Open-Source Random Numbers

February 20, 2025 by 26 Comments

Whether it’s a game of D&D or encrypting top-secret information, a wide array of methods are available for generating the needed random numbers with high enough entropy for their use case. For a tabletop game this might be a single die but for more sensitive applications a more robust method of generating random numbers is needed. Programmers might reach for a rand() function of some sort, but these pseudorandom numbers don’t cut the mustard for encryption. For that you’ll need a true random number generator (RNG), and this open-source hardware RNG uses one of the better methods we’ve seen.

The device, called RAVA, is based on a property found in many electronic devices called avalanche breakdown. Avalanche breakdown occurs when a high voltage (in this case approximately 25V) is applied in the reverse bias direction, with this device using a pair of Zener diodes. When this high voltage is applied, an “avalanche” of electrons occurs which allows the diodes conduct in the opposite direction that they would when they are forward biased. This isn’t a constant current flow, though; there are slight variations over time which can be amplified and used as the random number generator. The noise is amplified over a series of op amps and then fed to an ATmega32U4 microcontroller which can provide the user with 136.0 Kbit/s of random data.

Unlike other random number generators, this device is based on a method generally accepted to be truly random. Not only that, but since it’s based on discrete hardware it can be accessed directly for monitoring and replacement in case of faults, unlike other methods which are more “black boxes” and are more opaque in their processes which are thus harder to audit. We also appreciate it’s open-source nature as well, and for some more information on it be sure to check out the paper on it in IEEE. If you’re looking for something to generate random numbers but will also bring some extra flair to the next game night, take a look at this radioactive dice replacement.

DIY Yagi Antenna Sends LoRa Signals Farther

February 20, 2025 by 26 Comments

LoRa gear can be great for doing radio communications in a light-weight and low-power way. However, it can also work over great distances if you have the right hardware—and the right antennas in particular. [taste_the_code] has been experimenting in this regard, and whipped up a simple yagi antenna that can work at distances of up to 40 kilometers.

The basic mathematics behind the yagi antenna are well understood. To that end, [taste_the_code] used a simple online calculator to determine the correct dimensions to build a yagi out of 2 mm diameter wire that was tuned for the relevant frequency of 868 MHz. The build uses a 3D-printed boom a handle and holes for inserting each individual wire element in the right spot—with little measuring required once the wires are cut, since the print is dimensionally accurate. It was then just a matter of wiring it up to the right connector to suit the gear.

The antenna was tested with a Reyas RYLR998 module acting as a base station, with the DIY yagi hooked up to a RYLR993 module in the field. In testing, [taste_the_code] was able to communicate reliably from 40 kilometers away.

We’ve featured some other unique LoRa antenna builds before, too. Video after the break.

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UNIX Archaeology Turns Up 1972 “V2 Beta”

February 20, 2025 by 20 Comments

In 1997 a set of DEC tapes were provided by Dennis Ritchie, as historical artifacts for those interested in the gestation of the UNIX operating system. The resulting archive files have recently been analysed by [Yfeng Gao], who has succeeded in recovering a working UNIX version from 1972. What makes it particularly interesting is that this is not a released version, instead it’s a work in progress sitting somewhere between versions 1 and 2. He’s therefore taken the liberty of naming it “V2 Beta”.

If you happen to have a PDP-11/20 you should be able to run this operating system for yourself, and for those of us without he’s provided information on which emulator will work. The interesting information for us comes in the README accompanying the tapes themselves, and in those accompanying the analysis. Aside from file fragments left over from previous users of the same tape, we learn about the state of UNIX time in 1972. This dates from the period when increments were in sixtieths of a second due to the ease of using the mains power frequency in a PDP, so with a 32-bit counter they were facing imminent roll-over. The 1970-01-01 epoch and one second increments would be adopted later in the year, but meanwhile this is an unusual curio.

If you manage to run this OS, and especially if you find anything further in the files, we’d love to hear. Meanwhile, this is not the oldest UNIX out there.

Featured image: “PDP-11/20 Rocker Switches” by Don DeBold

Pico Gets A Speed Bump

February 20, 2025 by 28 Comments

The release notes for the 2.1.1 Raspberry Pi Pico SDK have a late holiday present: The RP2040 chip is now certified to run at 200 MHz if you use at least 1.15V as the supply voltage.

Previously, the certified speed was 125 MHz, although it was well-known you could overclock the device. By default, the 125 MHz figure is still what you’ll get, though. If you want a higher frequency, you need to set SYS_CLK_MHZ to 200 before doing a build. Continue reading “Pico Gets A Speed Bump” →

Microwave Motion Detector Notifies Your Smart Phone

February 20, 2025 by 16 Comments

Your garden variety motion detector uses IR, but these days, there are fancier technologies for achieving similar goals. If so desired, you can source yourself a microwave-based presence sensor instead. Indeed, like [N-08 Labs], you might like to whip one up into a basic intrusion detection system.

The idea is simple enough—take a RCWL-0516 microwave presence sensor, and set it up to detect motion and warn you when it happens. It’s a simple part to use—it simply drives a 3.3 volt logic output high if it detects someone or something. It basically just emits a microwave signal and detects a change in phase when someone or something—usually something fleshy—is in front of it. [N-08 Labs] simply hooked one up to an IO pin on an ESP8266, with the microcontroller board set up to communicate wirelessly with a Blynk IoT app, which then in turn fires off a smartphone notification that the sensor picked something up. The whole thing is built inside the shell of an AC adapter that provides power and let it easily hide in plain sight.

A project like this doesn’t just have to be for security purposes. You might even just use it to determine when your pet (or a racoon) is using the cat door, or similar. Indeed, we’ve seen great solutions to that particular problem, too. Video after the break.

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You’ve Got All Year To Print This Marble Machine Ornament For Your Christmas Tree

February 20, 2025 by 11 Comments

Most Christmas ornaments just hang there and look pretty. [Sean Hodgins] decided to whip up something altogether fancier and more mechanical. It’s a real working marble machine that hangs from the tree!

The build is simple enough, beginning with a translucent Christmas ornament shell readily available from most craft stores. Inside, a small motor spins a pinion, which turns a larger gear inside the body. As the larger gear spins, magnets embedded inside pick up steel balls from the base of the ornament and lift them up to the top. As they reach their zenith, they’re plucked off by a scoop, and then they roll down a spiral inside. As for power, [Sean] simply handled that with a couple of wires feeding the motor from a USB power bank. Just about any small battery pack would do fine.

The build is beautiful to watch and to listen to, with a gentle clacking as the balls circulate around. Files are on MakerWorld for the curious. We’ve featured some great Christmas decorations before, too. Video after the break.

Reconstructing 3D Objects With A Tiny Distance Sensor

February 20, 2025 by 7 Comments

There are a whole bunch of different ways to create 3D scans of objects these days. Researchers at the [UW Graphics Lab] have demonstrated how to use a small, cheap time-of-flight sensor to generate scans effectively.

Not yet perfect, but the technique does work…

The key is in how time-of-flight sensors work. They shoot out a distinct pulse of light, and then determine how long that pulse takes to bounce back. This allows them to perform a simple ranging calculation to determine how far they are from a surface or object.

However, in truth, these sensors aren’t measuring distance to a single point. They’re measuring the intensity of the received return pulse over time, called the “transient histogram”, and then processing it. If you use the full mathematical information in the histogram, rather than just the range figures, it’s possible to recreate 3D geometry as seen by the sensor, through the use of some neat mathematics and a neural network. It’s all explained in great detail in the research paper.

The technique isn’t perfect; there are some inconsistencies with what it captures and the true geometry of the objects its looking at. Still, the technique is young, and more work could refine its outputs further.

If you don’t mind getting messy, there are other neat scanning techniques out there—like using a camera and some milk.

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