although we’re not entirely sure what exactly is being sprayed on the lenses when they are being polished, perhaps someone in the comments section can illuminate that for us. Of course, there are other uses for Fresnel lenses than in lighthouses, and we’ve seen some great examples of them put to use for many different applications.

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Hackaday Links: March 20th, 2013

March 20, 2013 by Ryan Fitzpatrick 23 Comments

Giant fresnel lens is dangerous fun

Here’s an interesting, and rather dangerous, use for those old big screen TVs that are frequently listed for FREE on Craigslist. With the lens from the old TV built into an adjustable wooden frame, [Grant] was able to melt a stack of pennies, instantly burn wood, melt spots in concrete, and serve his family a cooked egg… Cool.

Projection mapping app helps create hologram like performance stage

projection-mapping-app-creates-live-desktop-stage

[Aimino] used an iPad, a mobile projector, and a mosquito screen to create a trippy hologram like stage. It might not seem like much at first, but it’s actually a pretty interesting effect. Watching the video makes me wonder what other applications this could have in the near future.

The world’s strongest magnet

worlds-strongest-magnet

At a cost of over $14 million dollars and weighing in at 35 tons, the 45 Tesla Hybrid is the strongest DC magnet on Earth. It’s powerful enough that the film crew couldn’t even safely get in to take footage of it. Over half of their camera tapes were wiped clean just while being in the same facility that houses it!

Virtual Body chair uses 4 of our 5 senses

virtual-body-chair

Created in the hopes of providing a VR experience for seniors with mobility problems who can no longer travel the world, Tokyo Metropolitan University’s Ikei Laboratory presents the ‘Virtual Body’ exhibition. Included are a 3D monitor, a pair of headphones, a fan to create breezes and spread scents, a chair that moves and vibrates, and moving foot pedals.

Iron Man laser gauntlet pops balloons with ease

functional-iron-man-laser-gauntlet

If you’re an Iron Man fan with disposable income, you might want to check out this functional full metal laser gauntlet. Built from scratch using no blueprints or guides, [AnselmoFanZero] sells them for around $3K USD.

Your Own Head-mounted Display For Under Two Bills

February 14, 2013 by Mike Szczys 39 Comments

CIMG1078

[D S] wanted his own head-mounted display. What you see here is just his mockup, but somewhere along the way he realized it’s closer to a finished build than just being a stating point. Not only does it work well for gaming, it came in at under $200 all in. You think your girlfriend makes fun of you now for wearing that big microphone headset while playing? Just wait until she gets a load of these!

We’ve embedded an image gallery after the break as well as the description he sent us with his email. The display itself is a 7″ LCD module from eBay that boasts a hair better than 720P resolution: 1280×800. He’s using a pair of ski goggles to strap the display to his noggin. The enclosure is made out of foam board which should help keep the weight down. Inside there’s a Fresnel lens but after reading his description of how he measured the focal length we’re still not 100% clear on how he figured out where to mount it.

Though it may be missing the 3d of the rift,a quick mod could fix that and he’ll be well on his way through the journey to building his own Holodeck.

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DIY Fresnel Reflector

January 9, 2012 by Brian Benchoff 14 Comments

Just like destroying an ant colony with a magnifying glass, there’s nothing like cooking hot dogs and roasting marshmallows with a nice parabolic reflector. Of course covering an old satellite dish with mylar or aluminum tape doesn’t take much skill, however cool it is. [Uwe] came up with a much more technical means of building a Fresnel reflector that will cook your hot dogs in seconds, but only on sunny days.

[Uwe] channeled a little bit of [Apollonius] when he realized that a flat cardboard ring with a section removed could be joined together into a conic section. The resulting section looks just like one concentric ring in a Fresnel reflector. [Uwe] wrote a small program in Visual Basic to calculate the necessary diameter and angle of his conic sections.

A bit of cardboard was cut out and pieced together with some very reflective aluminum tape. The resulting Fresnel reflector concentrates 117 times the normal solar radiation onto a small point. It’s more than enough to burn holes in construction paper, but we’ll be using a microwave for our lunch today.