Presence Sensor Locks Computer When You Step Away

Having a computer that locks its screen after a few minutes of inactivity is always a good idea from a security standpoint, especially in offices where there is a lot of foot traffic. Even the five- or ten-minute activity timers that are set on most workstations aren’t really perfect solutions. While ideally in these situations we’d all be locking our screens manually when we get up, that doesn’t always happen. The only way to guarantee that this problem is solved is to use something like this automatic workstation locker.

The project is based around the LD2410 presence sensor — a small 24 GHz radar module featuring onboard signal processing which simplifies the detection of objects and motion. [Enzo] paired one of these modules with a Seeed Studio XIAO nRF52840 development board to listen to the radar module and send the screen lock keyboard shortcut to the computer when it detects that the user has walked away from the machine. The only thing that [Enzo] wants to add is a blinking LED to let the user know when the device is about to timeout so that it doesn’t accidentally lock the machine when not needed.

One of the parts of this build that is a little bit glossed over is the fact that plenty of microcontroller platforms can send keystrokes to a computer even if they’re not themselves a USB keyboard. Even the Arduino Uno can do this, so by now this feature is fairly platform-agnostic. Still, you can use this to your advantage if you have the opposite problem from [Enzo] and need your computer to stay logged in no matter what.

Ask Hackaday: Incidental Earthquake Detection

It never seems to fail: at the very moment that human society seems to reach a new pinnacle of pettiness, selfishness, violence, and self-absorption, Mother Nature comes along and reminds us all who’s really in charge. The obvious case in point here is the massive earthquakes near the border of Turkey and Syria, the appalling loss of life from which is only now becoming evident, and will certainly climb as survivors trapped since the Monday quakes start to succumb to cold and starvation.

Whatever power over nature we think we can wield pales by comparison with the energy released in this quake alone, which was something like 32 petajoules. How much destruction such a release causes depends on many factors, including the type of quake and its depth, plus the soil conditions at the epicenter. But whatever the local effects on the surface, quakes like these have a tendency to set the entire planet ringing like a bell, with seismic waves transmitted across the world that set the needles of professionally maintained seismometers wiggling.

For as valuable as these seismic networks are, though, there’s a looser, ad hoc network of detection instruments that are capable of picking up quakes as large as these from half a planet away. Some are specifically built to detect Earth changes, while some are instruments that only incidentally respond to the shockwaves traveling through the planet. And we want to know if this quake showed up in the data from anyone’s instruments.

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Detect Starlink Satellites Passing By

The Starlink beta has semi-officially ended, but it seems as though the global chip shortage is still limiting how many satellites are flying around the world for broadband internet access for those that might not be served by traditional ISPs. Not every location around the world has coverage even if you can get signed up, so to check that status the hard way you can always build a special antenna that tracks the Starlink beacons as they pass overhead.

[Derek] is using this project to show of some of his software-defined radio skills, so this will require an SDR that can receive in the 1600 MHz range. It also requires a power injector to power the satellite receiver, but these are common enough since they are used to power TV antennas. The signals coming from the Starlink satellites have a very high signal-to-noise ratio so [Derek] didn’t even need a dish to focus the signals. This also helped because the antenna he is using was able to see a much wider area as a result. Once everything was set up and the computer was monitoring the correct location in the spectrum, he was able to see very clearly how often a satellite passed him by.

Of course, [Derek] lives in an area with excellent coverage so this might be a little more difficult for those in rural areas, but possibly not for long as the goal of Starlink is to bring broadband to people who otherwise wouldn’t have access to it. There is some issue with how much these satellites might interfere with other astronomical activities though, so take that with a grain of salt.

Thanks to [Spritle] for the tip!

More Software-Defined Radio Projects Using DragonOS

DragonOS, a Debian-based Linux distribution specifically packaged for software-defined radio functionality, roared onto the wavelengths during the beginnings of the various pandemic lockdowns last year. Since then [Aaron], the creator of the OS, has been busy adding features to the distribution as well as creating plenty of videos which show off its capabilities and also function as how-tos for people who might want to learn about software-defined radio. The latest is a video about using this software to detect radio signals in certain specified spectrums.

This build uses two  RTL-SDR devices paired with the DragonOS software suite to automatically detect active frequencies within a specified frequency range and that aslo exceed a threshold measured above the average noise floor. The video includes the setup of the software and its use in detecting these signals, but also includes setup of influxdb and Grafana which provide logging capabilities as well. Using this setup, multiple receivers either local or over the internet can then be configured to dump all the identified frequencies, powers, and time stamps into DragonOS.

[Aaron] has also been helping developers to build the SDR4space.lite application which includes GPS support, so he hopes that in a future video a user will be able to easily associate location to identified frequencies. Projects like these also serve as a reminder that getting into software-defined radio is as easy as buying a $10 USB radio receiver and configuring some free software to do anything that you can imagine like tracking ships and airplanes in real time.

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Detect Lightning Strikes With An Arduino

Lightning is a powerful and seemingly mysterious force of nature, capable of releasing huge amounts of energy over relatively short times and striking almost at random. Lightning obeys the laws of physics just like anything else, though, and with a little bit of technology some of its mysteries can be unraveled. For one, it only takes a small radio receiver to detect lightning strikes, and [mircemk] shows us exactly how to do that.

When lightning flashes, it also lights up an incredibly wide spectrum of radio spectrum as well. This build uses an AM radio built into a small integrated circuit to detect some of those radio waves. An Arduino Nano receives the signal from the TA7642 IC and lights up a series of LEDs as it detects strikes in closer and closer proximity to the detector. A white LED flashes when a strike is detected, and some analog circuitry supports an analog galvanometer which moves during lightning strikes as well.

While this project isn’t the first lightning detector we’ve ever seen, it does have significantly more sensitivity than most other homemade offerings. Something like this would be a helpful tool to have for lifeguards at a pool or for a work crew that is often outside, but we also think it’s pretty cool just to have around for its own sake, and three of them networked together would make triangulation of strikes possible too.

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Hackaday Links: May 17, 2020

Consider it the “Scarlet Letter” of our time. An MIT lab is developing a face mask that lights up to alert others when the wearer has COVID-19. The detection technology is based on sensors that were developed for the Ebola virus scare and uses fluorescently tagged DNA fragments freeze-dried onto absorbent strips built into the mask. The chemistry is activated by the moisture in the sputum expelled when the wearer coughs or sneezes while wearing the mask; any SARS-CoV-2 virus particles in the sputum bind to the strips, when then light up under UV. The list of problems a scheme like this entails is long and varied, not least of which is what would possess someone to willingly don one of these things. Still, it’s an interesting technology.

Speaking of intrusive expansions of the surveillance state, Singapore is apparently now using a Boston Dynamics Spot robot to enforce social-distancing rules in its public parks and gardens. The familiar four-legged, bright yellow dog-bot is carrying cameras that are relaying images of park attendees to some sort of image analysis program and are totally not capturing facial or personal data, pinky swear. If people are found to be violating the two-meter rule, Spot will bark out a prerecorded reminder to spread out a bit. How the system differentiates between people who live together who are out getting some fresh air and strangers who should be staying apart, and whether the operators of this have ever seen how this story turns out are open questions.

Those who lived through 9/11 in the United States no doubt remember the deafening silence that descended over the country for three days while every plane in the civil aviation fleet was grounded. One had no idea how much planes contributed to the noise floor of life until they were silenced. So too with the lockdown implemented worldwide to deal with the COVID-19 pandemic, except with the sometimes dramatic reduction in pollution levels. We’ve all seen pictures where people suddenly realize that Los Angeles isn’t necessarily covered by an orange cloud of smog, and that certain mountain ranges are actually visible if you care to look. But getting some hard data is always useful, and these charts show just how much the pollution situation improved in a number of countries throughout the world after their respective lockdowns. For some cities, the official lockdown was a clear demarcation between the old pollution regime and the new, but for some, there was an obvious period before the lockdown was announced where people were obviously curtailing their activity. It’s always interesting pore over data like this and speculated what it all means.

While the in-person aspects of almost every conference under the sun have been canceled, many of them have switched to a virtual meeting that can at least partially make up for the full experience. And coming up next weekend is Virtually Maker Faire, in the slot where Bay Area Maker Faire would normally be offered. The call for makers ends today, so get your proposals in and sign up to attend.

And finally, there aren’t too many times in life you’ll get a chance to get to visualize a number so large that an Evil Empire was named for it. The googol, or 10100, was a term coined by the nine-year-old nephew of mathematician Edward Kasner when he asked the child for a good name for a really big number. To put the immensity of that number into perspective, The Brick Experiment Channel on YouTube put together an improbably long gear train using Lego pieces we’ve never seen before with a reduction ratio of 10103.4:1. The gear train has a ton of different power transmission elements in it, from plain spur gears to worm drives and even planetary gears. We found the 2608.5:1 harmonic gear particularly fascinating. There’s enough going on to keep even a serious gearhead entertained, but perhaps not for the 5.2×1091 years it’ll take to revolve the final gear once. Something, something, heat-death of the universe. [Ed note: prior art, which we were oddly enough thinking of fondly just a few days ago. Synchronicity!]

Detecting Water Before It’s Too Late

[mcu_nerd] is like any engineer, which is why his problem of an occasionally leaky water heater sure looks like a research project with no end in sight. Sure there’s probably a commercial product out there that can be had for half the cost and a few clicks of the mouse, but what’s the point in actually solving the problem?

His log starts with research into detecting low battery voltages. Then it was a quick exploration in designing low-power circuits. When the Flexible PCB contest came along, he realized that there was a chance to design a better electrode, and he ended up winning one of the vouchers; which is where he’s at now.

It’s definitely a work in progress, and if anything it’s just a quick five minute read and an opportunity to commiserate with another wayward soul. We do like his clever use of a tealite candle tin as both the second electrode and case for his water detection circuit. There are also some KiCad files and code.