[Shelby] at Tech Tangents recently wrapped a project / obsession to obtain an old HP ScanJet 4C, get it running on a PC and put it through its paces. After after nearly five years, three scanners, and untold SCSI cards and drivers later, he finally succeeded. The first big problem was getting a working scanner. These don’t stand up well to shipping, and one arrived with broken mirrors. And when he finally got one that worked, sorting out SCSI controller and driver issues was surprisingly complicated, though ultimately successful.
The HP ScanJet 4C was introduced in 1995, and was notable for its scanning quality, its resolution ( 2400 DPI interpolated / 600 DPI optical ), and selling for under $1000. Except for replacement parts concerns, particularly the customized triphosphor fluorescent bulb assembly, it would still be a very competent scanner today. For this reason, [Shelby] will not be using it as his daily use scanner. Continue reading “Deep Dive Into The HP ScantJet 4C”→
Moore’s law isn’t strictly holding anymore, but it is still true that most computing systems are at least trending towards lower cost over time, if not also slightly smaller size. This means wider access to less expensive hardware, even if that hardware is still an 8-bit microcontroller. While some move on to more powerful platforms as a result of this trend, there are others still fighting to push these platforms to the edge. [lcamtuf] has been working to this end, stretching a small AVR microcontroller to not only play a classic video game, but to display it on a color display. Continue reading “Pushing Crates In 8-bit Color”→
A regular pair of pliers is fine most of the time, but for delicate work with squarish objects you can’t go wrong with a pair of parallel pliers. [Neil Paskin] decided to make his own pair from scratch. (YouTube)
The jaws were machined down from round stock in [Paskin]’s mill before heat treating and tempering. The steel portions of the handles were cut from 16 gauge plate steel and half of them were stamped on a fly press to make the bridging section around the pivot bolt. The filler for the handles is copper on one side and brass on the other as [Paskin] didn’t have enough brass of the correct size to do both.
The steel and filler were joined with epoxy and copper pins before beveling the edges and sanding to give a comfortable contour to the handles. The bolts for the pliers started as ordinary hex bolts before being machined down on the lathe to a more aesthetically-pleasing shape and size. The final touches included electrolytically etching a logo into the bridge and then spraying down the pliers with a combination lubricant and corrosion preventative spray. This is surely a pair of pliers worth handing down through the generations.
Over the past two decades, e-paper has evolved from an exotic and expensive display technology to something cheap enough to be used for supermarket price tags. While such electronic shelf labels are now easy to find, actually re-using them is often tricky due to a lack of documentation. Luckily, [Aaron Christophel] has managed to reverse engineer many types of shelf labels, and he’s demonstrated the results by turning one into an ultra-low-power clock called Triink. It’s based on a 128×296 pixel e-ink display paired with an nRF52832 BlueTooth Low-Energy SoC and uses just 65 micro-amperes on average: low enough to keep it running for more than a year on a single battery charge.
The clock is housed in an enclosure that’s simple but effective: a 3D-printed triangular prism with a slot for the screen and space for the 18650 lithium battery. One side can be opened to access the internal components, although that’s really only needed to charge the battery. You can see how cleverly everything snaps together in the video embedded below. Continue reading “Low Power Challenge: E-Paper Shelf Label Becomes Ultra-Frugal Clock”→
HF radios often use toroidal transformers and winding them is a rite of passage for many RF hackers. [David Casler, KE0OG] received a question about how they work and answered it in a recent video that you can see below.
Understanding how a conventional transformer works is reasonably simple, but toroids often seem mysterious because the thing that makes them beneficial is also what makes them confusing. The magnetic field for such a transformer is almost totally inside the “doughnut,” which means there is little interaction with the rest of the circuit, and the transformer can be very efficient.
The toroid itself is made of special material. They are usually formed from powdered iron oxide mixed with other metals such as cobalt, copper, nickel, manganese, and zinc bound with some sort of non-conducting binder like an epoxy. Ferrite cores have relatively low permeability, low saturation flux density, and low Curie temperature. The powder also reduces the generation of eddy currents, a source of loss in transformers. Their biggest advantage is their high electrical resistivity, which helps reduce the generation of eddy currents.
If you haven’t worked through how these common little transformers work, [David]’s talk should help you get a grip on them. These aren’t just for RF. You sometimes see them in power supplies that need to be efficient, too. If you are too lazy to wind your own, there’s always help.
Join Editor-in-Chief Elliot Williams and Managing Editor Tom Nardi as they explore the best and most interesting stories from the last week. The top story if of course the possibility that at least some of the unidentified flying objects the US Air Force valiantly shot down were in fact the work of amateur radio enthusiasts, but a quantitative comparison of NASA’s SLS mega-rocket to that of popular breakfast cereals is certainly worth a mention as well.
Afterwards the discussion will range from modular home furnishings to the possibility of using YouTube (or maybe VHS tapes) to backup your data and AI-generated Pong. Also up for debate are cheap CO2 monitors which may or may not be CO2 monitors, prosthetic limbs made from locally recycled plastic, and an answer to Jenny’s Linux audio challenge from earlier this month.
Check out the links below if you want to follow along, and as always, tell us what you think about this episode in the comments!
Ever since the first artificial satellite was launched into orbit, radio operators around the world have been tuning in to their space-based transmissions. Sputnik 1 only sent back pulses of radio waves, but in the decades to follow ever more advanced radio satellites were put into service that could support two-way communications from Earth to space and back again.
Pirates on these satellites have typically used them for illicit activities, and it is still illegal to use them for non-governmental or non-military purposes, so [Gabe] notes that he will only be receiving, not transmitting. The signals he is tuning in to are VHF transmissions, specifically around 220 MHz. That puts them easily within the reach of the RTL-SDR and common ham radio equipment, but since they are coming from space a more directional antenna is needed. [Gabe] quickly builds a Yagi antenna from scrap, tuned specifically to 255 MHz, and mounts it to an old remote-controlled security camera mount which allows him to point it exactly at the satellite and monitor transmissions.
From there he is able to pick up what looks like a few encrypted and/or digital transmissions, plus analog transmissions of likely pirates speaking a language he guesses to be Portuguese. He also hears what he thinks is a foreign TV broadcast, but oddly enough turns out to be NPR. These aren’t the only signals in space to tune to, either. There are plenty of purpose-built ham radio satellites available for any licensed person to use, and we’ve also seen this other RTL-SDR configured to snoop on Starlink signals.