A Relay-Based Pseudorandom Number Generator

There are a great variety of ways to build a random number generator, and similarly many ways to generate numbers that appear random, but in a pure mathematical sense generally aren’t. [Daniel Valuch] built a Christmas decoration that does the latter, displaying the results on an attractive flashing ornament.

The build relies on a 16-bit linear feedback shift register, or LFSR. The LFSR generates a stream of numbers, with each number dependent on the previous state of the register. Thus, the numbers generated are pseudorandom, not truly random, and depend on the initial seed value of the system. [Daniel] built the shift register using relays, which create a lovely clacking sound as the register operates, and LEDs, which glow depending on the values in the register.

The result is a cute Christmas ornament that blinks in a deterministic fashion, and has a great old-school look due to the exposed copper of the PCB and the retro LED colors used. The project also serves as a great way to learn about shift registers and basic relay logic, though the latter is rarely used these days for serious purposes. We’ve covered the topic before, too. Video after the break.

A PCB Diary

[Gijs Gieskes] has made another eye-catching PCB wonder, this time a diary built from several circuit boards which are assembled into a book, not unlike a PC/104 system. But with [Gijs]’s system you can easily open the stack-up to access single boards without disassembling the whole thing. We don’t see brass piano hinges on PCB assemblies very often, but [Gijs]’s PCB designs are anything but conventional. Hint: if you wanted to recreate this technique using more ordinary hardware, you can find hinged PCB standoffs from various suppliers.

Apparently it’s more than a passive piece of art.  Each board has several circuits, some of which (all?) are functioning is ways not clearly described, which seems to be intentional. According to his build log, different things happen when you mix and match the inter-board ribbon cables in various ways. We are told in the instructions “to just try and see what happens”. No schematics are posted, but there is a partial description of the circuits in the manual and parts on the two-layer boards are well-labeled. Although after spot checking a few circuits board photos, we’d guess that no small number of traces, and perhaps some parts, are wild goose chases.

The project claims to be a diary for the years 2018 and 2019, but we will leave it as an exercise for the reader to interpret the messages that [Gijs] has embedded into this fascinating piece. We have written about several of his projects over the years, such as this crazy bent Casio SK-1 from all the way back in 2005. And before dismissing this “book” style of circuit board stack-up as only for artists, check out this teardown of a Soyuz clock we covered back in January.

PET 2001 Emulator On \$2 Of Hardware

Since the late 60s, Moore’s law has predicted with precision that the number of semiconductors that will fit on a chip about doubles every two years. While this means more and more powerful computers, every year, it also means that old computers can be built on smaller and cheaper hardware. This project from [Bjoern] shows just how small, too, as he squeezes a PET 2001 onto the STM32 Blue Pill.

While the PET 2001 was an interesting computer built by Commodore this project wasn’t meant to be a faithful recreation, but rather to test the video output of the Blue Pill, with the PET emulation a secondary goal. It outputs a composite video signal which takes up a good bit of processing power, but the PET emulation still works, although it is slightly slow and isn’t optimized perfectly. [Bjoern] also wired up a working keyboard matrix as well although missed a few wire placements and made up for it in the software.

With his own home-brew software running on the \$2 board, he has something interesting to display over his composite video output. While we can’t say we’d emulate an entire PC just to get experience with composite video, we’re happy to see someone did. If you’d like to see a more faithful recreation of this quirky piece of computing history, we’ve got that covered as well.

CentOS Is Dead, Long Live CentOS

On Tuesday, December 8th, Red Hat and CentOS announced the end of CentOS 8. To be specific, CentOS 8 will reach end of life at the end of 2021, 8 years ahead of schedule. To really understand what that means, and how we got here, it’s worth taking a trip down memory lane, and looking at how the history of Red Hat Enterprise Linux (RHEL), CentOS, and IBM are intertwined.

Who Says Solder Paste Stencils Have To Be CNC Cut?

Imagine having a surface mount kit that you’d like to stencil with solder paste and reflow solder, but which doesn’t come with a solder stencil. That was what faced [Honghong Lu], and she rose to the challenge by taking a piece of PET sheet cut from discarded packaging and hand-cutting her own stencil. It’s not a huge kit, the Technologia Incognita 2020 kit, but her home-made stencil still does an effective job.

So how does one create a solder stencil from household waste? In the video we’ve put below the break, she starts with her packaging, and cuts from it a square of PET sheet. It’s 0.24mm thick, which is ideal for the purpose. She then lays it over the PCB and marks all the pads with a marker pen, before cutting or drilling the holes for the pads. The underside is then sanded to remove protruding swarf, and the stencil can then be used in the normal way. She proves it by stenciling the solder paste, hand placing the parts, and reflowing the solder on a hotplate.

It’s clear that this is best suited to smaller numbers of larger components, and we’ll never use it to replace a laser-cut stencil for a thousand tiny 0201 discretes. But that’s not the point here, it’s an interesting technique for those less complex boards, and it’s something that can be tried by anyone who is curious to give stenciling and reflowing a go and who doesn’t have a project with a ready-cut stencil. And for that we like it.

Making your own stencils doesn’t have to include this rather basic method. They can be etched, or even 3D printed.

Hyperloop: Fast, But At What Cost?

When it comes to travelling long distances, Americans tend to rely on planes, while the Chinese and Europeans love their high speed rail. However, a new technology promises greater speed with lower fares, with fancy pods travelling in large tubes held at near-vacuum pressures. It goes by the name of Hyperloop.

Spawned from an “alpha paper” put together by Elon Musk in 2013, the technology is similar to other vactrain systems proposed in the past. Claiming potential top speeds of up to 760 mph, Hyperloop has been touted as a new high-speed solution for inter city travel, beating planes and high speed rail for travel time. Various groups have sprung up around the world to propose potential routes and develop the technology. Virgin Hyperloop are one of the companies at the forefront, being the first to run a pod on their test track with live human passengers, reaching speeds of 100 mph over a short 500 meter run.

It’s an exciting technology with a futuristic bent, but to hit the big time, it needs to beat out all comers on price and practicality. Let’s take a look at how it breaks down.

Mind-Controlled Beer Pong Gets Easier As You Drink

Wouldn’t it be nice if beer pong could somehow get easier the more you drink? You know, so you can drink more? [Ty Palowski] has made it so with automated, mind-controlled beer pong.

[Ty] started by making a beer pong table that moves the cups back and forth at both ends. An Arduino Nano controls a stepper that controls a slider, and the cups move with the slider through the magic of magnets. The mind control part came cheaper than you might think. Back in 2009, Mattel released a game called Mind Flex that involves an EEG headset and using brain waves to guide a foam ball on a stream of air through a little obstacle course. These headsets are available for about \$12 on ebay, or at least they were before this post went up.

[Ty] cracked open the headset added an HC-06 Bluetooth module to talk to the Arduino. It’s using a program called Brainwave OSC to get the raw data from the headset and break it into levels of concentration and relaxation. The Arduino program monitors the attention levels, and when a certain threshold of focus is reached, it moves the cups back and forth at a predetermined speed ranging from 1 to an impossible-looking 10. Check out the two videos after the break. The first one covers the making of the the automatic beer pong part, and the second is where [Ty] adds mind control.

We’ve seen a different headset — the hacker-friendly NeuroSky Mindwave — pop up a few times. Here’s one that’s been hacked to induce lucid dreaming.