Reinforced Concrete: Versatile At Any Size?

September 26, 2021 by Jenny List 19 Comments

In our community we’re no strangers to making things, and there are plenty among us who devote their efforts to modelmaking. It’s uncommon, though, for a scale model of something to be made using the exact same techniques as whatever it’s copying. Instead a model might be made from card, foam, glassfibre, or resin. [tiny WORLD] takes an opposite tack, building scale model civil engineering projects just as they would have been for real. (Video, embedded below.)

Here, a scale model of the Hoover Dam bypass bridge is made as the original, from reinforced concrete. In place of rebar is a wire grid in place of wooden shuttering is what looks like foam board, the concrete is a much smoother mortar, but otherwise it’s the real thing. We see the various bridge parts being cast in situ, with the result being as strong as you’d expect from the original.

We can see that this is a great technique for modelling concrete buildings and structures, but it’s also a material that we think might have other applications at this scale. How would the rigidity, strength, and mass of small-scale reinforced cement compare to 20-20 extrusion, 3D-printed plastic, or wood, for example? Regardless, it’s interesting to watch, as you can see from the video below the break.

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Finding The Right Hack Is Half The Battle

September 18, 2021 by Elliot Williams 25 Comments

Sometimes you just get lucky. I had a project on my list for a long time, and it was one that I had been putting off for a few months now because I loathed one part of what it entailed — sensitive, high-accuracy analog measurement. And then, out of the blue I stumbled on exactly the right trick, and my problems vanished in thin air. Thanks, Internet of Hackers!

The project in question is a low-vacuum regulator for “bagging” fiberglass layups. What I needed was some way to read a pressure sensor and turn on and off a vacuum pump accordingly. The industry-standard vacuum gauges are neat devices, essentially a tiny little strain gauge on a membrane between the vacuum side and the atmosphere side, in a package the size of a dime. (That it’s a strain gauge is foreshadowing, but I didn’t know that at the time.) I bought one for $15 ages ago, and it sat on my desk, awaiting its analog circuitry.

See, the MPX2100 runs on 12 V and puts out a signal around 40 mV on top of a 6 V offset. That voltage level is inconvenient for modern 3.3 V microcontroller ADCs, and the resolution would get clobbered by the 6 V signal if I just put a voltage divider on it. This meant whipping together some kind of instrument amplifier circuit to null out the 6 V and amplify the 40 mV for the ADC. The circuits I found online all called for 1% resistors in values I didn’t have, and mildly special op-amps. No fun, for me at least. So there it sat.

Picture of sketchy-looking vacuum apparatus. — Cut the blue wire or the red wire? HX711 module and pressure sensor on the left.

Until I ran into this project that machetes through the analog jungle with one part, and it happened to be one I had on hand. A vacuum pressure sensor is a strain gauge, set up like a Wheatstone bridge, just like you would use for weighing something with a load cell. The solution? A load-cell ADC chip, the HX711, found in every cheap scale or online for under a buck. The only other trick was finding a low-voltage pressure sensor to work with it, but that turns out to be easy as well, and I had one delivered in two days.

In all, this project took months of foot-dragging, but only a few clicks and five minutes of soldering once I got the right idea. The industrial applications and manufacturers’ app notes all make sense if you are making hundreds or millions of these devices, where the one-time cost of prototyping up the hard bits gets amortized, but the hacker solution of using a weight-scale chip was just the ticket for a one-off. That just goes to show how useful sharing our tips and tricks can be — you won’t get this from the industry. So send us your success stories, and your useful failures too, and Read More Hackaday!

Taking A Deep Dive Into SPI

September 16, 2021 by Jim Heaney 9 Comments

With the prevalence of libraries, it has never been easier to communicate with hundreds of different sensors, displays, and submodules. But what is really happening when you type SPI.begin() into the Arduino IDE? In his most recent video, [Ben Eater] explores the Serial Peripheral Interface (SPI) and how it really works.

Most Hackaday readers probably know [Ben] from his breadboard-based computers, such as the 6502 build we featured in 2019. Since then he has been hard at work, adding new and interesting additions to his breadboard computer, as well as diving into different communication protocols to better understand and implement them. For this video, [Ben] set the goal of connecting the BME280, a common pressure, temperature, and humidity sensor with an SPI interface, to his breadboard 6502 computer. Along the way, [Ben] discusses how exactly SPI works, and why there is so much conflicting nomenclature and operations when looking at different SPI devices.

If breadboard computers aren’t your thing, there are tons of other uses for the BME280, such as helping to modernize a Casio F-91W.

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Powering Up With USB: Untangling The USB Power Delivery Standards

September 16, 2021 by Maya Posch 37 Comments

Powering external devices directly from a PC’s I/O ports has been a thing long before USB was even a twinkle in an engineer’s eye. Some of us may remember the all too common PS/2 pass-through leads that’d tap into the 275 mA that is available via these ports. When USB was first released, it initially provided a maximum of 500 mA which USB 3.0 increased to 900 mA.

For the longest time, this provided power was meant only to provide a way for peripherals like keyboards, mice and similar trivial devices to be powered rather than require each of these to come with its own power adapter. As the number of computer-connected gadgets increased USB would become the primary way to not only power small devices directly, but to also charge battery-powered devices and ultimately deliver power more generally.

Which brings us to the USB Power Delivery (USB-PD) protocol. Confusingly, USB-PD encompasses a number of different standards, ranging from fixed voltage charging to Programmable Power Supply and Adjustable Voltage Supply. What are the exact differences between these modes, and how does one go about using them? Continue reading “Powering Up With USB: Untangling The USB Power Delivery Standards” →

Two hands on a book labeled "hardware crowdfunding"

Successfully Crowdfunded Hardware: Everything Behind The Scenes

September 12, 2021 by Donald Papp 5 Comments

Crowdfunding hardware has its own unique challenges, and [Uri Shaked] wrote a fascinating report that goes into excellent detail about his experience bringing a crowdfunded hardware project to life.

[Uri]’s project was The Skull CTF, an electronic hardware puzzle that came in the shape of a PCB skull, and his detailed look behind the scenes covers just about every angle, from original concept to final wrap-up, along with his thoughts and feedback at every stage. His project reached its funding goal, got manufactured and shipped, and in the end was a success.

[Uri] started with a working project, but beyond that was virtually a complete novice when it came to crowdfunding. He eventually settled on using Crowd Supply to make his idea happen, and his writeup explains in great detail every stage of that process, including dollar amounts. What’s great to see is that not only does [Uri] explain the steps and decisions involved, but explains the research that went into each, and how he feels each of them ended up working out.

The entire thing is worth a read, but [Uri] summarizes the experience of crowdfunding a hardware project thus: an excellent way to test out the demand for an idea and bring a product into existence, but be aware that unless a project is a runaway success it probably won’t be much of an income generator at that stage. It was a great learning experience, but involved a lot of time and effort on his part as well.

[Uri] really knows his stuff, and considering his skill at hunting down pesky bugs, it’s probably no surprise that this wasn’t his first hardware puzzle.

Highly Configurable Open Source Microscope Cooked Up In FreeCAD

September 9, 2021 by Dave Rowntree 22 Comments

What do you get when you cross a day job as a Medical Histopathologist with an interest in 3D printing and programming? You get a fully-baked Open Source microscope, specifically the Portable Upgradeable Modular Affordable (or PUMA), that’s what. And this is no toy microscope. By combining a sprinkle of off-the-shelf electronics available from pretty much anywhere, a pound or two of filament, and a dash of high quality optical parts, PUMA cooks up quite possibly one of the best open source microscopy experiences we’ve ever tasted.

GitHub user [TadPath] works as a medical pathologist and clearly knows a thing or two about what makes a great instrument, so it is a genuine joy for us to see this tasty project laid out in such a complete fashion. Many a time we’ve looked into an high-profile project, only to find a pile of STL files and some hard to source special parts. But not here. This is deliberately designed to be buildable by practically anyone with access to a 3D printer and an eBay account.

The project is not currently certified for medical diagnostics use, but that is likely only a matter of money and time. The value for education and research (especially in developing nations) cannot really be overstated.

A small selection of the fixed and active aperture choices

The modularity allows a wide range of configurations from simple ambient light illumination, with a single objective, great for using out in the field without electricity, right up to a trinocular setup with TFT-based spatial light modulator enabling advanced methods such as Schlieren phase contrast (which allows visualisation of fluid flow inside a live cell, for example) and a heads-up display for making measurements from the sample. Add into the mix that PUMA is specifically designed to be quickly and easily broken down in the field, that helps busy researchers on the go, out in the sticks.

The GitHub repo has all the details you could need to build your own configuration and appropriate add-ons, everything from CAD files (FreeCAD source, so you can remix it to your heart’s content) and a detailed Bill-of-Materials for sourcing parts.

We covered fluorescence microscopy before, as well as many many other microscope related stories over the years, because quite simply, microscopes are a very important topic. Heck, this humble scribe has a binocular and a trinocular microscope on the bench next to him, and doesn’t even consider that unusual. If you’re hungry for an easily hackable, extendable and cost-effective scope, then this may be just the dish you were looking for.

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Arduino Powered Heat Pump Controller Helps Warm Your Toes

September 8, 2021 by Dave Rowntree 39 Comments

Heat pump heating technology is starting to pop up more and more lately, as the technology becomes cheaper and public awareness and acceptance improves. Touted as a greener residential heating system, they are rapidly gaining popularity, at least in part due to various government green policies and tax breaks.

[Gonzho] has been busy the last few years working on his own Arduino Powered Open Source heat pump controller, and the project logs show some nice details of what it takes to start experimenting with heat pumps in general, if that’s your game. Or you could use this to give an old system a new lease of life with an Arduino brain transplant.

In essence they are very simple devices; some kind of refrigerant is passed through a source of heat, absorbing some of it, it then flows elsewhere, and is compressed, which increases its temperature, before that increased heat is lost where the increase in temperature is desired.

This heat source could be a river, a mass of pipes buried in the ground, or simply the air around you. The source and quality of the heat source as well as the desired system operating temperature dictate the overall efficiency, and with ground-source systems it’s even possible to dump excess heat directly into the ground and store it for when required later. This could be the result of a residential cooling system, or even directly sourced from a solar heated setup.

This heat pumping process is reversible, so it is possible to swap the hot and cold ends, just by flipping some valves, and turn your space heater into a space cooler. This whole process can trace its roots back to the super talented Scottish professor, William Cullen who in 1748 was the first person on record to demonstrate artificial refrigeration.

The power needed to run the compressor pump and control gear is usually electrically derived, at least in non-vehicular applications, but the total power required is significantly less than the effective heating (or cooling) power that results.

We’ve covered a few heat pump hacks before, like this guy who’s been heating his house geothermally for years, but not so many platforms designed for experimentation from the ground up.

The associated GitHub project provides the gerber files as well as the Arduino code, so you’ve got a great starting point for your own heat pumping builds.