Polar Planimeter Quantifies Area By Plotting Perimeter

March 25, 2022 by Ryan Flowers 12 Comments

These days it’s hard to be carry the label “maker” or “hacker” without also being proficient in some kind of CAD- even if the C is for Cardboard. But before there was CAD there was Drafting and its associated arts, and one couldn’t just select a shape and see its area in the square unit of your choice. So how could an old school draftsman figure out the area of complex shapes? [Chris Staecker] introduces us to the polar planimeter, a measuring tool created specifically for the purpose and explained in full in the video below the break.

The polar planimeter being discussed is a higher end unit from the 1960’s. Interestingly, the first polar planimeters were invented in the early 19th century even before the math that describes their function was completed. A lever is placed in a fixed position on one end and into the planimeter on the other. The planimeter itself has another arm with a reticle on it. The unit is zero’d out with a button, and the outline of the shape in question is traced in a clockwise fashion with the reticle.

What makes the polar planimeter capable of measuring in multiple dimensions is the fixed arm. The fixed arm pivots around, allowing the planimeter to track angle changes which affects the output. So, the planimeter isn’t just measuring the length of the perimeter, but the size of the perimeter. The final measurement is output in square inches.

Overall it’s a really slick tool we didn’t know existed, and it’s fascinating to see how such problems were solved before everything could be done with a mouse click or two. Be sure to check out this 100+ year old reference set to round out your knowledge of past knowledge. Thanks to [Zane] for the great tip!

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Brick And Motor Table Saw Delivers Paper Cuts On Demand

March 23, 2022 by Ryan Flowers 11 Comments

Twenty Two Motors. Fifty gears. Eighty Two Hundred RPM. Hundreds of individual pieces, and one sheet of glossy paper cut into a disk. This isn’t a nightmare driven Rube Goldberg machine. Instead, it’s a Lego monstrosity created by [GazR] of [GazR’s Extreme Brick Machines!], and all of these parts are flying in formation for one Lego slicing purpose. In the video below the break, you can see what very well may be the worlds most powerful Lego and Paper table saw.

Starting out with a build that had a mere fourteen motors in a platform that looked quite a lot more like a table saw, [GazR] learned that having only fourteen motors turning a Lego based blade was not a good combination. In the next iteration, the same number of motors were used, but the gearing was increased to bring RPM up, and a Lego toy saw blade took care of cutting duties.

Seeing that higher speeds with thinner blades was a winning trend, [GazR] stepped it up to the aforementioned 8200 RPM twenty-two motored paper whirling Lego Death Machine. Yes, [GazR] cut Lego, carrots, carpet, and paper- all with circular sheet of paper.

Do Lego mechanisms turn your gears? You might enjoy this Legopunk Orrery from the Hackaday archives, too. Thanks to [Keith] for the great tip. Be sure to submit your own tips via the Hackaday Tips Line, or the #Submit-A-Tip channel in the Hackaday Discord server.

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Old School Mechanical Pong Still Amazes

March 23, 2022 by Elliot Williams 12 Comments

[Tom], of the YouTube channel ThingsTomLike, found a very sweet little mechanical Pong clone at a thrift store. It came in broken, but in only fifteen minutes of your time, [Tom] manages a complete teardown and repair. (Video, embedded below.)

The game works by balancing a lightbulb on the end of a pivot arm that projects a “ball” onto a screen, while players move their paddles up and down to hit the spring that surrounds the light assembly. The ball arm gets periodically kicked by a DC motor and cam assembly, which makes it careen wildly back and forth across the screen.

It’s a marvel of simple, no-IC engineering. Ironically, it might have been cheaper than making it out of silicon at the time, but viewed from today’s economy, just the human labor in adjusting that counterweight so that the “ball” floats would blow the budget.

Why a screen and lightbulb? Because it’s emulating Pong, a video game, the new kid on the block. But even 45 years later, we think it has got a charm all of its own that the cold digital logic of Pong lacks, even if the gameplay suffers.

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Great Computer Hacks Make Hackers Hacker Computers

March 18, 2022 by Ryan Flowers 14 Comments

In the year 1995, computers were, well… boring. The future wasn’t here yet, and computers were drab, chunky beige boxes. Sure, there were some cool-ish computers being sold, but the landscape was still relatively barren. But as you’ll see in the video below the break, it doesn’t have to be that way, and the [Hackers Curator] shows us the way by recreating Johnny Lee Miller’s computer from the 1995 movie Hackers.

Hackers wasn’t popular when it came out, but over the years it has gained quite a following. It portrayed computers and the people who loved them in completely new ways, representing a culture that has never existed. Even so, it inspired so many young hacker types. Among those inspired is the crew over at [Hackers Curator] and they have taken it upon themselves to, uh… curate… the props, costumes, and stories surrounding the movie.

Recreating Dade’s iconic camo “luggable” computer came with quite a lot of difficulty. It turns out that the original movie props were working custom computers that used hacked together customized cases and Mac Powerbook 180c internals. Dade’s (aka Zer0 Cool and Crash Override) was mashup of the a Compaq Portable 486c and the aforementioned Mac. [HackersCurator] have lovingly recreated this prop from two broken computers, but chose to run the internals with a Raspberry Pi.

The techniques used in the creation of this beastly cyberdeck are ones that can be used in building so many other projects, even if you’re not a Hackers hacker. Customizing the plastics and placing a trackball in the most awkward of spots was expertly done, and we’ll be referring to it in the future for guidance when doing similar projects.

Are movie replica hacks your thing? You’re in luck! It turns out that this isn’t [Hackers Curator]’s first build. In 2019 they tackled Lord Nikon’s laptop, and of course, we covered that one too!

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An Old Typewriter Speaks To The World

March 17, 2022 by Jenny List 20 Comments

Typewriters are something which was once ubiquitous, yet which abruptly faded away and are now a rare sight. There was a period of a few years in which electric typewriters and computers existed side-by-side though, and it’s one of these which [Jonah Brüchert] has experimented with connecting to a computer for use as a printer or terminal.

The machine in question is a SIGMA SM 8200i typewriter, which is a rebadged version of the East German Erika S3004. It has an intriguing 26-pin connector on its side which provides access to a 1200 baud serial port. It uses its own character encoding dubbed “gdrascii”, for which there is a Python library that he could port to Rust. The result is a terminal in the old style, from the days when access to a computer was through a teletype rather than a screen. All that’s missing is a punched tape reader at its side!

We’ve featured a lot of typewriters here over the ears, but this isn’t the first that has received a terminal conversion.

Simple Arduino Build Lets You Keep An Eye On Pi

March 15, 2022 by Tom Nardi 10 Comments

Are you a math aficionado in need of a new desk toy? Then do we have the project for you. With nothing more than an Arduino and a seven-segment LED module, [Cristiano Monteiro] has put together a little gadget that will slowly work its way through the digits of Pi forever…or until you get bored of looking at it and decide to use the parts for something else.

On the hardware side, we really can’t overstate how simple this project is. A common four-digit LED display is connected up to an Arduino Nano, which is then plugged into the computer for power. [Cristiano] is using a breadboard here, but you could just as easily use four female-to-female jumpers to connect the two devices together. We suppose this would be a pretty good project for anyone who’s looking to get some practical experience with PCB design as well.

The real magic is in the software, which [Cristiano] has been kind enough to release under the MIT license. Calculating Pi on such a resource-constrained chip as the ATmega328P is far from ideal, but by porting over a C++ algorithm developed by [Xavier Gourdon] and [Pascal Sebah] for their paper Computation of the n-th Decimal Digit of π with Low Memory he was able to pull it off, albeit slowly.

Now if you’ve got slightly better hardware, say a pair of Xeon processors and 96 GB of RAM, you could calculate Pi out to a few trillion digits for fun, but it wouldn’t look as cool as this little guy blinking away.

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DOOM Comes To The RP2040

March 15, 2022 by Matthew Carlson 14 Comments

To the point of being a joke, it seems like DOOM is adapted to run on everything these days. So it was only natural that we would see it ported to the RP2040 by [Graham Sanderson], the tiny chip powering the Raspberry Pi Pico.

You might be thinking, what’s different about this port? There have been 55 articles about DOOM here on Hackaday, showing it running on everything from web checkboxes to desk phones. The RP2040 has 256 K of RAM, two decently clocked processor cores, and 2 MB of flash, so it’s not the most constrained platform ever to have DOOM run it. But [Graham] also set some very lofty goals: all nine levels needed to be playable, faithful graphics and music, multiplayer, and it would output to VGA directly. It should play just like the original. DOOM has a demo that is stored as a sequence of input events. They form excellent regression tests as if the character gets stuck or doesn’t make it to the end; then you’re not accurate according to the original code.

There are two big problems right out the gate. First, a single level is larger than the 2 MB storage that the RP2040 has. And to drive the 320×200 display, you either need to spend a lot of your CPU budget racing the beam or allocate a vast amount of RAM to framebuffers, making level decompression much harder.

A default compression scheme wouldn’t cut it because it needed a high compression ratio and random access since decompressing into RAM wasn’t an option. However, carefully optimizing and compressing the different data structures yielded great results. Save game files are given a similar treatment to ensure they fit into the remaining flash after all the levels (34k).

The result is fantastic, and it supports DOOM, Ultimate DOOM, and DOOM II. The write-up goes into far more detail than we could here; enjoy the read. If you decide to make a day trip to the depths of Hell on your own Pi Pico, be sure to let us know in the comments.

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