A Super Simple DIY Ozone Generator

April 10, 2022 by Dave Rowntree 38 Comments

[Advanced Tinkering] needed a source of fresh ozone for some future chemistry related projects, and since buying an off-the-shelf unit would be, well, just plain boring, it was obvious what to do (Video, embedded below).

Wire mesh discharge surfaces separated with a glass tube

The concept of the corona-discharge ozone generator is pretty straightforward — a high-voltage AC potential is presented over a large surface area, such that any O₂ in the vicinity has the chance to get a decent dose of electrons ripping it apart and enabling the formation of the desired O₃.

The construction is quite simple, just a pair of cylindrical metal wire mesh electrodes, separated by a glass tube, with a second glass tube surrounding the whole assembly. The use of high voltage AC allows the discharge to form by capacitive coupling across the central tube, giving a very simple construction. A pair of 3D-printed PLA end caps complete the reaction vessel, although it is noted in the video that the PLA is not terribly resistant to the corrosive effects of ozone, and time will tell whether these go the whole mileage.

Feed oxygen from an external generator is pumped into one end cap, at the bottom, with ozone-enriched gas passing out the other end, at the top, giving the gas a more complex path through the assembly and maximizing the contact with discharge. It will be interesting to see what the produced ozone will be used for in these future projects.

We’ve not seen a vast number of ozone hacks, but we’re no strangers to high voltage applications, like this interesting hand disinfection device, and this simple hack that generates a six-figure voltage with little more than some glasses of water, well not much more anyway.

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The Bose headphone plug in question, with reverse-engineered schematic of the filter overlaid.

This 3.5mm Cable Distorts Signals, Hides Audio-Filtering Circuit

April 10, 2022 by Arya Voronova 57 Comments

[Avian]’s dad got a new ham radio transceiver with a 3.5 mm jack, and his pile-of-cables got him a headphone cable from Bose headphones. He built a DB9 to 3.5 mm adapter with that one – and it failed to let data through, outputting distorted garbage of a waveform instead. With a function generator and an oscilloscope, [Avian] plotted the frequency response of the cable, which turned out to be quite far from a straight line. What was up?

Taking the connector apart was a tricky job. A combination of blunt force and a nail polish remover soak didn’t quite get them all the way, so [Avian] continued to apply blunt force and took the jack apart with minimal casualties. Turned out that there was more to the 3.5 mm plug indeed — a whole PCB with a few resistors and capacitors, reverse-engineered into the schematic seen above.

Looks like Bose decided to tweak the audio characteristics of a specific pair of headphones, and an in-plug filter was, somehow, the most efficient solution. We probably shouldn’t expect to see this often, but it bears keeping in mind: next time your repurposed 3.5 mm cable doesn’t behave as expected, it would be prudent to do a capacitance test with your trusty meter or oscilloscope.

With how small MCUs have gotten, you can easily hide more than just a few capacitors! We don’t often see circuits built into cables, but when we do, it’s for malicious purposes.

A Turbocharged Robot Mop To Save Your Date

April 10, 2022 by Robin Kearey 4 Comments

Cleaning robots are great and all, but they don’t really excel when it comes to speed. If your room looks like a pigsty and your Tinder date is arriving in twenty minutes, you’ll need more than a Roomba to make a good impression. [Luis Marx] ran into this exact problem and decided to solve it by building the world’s fastest cleaning robot (video, embedded below).

[Luis] built his ‘bot from the ground up, inspired by the design of your average robot vacuum: round, with two driven wheels and some sensors to avoid obstacles. A sturdy aluminium plate forms the chassis, onto which two powerful motors are placed to drive a pair of large-diameter wheels. The robot’s body is made from 3D-printed components and sports a huge LED display on top that functions as a speedometer of sorts.

Building a vacuum system turned out to be rather difficult, and since [Luis] already had a robot vacuum anyway, he decided to make this a robot mop instead. A little tank stores water and soap, which is pumped onto a microfibre cloth that’s attached using a magnetic strip. Obstacle avoidance is implemented through three ultrasonic distance sensors: when the robot is about to run into something it will brake and turn in the direction where it senses the most empty space.

All of that sounds great, but what about the speed? According to [Luis]’s calculations, it should be able to reach 60 km/h, although his living room is too small to put that into practice. Whether it will provide much in the way of cleaning at that speed is debatable too, but who cares: having your own ultra-high-speed robot mop will definitely impress your date more than any amount of cleaning.

We’ve featured a home-made robot mop before, but it looks excruciatingly slow compared to this one. If you’re planning to build zippy indoor robots, you might want to look into fast navigation systems like tracking ceiling lights.

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Retrotechtacular: A DIY Television For Very Early Adopters

April 10, 2022 by Dan Maloney 21 Comments

By our very nature, hackers tend to get on the bandwagon of new technology pretty quickly. When something gee-whiz comes along, it’s folks like us who try it out, even if that means climbing steep learning curves or putting together odd bits of technology rather than waiting for the slicker products that will come out if the new thing takes off. But building your own television receiver in 1933 was probably pushing the envelope for even the earliest of adopters.

“Cathode Ray Television,” reprinted by the Antique Valve Museum in all its Web 1.0 glory, originally appeared in the May 27, 1933 edition of Popular Wireless magazine, and was authored by one K D Rogers of that august publication’s Research Department. They apparently took things quite seriously over there at the time, at least judging by the white lab coats and smoking materials; nothing said serious research in the 1930s quite like a pipe. The flowery language and endless superlatives that abound in the text are a giveaway, too; it’s hard to read without affecting a mental British accent, or at least your best attempt at a Transatlantic accent.

In any event, the article does a good job showing just what was involved in building a “vision radio receiver” and its supporting circuitry back in the day. K D Rogers goes into great detail explaining how an “oscillograph” CRT can be employed to display moving pictures, and how his proposed electronic system is vastly superior to the mechanical scanning systems that were being toyed with at the time. The build itself, vacuum tube-based though it was, went through the same sort of breadboarding process we still use today, progressing to a finished product in a nice wood cabinet, the plans for which are included.

It must have been quite a thrill for electronics experimenters back then to be working on something like television at a time when radio was only just getting to full market penetration. It’s a bit of a puzzle what these tinkerers would have tuned into with their DIY sets, though — the airwaves weren’t exactly overflowing with TV broadcasts in 1933. But still, someone had to go first, and so we tip our hats to the early adopters who figured things out for the rest of us.

Thanks to [BT] for the tip.

LoRa-Powered Birdhouses Enable Wireless Networking When The Internet’s Down

April 9, 2022 by Robin Kearey 26 Comments

One of the design requirements for the networks that evolved into the Internet was the ability to keep functioning, even if some nodes or links were disabled or destroyed in war. The packet-switched architecture that still powers today’s Internet is a direct result of that: if one link stops functioning, information is automatically re-routed towards its intended destination. However, with tech giants occupying increasingly large parts of the global internet, an outage at one of them might still cause major disruption. In addition, a large-scale power interruption can disable large parts of the network if multiple nodes are connected to the same grid.

Six pieces of wood, with a hammer next to them — Just six pieces of wood make up the birdhouse.

Enter the LoRa Birdhouse project by the Wellesley Amateur Radio Society that solves those two problems, although admittedly at a very small scale. Developed by amateur radio operators in eastern Massachusetts, it’s basically a general-purpose LoRa-based packet-switching network. As it’s based on open-source hardware and commonly available components, its design allows anyone to set up a similar network in their own area.

The network is built from nodes that can receive messages from their neighbors and pass them on towards their final destination. Each node contains a Semtech SX1276 transceiver operating in the 902-928 MHz band, which gets its data from an ESP32 microcontroller. The nodes are placed in strategic locations outside and are powered by solar panels to reduce their ecological footprint, as well as to ensure resilience in case of a power outage. To make the whole project even more eco-friendly, each node is built into a birdhouse that provides shelter to small birds.

Users can access the network through modified network nodes that can be hooked up to a PC using a USB cable. Currently, a serial terminal program is the only way to interact with the network, although a more user-friendly interface is being planned. FCC rules also require all users (except any avian residents) to be licensed amateur radio operators, and all traffic to remain unencrypted. Tests have shown that one kilometer between nodes can work in the right conditions, enabling the deployment of networks across reasonably large areas.

While the Birdhouse Network might not be a plug-and-play internet replacement in case of a nuclear apocalypse, it does provide an excellent system to experiment with packet-switching wireless network technology. We’ve seen similar LoRa-based network initiatives like Qmesh, Cellsol and Meshtastic, all of which provide some way to communicate wirelessly without requiring any centralized hardware.

SDR Listens In To Your Tires

April 9, 2022 by Al Williams 26 Comments

[Ross] has a 2008 Toyota Tacoma. Like many late model cars, each tire contains a direct tire pressure monitoring sensor or TPMS that wirelessly sends data about the tire status to the car. However, unlike some cars, the system has exactly one notification to the driver: one of your tires is low. It doesn’t tell you which one. Sure, you can check each tire, but [Ross] had a different problem. One sensor was bad and he had no way to know which one it was. He didn’t have any equipment to test the sensor, but he did have an RTL-SDR dongle and some know-how to figure out how to listen in on the sensors.

The key was to use some software called RTL-433 that is made to pick up these kinds of signals. It is available for Linux, Windows, or Mac, and supports hundreds of wireless sensors ranging from X10 RF to KlikAanKlikUit wireless switches.

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CAT Is Not Your Average Meow-cropad

April 9, 2022 by Kristina Panos 3 Comments

Are you completely over the idea of the keyboard in any flattish form and looking for something completely different for inputting your data? Or do you want a mega macropad for 3D design, GIMP or Inkscape work, or to use while relaxing with a nice first-person shooter? Then this ergonomic, double-fistable keyboard/controller mashup named CAT may be what you’re looking for.

Inside each of these slinky felines is pretty much what you’d expect to find — 25 or so switches and an Arduino Pro Micro. Interestingly enough, the switches are all lever-action and not push buttons. There are two breeds of CAT available to build or buy: one has 25 buttons, and the other has a joystick or trackball on the thumb between two upper and two lower buttons. You could have one type for each hand!

More information is available on the Lynx Workshop site, which is where you’ll also find tutorials and instructions for everything from the 3D printing to the electronics to the assembly and coding. There is even a bonus 3D modeling tutorial. Don’t want to invest the time to make your own CAT? These kitties are also available for pre-order. Claw past the break to check them out in action.

Looking for something with regular keyswitches? Oh, we have plenty of those.

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