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.

youtube.com/embed/cMhvfIiR5gs?…

Thanks to [Keith] for the tip!

hackaday.com/2025/05/15/automa…

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.

The term ‘laser-assisted etching’ is generally used for e.g. glass etching with HF or KOH in combination with a femtosecond laser to realize high-resolution optical features, ‘selective laser etching’ where the etchant is assisted by the laser-affected material, or the related laser-induced etching of hard & brittle materials. Beyond these there is a whole world of laser-induced or laser-activated etching or functionalized methods, all of which require that the chemical- and laser-based steps are used in unison.

Aside from this, the use of chemicals to etch away soldermask and copper does of course leave one with a similar messy clean-up as when etching new PCBs, but it can provide more control due to the selective etching, as a CNC’s carbide bit will just as happily chew through FR4 as copper. When reverse-engineering a PCB you will have to pick whatever method works best for you.

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

hackaday.com/2025/05/15/laced-…

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.

youtube.com/embed/X1sDYBe5wY0?…

Thanks [Fl.xy] for the tip!

hackaday.com/2025/05/15/mylar-…

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).
The 640 kB user area, 384 kB system area, and almost 64 kB of HMA in a PC (80286 or above)
Because of its transient nature, XMS wasn’t very useful for code, but it was a way to store data. If you weren’t using it, you could load some TSRs into the HMA to prevent taking memory from MSDOS.

Protected Mode Hacks

There is another way to access memory above the 1 MB line: protected mode. In protected mode, you still have a segment and an offset, but the segment is just an index into a table that tells you where the segment is and how big it is. The offset is just an offset into the segment. So by setting up the segment table, you can access any memory you like. You can even set up a segment that starts at zero and is as big as all the memory you can have.
A protected mode segment table entry
You can use segments like that in a lot of different ways, but many modern operating systems do set them up very simply. All segments start at address 0 and then go up to the top of user memory. Modern processors, 80386s and up, have a page table mechanism that lets you do many things that segments were meant to do in a more efficient way.

However, MS-DOS can’t deal with any of that directly. There were many schemes that would switch to protected mode to deal with upper memory using EMS or XMS and then switch back to real mode.

Unfortunately, switching back to real mode was expensive because, typically, you had to set a bit in non-volatile memory and reboot the computer! On boot, the BIOS would notice that you weren’t really rebooting and put you back where you were in real mode. Quite a kludge!

There was a better way to run MSDOS in protected mode called Virtual86 mode. However, that was complex to manage and required many instructions to run in an emulated mode, which wasn’t great for performance. It did, however, avoid the real mode switch penalty as you tried to access other memory.

Unreal Mode

In true hacker fashion, several of us figured out something that later became known as Unreal Mode. In the CPU documentation, they caution you that before switching to real mode, you need to set all the segment tables to reflect what a segment in real mode looks like. Obviously, you have to think, “What if I don’t?”

Well, if you don’t, then your segments can be as big as you like. Turns out, apparently, some people knew about this even though it was undocumented and perhaps under a non-disclosure agreement. [Michal Necasek] has a great history about the people who independently discovered it, or at least, the ones who talked about it publicly.

The method was doomed, though, because of Windows. Windows ran in protected mode and did its own messing with the segment registers. If you wanted to play with that, you needed a different scheme, but that’s another story.

Modern Times

These days, we don’t even use video cards with a paltry 1 MB or even 100 MB of memory! Your PC can adroitly handle tremendous amounts of memory. I’m writing this on a machine with 64 GB of physical memory. Even my smallest laptop has 8 GB and at least one of the bigger ones has more.

Then there’s virtual memory, and if you have solid state disk drives, that’s probably faster than the old PC’s memory, even though today it is considered slow.

Modern memory systems almost don’t resemble these old systems even though we abstract them to pretend they do. Your processor really runs out of cache memory. The memory system probably manages several levels of cache. It fills the cache from the actual RAM and fills that from the paging device. Each program can have a totally different view of physical memory with its own idea of what physical memory is at any given address. It is a lot to keep track of.

Times change. EMS, XMS, and Unreal mode seemed perfectly normal in their day. It makes you wonder what things we take for granted today will be considered backward and antiquated in the coming decades.

hackaday.com/2025/05/15/rememb…

Vi segnalo questo podcast in cui se n'è parlato:

Lo trovate un po' su tutte le piattaforme, compreso su Antenna Pod.

In particolare, si spiega perché il testo legato alla raccolta firme che sta girando non è accurato.

open.spotify.com/episode/2QAdk…

#MatrimonioEgualitario #matrimonio #diritti #EQUITA #referendum #gaymarriage #samesexmarriage #Matrimoniogay #lgbtquia #lgbt #italia #repubblicadellebanane

Un nuovo referendum in vista

Closer · Episode

^{Un nuovo referendum in vista (Spotify)}

Qualcuno esperto in #legge , magari un #avvocato, mi aiuti a capire, per favore.

Tutto felice e contento ho firmato il referendum di cui si parla, condiviso da alcuni amici, ma sembrerebbe che sia addirittura controproducente una raccolta firme. Che fare, in questo caso? Sarà corretto quello che dice la rete Lenford? (fonte in chiusura del post).

Sono davvero amareggiato e confuso.

"NON ESISTE UN REFERENDUM SUL MATRIMONIO TRA PERSONE DELLO STESSO SESSO
In questi giorni sta circolando online la richiesta di firme per un referendum, che viene descritto dal partito promotore con queste parole: ‘si firma per il referendum sul matrimonio delle coppie same sex’.
Non è così.
Anche se si raccogliessero almeno 500.000 firme entro il 3 agosto 2025 e anche se il referendum venisse giudicato ammissibile (e, quindi, effettivamente proponibile) dalla Corte costituzionale, un esito favorevole nelle urne NON introdurrebbe in Italia il matrimonio per coppie formate da persone dello stesso sesso.
Quel referendum, infatti, vuole mantenere le unioni civili introdotte nel 2016, eliminando le parti che le differenziano dal matrimonio anche rispetto alla filiazione.
La conseguenza di una vittoria dei ‘SÌ’ sarebbe, perciò, questa: le coppie same sex potrebbero continuare soltanto a unirsi civilmente, parificando gli effetti della loro unione a quelli matrimoniali, ma non potrebbero sposarsi.
Questo è un punto che deve essere molto chiaro e che Rete Lenford, nata nel 2007 proprio con la campagna ‘Affermazione civile’ volta a introdurre in Italia il matrimonio per persone dello stesso sesso, ha il dovere di chiarire pubblicamente, a seguito di decine di richieste che ci stanno giungendo nelle ultime ore.
Nei prossimi giorni, e con ampio margine di anticipo rispetto alla scelta che potrà essere fatta sulla firma della proposta referendaria, Rete Lenford lavorerà a una nota illustrativa con uno sguardo ‘bifocale’:
1) tecnico, per un approfondimento sui singoli quesiti e sulla loro dubbia ammissibilità, anche (e soprattutto) per le contraddittorie conseguenze in punto di filiazione, specialmente con riguardo alle coppie conviventi e alla legge sulla procreazione medicalmente assistita (la quale, anche dopo il referendum, continuerebbe a mantenere il requisito esplicito della ‘diversità di sesso’ della coppia richiedente);
2) politico, per le significative implicazioni che questo referendum potrebbe generare sia sul percorso di introduzione del ‘matrimonio same sex’, sia su quello di riconoscimento delle famiglie omogenitoriali.
Naturalmente, e anche al fine di elaborare una posizione condivisa in vista del termine del 3 agosto prossimo, non mancheremo di attivare un confronto con le altre realtà associative, tenute sorprendentemente escluse da questa iniziativa partitica.
Nel frattempo, ci è risultato doveroso prenderci del tempo, ma allo stesso tempo chiarire sin da subito quale sarebbe l’esito del referendum, così da favorire soltanto firme consapevoli da parte di chi, già in questi giorni, decidesse di non aspettare una elaborazione delle realtà LGBT+ e volesse esprimere online la propria posizione."

facebook.com/Rete.Lenford/post…

@Alberto

#lgbt
#LGBTQIA #samesexmarriage #MatrimonioEgualitario

Rete Lenford - Avvocatura per i diritti LGBTI+

NON ESISTE UN REFERENDUM SUL MATRIMONIO TRA PERSONE DELLO STESSO SESSO In questi giorni sta circolando online la richiesta di firme per un referendum, che viene descritto dal partito promotore con...

^{www.facebook.com}