Jet burner and close-up

$7 Tent Heater Provides Comfort On A Budget

At Hackaday’s Minnesota office, we appreciate central heat and hot coffee because the outdoor temperature is sub-zero in Celsius and Fahrenheit. Not everyone here has such amenities, and families living in tents could use heater help. If you live somewhere inhospitably cold and have the resources (time being the most crucial), please consider building and donating alcohol jet burners.

Alcohol burners like these are great for tents because if they tip over, they self-extinguish. You can fill them with 70% rubbing alcohol and they’ll heat a small space, and if running on denatured alcohol, they can be used to cook with. They won’t do you much good outdoors unless you have significant wind protection, as the tiny jet is likely to blow out. The first time you light one, you must heat the coil with a lighter or another heater to vaporize incoming fuel, then it can sustain itself by wicking fluid up from the reservoir jar. Relighting after a tip or accidental gust only takes a spark since the copper is already hot.

If you came for a hack, note how they fill the small tubes with salt funneled through a condiment cap before bending them. Sure, there are springy pipe bending tools, but who doesn’t already have salt and tape? Keeping humans warm is crucial, but heating metal takes a different approach.

Thank you for the tip, [cyberlass]

This Ham Radio Is Unsafe At Any Frequency

When we were kids we rode bicycles without pads and helmets. We drank sugary drinks. We played with chemistry sets and power tools. We also built things that directly used AC line current. [Mike] remembers and built one, presumably more to discuss the safety precautions around things that can shock you and not entice you to duplicate it. He calls it The Retro QRP Widowmaker, if that’s any kind of a hint. (Video of this unsafe transmitter also embedded below.)

The design showed up from time to time in old electronic magazines. Built on an open board and with no ground wire, the radio didn’t need a complex power supply. This wasn’t limited to transmitters, either. Some TVs and radios had a “hot chassis.” That’s why we were taught to touch an unknown chassis with the back of your hand first. A shock will contract your muscles and that will pull your arm away instead of making you grab the electrically active part.

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Bug Clive goes into detail about electrical safety even at the most basic level of wearing gloves.

The Unofficial Guide To (Avoiding) Electrocution

If you’re reading this sentence, there’s a pretty good chance that you interact with electricity more than just as an end-user. You’re a hacker. You aren’t afraid of a few volts, and your projects may involve both DC and AC voltage. Depending on what you’re working on, you might even be dealing with several thousand volts. And it’s you who Big Clive made the video below the break for.

“Familiarity breeds contempt” as the old saying goes, and the more familiar we are with electronics, the more cavalier we may tend to get. If we allow ourselves to get too lax, we may be found working on live circuits, skimping on safety for the sake of convenience, or jokingly saying “safety third!” far too often as we tear into a hazardous situation without scoping it out first.

Who better to bring us down to earth than Big Clive. In this video, he explains how electricity has the potential to impede the beating of our hearts, the action of our lungs, and even break bones. You’ll find a candid discussion about what electric shock does to a person, how to avoid it, and how to help if someone near you suffers electric shock.

Of course, if safety isn’t your thing, then maybe you’re ready to Shake Hands With Danger.

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Building A Bicycle Dash Cam With Advanced Capabilites

Riding a bicycle is a wonderful and healthy way to get around. However, just like with any other vehicle on the road, it can be useful to have a camera to record what goes on in traffic. [Richard Audette] built just such a rig.

The original setup relies on a Raspberry Pi 3, which takes a photo every 10 seconds using the attached Pi Camera. It then processes these photos using OpenALPR, which is a piece of software for reading licence plates. Licence plates detected while cycling can be stored on the Raspberry Pi for later, something which could be useful in the event of an accident.

However, [Richard] has developed the concept further since then. The revised dashcam adds blind spot detection for added safety, and uses a Luxonis OAK-D camera which provides stereo depth data and has AI acceleration onboard. It’s paired with a laptop carried in a backpack instead of a Raspberry Pi, and can stream video to a smartphone sitting on the handlebars as a sort of rear-view mirror.

Anyone who has commuted on a bicycle will instantly see the value in work like [Richard]’s. Just avoiding one accident from a car coming from behind would be of huge value, and we’re almost surprised we don’t see more bicycle rear view kits in the wild.

Alternatively, if you just want to scan your surroundings as you ride, consider building a landscape scanner instead. Video after the break.

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Test For 3D Printer Runaway

A few 3D printers have had a deserved reputation for bursting into flames. Most — but apparently not all — printers these days has firmware that will detect common problems that can lead to a fire hazard. If you program your own firmware, you can check to see if you have the protection on, but what if you have a printer of unknown provenance? [Thomas] shows you how to check for a safe printer. Also check out his video, embedded below.

The idea is to fake the kind of failures that will cause a problem. Primarily, you want to have the heaters turned on while the thermistor isn’t reading correctly. If the thermistor is stuck reading low or is reading ambient, then it is possible to just drive the heating element to get hotter and hotter. This won’t always lead to a fire, but it could lead to noxious fumes.

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Building A Stump Grinder From The Ground Up

Felling a tree properly is a skill that takes some practice to master, especially without causing any injuries or property damage. Getting the tree cut down though is sometimes only half of the battle, as the stump and roots need to be addressed as well. Unless you have a few years to wait for them to naturally decompose you might want to employ a stump grinder, and unless you want to spend a chunk of money on a stump grinding service or buy your own, you might want to do what [Workshop from Scratch] did and build your own.

This stump grinder isn’t anything to scoff at, either, and might even fool some into thinking it’s a consumer grade tool from a big box store. Far from it though, as almost everything down to the frame is custom machined specifically for this build. The only thing that isn’t built from scratch, including the cutting wheel, is the beefy 15 horsepower motor. Once it gets going it is able to carve stumps down to the ground in no time thanks especially to some gear reductions in the drive line from the motor to the cutting head.

Before anyone mentions safety, it looks like [Workshop from Scratch] has made some upgrades since his last project which was a gas-powered metal cutting chainsaw. Since then it looks like he has upgraded the sheet metal to something a little thicker, even though a stump grinder has arguably lower risk due to the slower speed of the cutting wheel and also to the fact that the cutting medium is wood and not metal. There are also brakes and an emergency shutoff switch. It sure seems like a fine addition to his collection of completely custom tools.

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Hackaday Links: April 18, 2021

More bad news from Mars this week, and this time not just from Perseverance. Last week the eagerly anticipated first flight of the helicopter Ingenuity was delayed for a couple of days after failing a full-speed spin-up test of its rotors. That appears to have been a bigger deal than initially thought, as it required a significant rewrite of the helicopter’s software. That meant testing, of course, and subsequent upload to the UAV, which at 174 million miles away takes a bit of doing. The good news is that they were able to complete the full-speed rotor test without the full program upload, so we’re one step closer to flight, which may take place as early as Monday morning.

Meanwhile, over at Elysium Planitia, the Mars InSight lander has troubles of its own. The geophysical laboratory, which has been trying to explore the inner structure of Mars since landing in 2018, entered an “emergency hibernation” state this week because of a lack of sufficient power generation. Unlike the radioisotope-powered Perseverance rover, InSight relies on a pair of solar panels for its electricity, and those panels are being obscured by Martian dust. The panels normally get blown clean by Martian winds, but things have been calm lately and the dust has really built up. If this seems like deja vu all over again, it’s probably because a planet-wide dust storm is what killed the plucky Opportunity rover back in 2018. Here’s hoping the wind picks up a little and InSight can get back to work.

Funny what crops up in one’s newsfeed, especially when one is responsible for putting out content that populates others’ newsfeeds. We recently took a look at the dangers of “zinc fever”, a flu-like illness that can crop up after inhaling gasses produced by molten zinc. That resulted in stumbling across an article from last year about mild steel welding fumes being classified as a human carcinogen. This comes from the Health and Safety Executive, a UK government agency concerned with workplace health issues. The release is an interesting read, and it suggests that mild steel fumes can cause not only lung cancer but kidney cancer. The announcement is mainly concerned with British workplaces, of course, but there are some interesting tidbits in there, such as the fact that welding fumes make dust particles so small that they can reach down into the very lowest reaches of lungs, the alveoli where gas exchange occurs. It’s enough to make one invest in PAPR or some kind of fume extractor.

For those of a certain vintage, our first computer was probably something that bore little resemblance to a PC or laptop. It was likely a single-board affair or something like a C64, and acquiring the essential bit of hardware usually left little in the budget for a proper monitor. Little 12″ B&W TVs were a dime a dozen, though, and easily — if grainily — enlisted into service as a monitor by way of an RF modulator. To recreate a little of that magic with modern hardware, Hackaday contributor Adam Zeloof came up with the PiMod Zero, an RF-modulator hat for the Raspberry Pi Zero that turns the component video into an NTSC analog signal. He’s open-sourced the design files, or there’s a CrowdSupply campaign for those who prefer to buy.

And finally, if you somehow traveled back in time to the 1940s with a laptop, how long would it have taken you to crack the Enigma code? Longer than you think, at least according to Dr. Mike Pound over at Computerphile, who released a fascinating video on how Enigma worked and what it took for Turing and the gang at Bletchley to crack the code. We knew some of the details of Enigma’s workings before seeing this video, but Mike’s explanation was really good. And, his explanation of the shortcut method he used to decode an Enigma message made the whole process clearer to us than it’s ever been. Interesting stuff.

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