Author: Dan Maloney

3363 Articles

Going Ham Mobile On A Bicycle

July 8, 2024 by 19 Comments

It’s said that “Golf is a good walk spoiled,” so is attaching an amateur radio to a bike a formula for spoiling a nice ride?

Not according to [Wesley Pidhaychuk (VA5MUD)], a Canadian ham who tricked out his bike with a transceiver and all the accessories needed to work the HF bands while peddling along. The radio is a Yaesu FT-891, a workhorse mobile rig covering everything from the 160-meter band to 6 meters. [Wes] used some specialized brackets to mount the radio’s remote control head to the handlebars, along with an iPad for logging and a phone holder for streaming. The radio plus a LiFePO4 battery live in a bag on the parcel rack in back. The antenna is a Ham Stick mounted to a mirror bracket attached to the parcel rack; we’d have thought the relatively small bike frame would make a poor counterpoise for the antenna, but it seems to work fine — well enough for [Wes] to work some pretty long contacts while pedaling around Saskatoon, including hams in California and Iowa.

The prize contact, though, was with [WA7FLY], another mobile operator whose ride is even more unique: a 737 flying over Yuma, Arizona. We always knew commercial jets have HF rigs, but it never occurred to us that a pilot who’s also a ham might while away the autopilot hours working the bands from 30,000 feet. It makes sense, though; after all, if truckers do it, why not pilots?

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Hackaday Links: July 7, 2024

July 7, 2024 by 7 Comments

Begun, the Spectrum Wars have. First, it was AM radio getting the shaft (last item) and being yanked out of cars for the supposed impossibility of peaceful coexistence with rolling broadband EMI generators EVs. That battle has gone back and forth for the last year or two here in the US, with lawmakers even getting involved at one point (first item) by threatening legislation to make terrestrial AM radio available in every car sold. We’re honestly not sure where it stands now in the US, but now the Swiss seem to be entering the fray a little up the dial by turning off all their analog FM broadcasts at the end of the year. This doesn’t seem to be related to interference — after all, no static at all — but more from the standpoint of reclaiming spectrum that’s no longer turning a profit. There are apparently very few analog FM receivers in use in Switzerland anymore, with everyone having switched to DAB+ or streaming to get their music fix, and keeping FM transmitters on the air isn’t cheap, so the numbers are just stacked against the analog stations. It’s hard to say if this is a portent of things to come in other parts of the world, but it certainly doesn’t bode well for the overall health of terrestrial broadcasting. “First they came for AM radio, and I did nothing because I’m not old enough to listen to AM radio. But then they came for analog FM radio, and when I lost my album-oriented classic rock station, I realized that I’m actually old enough for AM.”

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Smartwatch Snitches On Itself And Enables Reverse Engineering

July 4, 2024 by 10 Comments

If something has a “smart” in its name, you know that it’s talking to someone else, and the topic of conversation is probably you. You may or may not like that, but that’s part of the deal when you buy these things. But with some smarts of your own, you might be able to make that widget talk to you rather than about you.

Such an opportunity presented itself to [Benjamen Lim] when a bunch of brand X smartwatches came his way. Without any documentation to guide him, [Benjamen] started with an inspection, which revealed a screen of debug info that included a mysterious IP address and port. Tearing one of the watches apart — a significant advantage to having multiple units to work with — revealed little other than an nRF52832 microcontroller along with WiFi and cellular chips. But the luckiest find was JTAG pins connected to pads on the watch face that mate with its charging cradle. That meant talking to the chip was only a spliced USB cable away.

Once he could connect to the watch, [Benjamen] was able to dump the firmware and fire up Ghidra. He decided to focus on the IP address the watch seemed fixated on, reasoning that it might be the address of an update server, and that patching the firmware with a different address could be handy. He couldn’t find the IP as a string in the firmware, but he did manage to find a sprintf-like format string for IP addresses, which led him to a likely memory location. Sure enough, the IP and port were right there, so he wrote a script to change the address to a server he had the keys for and flashed the watch.

So the score stands at [Benjamen] 1, smartwatch 0. It’s not clear what the goal of all this was, but we’d love to see if he comes up with something cool for these widgets. Even if there’s nothing else, it was a cool lesson in reverse engineering.

Lasers Al Fresco: Fun With Open-Cavity Lasers

July 3, 2024 by 11 Comments

Helium-neon lasers may be little more than glorified neon signs, but there’s just something about that glowing glass tube that makes the whole process of stimulated emission easier to understand. But to make things even clearer, you might want to take a step inside the laser with something like [Les Wright]’s open-cavity He-Ne laser.

In most gas lasers, the stimulated emission action takes place within a closed optical cavity, typically formed by a glass tube whose ends are sealed with mirrors, one of which is partially silvered. The gas in the tube is stimulated, by an electrical discharge in the case of a helium-neon laser, and the stimulated photons bounce back and forth between the mirrors until some finally blast out through the partial mirror to form a coherent, monochromatic laser beam. By contrast, an open-cavity laser has a gas-discharge tube sealed with the fully silvered mirror on one end and a Brewster window on the other, which is a very flat piece of glass set at a steep angle to the long axis of the tube and transparent to p-polarized light. A second mirror is positioned opposite the Brewster window and aligned to create a resonant optical cavity external to the tube.

To switch mirrors easily, [Les] crafted a rotating turret mount for six different mirrors. The turret fits in a standard optical bench mirror mount, which lets him precisely align the mirror in two dimensions. He also built a quick alignment jig, as well as a safety enclosure to protect the delicate laser tube. The tube is connected to a high-voltage supply and after a little tweaking the open cavity starts to lase. [Les] could extend the cavity to almost half a meter, although even a waft of smoke was enough obstruction to kill the lasing at that length.

If this open-cavity laser arrangement seems familiar, it might be because [Les] previously looked at an old-school particle counter with such a laser at its heart. Continue reading “Lasers Al Fresco: Fun With Open-Cavity Lasers” →

Putting Some Numbers On Your NEMAs

July 2, 2024 by 13 Comments

It’s official: [Engineer Bo] wins the internet with a video titled “Finding NEMA 17,” wherein he builds a dynamometer to find the best stepper motor in the popular NEMA 17 frame size.

Like a lot of subjective questions, the only correct answer to which stepper is best is, “It depends,” and [Bo] certainly has that in mind while gathering the data needed to construct torque-speed curves for five samples of NEMA 17 motors using his homebrew dyno. The dyno itself is pretty cool, with a bicycle disc brake to provide drag, a load cell to measure braking force, and an optical encoder to measure the rotation of the motor under test. The selected motors represent a cross-section of what’s commonly available today, some of which appear in big-name 3D printers and other common applications.

[Bo] tested each motor with two different drivers: the TMC2209 silent driver to start with, and because he released the Magic Smoke from those, the higher current TB6600 module. The difference between the two drivers was striking, with lower torque and top speeds for the same settings on each motor using the TB6600, as well as more variability in the data. Motors did better across the board with the TBC6600 at 24 volts, showing improved torque at higher speeds, and slightly higher top speeds. He also tested the effect of microstepping on torque using the TBC6600 and found that using full steps resulted in higher torque across a greater speed range.

At the end of the day, it seems as if these tests say more about the driver than they do about any of the motors tested. Perhaps the lesson here is to match the motor to the driver in light of what the application will be. Regardless, it’s a nice piece of work, and we really appreciate the dyno design to boot — reminds us of a scaled-down version of the one [Jeremey Fielding] demonstrated a few years back.

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Hackaday Links: June 30, 2024

June 30, 2024 by 14 Comments

A couple of weeks back we featured a story (third item) about a chunk of space jetsam that tried to peacefully return to Earth, only to find a Florida family’s roof rudely in the way. The 700-gram cylinder of Inconel was all that was left of a 2,360-kg battery pack that was tossed overboard from the ISS back in 2021, the rest presumably turning into air pollution just as NASA had planned. But the surviving bit was a “Golden BB” that managed to slam through the roof and do a fair amount of damage. At the time it happened, the Otero family was just looking for NASA to cover the cost of repairs, but now they’re looking for a little more consideration. A lawsuit filed by their attorney seeks $80,000 to cover the cost of repairs as well as compensation for the “stress and impact” of the event. This also seems to be about setting a precedent, since the Space Liability Convention, an agreement to which the USA is party, would require the space agency to cover damages if the debris had done damage in another country. The Oteros think the SLC should apply to US properties as well, and while we can see their point, we’d advise them not to hold their breath. We suppose something like this had to happen eventually, and somehow we’re not surprised to see “Florida Man” in the headlines.

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Spinning Magnets Do Your Dice Rolling For You

June 28, 2024 by 6 Comments

Dice are about the simplest machines possible, and they’ve been used since before recorded history to generate random numbers. But no machine is so simple that a little needless complexity can’t make it better, as is the case with this mechanical spinning dice. Or die. Whatever.

Inspiration for the project came from [Attoparsec]’s long history with RPG and tabletop games, which depend on different kinds of dice to generate the randomness that keeps them going — that and the fortuitous find of a seven-segment flip-dot display, plus the need for something cool to show off at OpenSauce. The flip-dot is controlled by an array of neodymium magnets with the proper polarity to flip the segments to the desired number. The magnets are attached to an aluminum disk, with each array spread out far enough to prevent interference. [Attoparsec] also added a ring of magnets to act as detents that lock the disk into a specific digit after a spin.

The finished product ended up being satisfyingly clicky and suitably random, and made a good impression at OpenSauce. The video below documents the whole design and build process, and includes some design dead-ends that [Attoparsec] went down in pursuit of a multiple-digit display. We’d love to see him revisit some of these ideas, mechanically difficult though they may be. And while he’s at it, maybe he could spice up the rolls with a little radioactivity.

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