Current Sensor Makes Intriguing Use Of Concrete

Getting a product to market isn’t all about making sure that the product does what it’s supposed to. Granted, most of us will spend most of our time focusing on the functionality of our projects and less on the form, fit, or finish of the final product, especially for one-off builds that won’t get replicated. For those builds that do eventually leave the prototyping phase, though, a lot more effort goes into the final design and “feel” of the product than we might otherwise think. For example, this current sensor improves its feel by making use of cast concrete in its case.

The current sensor in this build is not too much out of the ordinary. [kevarek] built the sensor around the MCA1101-50-3 chip and added some extra features to improve its electrostatic discharge resistance and also to improve its electromagnetic compatibility over and above the recommended datasheet specifications. The custom case is where this one small detail popped out at us that we haven’t really seen much of before, though. [kevarek] mixed up a small batch of concrete to pour into the case simply because it feels better to have a weightier final product.

While he doesn’t mention building this current sensor to sell to a wider audience, this is exactly something that a final marketable product might have within itself to improve the way the device feels. Heavier things are associated, perhaps subconsciously, with higher quality, and since PCBs and plastic casings don’t weigh much on their own many manufacturers will add dummy weights to improve the relationship between weight and quality. Even though this modification is entirely separate from the function of the product, it’s not uncommon for small changes in design to have a measurable impact on performance, even when the original product remains unmodified.

Thanks to [Saabman] for the tip!

Hackaday Podcast 087: Sound-Shattering Gliders, Pressing Dashcam Buttons, And Ratcheting Up Time

Hackaday editors Mike Szczys and Elliot Williams dish up a hot slice of the week’s hardware hacks. We feature a lot of clocks on Hackaday, but few can compare to the mechanical engineering elegance of the band-saw-blade-based ratcheting clock we swoon over on this week’s show. We’ve found a superb use of a six-pin microcontroller, peek in on tire (or is that tyre) wear particles, and hear the sounds of 500 mph RC gliders. It turns out that 3D printers are the primordial ooze for both pumping water and positioning cameras. This episode comes to a close by getting stressed out over concrete.

Take a look at the links below if you want to follow along, and as always, tell us what you think about this episode in the comments!

Direct download (~60 MB)

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A Good, Hard Look At Pre-Stressed Concrete

From the looks of the average driveway or sidewalk, it may seem as though concrete is just destined to crack. But if concrete is so prone to cracking, how are we able to use it in so many high-stress applications like bridges and skyscrapers? This question came about while I was researching 3D-printed thermite for an article. Thermite is often used in welding railroad tracks, and I linked a video of fresh tracks being welded that had concrete ties. I knew I had to find out how concrete could be made to withstand the pressure of freight trains.

On its own, concrete is brittle and has no give to it at all. But that doesn’t mean it isn’t strong. Although concrete has good compression strength, the tensile strength is quite poor. Around the late 1800s, someone thought to fortify spans of concrete with steel reinforcing bars, better known as rebar. Steel can stretch, adding steel bars gives the concrete some tensile strength to go along with its compressive strength. Rebar also allows for thinner slabs and other members.

Rebar Only Goes So Far

Parking blocks are meant to be replaced occasionally. Image via Checkers Safety

Rebar or mesh-enforced concrete is good for things like parking lot blocks and roads, but it still fails before it ought to. In fact, it usually has to crack before the rebar can chip in any of its tensile strength.

In high-stress concrete applications like bridges and skyscrapers, it’s terrifically important to avoid deflection — that’s when a concrete member flexes and bends under load. Deflection can cause the modern glass skins to pop off of skyscrapers, among other problems.

A solid, rigid bridge is much nicer to walk, drive, and bicycle on than a bridge that sways in the breeze. But how do you do make a rigid bridge? One solution is to apply stresses to the concrete before it ever bears the load of cars and trucks or a steady schedule of freight trains.

Pre-stressed concrete is like rebar-enforced concrete, but with the added power of tension baked in. By adding stress to the concrete before it goes into service, deflection will be reduced or perhaps eliminated altogether. With the addition of tensile strength, more of the concrete’s own strength is able to come into play.

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Ideas To Prototypes Hack Chat With Nick Bild

Join us on Wednesday, July 29 at noon Pacific for the Ideas to Prototypes Hack Chat with Nick Bild!

For most of us, ideas are easy to come by. Taking a shower can generate half of dozen of them, the bulk of which will be gone before your hair is dry. But a few ideas will stick, and eventually make it onto paper or its electronic equivalent, to be played with and tweaked until it coalesces into a plan. And a plan, if we’re lucky, is what’s needed to put that original idea into action, to bring it to fruition and see just what it can do.

No matter what you’re building, the ability to turn ideas into prototypes is what moves projects forward, and it’s what most of us live for. Seeing something on the bench or the shop floor that was once just a couple of back-of-the-napkin sketches, and before that only an abstract concept in your head, is immensely satisfying.

The path from idea to prototype, however, is not always a smooth one, as Nick Bild can attest. We’ve been covering Nick’s work for a while now, starting with his “nearly practical” breadboard 6502 computer, the Vectron, up to his recent forays into machine learning with ShAIdes, his home-automation controlling AI sunglasses. On the way we’ve seen his machine-learning pitch predictor, dazzle-proof glasses, and even a wardrobe-malfunction preventer.

All of Nick’s stuff is cool, to be sure, but there’s a method to his productivity, and we’ll talk about that and more in this Hack Chat. Join us as we dive into Nick’s projects and find out what he does to turn his ideas into prototypes.

join-hack-chatOur Hack Chats are live community events in the Hackaday.io Hack Chat group messaging. This week we’ll be sitting down on Wednesday, July 29 at 12:00 PM Pacific time. If time zones have you down, we have a handy time zone converter.

Click that speech bubble to the right, and you’ll be taken directly to the Hack Chat group on Hackaday.io. You don’t have to wait until Wednesday; join whenever you want and you can see what the community is talking about. Continue reading “Ideas To Prototypes Hack Chat With Nick Bild”

Bricking Your 3D Printer, In A Good Way

In our vernacular, bricking something is almost never good. It implies that something has gone very wrong indeed, and that your once-useful and likely expensive widget is now about as useful as a brick. Given their importance to civilization, that seems somewhat unfair to bricks, but it gets the point across.

It turns out, though, that bricks can play an important role in 3D-printing in terms of both noise control and print quality. As [Stefan] points out in the video below, living with a 3D printer whirring away on a long print can be disturbing, especially when the vibrations of the stepper motors are transmitted into and amplified by a solid surface, like a benchtop. He found that isolating the printer from the resonant surface was the key. While the stock felt pad feet on his Original Prusa i3 Mk 3S helped, the best results were achieved by building a platform of closed-cell packing foam and a concrete paver block. The combination of the springy foam and the dampening mass of the paver brought the sound level down almost 8 dBA.

[Stefan] also thoughtfully tested his setups on print quality. Machine tools generally perform better with more mass to damp unwanted vibration, so it stands to reason that perching a printer on top of a heavy concrete slab would improve performance. Even though the difference in quality wasn’t huge, it was noticeable, and coupled with the noise reduction, it makes the inclusion of a paver and some scraps of foam into your printing setup a no-brainer.

Not content to spend just a couple of bucks on a paver for vibration damping? Then cast a composite epoxy base for your machine — either with aluminum or with granite.

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Pumping Concrete

Due to social distancing, gym rats throughout the world are turning everyday objects into exercise equipment to keep up the routine without actually hitting the gym. A particularly pleasing version of this are these concrete dumbbells whipped up by the unfortunately named hacker [ShitnamiTidalWave].

If you happen to have half a bag of concrete — quick set or otherwise — out in the shed you can follow the lead on this one. But even if you’re not the kind of person who has “arm day” on your calendar (most of us here in the Hackaday bunker do not) this hack is still worth your time. Mold making is one of the uber-useful skills you should have in your hacker toolkit and [ShitnamiTidalWave] has done both an excellent job of building a mold, and of explaining the process.

Raw material for this one couldn’t be easier; each mold is made out of plywood, 2×4 stud, and nails, along with handles made of 3/4″ PVC pipe. The studs were ripped down and used to create the 45 degree chamfers at each edge. Mold-making veterans will tell you that release agent is a must and in this case rubbing the insides of the molds with wax made it a snap to pry the wooden forms off of the set concrete.

Concrete has a tendency to crack as it cures so if you’re casting large pieces like this touch-sensitive concrete countertop you might want to throw in some fiber reinforcement to the mix. If you’re keen on seeing some of the more impressive mold-making skills at work, check out how metal parts are cast from 3D-printed molds and how a master duplicates parts using silicone molds.

[via r/DIY]

Printing Liquid Concrete

In the world of additive manufacturing, there’s always need materials being added to the list of potential filaments to use for printing objects. A method of rapid liquid printing of concrete designed by [Anatoly Berezkin] of Stoneflower 3D makes it possible to print a large variety of shapes from concrete while avoiding the negative effects of fast dehydration. The technique is based on an approach to printing polyurethanes, developed by MIT in 2017. This technique requires physically drawing a 3D object within a gel suspension using a chemical curing process. The gel allows gravity to not affect the printing process, as well as helping out with the curinng. Berezkin, an engineer and hobbyist working out of his garage, has published other work including print heads, ceramic printing, and micro printing sets.

One might be skeptical of whether the weight of the material could cause potential collapse during the printing process, or whether it is simply unrealistic to print objects given the time needed for the concrete to dry. Their demo shows the process being done in household items – bowls and tupperware – combining affordable items such as clay, concrete, and sand for the matrix and mortar. The viscous clay is strong enough to act as a good scaffold for keeping the concrete structure in place as it is being printed. As their video demonstrates, at least for simply objects, the process seems relatively fast.

RLPC doesn’t require toxic chemicals or proprietary components such as gels and suspensions. Its immersion of the final printed object in a humid environment is also superior to the standard process of liquid deposition for hardening concrete. Moreover, the process simply requires clay or retarded mortar for the matrix and mortar paste for turning into concrete. It’s advertised as eco-friendly, but just the simplicity of the materials needed for the matrix and mortar make this a promising technique.

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