Sometimes it seems as though everything old is new again. The earliest computers used magnetic memory such as magnetic core. As practical as that was compared to making for example each bit of memory be a vacuum tube or relay flip flop, newer technology such as SRAM and DRAM displaced core and similar technologies. However, some of the newest technologies once again use magnetic fields. FRAM or ferroelectric RAM and magnetoresistive or MRAM both use magnetic fields to store data. Now Japanese researchers think they are on track to make MRAM more competitive with traditional RAM chips.

The Tokyo Institute of Technology researchers use new material combinations to make chips that store data based on the spin of electrons — the underlying reason for the way magnets behave. Their recent paper discusses USMR or Unidirectional spin Hall magnetoresistance and using this effect could greatly simplify the construction of MRAM cells.

How much simpler? Conventional MRAM requires up to 30 fabrication layers. The new technology requires only two.

There are two different exotic materials and the magic happens at their interface, at which electrons with the same spin accumulate. By injecting them into the ferromagnetic layer, that layer flips its magnetic field. This works as a write operation and also changes the resistance of the structure due to USMR. An external circuit can measure this resistance change, but it is very small, especially in conventional MRAM cells — less than a 1% change.

The new materials break the 1% barrier. This makes them much simpler to read and combined with the easier fabrication should result in cheaper and denser MRAM devices.

There have been many memory technologies used over the years to store data. Among them were the really odd devices like the Radechon.

source https://hackaday.com/2020/01/07/spintronic-ram-gets-a-little-closer-to-sram/

Some folks bring out an heirloom table runner when they have company, but what if you sewed your own and made it musical? We’d never put it away! [kAi CHENG] has an Instructable about how to recreate his melodic material, and there is a link to his website, which describes his design process, not just the finished product. We have a video below showing a jam session where he exercises a basic function set.

GarageBand is his DAW of choice, which receives translated MIDI from a Lilypad. If you don’t have a Lilypad, any Arduino based on the ATmega328P chip should work seamlessly. Testing shows that conductive threads in the soft circuit results in an occasional short circuit, but copper tape makes a good conductor  at the intersections. Wide metallic strips make for tolerant landing pads beneath modular potentiometers fitted with inviting foam knobs. Each twist controls a loop in GarageBand, and there is a pressure-sensitive pad to change the soundset. Of course, since this is all over MIDI, you can customize to your heart’s content.

MIDI drums come in all shapes and sizes, from a familiar game controller to hand rakes.

source https://hackaday.com/2020/01/07/fabricated-drum-machine/

Problem: your electronic load works fine, except for the occasional MOSFET bursting into flames. Solution: do what [tbladykas] did, and build a water-cooled electronic load.

One can quibble that perhaps there are other ways to go about preventing your MOSFETs from burning, including changes to the electrical design. But he decided to take a page from [Kerry Wong]’s design book and go big. [Kerry]’s electronic load was air-cooled and capable of sinking 100 amps; [tbladykas] only needed 60 or 70 amps or so. Since he had an all-in-one liquid CPU cooler on hand, it was only natural to use that for cooling.

The IXYS linear MOSFET dangles off the end of the controller PCB, where the TO-247 device is soldered directly to the copper cold plate of the AiO cooler. This might seem sketchy as the solder could melt if things got out of hand, but then again drilling and tapping the cold plate could lead to leakage of the thermal coupling fluid. It hasn’t had any rigorous testing yet – his guesstimate is 300 Watts dissipation at this point – but as his primary endpoint was to stop the MOSFET fires, the exact details aren’t that important.

We’ve seen a fair number of liquid-cooled Raspberry Pis and Arduinos before, but we can’t find an example of a liquid-cooled electronic load. Perhaps [tbladykas] is onto something with this design.

source https://hackaday.com/2020/01/07/liquid-cooling-keeps-this-electronic-loads-mosfets-from-burning/

Guitar Hero was a big deal, right up until it wasn’t. The best efforts of the video game industry couldn’t resurrect the once-off rush of enthusiasm for rhythm gaming, and thrift stores around the globe are now littered with little plastic instruments. [Analog Sketchbook] decided to give one of these guitars for the Wii a new life, repurposing it as a synth controller.

The build is a straightforward one, thanks to the prevalence of modern maker solutions to electronic problems. Hooking up to the guitar is a solved problem, with an Adafruit Nunchucky breakout board allowing the Guitar Hero controller to be connected via jumper wires to the Raspberry Pi’s IO pins.

Communication is via I2C, and is easy to work with in Pure Data, running on the Pi. [Analog Sketchbook] created a patch that runs a synthesizer, controlled by the buttons and controls on the guitar itself. With this setup, you could create any number of different routines to allow the guitar to be played differently. We’d love to see a chiptune-esque arpeggio patch, or something that plays fat FM synth tones a la the Genesis, but that’s just our opinion. The sky really is the limit here, with plenty of grunt on the Pi for various forms of synthesis.

It’s a fun build that gives new life to an otherwise forgotten gaming accessory. We’ve seen them repurposed before too, as far back as 2010. Video after the break.

source https://hackaday.com/2020/01/07/guitar-hero-controller-gets-a-new-musical-life/

Many a hacker has looked at their scooter, bike, or skateboard, and decided that it would be even better if only it had a motor on it. Setting out to electrify one’s personal transport can be an exciting and productive journey, and one that promises to teach many lessons about mechanical and electronic engineering. Fundamentally, the key to any build is the battery, which has the utmost say in terms of your vehicle’s performance and range. To help out, we’ve prepared a useful guide on selecting the right battery for your needs.

One Chemistry To Rule Them All

Batteries come in all shapes and sizes, and a variety of different chemistries that all have their own unique properties and applications. When it comes to small electric vehicles, it’s desirable to have a battery with a low weight, compact size, plenty of current delivery for quick acceleration, and high capacity for long range.

30 years ago, options were limited to lead acid, nickel cadmium, and nickel metal hydride batteries. These were heavy, with low current output, poor capacity, and incredibly slow charge times. Thankfully, lithium polymer batteries have come along in the meantime and are more capable across the board. Offering huge discharge rates, fast charging, light weight and high capacity, they’re undeniably the ultimate choice for a high performance electric vehicle. They’re also wildly popular, and thus cheap, too!

There are some hangups, however. It’s important to keep all the cells in a pack at the same voltage in order to avoid cells back-charging each other. This can cause damage to the pack, or even explosions or fire. Maintaining the battery voltages to avoid this is called “balancing”. It can be handled in various ways, depending on the exact style of battery you’re using, as we’ll cover later.

Additionally, lithium batteries do not like being over-discharged. As a rule of thumb, it’s a good idea not to let your batteries drop below 3.0 V per cell. Failure to keep this in check can lead to ruining a pack, hurting its maximum capacity and ability to deliver current.

There are thankfully ways around these issues, and which ones you use depends on the battery you choose for your application.

But Which Battery, Exactly?

It’s one thing to say you should use a lithium polymer battery, but they come in a wide variety of flavors for different applications. Which type you use will depend on the vehicle you’re trying to build, your goals for performance and range, and your own abilities and desire to build or buy.

A Word About Voltage and Capacity

Lithium polymer cells are rated nominally at 3.6 V, and their capacity is measured in amp-hours or milliamp-hours. When looking at a pack for your electric vehicle, you’ll want to note the total pack voltage and the capacity. Higher voltages are good for higher performance vehicles and improved efficiency, as more power can be delivered at lower currents with less losses. However, this requires stacking more cells in series, which can add cost, and also requires more expensive controllers and charging solutions. Higher capacities are good for longer range, and are often achieved by stacking more cells in parallel.

Homebrew 18650 Packs

Many home-built electric vehicles are created by hackers with a strong DIY ethos, and that often extends to the individual components, too. In these circles, many elect to create their own battery solution, relying on the popular 18650 cell as the basis for the pack. These can be readily harvested from laptops, power drills and other sources, or picked up from recycling centers, as well as bought new. The cells have a strong metal case and are mechanically quite robust. However, the individual cells are limited to a maximum of around 3600 mAh, despite what you may read on eBay.

Due to the limited capacity of the individual cells, many packs for e-bikes and electric vehicles stack several cells in parallel. 18650-based packs are often referred to with designations like 10S4P, indicating there are 4 parallel sets of 10 cells each in the battery. Such a battery would have a nominal voltage of 36 V, with a capacity of between 10-14 Ah depending on the particular 18650 cells used.

To assemble a pack, soldering is a poor option due to the danger of heating the cells, and the results are typically weak from a mechanical standpoint. The most reliable way is through the use of a spot welder to connect the cells with metal strips from terminal to terminal. Some elect to build their own spotwelders, but if you’re just trying to get your vehicle rolling, this would be considered as unnecessary yak shaving. They can be bought instead. Either way, once the cells are connected, individual leads can be added to the various cells for connection to a battery management system, or BMS – a board that monitors the individual voltages of the cells in the pack. This board accepts a connection from a wall charger that sits at the battery’s maximum voltage, and handles charging and balancing to keep the battery in good health, and also protects against over-discharge and over-current events. All this can then be wrapped up in the enclosure of your choice. Thanks to the metal case of the individual cells, often a simple plastic wrap can suffice.

Homebuilt 18650 packs are useful if you want to customise a pack to your own exacting specifications, or if you wish to build on the cheap with recycled parts. However, there’s plenty of work involved, and you may find that the money you spend on tools to get the job done outweighs the savings along the way.

Pros: can be cheap, customizable voltage, capacity and packaging
Cons: significant work involved, can be heavier than other options

eBay E-bike Packs

For those uninterested in building their own packs, there is another option. With the proliferation of e-bikes around the world, parts are now readily available to those wishing to strike out on their own. A wide variety of battery packs for e-bikes are now available, most of which are built with the exact same tools and techniques as the homebrew packs mentioned above. The major benefit of these ones, however, is that someone else has done all the hard work!

Consisting of 18650 cells laced together in various configurations to suit different applications, they’re available in a range of voltages from 36 V-60 V and occasionally higher, with large capacities for long range. The vast majority come with an integrated battery management system and a charge connector already hooked up, and many sellers will throw in a suitable wall charger, too.

They’re a great choice if you want a high-capacity pack that’s ready to go, off the shelf, without a lot of fuss. One drawback, however, is that many of these packs are somewhat hobbled from the factory in terms of current output. While the average 18650 is capable of delivering significant current without breaking a sweat, it’s not uncommon to find a 36 V battery limited to a relatively low output of 15 A by the integrated BMS. This is fine if you’re building a 200 watt e-bike to cruise by the beach, but if you’re trying to build a quick scooter to tear along gravel paths with a 500 watt motor, you’re going to run into problems with the BMS cutting the power. This can often be hacked around, but it takes the shine off the convenience of these ready-to-go packs.

Pros: Ready to go, complete solution, fairly robust
Cons: Can have issues with current limits, limited packaging options

RC Flight Packs

Lithium polymer batteries have been a boon for the model flight hobby, with their high power density and ability to deliver huge gobs of current at a moment’s notice. These typically use pouch cells, wherein the electrolyte is contained in a plastic pouch without a hard outer shell. These have great packing efficiency and are much lighter than metal cased cells, but are also much more delicate. The cells tend to swell a little over time, and are easy to damage if squeezed or pierced. This can lead to fires or explosion, and thus such cells must be installed in such a way to protect them against accidental damage.

Designed for the demands of high-powered RC aircraft, these cells are capable of current delivery at an immense rate, with 20 times the total battery capacity, or 20C, being common. High-end packs are readily available that can top 75C, which for a 2 Ah pack, is 150 A. This makes these RC packs useful for high-performance applications, where large motors are drawing several kilowatts of power under load. The tradeoff is in storage, with RC packs generally being fairly large for a given capacity, due to the size of the electrodes needed to sustain such high current draws. These packs usually only come as packs of up to 6 cells in series; often you’ll need two or more ganged up to reach a more suitable voltage for your electric vehicle where 10 S to 12 S is usually more desirable.

The high performance packs also come at a high cost, particularly compared to 18650 cells which have the benefits of economies of scale behind them. They also come without any protection or battery management systems. When used in an electric vehicle, they can either be removed after use and hooked up to a standard RC charger, or wired up to a BMS for a more contained solution for charging. Either way, it’s important to pay attention to balancing and maintenance, as these high current packs are more prone to fire and explosions than others.

Pros: Huge current delivery, light weight
Cons: Price, must be handled delicately, needs a charging solution fitted

Power Tool Packs

Lithium polymer cells have also revolutionized the power tool industry, and made cordless tools far more practical than ever before. Most tools on the market use 18 V, or five-cell packs, with different manufacturers using 18650 cells or pouch cells depending on their tastes. They usually come in a hard plastic case with a proprietary connector to hook up to a certain brand of tools. Inside, there’s usually a basic BMS to handle cell balance and to shut things down if anything goes wrong.

Power tool packs have the benefit of being highly rugged, as they’re designed to withstand the construction environment. Tools can be quite power hungry, so current delivery is usually pretty solid, too. A drawback is that these packs can be quite expensive, because manufacturers want to lock consumers into their own tool ecosystem. Interfacing with them can be a pain too, due to the proprietary connectors. Common workarounds involve nails and tape, 3D printing, or simply gutting old tools. Charging is simply handled by plugging into the standard charger, with the batteries having the benefit of being easily hot-swappable by design. As they’re often already lying around, they can be a great way to test out an electric vehicle build before investing in a more suitable permanent battery solution.

Pros: Easily hot-swappable, you’ve already got some, rugged
Cons: Expensive, not particularly space efficient, proprietary connectors

Summary

We’re blessed to have more battery options now than ever before, and as capacities and power outputs continue to rise, we continue to see new and more innovative electric vehicles than ever before. By weighing the relevant factors, and choosing carefully, you can pick the optimum solution for the special vehicle in your life. Hopefully, you’ll find this guide useful to point you in the right direction with your own builds, and when you’re done, be sure to drop us a line!

source https://hackaday.com/2020/01/07/choosing-the-right-battery-for-your-electric-vehicle-build/

It’s fair to say that the hearts and minds of Hackaday readers lie closer to the technology centres of Shenzhen or Silicon Valley than they do to the soybean fields of Minnesota. The common link is the desire to actually own the hardware we buy. Among those working the soil there has been a surge in demand (and consequently a huge price rise) in 40-year-old tractors.

Second-hand farm machinery prices have made their way to the pages of Hackaday due to an ongoing battle between farmers and agricultural machinery manufacturers over who has the right to repair and maintain their tractors. The industry giant John Deere in particular uses the DMCA and end-user licensing agreements to keep all maintenance in the hands of their very expensive agents. It’s a battle we’ve reported on before, and continues to play out across the farmland of America, this time on the secondary market. Older models continue to deliver the freedom for owners to make repairs themselves, and the relative simplicity of the machines tends to make those repairs less costly overall.

Tractors built in the 1970s and 80s continue to be reliable and have the added perk of predating the digital shackles of the modern era. Aged-but-maintainable machinery is now the sweetheart of farm sales. It confirms a trend I’ve heard of anecdotally for a few years now, that relatively new tractors can be worth less than their older DMCA-free stablemates, and it’s something that I hope will also be noticed in the boardrooms. Perhaps this consumer rebellion can succeed against the DMCA where decades of activism and lobbying have evidently failed.

They just don’t build ’em like they used to.

[Image Source: John Deere 2850 by Raf24 CC-BY-SA 3.0]

[Via Hacker News]

source https://hackaday.com/2020/01/07/dmca-locked-tractors-make-decades-old-machines-the-new-hotness/

When was the first nuclear reactor created? You probably think it was Enrico Fermi’s CP-1 pile built under the bleachers at the University of Chicago in 1942. However, you’d be off by — oh — about 2 billion years.

The first reactors formed naturally about 2 billion years ago in what is now Gabon in West Africa. This required several things coming together: natural uranium deposits, just the right geology in the area, and a certain time in the life of the uranium. This happened 17 different times, and the average output of these natural reactors is estimated at about 100 kilowatts — a far cry from a modern human-created reactor that can reach hundreds or thousands of megawatts.

The reactors operated for about a million years before they spent their fuel. Nuclear waste? Yep, but it is safely contained underground and has been for 2 billion years.

The Basics of Fission Reactors

Any fission reactor basically works the same. An unstable atom like uranium or plutonium breaks apart, creating fast neutrons. There’s a chance some of those neutrons will strike nearby unstable atoms, causing them to break apart too. However, because these neutrons are fast, statistically this won’t happen very often. However, if a moderating substance like water or graphite slows down the neutrons, they have more time to interact with other unstable atoms, so more atoms break down.

If you balance it right, the atoms breaking apart will cause a chain reaction that sustains itself. That is, neutrons hit atoms, releasing more neutrons, which hit more atoms. The heat released is substantial and we usually use it to make steam to drive an electric generator.

Nuclear Fuel Used to Be Much Better

The original CP-1 reactor used natural uranium and so it took a lot of fuel since ordinary uranium is relatively stable. If that uranium is refined into higher concentrations of specific isotopes, a more powerful reaction is possible with less fuel.

There are three isotopes of uranium: U-238, U-235, and U-234. Uranium decays naturally, and highly active isotopes are now in short supply. Apparently, whatever process created the uranium on Earth, it all appeared at the same time (and has been decaying ever since) because no matter where you mine uranium today it is about 99.275% U-238.

U-235 is better for reactors but, today accounts for only 0.72% of what comes out of the ground. We enrich uranium artificially to have about 3% U-235 for use as fuel. Scientists think that when the Earth formed, U-235 was 30% of the crust’s uranium. That number keeps falling, of course, and 2 billion years ago, the proportion would be about 3.6% — just right for nuclear fuel.

When Mined Uranium Came up “Light”

In 1972 a French team mining uranium in Gabon noticed something strange. The ore didn’t have the expected 0.72% of U-235 but instead had 0.717%. That sounds like a tiny bit — and it is — but U-235 content is remarkably consistent all over the world (and on the moon, too). Further investigation confirmed that the missing U-235 was fissioned away in a natural nuclear reactor. In particular, all five fission products you’d expect were located. The amount of Xenon gas trapped in the reactor made it possible to calculate the operating cycle of the reactors.

Eventually, they would find 17 of these natural reactors. You might wonder why there are not even older natural reactors. After all, if 3.6% is a good fuel, wouldn’t 5% or 10% be even better?

The conditions had to be just right. A little over 2 billion years ago, there wasn’t much oxygen in the Earth’s atmosphere and this made it difficult for uranium to concentrate. So to get a natural reactor you need a concentration of uranium that has a high percentage of U-235. There also needs to be a suitable geometry of the material, a moderator like water, and no neutron-absorbing material in the area.

You can see in the figure that the uranium ore (3) is surrounded by porous sandstone (2) all on a layer of granite (4). The black zones (1) represent some of the natural fission zones.

Enough water would seep down through the sandstone and cause a reaction that would boil off the water within a half-hour. The reaction would then stop until sufficient water seeped in again creating a 3 hour total cycle time. This allowed the reactors to be very stable and appears to have allowed the reactors to run for about one million years.

There could be more reactors yet to be found or that operated and then did not survive the intervening 2 billion years for us to find. Conditions in Gabon were also just right to preserve the reactors.

Modern Times

If you are worried this could happen today, don’t fret. The U-235 content today is insufficient for this to happen again naturally. However, scientists have studied how waste products have been contained as it might lead to better ways for us to store nuclear waste we are creating.

As an interesting side note, there is a controversial theory that the moon was blown out of the Earth about 4.5 billion years ago by another natural reactor near the edge of the Earth’s mantle. While this hasn’t been disproven, as far as we can tell, most scientists seem to accept that the moon formed due to an impact on the early Earth.

source https://hackaday.com/2020/01/07/the-oldest-nuclear-reactor-natures-2-billion-year-old-experiment/

We tend to think that the lowest point of entry for machine learning  (ML) is on a Raspberry Pi, which it definitely is not. [EloquentArduino] has been pushing the limits to the low end of the scale, and managed to get a basic classification model running on the ATtiny85.

Using his experience of running ML models on an old Arduino Nano, he had created a generator that can export C code from a scikit-learn. He tried using this generator to compile a support-vector colour classifier for the ATtiny85, but ran into a problem with the Arduino ATtiny85 compiler not supporting a variadic function used by the generator. Fortunately he had already experimented with an alternative approach that uses a non-variadic function, so he was able to dust that off and get it working. The classifier accepts inputs from an RGB sensor to identify a set of objects by colour. The model ended up easily fitting into the capabilities of the diminutive ATtiny85, using only 41% of the available flash and 4% of the available ram.

It’s important to note what [EloquentArduino] isn’t doing here: running an artificial neural network. They’re just too inefficient in terms of memory and computation time to fit on an ATtiny. But neural nets aren’t the only game in town, and if your task is classifying something based on a few inputs, like reading a gesture from accelerometer data, or naming a color from a color sensor, the approach here will serve you well. We wonder if this wouldn’t be a good solution to the pesky problem of identifying bats by their calls.

We really like how approachable machine learning has become and if you’re keen to give ML a go, have a look at the rest of the EloquentArduino blog, it’s a small goldmine.

We’re getting more and more machine learning related hacks, like basic ML on an Arduino Uno, and Lego sortings using ML on a Raspberry Pi.

source https://hackaday.com/2020/01/07/tiny-machine-learning-on-the-attiny85/

Many of us have experimented with the ESP32 microcontroller, attracted by its combination of WiFi and a powerful processor core, but how many of us will have explored all of its many on-board features? One of the more interesting capabilities of this chip comes in the form of its ultra-low-power (ULP) co-processor, an extra core that allows an ESP32 to function while sipping tiny quantities of power with the ever-hungry main cores turned off.

It’s a feature that [Max.K] has used to great effect in his low power ESP32 handheld computer, where he’s paired the chip with a low-power Sharp Memory LCD and used the ESP32’s ULP core to keep the display alive while the ESP cores are sleeping. Software wise the device sports basic PDA and clock functionality including an RSS parser, all of which can be seen in the video below the break. Its inspiration came from Panic’s crank-equipped Playdate console, with which it shares the Sharp display.

Seeing this device reminds us of some of the badges featuring ESP32 power that we’ve seen over the last few years. An event badge creator has a constant battle to give the device enough battery life to last the distance. It’s a problem the designers of the SHA 2017 badge solved with an e-ink unit, but perhaps the Sharp display could offer a cost-effective alternative for new designs.

source https://hackaday.com/2020/01/07/how-low-can-an-esp32-go/

What’s worse than unleashing a monster on the internet? Allowing the internet to control the monster! But that’s just what [8BitsAndAByte] did, created a monster that anyone on the internet can control. Luckily for us, this monster only talks.

This is a very simple project and most of the parts are off the shelf. Hardware wise the monster’s body is made out of a plastic flowerpot; its mouth is a bit of wood that covers the top of the flowerpot; its eyes, two halves of a plastic sphere painted white with some felt for irises. And then whole thing is covered in some blue fake fur.

Electronics wise, a Raspberry Pi is running the show and handling the text-to-speech is an AIY Voice Hat. A servo fits inside the flowerpot to open and close the monster’s mouth. On the software end of things, a bit of Python has been written that waits for a bit of text, sends it off to the Voice Hat’s text-to-speech module and moves the servo to open and close the mouth. The scary part, connecting the monster to the internet, is done with remo.tv, which is some open-source code hosted on GitHub specifically for allowing control of robots over the internet.

This is a neat little project which is simple enough that kids could build one themselves. The instructions and the python script are up on the Instructables page, and you can see the monster in action at its page on remo.tv. Perhaps [8BitsAndAByte] could add a couple of these internet controlled robot arms to the monster to create a monster that could create some real havoc!

source https://hackaday.com/2020/01/06/the-internet-controls-this-monster/

There’s an old saying that we have one mouth and two ears so you can listen twice as much as you talk. However, talking and listening at the same time is fairly difficult and doing it with radio signals is especially hard. A company called Kumu Networks has an analog module that can use self-interference cancellation which allows transmitting and receiving on the same frequency with around 50 dB of the transmitted signal in the transceiver. You can see a video about Kumu’s claims its technology below.

You may think that cell phones and ham radio repeaters transmit and receive at the same time, which of course they do, but usually on different frequencies to avoid direct interference. A diplexer is a device that sorts out the two frequencies while a duplexer sorts them out by the direction of the signal, but they are tricky to use. A duplexer can operate on a single frequency in applications such as radar, and even then it is still very difficult to prevent leakage from the transmitter from overloading and desensitizing the receiver.

While 50 dB might not sound like much, it is a factor of 100,000 which should open up new opportunities for radio transmitters and receivers to coexist even on the same frequency. The device is analog, so it uses circuitry to invert the transmitted signal and reincorporate it at the receiver.

IEEE Spectrum recently had a post claiming the company is releasing the K6 module that can be “easily installed in most any wireless system.” RF can seem like black magic, but we can envision how this should work in theory. You’d need to adjust the phase of the inversion network to match the phase delay between where you pick up the signal (presumably before power amplification) and where you mix the canceling signal with the receiver.

Sounds good, but then again, noise-canceling headphones sound straightforward too and we all know that even an expensive pair can leave something to be desired.

source https://hackaday.com/2020/01/06/full-duplex-radio-claimed-easier-with-analog-module/

Thermoelectric devices are curious things, capable of generating electricity via the Seebeck effect from a temperature differential across themselves. The Seebeck effect does not produce a huge potential difference, but when employed properly, it can have some useful applications. [MJKZZ] decided to apply the technology to build a reading light, powered by a hot cup of coffee.

The build is based around four Peltier modules, 40mm x 40mm in size, sandwiched between a pair of copper sheets. The modules are wired in series to create a greater output voltage, and an aluminium heatsink is fitted to one side to create a higher temperature differential. The set-up produces just 230 mV from human body temperature, but over 8 volts when warmed directly with a heat gun. Boiling water in a mug produces a more restrained 2.1V output.

On its own, this voltage is a little weak to do anything useful. Thus, the electricity from the Peltier modules is fed through a joule thief, which helps step up the voltage to a more useful range to run an LED. With a mug of coffee on the copper plate, the assembly isn’t quite able to light the LED enough to allow the user to read comfortably. However, it flickers into life just a touch, demonstrating the basic concepts in action.

While it’s not the most practical build, and it’s likely to cool your coffee faster than you’d like, it’s a fun project that serves to educate about the mechanics of the Seebeck effect and using Peltier devices to generate it. Another fun application is to use them in a cloud chamber. Video after the break.

source https://hackaday.com/2020/01/06/reading-light-not-quite-powered-by-your-favorite-hot-beverage/

Like a number of hackers before him, [MarcelMG] was impressed with Weller’s RT soldering iron tips, but considerably less enthused about the high purchase price on the station they’re designed to go into. Inspired by similar projects, he decided to try his hand at building his own soldering station which reaps the benefits of these active tips without the sticker shock.

The station’s user interface was kept intentionally simple, with little more than a four digit LED display to show the temperature and a rotary encoder to set it. The display alternates between the current temperature and the set temperature every few seconds while the knob is being turned, and if you push it in, the set temperature will be saved as the default for next time.

[MarcelMG] also included a feature that drops the iron’s temperature when it’s sitting in the holder, reducing tip wear and energy consumption. He originally planned on using a Hall effect sensor to detect when the iron was holstered without needing to physically interface with it, but in the end he realized the easiest approach was to simply connect one of the input pins on the microcontroller to the metal holder. Since the tip is grounded, he could easily detect if it was in place with a couple lines of code.

Speaking of which, the station is powered by an ATtiny24A with firmware written in C using the Atmel Studio IDE. [MarcelMG] mentions that the limited storage on the 24A was a bit of a challenge to work around, and suggests that anyone looking to follow in his footsteps uses something with a bit more flash under the hood. The LED display is a very common TM1637 type, the rotary encoder was salvaged from a radio, and the power supply was from an old laptop. All told, this looks like a very economical build.

Depending on your needs, a DIY soldering station can either have features to rival the commercial models or be exceedingly simplistic. In either case, the advent of low-voltage irons and active tips have made self-built soldering stations much more approachable. Attempts without the use of these modern niceties tended to be somewhat less glamorous.

source https://hackaday.com/2020/01/06/a-homebrew-weller-rt-soldering-station/