Doubling Thermal Printer Resolution By Wiggling

September 2, 2026 by 20 Comments
Insides of the Sears 12 calculator. (Credit: Danalog, YouTube)
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 23 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 1 Comment

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 56 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 69 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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HDMI For The Color Computer 2

September 2, 2026 by 8 Comments

[Scott Baker] bought a TRS-80 Color Computer off eBay some five years ago. He’d always intended to add a CoCoVGA or CoCoDV upgrade to hook it up to a monitor, but the device was sold out and his name never made it off the waitlist. Thus, he decided to build his own solution to give the classic machine a proper HDMI output.

The concept behind the project is simple enough—grab the digital signals that feed the MC6847 IC responsible for generating the analog video output, and use them to create an all-digital video output over HDMI. [Scott] achieved this by using a Tang Nano board, which hosts a Gowin GW1N-1 FPGA. It’s able to snoop the signals heading to the MC6847 and, with some supporting components and level shifters, it can spit out video befitting modern screens. To make the system nicely complete, an analog-to-digital converter is also included to pick up the analog sound output from the TRS-80 and spit it out down the same HDMI cable. Such convenience!

There’s something strangely anachronistic about grabbing a TRS-80 off the shelf and hooking it up to a flatscreen with a single HDMI cable. Regardless, it’s a pretty great way to play with your old machine without having to futz with heavy old CRTs. We’ve featured plenty of similar projects before, too. Continue reading “HDMI For The Color Computer 2” →

Creating The Greenest Possible Clothing With Living Fungi

September 2, 2026 by 22 Comments

Despite the wide variety of fabrics used for our clothing, they all share the property of not being living tissues. This could be due to them never having been part of an organism, or having been removed from said organism. Another approach here entails so-called engineered living materials (ELMs), with a recent research article by [Ke Li] et al. in Science Advances providing a good example of a fungal platform for such living textiles.

Although it may seem frivolous to create something like this, the direct benefits would be to have a fabric that can self-heal and respond to its environment, including blocking UV radiation and changing its coloring through pigmentation.

The research demonstrated in this paper covers essentially a platform for creating a living textile that can be adapted to a wide variety of applications and colorizations. Of note is that the researchers have not yet tested aspects like washability, abrasion resistance, breathability and wearer comfort, so this should definitely be regarded as setting the stage for more research.

For the basic material the fungi Cordyceps militaris was chosen, which were subsequently placed between films. To this additional microbial cultures were added, including the pigment-producing S. cerevisiae and melanized A. niger for UV blocking.

As for what it can look like with clothing, this article at De Zeen gives somewhat of an idea, as well as how the living textile is prepared.