Reverse Polish Notation And Its Mildly Confusing Elegance

October 24, 2017 by Jenny List 132 Comments

The best rummage sale purchase I ever made was a piece of hardware that used Reverse Polish Notation. I know what you’re thinking… RPN sounds like a sales gimmick and I got taken for a fool. But I assure you it’s not only real, but a true gem in the evolution of computing.

Sometime in the 1980s when I was a spotty teen, I picked up a calculator at a rummage sale. Protected by a smart plastic case, it was a pretty good condition Sinclair Scientific that turned out when I got it home to have 1975 date codes on its chips, and since anything with a Sinclair badge was worth having it became mine for a trifling amount of money. It had a set of corroded batteries that had damaged one of its terminals, but with the application of a bit of copper strip I had a working calculator.

And what a calculator! It didn’t have many buttons at a time when you judged how cool a scientific calculator was by the prolific nature of its keyboard. This one looked more akin to a run-of-the-mill arithmetic calculator, but had button modes for trigonometric functions and oddly an enter key rather than an equals sign. The handy sticker inside the case explained the mystery, this machine used so-called Reverse Polish Notation, or RPN. It spent several years on my bench before being reverently placed in a storage box of Sinclair curios which I’ve spent half a day turning the house over to find as I write this article.

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Are Microwave Guns For Real?

October 23, 2017 by Lewin Day 65 Comments

Almost exactly one year ago, [Kreosan] published a video detailing an EM “weapon” built out of three magnetrons, some batteries, and a taser. It all seemed a bit too good to be true, so [Allen] decided to try and replicate the results for himself.

[Kreosan]’s original video was impressive, showing everything from home stereos to a humble moped exploding when in the presence of their powerful device. However, many of those watching the video doubted the footage. Most criticism centered around the nature of the power supply to the magnetron falling short of the usual 700-1000W seen in a microwave oven.

Initial testing with a single magnetron. This setup could light the bulb at a distance of a few centimeters.

[Allen] starts by experimenting with a single magnetron, successfully using it to light a compact fluorescent bulb at a range of a few centimeters. Scaling up to the full triple magnetron setup with a cardboard and foil feedhorn, [Allen] is, at best, able to crash a calculator at a distance of a few feet.

The microwaves cause no explosions, and the device doesn’t seem to have anywhere near the 50-foot range claimed by [Kreosan] for their device. [Allen] puts forth the theory that the explosions seen in the original footage are far more likely to be from small firecrackers rather than any electronic components dying from microwaves.

Overall it’s a solid attempt to recreate someone else’s work to verify the results, a cornerstone of science. We did bristle somewhat at the valiant 18650 being described as a “vape battery”, however. For more microwave goodness, check out this attempt to recreate the TSA’s body scanners .

SegaPi Zero Shows Game Gear Some Respect

October 21, 2017 by Tom Nardi 15 Comments

If you were a gamer in 1991, you were presented with what seemed like an easy enough choice: you could get a Nintendo Game Boy, the gray brick with a slightly nauseating green-tinted screen that was already a couple of years old, or you could get yourself a glorious new Sega Game Gear. With full color display and games that were ported straight from Sega’s home consoles, it seemed like the Game Gear was the true future of portable gaming. But of course, that’s not how things actually went. In reality, technical issues like abysmal battery life held the Game Gear back, and conversely Nintendo and their partners were able to squeeze so much entertainment out of the Game Boy that they didn’t even bother creating a true successor for it until nearly a decade after its release.

While the Game Gear was a commercial failure compared to the Game Boy back in the 1990s and never got an official successor, it’s interesting to think of what may have been. A hypothetical follow-up to the Game Gear was the inspiration for the SegaPi Zeo created by [Halakor]. Featuring rechargeable batteries, more face buttons, and a “console” mode where you can connect it to a TV, it plays to the original Game Gear’s strengths and improves on its weaknesses.

As the name implies the SegaPi Zero is powered by the Raspberry Pi Zero, and an Arduino Pro Micro handles user input by tactile switches mounted behind all the face buttons. A TP4056 charging module and step-up converter are also hiding in there, which take care of the six 3.7 lithium-Ion 14500 batteries nestled into the original battery compartments. With a total capacity of roughly 4,500 mAh, the SegaPi Zero should be able to improve upon the 3 – 4 hour battery life that helped doom the original version.

There’s no shortage of projects that cram a Raspberry Pi into a classic game system, but more often than not, they tend to be Nintendo machines. It could simply be out of nostalgia for Nintendo’s past glories, but personally we’re happy to see another entry into the fairly short list of Sega hacks.

One Chip, Sixteen Times The RAM

October 20, 2017 by Jenny List 16 Comments

Have you ever upgraded your computer’s memory sixteen-fold, with a single chip? Tynemouth Software did for a classic Sinclair micro.

For owners of home computers in the early 1980s, one of the most important selling points was how much RAM their device would have. Sometimes though there just wasn’t much choice but to live with what you could afford, so buyers of Sinclair’s budget ZX81 computer had to put up with only 1 kiB of memory. The system bytes took up (by this writer’s memory) around 300 bytes, so user programs were left with only around 700 bytes for their BASIC code. They were aided by Sinclair’s BASIC keywords stored as single bytes, but still that was a limit that imposed coding economy over verbosity.

Sinclair sold a 16 kiB upgrade, the so-called “Rampack”, which located on the ’81’s edge connector and was notorious for being susceptible to the slightest vibration. Meanwhile the mainboard had provision for a 2 kiB chip as a drop-in that was never sold in the UK, and enterprising users could fit larger capacities with soldered combinations of other chips piggybacking the original. And this is what the Tynemouth people have done, they’ve replaced their machine’s dual 1 kiB x 4 chips with a single 62256, and with a bit of pin-bending they’ve managed to do it without the track-cutting that normally accompanies this mod.

Adding chips to a 36-year-old home computer for which there are plenty of available Rampacks might seem a bit of a niche, but in doing so they’ve made a standalone ’81 that’s just a little bit more useable. They’ve also brought a few other components up-to-date, with a composite video mod, switching regulator, and heatsink for the rare ULA chip. If you are of a Certain Generation, it might just bring a tear to your eye to see a ZX81 being given some love.

Did you lose your ZX81 along the way? How about emulating one in mbed?

Amiga Gets A PS/2 Keyboard Port

October 20, 2017 by Dan Maloney 30 Comments

Name any retrocomputer — Apple II, Sinclair, even TRS-80s — and you’ll find a community that’s deeply committed to keeping it alive and kicking. It’s hard to say which platform has the most rabid fans, but we’d guess Commodore is right up there, and the Amiga aficionados seem particularly devoted. Which is where this Amiga PS/2 mouse port comes from.

The Amiga was a machine that was so far ahead of its time that people just didn’t get it. It was a true multimedia machine before multimedia was even a thing, capable of sound and graphics that hold up pretty well to this day. From the looks of [jtsiomb]’s workstation, he’s still putting his Amiga to good use, albeit with an inconvenient amount of cable-swapping each time he needs to use it. The remedy this, [jtsiomb] put together an emulator that translates scancodes from an external PS/2 keyboard into Amiga keyboard signals. Embedded inside the Amiga case where it can intercept the internal keyboard connector, the emulator is an ATmega168 that does a brute-force translation by way of lookup tables. A switch on the back allows him to choose the internal keyboard or his PS/2 keyboard via a KVM switch.

Are Amigas really still relevant? As of two years ago, one was still running an HVAC system for a school. We’re not sure that’s a testament to the machine or more a case of bureaucratic inertia, but it’s pretty impressive either way.

[via r/electronics]

The Nixie Tube Killer That Never Was

October 19, 2017 by Dan Maloney 33 Comments

With the wealth of Nixie projects out there, there are points at which Hackaday is at risk of becoming Nixieaday. Nixie clocks, Nixie calculators, Nixie weather stations, and Nixie power meters have all graced our pages. And with good reason – Nixie tubes have a great retro look, and the skills needed to build a driver are a cut above calculating the right value for a series resistor for an LED display.

But not everyone loved Nixies back in the day, and some manufacturers did their best to unseat the venerable cold cathode tubes. [Fran Blanche] came across one of these contenders, a tiny cathode ray tube called the Nimo, and after a long hiatus in storage, she decided to put the tube to the test. After detailing some of the history of the Nimo and its somewhat puzzling marketing — its manufacturer, IEE, was already making displays to compete with Nixies, and seven-segment LEDs were on the rise at the time — [Fran] goes into the dangerous details of driving the display. With multiple supply voltages required, including a whopping 1,700 V DC for the anode, the Nimo was anything but trivial to integrate into products, which probably goes a long way to explaining why it never really caught on.

If you happen to have one of these little bits of solid unobtanium, [Fran]’s video below will go a long way to bringing back its ghostly green glow. You might say that [Fran] has a thing for oddball technologies of the late 60s — after all, she’s recreating the Apollo DSKY electroluminescent display, and she recently helped a model Sputnik regain its voice.

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DIY 9V Battery

October 19, 2017 by Al Williams 13 Comments

Volta’s pile — the first battery — was little more than silver and zinc discs separated by paper soaked in salt water. A classic classroom experiment is to build a pile from copper pennies, tin foil, and vinegar or lemon juice. [Omars2] has a different take on this old experiment. He creates a 9V battery using some zinc screws, copper wire, and salt water. There’s a video of the battery, below.

A syringe piston serves as a substrate for the cells, and each cell is just a screw with paper wrapped around it and then 35 turns of copper wire on top of that. The battery is soaked in salt water, although we suspect vinegar or lemon juice would work even better. Heating the electrolyte is also a good idea.

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