This Air Compressor Sucks

Vacuum is something most people learn about as children, when they’re first tasked with chores around the home. The humble vacuum cleaner is a useful home appliance and a great way to lose an eye as an inquisitive child. When it comes to common workshop tasks though, they can be a bit of a let down. When you need to pull some serious vacuum, you might wanna turn to something a little more serious – like this converted air compressor.

The build starts with a cheap off-the-shelf tyre inflator. These can be had for under $20 from the right places. They’re prone to overheating if used at too high a duty cycle, but with care they can last just long enough to be useful. The hack consists of fitting a hose barb connection over the intake of the pump, to allow air to be sucked out of whatever you’re trying to pull vacuum on. This is achieved with some hardware store parts and a healthy dose of JB-Weld. It’s then a simple matter of removing the valve adapter on the tyre inflator’s outlet so it can flow freely.

You might also consider adding a check valve, but overall this remains a cheap and easy way to get an electric vacuum pump for your workshop up and running. If that’s not quite your jam, you can always go down the handpump route instead.

Posted in air compressor, tool hacks, tyre inflator, vacuum, vacuum pump | Leave a comment

Casting CNC Parts In Aluminium

When it comes to machining, particularly in metal, rigidity is everything. [Tailortech] had a homebuilt CNC machine with a spindle held in place by a plastic bracket. This just wasn’t up to the job, so the decision was made to cast a replacement.

[Tailortech] decided to use the lost PLA process – a popular choice amongst the maker crowd. The spindle holder was first sketched out, then modeled in Fusion 3D. This was then printed in PLA slightly oversized to account for shrinkage in the casting process.

The PLA part was then used to make a plaster mold. [Tailortech] explains the process, and how to avoid common pitfalls that can lead to problems. It’s important to properly heat the mold once the plaster has set to remove moisture, but care must be taken to avoid cracking or wall calcination. It’s then necessary to slowly heat the mold to even higher temperatures to melt out the PLA prior to casting. With the mold completed, it can be filled with molten aluminium to produce the final part. When it’s cooled off, it’s then machined to final tolerances and installed on the machine.

Lost PLA casting is a versatile process, and goes to show that not everything has to be CNC machined out of billet to do the job. It’s also readily accessible to any maker with a furnace and a 3D printer. If you’ve got a casting project of your own, be sure to let us know. Video after the break.

Posted in aluminium casting, casting, cnc, lost pla casting, tool hacks | Leave a comment

Circular Linear Motor Becomes A Micro Motor Raceway

Over on Hackaday.io we have a lot of people playing around with the possibilities presented by cheap printed circuit boards. Whether that means making a quadcopter from fiberglass or a speaker from etched copper, we’ve seen just about everything. Now, finally, we have a miniature magnetic racetrack. It’s an ant highway, or a linear motor wrapped around into a circle. Or a tiny-scale model railroad. Either way it’s very, very cool.

The ant highway comes from [bobricius], one of the many makers tinkering around with coils and traces. This time he’s built a ten centimeter square board that is, effectively, a linear motor. It’s a three-phase motor made out of PCB coils, with a small magnetic ‘car’ that’s pushed forward. These coils are controlled by an ATtiny10 and a trio of MOSFETs. Wrap that linear motor into a circle and you have a neat little circular track that’s the smallest model car raceway you’ve ever seen.

As with all of [bobricius]’ circuit boards, this one demands a video, and that’s available below. This is an interesting bit of technology, and it’s more than just a raceway for tiny magnetic cars. This could be the beginnings of an analog clock with a digital heart, or the start of the smallest model train layout you’ve ever seen. There’s impressive work being done with PCB motors now that printed circuit boards are so cheap, and we can’t wait to see what’s next.

A quick Hackaday search will reveal [bobricius] as a prolific source of projects whose work we’ve featured multiple times. Favorites include a brushless PCB motor, and an FR4 cell phone.

Posted in circular motor, linear motor, misc hacks, model car, pcb motor | Leave a comment

Piezoelectric Antennas For Very, Very Low Frequencies

If you want to talk about antennas, the amateur radio community has you covered, with one glaring exception. Very low frequency and Extremely Low Frequency radio isn’t practiced very much, ultimately because it’s impractical and you simply can’t transmit much information when your carrier frequency is measured in tens of Hertz. There is more information on Extremely Low Frequency radio in Michael Crichton’s Sphere than there is in the normal parts of the Internet. Now there might be an easier way to play with VLF radiation, thanks to developers at the National Accelerator Laboratory. They’ve developed a piezoelectric transmitter for very long wavelengths.

Instead of pushing pixies through an antenna, this antenna uses a rod-shaped crystal of lithium niobate, a piezoelectric material. An AC voltage is applied to the rod makes it vibrate, and this triggers an oscillating electric current flow that’s emitted as VLF radiation. The key is that it’s these soundwaves bouncing around that define the resonant frequency, and the speed of sound in lithium niobate is a lot slower than the speed of light, but they’re translated into electric signals because of its piezoelectricity. For contrast, if this were a wire quarter-wave antenna it would be tens of kilometers long.

The application for this sort of antenna is ideally for where regular radio doesn’t work. Radio doesn’t work underwater, but nuclear subs trail an antenna out of the back to receive messages using Extremely Low Frequency radio. A walkie talkie doesn’t work in a mine, and this could potentially be used there. There is a patent for this piezoelectric antenna, so if anyone knows of a source of lithium niobate, put a link in the comments.

We’ve seen this trick before to make small antennas even smaller, but this is the first time we’ve seen it used in the VLF band, where it’s arguably even more impressive.

Posted in antenna, news, piezo, piezoelectric, radio, radio hacks, vlf | Leave a comment

Picking the Right Sensors for Home Automation

Imagine that you’re starting a project where you need to measure temperature and humidity. That sounds easy in the abstract, but choosing a real device out of many involves digging into seemingly infinite details and trade-offs that come with them. If it’s a low-stakes monitoring project, picking the first sensor that comes to mind might suffice. But when the project aims to control an AC system in an office of temperature-sensitive coders, it pays to take a hard look at the source of all information: the sensor.

Continuing a previous article I would like to use that same BMaC project from that article as a way to illustrate how even a couple of greenhorns can figure out how to pick everything from environmental sensors to various actuators, integrating it into a coherent system that in the end actually does what it should.

Popularity Isn’t a Good Indicator

A major issue when it comes to figuring out which components one needs is that there are a lot of (online) articles, forum posts and other commentary out there by people who are using the same sensors and actuators without ever really questioning why they are using those devices and not others. A good example of this are the DHT11, DHT22, and AM2302 temperature and hygrometer sensors. While very popular and used by everyone and their dog, they come with a whole range of potential issues.

This sensor and a number of others were recently compared in a comprehensive test. The findings of that test showed that across six different sensor devices (specifically the DHT22, BME280, SHT71, AM2320, HTU21D and Si7021), the DHT22 performed the worst, with three out of six sensors outright dying over the course of two years.

They also showed issues with variability between individual sensors and a lack of long-term stability and reliability. Long-term stability cannot be expected, self-heating is an issue, and there’s no reliable way to detect strong heating or cooling as compared to a failing sensor.

Another issue that makes this range of sensors so annoying to work with is that they use their own, proprietary interface and protocol. This protocol is somewhat similar to the 1-wire protocol as invented by Dallas Semiconductor, but uses its own timing system and without the bus-mastering additions. With only its from Chinese translated datasheet to base a library on, one has to raise serious questions about the reliability of any system that includes one of these sensors.

In the BMaC project we initially started out with these DHT22 sensors as well. They were cheap and plentiful, and at first glance they seemed to be just fine. Unfortunately the breakout boards we had did not include the proper resistors on the breakout board, so humidity measurements were off by a few percent RH, as we found out later. These sensors, especially including the breakout boards, are rather bulky as well, making them hard to integrate into projects.

At some point we came across this MEMS sensor from Bosch, the BME280. It was similar to the BMP180, another quite popular MEMS temperature and relative humidity sensor. The BME280 does pretty much the same, only a bit more accurately, and also adds air pressure measurements. Even better, these sensors on a nifty little breakout board cost little more than the DHT22 boards we’d been using until that point.

These Bosch sensors all use either an I2C or SPI bus. This means that one can hook multiple of these sensors to a single I2C bus and communicate with them using an industry-standard protocol. This massively simplifies the sensor code, as it only has to concern itself with reading out the appropriate registers, instead of also the timing and interpretation of the received bits.

So in short, these BME280 sensors turned out to be the superior choice for the project. They are much smaller and more accurate, use a standard interface, and make it easy to chain multiple sensors to a single microcontroller and gaining air pressure readings in the process.

Devil is in the Details

With hygrometers, self-heating can lead to inaccurate results. The act of measuring the temperature simply causes the device itself to heat up. While working on the initial BMaC project, we struggled trying to determine the accuracy of our thermometers, both DHT22s and BME280s, in the absence of some absolute reference sensor.

There are plenty of forum and mailing list threads where people note that their BME280 sensor is measuring two degrees higher than it should, or their DHT22’s measurements are completely out of whack. While the latter we unfortunately found out ourselves to be the case for certain breakout boards, the former issue with the BME280 was harder to pin down as being true.

Since that time, people including the very same who did the aforementioned hygrometer shootout also did an absolute temperature test of the BME280 and DS18B20 sensors, with the conclusion that there’s no sign of self-heating apparent. Possibly one could induce some level of self-heating in the case of rapid and sustained measurements, but then one would have to wonder about what kind of environment would have a temperature that changes so quickly that one-second temperature updates are necessary.

For the BMaC project we used a measuring interval of 30 seconds, which was more than sufficient for general room temperature measurement. Even when we moved to using the BME280 sensors as inputs for the air conditioning control system, we got nice and tight feedback loops between the AC and the temperature response, as can be seen in this image:

The blue graph (MemoryLeak) is the temperature reported from the ceiling-mounted BME280 sensor in a meeting room with two AC units, whereas the other two squiggly lines (Großraum 3) were from the same type of sensor setup in the center of a line of three AC units in an open-plan office.  Finally, the sensor readings post-fixed with my name were DHT22-based setups on my desk in that same open-plan office.

The sensor setup in the open plan office was also controlling the AC unit’s fan coil unit (FCU) while measuring the temperature in the same space. The difference between the meeting room and general room readings show how different both systems are configured and measure. The original AC controller with a wall-mounted sensor and aggressive heating pattern ramped up the fan quickly, easing off when the target temperature got reached.

In comparison, my ceiling-mounted sensor and controller took a more gradual approach, preferring to slowly ramp up the fan speeds in small increments and constantly adjust using the temperature readings from the nearby BME280 sensor. Obviously, for critter comfort, it’s important that such systems are non-obtrusive and – above all – accurate.

Time to Actuate Serious Business

While playing around with temperature is fine and everything, the real fun starts when one starts manipulating the water valves and other toys that are hidden in the suspended ceilings of office buildings. Changing the fan speed of the FCUs was easy enough – using a 0-10 V DC signal into a header on the original FCU controller board – the valves controlling the flow of hot and cold water (as described in the aforementioned previous article) required a few bits of custom hardware.

The valves near the FCUs are usually the linear thermoelectric actuator type, whereby a material inside the valve is heated through resistive heating in order to cause a linear motion. This motion in turns either opens or closes the valve. The ones we came across were made by Honeywell, with the 24 VAC version installed. These look similar to these:

This was high stakes hacking. There was every potential that by using the valves in the wrong way, leaving them open for too long, or drawing too much current we could irreparably damage something, or worse: disable the AC system in the entire building. That’s the kind of scenario where you wish that you had paid more attention to a robust system for the actuators.

The system that we ended up implementing for the air conditioning valves either used the standard control signal via a relay for whole-floor-section switches, or the 24 VAC supply that was already present on the original valve control line for the FCUs, bypassing the original relay. For the latter we used an industrial Phoenix Contact SPST relay, driven by a Darlington array from an MCP23008  I2C-based GPIO expander.

The advantage of this system is that it uses off-the-shelf components that are meant to be used in an industrial setting. By ensuring that especially the mechanical (relay) parts are rated for the conditions in which they are meant to be used (mounted in a stuffy, hot space above a suspended ceiling), failure over time should be unlikely.

When One Can Afford to Learn Lessons

As the BMaC project (or ‘playing with IoT stuff’ as it was still known back then) kicked off, there was nothing crucial about anything we did. Using DHT22 sensors, only to find out that they weren’t that good was therefore totally okay. As the project escalated from merely making measurements to controlling parts of the building’s systems, it soon became clear that the stakes had risen dramatically.

In any project that uses sensors and/or actuators, the need to validate sensor and actuator accuracy and reliability over time is directly linked with the consequences if any of them were to fail. Having inaccurate room temperature measurements displayed on a Grafana dashboard is embarrassing, having a dodgy coffee machine is annoying, having a non-functioning air conditioning system can cost the company thousands of Euros in lost productivity, or worse.

This leads to the take-away message of this article; the most essential part of any serious project is to know what the cost of failure is, and how to hard to try to avoid this by picking the right system components.

Posted in bme280, co2, dht11, dht22, Hackaday Columns, hardware, home hacks, mh-z19, sensors | Leave a comment

Analysing National Budgets With File System Tools

Understanding a national budget can be difficult, with political interests and distorted talking points obscuring the truth. There’s no substitute for diving into the hard data yourself, but it can be difficult to know where to start. [D. Scott Williamson] wanted to do just that, and took an unconventional path – using file system tools to analyse the 2019 US budget.

The basic idea is simple. A file is created for every line item on the budget, and this file is filled with a $ for every million dollars that item costs. These files are sorted into folders for the relevant bureaus and agencies responsible, creating a Fiscal File System representation of the entire budget. The file system can then be analysed with standard tools to get a look at the overall make up of the budget – in this case, WinDirStat does a particularly good job.

It’s a novel way to go about budget analysis, and fills a gap in the market now that Time Plots aren’t producing their Death and Taxes infographics anymore. Pre-cooked file systems covering budgets back to 1977 are available for your perusal, should you need to investigate how things have changed over time.

Unsurprisingly, we haven’t covered the national budget before, but we’re always down to talk file systems.

Posted in file system, filesystem, misc hacks, national budget, US budget, US national budget | Leave a comment

Random Word Pairings Mark The Time On This Unusual Clock

Gosh, the fun we had when digital calculators became affordable enough that mere grade school students could bring one to class. The discovery that the numbers could be construed as the letters of various dirty words when viewed upside down was the source of endless mirth. They were simpler times.

This four-letter-word “clock” aims to recreate that whimsical time a bit, except with full control over the seven-segment displays and no need to look at it upside down. This descends from a word clock [WhiskeyTangoHotel] made previously and relies on a library of over 1000 four-letter words that can be reasonably displayed using seven-segment displays, most of them SFW but some mildly not. A PICAXE is used to select two of the four-letter words to display every second or so, making this a clock only by the loosest of definitions. Word selection is pseudorandom, seeded by noise from a floating ADC pin, but some of the word pairings in the video below seem to belie a non-random sense of humor. As is, there are over a million pairings possible; it might be fun to add in the full set of two- and three-letter words as well and see what sort of merriment ensues.

While we like the Back to the Future vibe here, we’ve seen some other really nice word clocks lately. There was the one that used PCBs as the mask for the characters, and then a rear-projection word clock that really looks great.

Posted in clock hacks, led, PICAXE, prng, seven segment, word clock | Leave a comment

Flexible PCB Contest Round Up

The 2019 Hackaday Prize, which was announced last week, is very much on everyone’s mind, so much so that we’ve already gotten a great response with a lot of really promising early entries. As much as we love that, the Prize isn’t the only show in town, and we’d be remiss to not call attention to our other ongoing contest: The Flexible PCB Contest.

The idea of the Flexible PCB Contest is simple: design something that needs a flexible PCB. That’s it. Whether it’s a wearable, a sensor, or a mechanism that needs to transmit power and control between two or more moving elements, if a flexible PCB solves a problem, we want to know about it.

We’ve teamed up with Digi-Key for this contest, and 60 winners will receive free fabrication of three copies of their flexible PCB design, manufactured through the expertise of OSH Park. And here’s the beauty part: all you need is an idea! No prototype is necessary. Just come up with an idea and let us know about it. Maybe you have a full schematic, or just a simple Fritzing project. Heck, even a block diagram will do. Whatever your idea is for a flexible PCB project, we want to see it.

To get the creative juices going, here’s a look at a few of the current entries

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The Flexible PCB Contest goes through May 29, so you’ve got plenty of time to get an idea together.

Posted in actuator, coils, contests, digikey, flex board, Flexible PCB Contest, Kapton, osh park, POV, sensor, wearable | Leave a comment

Undertale Pinball Machine Is A Work Of Art

Undertale came out in 2015 and took the world by storm. With a heartwrenching story, compelling characters and a soulful soundtrack, it won legions of fans and became an indie gaming legend. Years later,  [Gornkleschnitzer] decided to begin a pinball machine build, and it became a tribute of epic proportions.

No expense was spared on getting the artwork professionally printed, and the results speak for themselves.

Yes, we’re talking about a living, clacking, and breathing Undertale pinball build. [Gornkleschnitzer] demonstrates not only a deep knowledge of the source content, but also a mastery of pinball construction. The build began with a design in Virtual Pinball, which allowed the basic design to be dialled in. This allows things like trick shots and other features to be tested before cutting real parts. With the design roughed out, the real work starts. Full sets of cabinet and playfield decals were professionally printed, flashers installed, and subway tunnels lasercut in steel. All manner of flippers, slingshots and ball troughs were installed, tested, and tweaked in the pursuit of perfection.

The attention to detail is where this machine really shines. The artwork is stunning, and the game is complete with the original soundtrack, including the death theme. There’s even hidden gems like the Tem Shop and bonuses galore to be had.

It’s a stunning pinball machine, and one we’re dying to play for ourselves. If you’re keen to get your feet wet, why not consider starting with a cardboard build? Video after the break.

Posted in classic hacks, pinball, undertale | Leave a comment

Nanoparticles Make Mega Difference for “Unweldable” Aluminum

Though much of it is hidden from view, welding is a vital part of society. It’s the glue that holds together the framework of the cars we drive, the buildings we occupy, the appliances we use, and the heavy machinery that keeps us moving forward. Every year, the tireless search continues for stronger and lighter materials to streamline our journey into the future of transportation and space exploration.

Some of these futuristic materials have been around for decades, but the technology needed to weld them lagged behind. A group of researchers at UCLA’s Samueli School of Engineering recently found the key to unlocking the weldability of aluminium alloy 7075, which was developed in the 1940s. By adding titanium carbide nanoparticles to the mix, they were able to create a bond that proved to be stronger than the pieces themselves.

A blacksmith at work. Via BBC.

The Hot and Dirty History of Welding

In the simplest terms, welding is defined as ‘the joining of metals and plastics without the use of fasteners’. The most common type is known as fusion welding, where the parent metals are melted together with a flame or an electrode. Non-fusion welding includes soldering and brazing. In these methods, a third metal is used as a filler to help join the pieces.

Welding dates back to the Middle Ages, and the first weldors were blacksmiths. These brave, soot-covered men both cut and joined pieces of iron together using nothing but fire, hammers, and a deep well of patience. The Industrial Revolution increased the demand for welding by several orders of magnitude, because much of the machinery from that era was made by casting molten metal. This brought about an entire sub-industry built on a new cast welding process, which involved heating the broken bits, bolting a mold around them, and pouring in molten metal.

When electricity arrived in the 20th century, the carbon-arc rods used in lighting fixtures sparked the idea of arc welding. Arc welding works by creating a circuit between a power supply (the arc welder) and the metals to be welded. The ground lead is clamped to the work piece, and the positive lead runs to a spring-loaded clamp that holds a 12-14″ electrode. This rod consists of a parent-matched filler metal coated with a flux material that turns into a gas when heated. This gas shields the work piece and the filler metal from impurities in the air while the bead is formed. The downside is that it also creates a solidified slag of filth that must be chipped away.

Oxy-acetylene gas welding came soon after arc welding, and WWI advanced both of these methods. As the aircraft industry began to take off, the demand for lightweight, durable metals and the people to weld them together skyrocketed. A newer style of welding known as GTAW (gas tungsten arc welding), Heli-Arc, or TIG (tungsten inert gas) began to gain popularity. Though difficult to master, TIG welding offers finer control and gives excellent results.

AA7075 plate, available from Midwest Steel and Aluminium

Not All Alloys are Allies

Many commonly welded metals are alloys of several different metals. This is because pure metals are too soft (and valuable) for the frames of cars and buildings. The only problem is that some alloys’ constituent metals don’t melt together well. When heated, the different metals flow unevenly, and cracks develop along the welded joint. This Achilles heel renders a number of otherwise strong and reputable alloys useless for welded applications.

AA7075 is one of these alloys. This decades-old concoction of aluminium, zinc, magnesium, and copper is extremely strong yet lightweight. It’s ideal for a number of applications, especially where fuel efficiency and battery conservation are valued. The only problem is that AA7075 is highly susceptible to cracking when welded. Though it is widely used in riveted-together airplane fuselages, AA7075 generally considered to be unweldable by any means.

Successful arc weld of AA7075 using titanium carbide-infused filler rod. Via UCLA.

Killer Filler

A UCLA research team led by graduate student Maximilian Sokoluk and Professor Xiaochun Li have given the alloy a new lease on life. They’ve found a way to TIG weld two pieces of AA7075 together without any cracking whatsoever.

TIG (tungsten inert gas) welding uses a non-consumable tungsten electrode situated inside a torch. During welding, the torch releases helium or argon, which shields the weld from impurities. A separate filler wire made from a compatible alloy can be fed in to complete the joint, though it’s not required for thicker base metals.

The paper describes how adding titanium carbide nanoparticles to the mix allowed them to create a bond that proved to be stronger than the pieces themselves. The wire’s filler metal is infused with titanium carbide nanoparticles, which strengthen the mechanical properties of the metal in the melt zone. Using electron microscopes, the researchers studied cross-sections of the joints and found that the nanoparticles changed the alloy’s solidification mechanisms. In fact, they provide so much reinforcement that the metal in the melt zone actually becomes harder than the parent metals.

Results of welding with AA7075 filler, ER5356 filler, and nanotreated AA7075 filler rods. Notice the cracking in (b) and (c) but not (d). Via Nature.

The resulting joint is quite strong, with a tensile strength up to 392 megapascals. To put that in slightly more accessible terms, that means it can withstand more than three times the pressure at the bottom of the Mariana, the deepest oceanic trench in the world. Not only is this great news for AA7075, it could create new opportunities for other high-grade, previously unweldable alloys.

Posted in aluminium, arc welding, chemistry hacks, Engineering, Featured, filler rod, nanoparticles, TIG welding, welding | Leave a comment