Day: May 15, 2025

Not A Sewing Machine: A Multimedia Briefcase

May 15, 2025 by 11 Comments

When you think of Singer, you usually think of sewing machines, although if you are a history buff, you might remember they diversified into calculators, flight simulation, and a few other odd businesses for a while. [Techmoan] has an unusual device from Singer that is decidedly not a sewing machine. It is a 1970s-era multimedia briefcase called the Audio Study Mate. This odd beast, as you can see in the video below, was a cassette player that also included a 35mm filmstrip viewer. Multimedia 1970s-style!

The film strip viewer is a bright light and a glass screen with some optics. You have to focus the image, and then a button moves the film one frame. However, that’s for manual mode. However, the tape could encode a signal to automatically advance the frame. That didn’t work right away.

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Voyager 1’s Primary Thrusters Revived Before DSN Command Pause

May 15, 2025 by 43 Comments

As with all aging bodies, clogged tubes form an increasing issue. So too with the 47-year old Voyager 1 spacecraft and its hydrazine thrusters. Over the decades silicon dioxide from an aging rubber diaphragm in the fuel tank has been depositing on the inside of fuel tubes. By switching between primary, backup and trajectory thrusters the Voyager team has been managing this issue and kept the spacecraft oriented towards Earth. Now this team has performed another amazing feat by reviving the primary thrusters that had been deemed a loss since a heater failure back in 2004.

Unlike the backup thrusters, the trajectory thrusters do not provide roll control, so reviving the primary thrusters would buy the mission a precious Plan B if the backup thrusters were to fail. Back in 2004 engineers had determined that the heater failure was likely unfixable, but over twenty years later the team was willing to give it another shot. Analyzing the original failure data indicated that a glitch in the heater control circuit was likely to blame, so they might actually still work fine.

To test this theory, the team remotely jiggled the heater controls, enabled the primary thrusters and waited for the spacecraft’s star tracker to drift off course so that the thrusters would be engaged by the onboard computer. Making this extra exciting was scheduled maintenance on the Deep Space Network coming up in a matter of weeks, which would have made troubleshooting impossible for months.

To their relief the changes appears to have worked, with the heaters clearly working again, as are the primary thrusters. With this fix in place, it seems that Voyager 1 will be with us for a while longer, even as we face the inevitable end to the amazing Voyager program.

Automatic Transmission For Manual Transportation

May 15, 2025 by 31 Comments

The drivetrain of most modern bicycles has remained relatively unchanged for nearly a century. There have been marginal upgrades here and there like electronic shifting but you’ll still mostly see a chain with a derailleur or two. [Matthew] is taking a swing at a major upgrade to this system by replacing the front derailleur with a torque converter, essentially adding an automatic transmission to his bicycle.

Most of us will come across a torque converter in passenger vehicles with automatic transmissions, but these use fluid coupling. [Matthew] has come up with a clever design that uses mechanical coupling instead using a ratchet and pawl mechanism. There are two gear ratios here, a 1:1 ratio like a normal bicycle crank and a 1.5:1 ratio that is automatically engaged if enough torque is applied to the pedals. This means that if a cyclist encounters a hill, the gear automatically shifts down to an easier gear and then will shift back once the strenuous section is finished.

[Matthew] machined all the parts for this build from scratch, and the heavy-duty solid metal parts are both impressive but also show why drivetrains like this haven’t caught on in the larger bicycling world since they’re so heavy. There have been some upgrades in internally geared hubs lately though, which do have a number advantages over traditional chain and derailleur-based bikes with the notable downside of high cost, and there have been some other interesting developments as well like this folding mechanical drivetrain and this all-electric one.

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Exposed inner copper on multilayer PCB. (Credit: mikeselectricstuff, YouTube)

LACED: Peeling Back PCB Layers With Chemical Etching And A Laser

May 15, 2025 by 8 Comments

Once a printed circuit board (PCB) has been assembled it’s rather hard to look inside of it, which can be problematic when you have e.g. a multilayer PCB of an (old) system that you really would like to dissect to take a look at the copper layers and other details that may be hidden inside, such as Easter eggs on inner layers. [Lorentio Brodeso]’s ‘LACED’ project offers one such method, using both chemical etching and a 5 Watt diode engraving laser to remove the soldermask, copper and FR4 fiberglass layers.

This project uses sodium hydroxide (NaOH) to dissolve the solder mask, followed by hydrogen chloride (HCl) and hydrogen peroxide (H2O2) to dissolve the copper in each layer. The engraving laser is used for the removing of the FR4 material. Despite the ‘LACED’ acronym standing for Laser-Controlled Etching and Delayering, the chemical method(s) and laser steps are performed independently from each other.

This makes it in a way a variation on the more traditional CNC-based method, as demonstrated by [mikeselectricstuff] (as shown in the top image) back in 2016, alongside the detailed setup video of how a multi-layer PCB was peeled back with enough resolution to make out each successive copper and fiberglass layer.

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Mylar Space Blankets As RF Reflectors

May 15, 2025 by 11 Comments

Metalized Mylar “space blankets” are sold as a survivalist’s accessory, primarily due to their propensity for reflecting heat. They’re pretty cheap, and [HamJazz] has performed some experiments on their RF properties. Do they reflect radio waves as well as they reflect heat? As it turns out, yes they do.

Any antenna system that’s more than a simple radiator relies on using conductive components as reflectors. These can either be antenna elements, or the surrounding ground acting as an approximation to a conductor. Radio amateurs will often use wires laid on the ground or buried within it to improve its RF conductivity, and it’s in this function that he’s using the Mylar sheet. Connection to the metalized layer is made with a magnet and some aluminium tape, and the sheet is strung up from a line at an angle. It’s a solution for higher frequencies only due to the restricted size of the thing, but it’s certainly interesting enough to merit further experimentation.

As you can see in the video below, his results are derived in a rough and ready manner with a field strength meter. But they certainly show a much stronger field on one side resulting from the Mylar, and also in an antenna that tunes well. We would be interested to conduct a received signal strength test over a much greater distance rather than a high-level field strength test so close to the antenna, but it’s interesting to have a use for a space blanket that’s more than just keeping the sun away from your tent at a hacker camp. Perhaps it could even form a parabolic antenna.

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Remembering More Memory: XMS And A Real Hack

May 15, 2025 by 28 Comments

Last time we talked about how the original PC has a limit of 640 kB for your programs and 1 MB in total. But of course those restrictions chafed. People demanded more memory, and there were workarounds to provide it.

However, the workarounds were made to primarily work with the old 8088 CPU. Expanded memory (EMS) swapped pages of memory into page frames that lived above the 640 kB line (but below 1 MB). The system would work with newer CPUs, but those newer CPUs could already address more memory. That led to new standards, workarounds, and even a classic hack.

XMS

If you had an 80286 or above, you might be better off using extended memory (XMS). This took advantage of the fact that the CPU could address more memory. You didn’t need a special board to load 4MB of RAM into an 80286-based PC. You just couldn’t get to with MSDOS. In particular, the memory above 1 MB was — in theory — inaccessible to real-mode programs like MSDOS.

Well, that’s not strictly true in two cases. One, you’ll see in a minute. The other case is because of the overlapping memory segments on an 8088, or in real mode on later processors. Address FFFF:000F was the top of the 1 MB range.

PCs with more than 20 bits of address space ran into problems since some programs “knew” that memory access above that would wrap around. That is FFFF:0010, on an 8088, is the same as 0000:0000. They would block A20, the 21st address bit, by default. However, you could turn that block off in software, although exactly how that worked varied by the type of motherboard — yet another complication.

XMS allowed MSDOS programs to allocate and free blocks of memory that were above the 1 MB line and map them into that special area above FFFF:0010, the so-called high memory area (HMA). Continue reading “Remembering More Memory: XMS And A Real Hack” →

Picture of self landing drone satellite with orange and black body. Propellors are extended.

FPV Drone Takes Off From A Rocketing Start

May 15, 2025 by 24 Comments

Launching rockets into the sky can be a thrill, but why not make the fall just as interesting? That is exactly what [I Build Stuff] thought when attempting to build a self-landing payload. The idea is to release a can sized “satellite” from a rocket at an altitude upwards of 1 km, which will then fly back down to the launch point.

The device itself is a first-person view (FPV) drone running the popular Betaflight firmware. With arms that swing out with some of the smallest brushless motors you’ve ever seen (albeit not the smallest motor), the satellite is surprisingly capable. Unfortunately due to concerns over the legality of an autonomous payload, the drone is human controlled on the descent.

Using collaborated efforts, a successful launch was flown with the satellite making it to the ground unharmed, at least for the most part. While the device did show capabilities of being able to fly back, human error led to a manual recovery. Of course, this is far from the only rocketry hack we have seen here at Hackaday. If you are more into making the flight itself interesting, here is a record breaking one from USC students.

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