Switch Mod Fixes Fiddly Car Door Projector

September 2, 2026 by Tom Nardi 2 Comments

While the Citroën logo they project onto the pavement looks great, [OrangeTungsten] wasn’t thrilled with how their door-mounted projectors actually functioned. The mechanism for detecting when they should kick on was a bit too clever for its own good, and needed to be simplified a bit. Luckily for us, the process was meticulously documented for anyone else who might find themselves in a similar situation.

Originally, the projector detected when it should turn on by sensing the presence of a tiny magnet using a Hall effect sensor. There are certainly some advantages to this approach, but in practice, [OrangeTungsten] says the retrofitted magnet would keep falling off and leaving the projector inoperative. The fix was simple enough: figure out how the circuit worked, pull out the Hall effect sensor, and replace it with a simple button that would physically make contact with the door frame.

It’s not a terribly complex fix, but it’s a clever solution and well documented, and that goes pretty far around these parts. We were also interested in this one because an examination of the electronics inside the projector uncovered a 8-pin microcontroller — the sole purpose of which would appear to be polling the Hall effect sensor and using its status to throw a transistor which in turn powers the LED.

It’s hard to believe that whoever designed this gadget couldn’t figure out how to turn an LED on and off without a MCU, but we’re living in strange times. We assume there’s some kind of justification for this, such as some flashing or fading effects, but [OrangeTungsten] never mentions the things doing anything more complex than simply turning on and off.

Whatever the rationale was behind the original design of these projectors, the important thing is that the application of some hardware from the parts bin got them up and working again, which is something we never get tired of seeing.

Has FDM 3D Printing Hit Its Peak?

September 2, 2026 by Jenny List 8 Comments

Over the time Hackaday has been in existence, the art of 3D printing has evolved from a relatively crude hit-and-miss affair to something approaching what we all imagined back then. You can’t yet walk up to a Star Trek replicator and ask for a part, but a modern state of the art consumer or prosumer grade printer will deliver consistent high-resolution parts, and in a surprisingly short time. [The Next Layer] asks whether consumer FDM printers have now reached the point at which they’re about as good as they’re going to get, and whether other technologies hold the future.

It’s a fair point to make that the resolution of a consumer FDM printer may be close to its mechanical limit. Techniques such as input shaping and the adoption of better CoreXY mechanisms mean that prints which once might have relied on SLA can be done in FDM. Healthy competition in the marketplace has delivered high quality colour printing, with tool-changing printers being no longer solely the preserve of the professional. He uses the example of a mobile phone to make the point that new machines have less of a wow factor to deliver, as increments have become less grand.

It’s a persuasive argument, and looking at the printers around us we can see it in action. The difference in ability between a 2020-ish and a 2026 FDM printer are far smaller than those between the same time periods in the last decade. Compare a MakerBot Cupcake and an Ultimaker II, or the Ultimaker and a Prusa Mini, and each is light years ahead of the last. But the best the Mini can do is surprisingly not as far behind as you’d expect to that of their latest, or of the equivalent from Bambu Labs.

Does this means that nothing new is coming in 3D printing? Of course not. UV printing is coming through and will deliver incredible results, as will SLS printing. It’s interesting he devotes little time to SLA printing, perhaps because it’s not as easy a process as FDM. He makes the point that we’ve never had it so good, as the high-end FDM features will appear in modestly priced machines, and we have those other technologies to look forward to.

It’s an interesting discussion, and you can see it below the break.

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Doubling Thermal Printer Resolution By Wiggling

September 2, 2026 by Maya Posch 3 Comments

Insides of the Sears 12 calculator. (Credit: Danalog, YouTube)

Thermal printers are still extremely common today, using small heating elements in combination with temperature-sensitive paper to create a dot matrix-like effect without messing with ink ribbons and complex mechanisms. Of course, even with just a line of elements you still needed one of these per pixel, which at least in the 1970s when the Sears 12 calculator was released added significantly to the cost. The solution here was to wiggle the elements, doubling the resolution of the print head, as detailed in this video by [Danalog].

Using a contemporary Texas Instruments TI-5015 calculator as comparison with its non-wiggling print head, it’s easy to see the advantages here. In an era where electronic calculators didn’t have displays but a thermal printer, this print quality was the selling point, yet adding more thermal elements added to the price tag of the final device and more complexity to the design in terms of driving circuitry.

In this regard adding a way to make the print head move side-to-side at a set rate and tying this fact into the printing would save about half of that circuitry. Inside the Sears 12 is a fairly standard Mitsubishi M58671 calculator IC, but also the whole printer mechanism. When operating, as demonstrated in the video with the cover removed, you can see the whole print head moving rapidly.

With this mechanism this much cheaper Sears 12 definitely gives the TI-5015 a run for its money, even if as noted by [Danalog] the timing would go off a bit after a longer session, resulting slightly wavy printing. Presumably with the massive cost savings of buying a Sears calculator over a TI one, this was deemed an acceptable trade-off.

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Harvesting Namib Desert Fog With High Voltage

September 2, 2026 by Maya Posch 10 Comments

As fun as mucking about with simulated environments in a laboratory is, at some point you have to do those field tests to demonstrate that your prototype actually works in the real world, under real conditions. This is what the [Plasma Channel] recently did for their fog harvesting system by setting it up in the Namib desert.

We previously covered the atmospheric water harvesting attempts, using electrostatic precipitation to draw the moisture in the air onto the collectors where it can then be harvested. This is rather different from existing approaches with e.g. fine meshes and hoping that enough water molecules bump into your mesh, so theoretically it should be much more efficient. In the lab it worked well, but reality always has the last word.

The Namib desert is at the top of the world’s most arid regions, competing with the Atacama desert. What it does have going for it is regular fog rolling in that lasts until sunrise, providing a good target for water harvesting. Interestingly, this field test was performed together with the University of Namibia.

Of course, moving the prototype in check-in luggage for the flight to Namibia took some redesigning and testing. Fortunately everything, including the solar panel, arrived intact, allowing trials to commence. This initially took place at the campus of the University of Namibia, joining a number of other atmospheric water harvesting projects that had been previously installed there.

Unfortunately the fog proved to be rather elusive, leading to a few fruitless attempts. It also proved that the salt in the air from the ocean spray, even a few kilometers inland, was highly corrosive, especially to high-voltage electronics. Although the system basically worked, happily harvesting water under the right conditions, it does need some redesign before it’ll be tested next in the Atacama desert.

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FLOSS Weekly Episode 880: The Two Wolves

September 2, 2026 by Jonathan Bennett No comments

This week Jonathan chats with Benjamin Samuels of Trail of Bits! The conversation focuses on Patch the Planet, a new initiative to help Open Source projects deal with the fallout from AI coding and vulnerability research. What’s the unexpected dichotomy driving the polarized response to LLMs? And what does the future look like for Open Source in the age of AI? Watch to find out!

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How A 1981 RAM Expansion Worked

September 2, 2026 by Jenny List 25 Comments

Sir Clive Sinclair and his company were notorious for pushing the limits of electronic parts in search of a low price, and his ZX series 8-bit computers were fine examples of this art. The ZX81 came with a meagre 1K of memory, and a popular upgrade was a 16K RAM pack. [Happy Little Diodes] has opened one up, and to his surprise, found many more parts than expected.

Inside the box is a pair of PCBs connected by ribbon cables, one of which has a selection of 74 chips and the other the 4116 RAM chips and a discrete component power circuit. This complexity comes from that cheapness, the 4116 is an inexpensive DRAM chip and requires an eclectic set of power supplies.

The functions of address selection are straightforward enough, as is the DRAM refresh circuitry. The power supply is clever in that it’s a self-oscillating switcher that provides +12 and -5 volts with a single transistor. We particularly like the quench diode in the 12 V Zener diode regulator circuit.

The ZX81 gave a huge number of British kids their first taste of computing, and learning to use a limited memory space is something that stays with you for life. The film doesn’t mention the most notorious feature of the 16K pack though, that it had been developed with a machine clamped to the desk. Using one in a real-life location was an exercise in not jogging your machine, because the slightest disturbance would trigger a reset.

The ’81 was also famous for its membrane keyboard. Another popular upgrade back then was a new one.

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“I’m Not Dead Yet!” Reverse Polish Notation Calculators You Can Still Buy

September 2, 2026 by Al Williams 52 Comments

If you used a scientific calculator in the 1970s or 1980s, there was a fair chance that it worked differently from almost every calculator you see today. Instead of typing:

2 + 3 =

you entered:

2 ENTER 3 +

There wasn’t even an equals key. Hewlett-Packard made this system — Reverse Polish Notation, or RPN — practically synonymous with serious scientific calculators until other players like TI and Casio got serious. Once you got used to it, ordinary algebraic calculators could feel annoyingly clumsy.

Today, RPN calculators look like a nearly extinct species. HP left the calculator market, licensing the HP calculator line to Moravia Consulting. Old HP-15Cs, 16Cs, 32Ss, 42Ss, and 48s have become collectibles. But RPN isn’t dead. You can still buy new hardware, build your own, or turn almost any computer or phone into a very capable RPN machine. There are reasons some of us still want to.

But Why Polish?

The name goes back to Polish logician [Jan Łukasiewicz], who devised a notation in which operators precede their operands. Instead of writing:

A + B

you can write:

+ A B

The big advantage is that parentheses aren’t required. The structure of the expression tells you exactly what operates on what. Reverse Polish notation simply puts the operator at the other end:

A B +

[Łukasiewicz] wasn’t designing calculators, of course, but the same idea turned out to be extremely convenient for computers and calculators. Your software doesn’t have to remember what operation is in progress. Each operator is ready to go and can simply work on the operands that you’ve already read.

RPN isn’t exactly the way people calculate with pencil and paper, and it certainly wasn’t derived from the slide rule, but there is a similarity in the way you work. With a slide rule, you generally establish some value, operate on it, and continue from the result. When doing a long-hand calculation, you often calculate a subexpression, write down the answer, and use that answer in the next step. You will probably start with the inner parenthesis and work outward, just like someone with an RPN calculator does. RPN formalizes that process with a stack.

Suppose you want:

(3 + 4) × (5 + 6)

On a conventional calculator, you either need parentheses, or you have to calculate one result and remember it. On an RPN calculator:

3 ENTER

4 +

5 ENTER

6 +

×

The first + leaves 7 on the stack. The second leaves 11 above it. The multiply consumes both and leaves 77.

Notice what’s missing: parentheses, an equals key, and any need to tell the calculator about precedence. This isn’t much of a win for a five-key calculation. It becomes more apparent with something like computing the value of a bunch of parallel resistors:

R=1/(1/R1+1/R2+1/R3…)

An RPN user can calculate each reciprocal, add it to the running result on the stack, and finally take the reciprocal. Intermediate answers stay in the calculator naturally instead of being stuffed into memory registers or enclosed in increasingly impressive collections of parentheses.

Is RPN better? Calculator users have been arguing about that for half a century. But once RPN gets wired into your fingers, it can be surprisingly hard to give up.

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