Mysterious Files PH

The hope is always that a good business card will leave a good impression. For those in the electronics field, they also serve as an opportunity to showcase creative design skills. [Wilson Harper] demonstrates that ably with a rather nifty energy-harvesting build.

The card is based around a thin PCB in the typical business card size. It’s populated by 21 Charlieplexed LEDs, a small microcontroller, and some supporting components. Now, this is normally where you might expect the device to be powered by a small coin cell, maybe deftly integrated into the PCB thickness itself to make the card less cumbersome. But no—[Wilson] went a different route. The thing is that in 2026, most of us are carrying phones with NFC readers built in. Thus, the card was built to harvest this source of energy with a PCB trace antenna, designed with the aid of STM’s antenna inductance tools and an LLM script lobbed into KiCad. All one needs to do is to pop the card on the back of a phone and the LEDs animate joyfully.

Design files are on Github for the curious. You might also like to check out some of the fancy business cards we’ve featured in the past. Of course, if you’re working on just such a project yourself, you’re more than welcome to send it in to the tipsline!

When it comes to building real-world flying vehicles, testing can be arduous and expensive. You have to find somewhere to fly, then you have to contend with environmental conditions and the possibility of damaging your craft if things go wrong. Simulation is a great solution to this, allowing testing without so much risk. To that end, [AlexanderRex] whipped up a platform for testing UAVs from the comfort of your computer desk.

PteroSim is intended as a comprehensive test bench for simulating autonomous aerial vehicles. It can run PX4, ArduPilot, and Betaflight binaries right in the simulator. The autopilot code is given simulated sensor data, and in turn responds with actuator commands, just as it would in a real craft. The simulator runs the flight dynamics using JSBSim, and the resulting scene is rendered in Unreal Engine 5.

If you’ve ever wanted to quickly road test different autopilot settings without heading out to the field or risking hardware, this is a great way to do so. It’s hard to beat the speed of iteration that is possible when testing on the computer on your desk. We’ve featured similar work before, too.

The average hot water is a relatively simple appliance to understand. It uses gas or electricity to dump energy into water in the form of heat, keeping it at a pleasant temperature for uses like bathing and cleaning. Basic mechanisms are in place to ensure the water stays at a relatively constant temperature, neither too hot where it could cause burns, nor too cold such that it wouldn’t be fit for purpose.

One of the problems, though, is that sometimes storing water at the desired temperature can create the perfect breeding ground for bacteria. However, a neat little trick developed by NIST could solve that problem rather elegantly.

You’re Hot And You’re Cold

One of the interesting problems of our modern era is that changing our water usage has changed the risk profile for pathogens growing in hot water. NIST has noted for some time that while the pipes in our walls haven’t changed size, things like our shower heads have changed their flow rate to save water. Less flow rate in the same sized pipes means that water stays in the pipes for longer, increasing the time in which harmful pathogens have to grow in that environment.

Chief amongst these pathogens? The one most commonly feared is legionella pneumophila, the bacterium responsible for causing Legionnaires’ disease. The severe form of pneumonia comes with a fatality rate of 10%, and infection typically comes from inhaling aerosolized droplets containing the bacteria.

Of course, a great way to create aerosolized droplets filled with bacteria is to spray not-quite-hot water through a shower head. This is why hot water systems, particularly in large multi-occupancy buildings, are a risk for such infections. Legionnaires’ disease is rare, but it’s always out there, with 6000 confirmed cases showing up in the US each year. It’s possible that the true number is up to 10 times higher because the disease isn’t routinely tested for. The disease’s rarity is in part because engineers and tradespeople put in plenty of work to minimize the ability for the bacterium to breed in hot water systems. As NIST’s work demonstrates, though, there is possibly even more that could be done to tackle this problem.

Ideally, your hot water pipes in your house would not host any nasty bacteria. But often, hot water systems sit around 49 °C (120 °F), a temperature that’s hot enough to be useful and pleasant without a major scalding risk. Legionella pneumophila won’t easily grow at that temperature; the bacteria thrives between 20 °C to 45 °C (68 °F – 113 °F). Unfortunately, though, it’s not hot enough to kill the bacteria completely. Furthermore, water cools as it travels through pipes to an outlet, and thus pipes can be a perfect environment to spur further growth.

The simple solution would be to simply jack up the hot water system to store water at a much higher temperature, say around 70 °C (160 °F).  This could be undesirable in many contexts, though, as water that hot can more easily cause burns. It would be ideal to store the water at a higher temperature, while making sure it was delivered at a slightly lower temperature so it didn’t hurt anybody when it left the tap or shower head.

It turns out that there is a remarkably simple way to achieve this. NIST developed a simple heat exchanger which can be mounted atop any old hot water system. It’s designed such that the hot water leaving the tank passes through a heat exchanger where it’s surrounded by cold water which is running to the water heater’s intake pipe. This has dual benefits. The hot water inside the tank can be stored in the tank at 70 °C, which kills almost all legionella peumophila almost instantly. That water, though, is then cooled to a slightly safer temperature as it passes through the heat exchanger and out to the tap or shower. The hot water remains at a safe temperature for the user, and contains far less harmful bacteria, and cooling it doesn’t introduce any pathogens from another source. In turn, the cold water coming into the tank is pre-warmed slightly by the hot water, so the energy isn’t simply wasted.

This trick isn’t just simple, it’s also cheap. NIST engineers were able to fabricate a prototype unit to fit to a residential water heater using just $100 of components. It could be a useful addition for homeowners looking to make their hot water service a little cleaner. However, the real benefits are likely to be for larger operators of multiple-occupancy facilities, like nursing homes and hotels. These facilities often have to take great care to avoid the build up of harmful bacteria in building-wide hot water systems. Having the ability to increase the tank temperature to the point that legionella pneumophila bacteria simply die off would be a huge boon to this effort.

Sometimes, it’s possible to make great gains with a simple hack. Using the cold water service to cool hotter outgoing water is a smart trick that uses only minimal additional equipment to offer a safer hot water supply. It could yet become a common install for hot water systems in order to fight the good fight against a harmful disease that likes to lurk in our pipes. If you happen to see a heat exchanger atop a hot water heater in future, you can smile that someone has done the work to try and make that hot water supply just a little safer going forward.

In the modern world USB has become a truly universal connector, with its inclusion on almost every major piece of consumer electronics. It has even expanded well beyond things that we’d think of as consumer electronics, like the solenoids on automatic sprinkler systems.

This project comes to us from opensprinkler.org who have been working on various ways of controlling the old sprinkler standards, which generally rely on a 24 VAC power supply to drive solenoids. This tests uses the power available from USB-PD and closely examines four methods of energizing the solenoids: unipolar PWM, dual voltage, synthesizing an AC wave from a DC supply, and producing a bipolar square wave. The bipolar square wave had some interesting results, being able to get pretty close to the behavior of a true sine wave while minimizing the demand on power electronics.

For those working on old sprinkler systems, or many other antiquated systems that still rely on 24 VAC, this project shows that USB can deliver a surprising amount of power in unique ways, and the fact that it’s near-ubiquitous and affordable makes it that much easier to adapt into situations it was never really designed for.

These old sprinkler systems have other ways of working on modern systems as well, like this one which replaces the AC source for a DC one, but with a few caveats.

If you’re intending to transmit on the VHF band, you’re probably going to reach for a handheld or some kind of rackmount rig in your ham shack. But you needn’t bother with all that complexity, when you can use the computer on your desk to spit out such signals using a simple browser tool from [Efe].

The concept is straightforward—[Efe]’s tool manipulates pixel clocks in order to create spurious transmissions from your computer’s graphics hardware. The math pencils out pretty easily—multiply the horizontal resolution by the vertical resolution by the refresh rate, while paying attention to the precise timing of the video standard your monitor is using, and you’ve got your transmission frequency. For example, for a screen displaying 1080p at 60 Hz, with the CEA-861 timing standard, your horizontal and vertical resolutions are 2200 and 1125 respectively when paying attention to the requisite blanking intervals. Multiply those by 60 hz, and you’ll find you’re creating a signal at 148.500 MHz. Leverage this by displaying the right pattern of black and white pixels to maximise changes in voltage state on the HDMI or DisplayPort lines, and you might create a strong enough signal that you can actually pick something up. [Efe] created a tool to display these patterns to send simple Morse code messages over VHF just by flickering your screen just right.

You can test the transmitter tool for yourself here, right in your browser. You’ll want to hold your radio’s antenna nice and close to the monitor to see if you can pick up much of a signal. After all, the monitor, connectors, and cable are all built to optimize for clear signal transmission to the display, while preventing signal from leaking out to interfere with surrounding equipment.

Of course, a fair warning—you’re not supposed to intentionally transmit on bands you’re not licensed for, even if it’s incredibly weak and unlikely for anyone else to notice in a scenario like this. Still, it’s an interesting project that shows you just how electromagnetic interference can leak out of just about anything under the right conditions.

The big news today is, of course, the successful launch and deployment of NASA’s Nancy Grace Roman Space Telescope earlier this morning. The space agency’s latest observatory lifted off at 7:26 AM Eastern from Launch Complex 39A at Kennedy Space Center aboard a SpaceX Falcon Heavy, and by 8:00 AM it was separated from the rocket’s upper stage and flying on its own.

While the sound and fury of launch is exciting, it’s just the beginning of the journey for Roman. It will take several months for the spacecraft to complete its roughly 1.5 million-kilometer trek out to Earth’s second Lagrange point (L2), where it will set up shop near — in cosmic terms, anyway — the James Webb Space Telescope (JWST). Along the way, it will switch on and test various systems and components, with its primary 300 megapixel infrared camera scheduled to power up in three weeks or so.

There’s a lot to cover about the Roman Space Telescope. Built from spy satellite spare parts donated by the National Reconnaissance Office and featuring a field of view 100 times greater than that of Hubble, its launch is widely considered to be one of the most important scientific milestones of the decade. We’ll be bringing you more about the past, present, and future of this flagship mission as it progresses.

From real space missions to virtual ones, this week the developers of EVE Online announced that 2.4 million lines of code that keep the massively multiplayer online role-playing game running would finally be making the switch to Python 3. Given the immense complexity of the codebase, it’s been stuck at Python 2.7 since their last overhaul back in 2010, a situation which has become increasingly difficult to manage as time goes on.

The announcement goes into a surprising amount of depth about the state of Python in EVE. We imagine most players couldn’t care less, but naturally the developers have strong feelings about the situation and perhaps thought it would benefit others in a similar situation to get their thoughts out there.

While there’s certainly an argument to be made that the only justification they really need for making the migration is that 2.7 hit end-of-life back in 2020, the developers explain that the more immediate problem for them was that various tools and libraries they wanted to use were no longer compatible with the Python 2.x series. They also point out hopes that speed improvements made in the latest version of Python will eventually translate into better game performance down the road.

In more terrestrial news, this week the necessary regulatory amendments were passed to make plug-in solar systems legal in the United Kingdom. Assuming the wiring meets the necessary requirements, consumers can pick up the hardware and install it themselves without involving an electrician, although they may still need to contend with landlords and local ordinances that may limit their ability to physically mount the panels. The rules as they stand now allow each residence to have four panels with a total combined output rating of no more than 2,000 watts, although critically, the system is only allowed to generate a maximum of 800 watts at the inverter. As the government and consumers get more comfortable with plug-in solar systems, these numbers will likely increase over time.

Solar isn’t the only area where DIY approaches are moving into the mainstream. This week, Citrix pitched a “different approach to endpoint resiliency”: an isolated Linux-based operating system called UniconOS that users can boot into should the computer’s primary Windows installation become compromised or otherwise inoperable. The idea is that an independent, read-only backup OS kept on its own partition will reduce downtime, since the computer can still be used while IT figures out what the hell happened.

This solution will sound suspiciously familiar to anyone who’s booted a live Linux system from CD/DVD/USB in the last few decades. Try not to keep yourself up all night wondering why you never pitched the idea to some hungry venture capitalists in exchange for a yacht in the Bahamas.

Finally, on the theme of new technology embracing the old ways, we bring you Defrag98, a web reincarnation of Microsoft’s dial-up era Disk Defragmenter tool. While it won’t actually improve the performance of your modern solid-state drive, you may find your own mood boosted by the wave of nostalgia when you see — and hear — the classic tool go to work.

That’s right, not only do the blocks dutifully flip from red to blue just like you remember, but all the while you’ll be treated to the unmistakable whirs and clicks of a spinning hard drive circa the turn of the millennium. Never forget what they took from us.

See something interesting that you think would be a good fit for our weekly Links column? Drop us a line; we’d love to hear about it.

The world’s refusal to standardize on a single type of mains power outlet has led to a vibrant market of so-called travel adapters, all of which try to outdo each other in convenience and universality. This comes at the cost of complexity, something which ultimately reflects in the price. The cheapo $9.26 universal travel adapter that [Brainiac 75] got off an online retailer’s site is thereby a good example of how safety suffers if the overarching goal is to ‘make it cheap’.

The first exciting discovery is that when you plug any of its three sets of connectors into an outlet, the others become live at the same voltage. This would suggest that they’re just wired together, a fact soon confirmed with a quick resistance check between the respective prongs. Though to the adapter’s credit, the prongs are not live when fully retracted into the enclosure. Yet as demonstrated in the video, the retracting of prongs is not enforced, so mistakes here are possible.

The adapter also has two USB ports that claim to provide 5 V at 2.1 A, with as it turns out no hard cut-off. This is probably the best part of the adapter despite not featuring any advanced charging features. After opening the adapter, you can see that the sliding mains prongs connect to a central bus bar when either unfolded or extended, which is definitely straightforward, but doesn’t enforce that only one type of prongs can be used at any given time.

To make it safer, [Brainiac75] removed the less useful US and UK plugs, taping over the empty holes. It’s now just a USB charger with a universal mains port to plug random non-EU plugs into, which is probably relatively safe and a better idea than really using it as a travel adapter.