Curved Wood LED Lamp Needs No Fancy Tools

Those of us who aren’t familiar with woodworking might not expect that this curved wood and acrylic LED lamp by [Marija] isn’t the product of fancy carving, just some thoughtful design and assembly work. The base is a few inches of concrete in a plastic bowl, then sanded and given a clear coat. The wood is four layers of beech hardwood cut on an inverted jigsaw with the middle two layers having an extra recess for two LED strips. After the rough-cut layers were glued together, the imperfections were rasped and sanded out. Since the layers of wood give a consistent width to the recess for the LEDs, it was easy to cut a long strip of acrylic that would match. Saw cutting acrylic can be dicey because it can crack or melt, but a table saw with a crosscut blade did the trick. Forming the acrylic to match the curves of the wood was a matter of gentle heating and easing the softened acrylic into place bit by bit.

Giving the clear acrylic a frosted finish was done with a few coats of satin finish clear coat from a spray can, which is a technique we haven’t really seen before. Handy, because it provides a smooth and unbroken coating along the entire length of the acrylic. This worked well and is a clever idea, but [Marija] could still see the LEDs and wires inside the lamp, so she covered them with some white tape. A video of the entire process is embedded below.

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Biologic Additive May Lead to Self-Healing Concrete

If you get a cut or break a bone, your body heals itself. This everyday miracle is what inspired [Congrui Jin] to try to find a way to make concrete self-healing. The answer she and her colleagues are working on might surprise you. They are adding fungus to concrete to enable self-repair.

It isn’t just any fungus. The conditions in concrete are very harsh, and after testing twenty different kinds, they found that one kind — trichoderma reesei — could survive inside concrete as spores. This fungus is widespread in tropical soil and doesn’t pose any threat to humans or the ecology. Mixing nutrients and spores into concrete is easy enough. When cracks form in the concrete, water and oxygen get in and the spores grow. The spores act as a catalyst for calcium carbonate crystals which fill the cracks. When the water is gone, the fungi go back to spores, ready to repair future cracking.

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Conductive Concrete Confounds Circuitry

There’s a fairly good chance you’ve never tried to embed electronics into a chunk of concrete. Truth be told, before this one arrived to us via the tip line, the thought had never even occurred to us. After all, the conditions electronic components would have to endure during the pouring and curing process sound like a perfect storm of terrible: wet, alkaline, and with a bunch of pulverized minerals thrown in for good measure.

But as it turns out, the biggest issue with embedding electronics into concrete is something that most people aren’t even aware of: concrete is conductive. Not very conductive, mind you, but enough to cause problems. This is exactly where [Adam Kumpf] of Makefast Workshop found himself while working on a concrete enclosure for a color-changing barometer called LightNudge.

While putting a printed circuit board in the concrete was clearly not workable, [Adam] was hoping to simplify manufacturing of the device by embedding the DC power jack and capacitive touch sensor into the concrete itself. Unfortunately, [Adam] found that there was a resistance of about 200k Ohm between the touch sensor and the power jack; more than enough to mess with the sensitive measurements required for the touch sensor to function.

Even worse, the resistance of the concrete was found to change over time as the curing process continued, which can stretch out for weeks. With no reliable way to calibrate out the concrete’s internal conductivity, [Adam] needed a way to isolate his electronic components from the concrete itself.

Through trial and error, [Adam] eventually found a cheap method: dipping his sensor pad and wire into an acrylic enamel coating from the hardware store. It takes 24 hours to fully cure, and two coats to be sure no metal is exposed, but at least it’s an easy fix.

While the tip about concrete’s latent conductivity is interesting enough on its own, [Adam] also gives plenty of information about casting concrete parts which may be a useful bit of knowledge to store away for later. We have to admit, the final result is certainly much slicker than we would have expected.

This is the first one we’ve come across that’s embedded in concrete, but we’ve got no shortage of other capacitive touch projects if you’d like to get inspired.

The Engineering That Survives Hurricanes

Florida is a great place to live, especially around January when it’s sunny and 24 degrees outside (76F) while all of your friends from back home are dealing with scraping ice off of their windshields every morning. In the late summer, though, this pleasant tropical paradise can sometimes take a turn for the worse, because Florida is one of the handful of places that frequently see some of the worst storms on the planet: hurricanes. As a Floridian myself, perhaps I can shed some light on some of the ways that the various local governments and their residents have taken to mitigate the destruction that usually accompanies these intense tropical storms when it seems that, to outsiders, it might be considered unwise to live in such a place.

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3D Print Your Next Dwelling In A Day

What’s the shortest amount of time in which a 400 square foot home can be built? A few weeks? Try a fully printed structure in 24 hours for a little over $10,000.

This radial residence was materialized out of concrete in Stupino, Russia by [Apis Cor], and six collaborating companies, as a prototype. As opposed to traditional — such as it is for tech largely in its infancy — assembly of pre-printed or fabricated pieces, the building was printed as a whole, with the printer removed by crane before finishing the rest of the construction. It features a bathroom, hallway, living room, and a compact kitchen — everything a bachelor or bachelorette needs.

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Bulking up a Lightweight Lathe with a Concrete Cart

When it comes to machine tools, a good rule of thumb is that heavier is better. A big South Bend lathe or Bridgeport mill might tip the scales at ludicrous weight, but all that mass goes to damping vibration and improving performance. So you’d figure a lathe made of soda cans could use all the help it could get; this cast concrete machine cart ought to fit the bill nicely

Perhaps you’ve caught our recent coverage of [Makercise]’s long and detailed vlog of his Gingery lathe build. If not, you might want to watch the 5-minute condensed video of the build, which shows the entire process from melting down scrap aluminum for castings to first chips. We love the build and the videos, but the lightweight lathe on that wooden bench never really worked for us, or for [Makercise], who notes that he was never able to crank the lathe up to full speed because of the vibrations. The cart attempts to fix that problem the old fashioned way – more mass.

There are a few “measure twice, cut once” moments in the video below, as well as a high pucker-factor slab lift that could have turned into a real disaster. We might have opted for a countertop-grade concrete mix that could be dyed and polished, but that would be just for looks. When all is said and done, the cart does exactly what it was built to do, and there’s even room on it for the shaper that’s next on the build list. We’re looking forward to that.

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Touch Sensitive Cement with Just a Dash of Neon

For quite some time now we’ve seen people casting their own countertops and other surfaces out of cement. It’s a combination of mold-making and surface finishing that produces a smooth and durable surface at quite a low cost, if you don’t factor in damage done to your back when lifting the thing for installation.

This offering is a little bit different. [Elliott Spelman] built his own touch sensitive cement table top. When you place your grubby hands on the polished surface, a loop of neon lighting is switched on. This is thanks to a 4:1 mix of quick setting cement and iron oxide powder. Bare copper wire was laid around the edges of the surface to be encased by the cement for making connections later.

There were some sad moments when [Elliott] was removing the cast surface from the mold. He ended up cracking it and suggests others be liberal with their use of both wax on the mold before casting, and patience in removing the cement afterward. We might also suggest a strengthening agent like fiber reinforcement. The edges and surface can be sanded to the finish desired and in this case, attaching table legs was easy since the wooden underside of the mold remains on the bottom of the cement.

The neon lighting adds a retro touch to this build. It’s sad to see this technology dying away, so a resurgence of artisanal neon is great in our book. [Elliott] found a Bay Area arts collective called the Crucible which does a lot of art glass education to help him make two hoops of glass tube and fill them with the appropriate gasses. A capacitive touch sensor (once Atmel, now Microchip part) AT42QT2120 (datasheet) monitors the wire coming from the slab and switches the power supply for the tubes using a combination of relay board and Arduino Uno.

We find the prospect of positional sensing in doped cement fascinating. Anyone have ideas for adapting this technique so that a more long and narrow slab could have positional awareness within, say, a few inches? Let us know in the comments.

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