Clocks are almost the ideal devices to inspire creativity in hackers — they have a simple, well-defined task, but there’s an almost unlimited number of ways to carry it out. [ekaggrat singh kalsi]’s OVODYO is a particularly intriguing approach, tumbling a pair of icosahedral counters to display the current time.

Each 3D-printed icosahedron has numerals sunk through each of its twelve sides, and is raised above the base of the clock on a brass support shaft. An inner drive shaft runs through the center of the support shaft and drives a set of beveled gears. These spin the outer shells around two axes, periodically cycling through all twelve faces. The pattern in which an icosahedron rotates means that only set of numerals appears upright at a time, making it easier to distinguish the time.

A split path around the icosahedra both lets them rotate around the support shaft and shows off the internal gearing. On the control side, an ATmega8 drives a pair of stepper motors with drv8833 motor drivers, using a hall effect sensor to detect each indicator’s position. Since the minutes dial only gives the time in five-minute intervals, it also drives an LED strip to indicate the exact minute.

[ekaggrat] has a long history of creative clock designs, from this dynamic chain-link sculpture to a hair-tie clock or a mechanical seven-segment display.

We tend to think of breaking the sound barrier as a comparatively modern accomplishment, but on a smaller scale, cattle herders have been breaking it for centuries: the cracking sound of the tip of a bullwhip snapping comes from a small-scale sonic boom. Reliably getting a crack out of a whip takes skill and practice, though, which is why [Craig Turner] built a whip-cracking machine.

The first step was to build the whip itself, which was surprisingly complicated. Bullwhips taper down toward the end of the whip. As the whip uncurls during a crack, momentum passes down the whip; since the whip becomes continually narrower and lighter, conservation of momentum means that different stretches of the whip must move progressively faster. To get this effect, [Craig] joined together a series of increasingly thin and light ropes. The heavy end of the whip terminated in an eyelet connected to a length of elastic shock cord. Stretching the whip back on the shock cord and releasing it whipped it around, resulting in a fairly reliable crack.

For greater convenience, [Craig] built this into a launcher mechanism, with the elastic cord wrapped around the end of the launcher, an electrical-conduit guide for the whip, and a spring-loaded trigger mechanism to release it. This worked even better than expected, getting a reliable crack every time. The tip of the whip could slice leaves, tear open aluminium cans, put out candle flames, knock the cap off a bottle without tipping it over, and reliably hit small targets on the first shot.

As [Craig] mentioned, this setup would make it much easier to study the cracking effect with a schlieren imaging setup.

If you’ve never heard of the Spin Semiconductors FP-1 digital signal processor chip, don’t worry– that just means you haven’t been deep into guitar petals and audio effects hardware lately. [adamjvr], a.k.a. [avr] has, and he’s gone to the point of creating a PC-based emulator of this sound chip to simplify development.

If you don’t see the utility, stop and think about the development cycle without a simulation like this: you program, you flash to a board, and you test there. Not only does the ‘flash to the board’ step add time and friction, you do also have a limited number of flashes on the board’s memory. With an emulator on your PC, the workflow tightens to ‘code, test’ and you don’t flash the board until the simulated DSP is doing the sounds you want it to.

As for the FV-1 itself, it’s an interesting little chip in that it’s quite a full-featured DSP– rather, it’s small instruction set is focused entirely on audio effects. If you’re into that world– be it guitar pedals or otherwise– you may find this project very useful. There are releases for Linux, MacOS and Windows, and it’s all open-source on GitHub, under the Mozilla Public License. It’s not the most common choice, but we’re hardly going to complain about licenses to anyone willing to share their hard work.

If you like the idea of testing your work before you go to the bench, we’ve seen software that offer the same functionality for Arduino projects, as well as other AVR and PIC micros. It’s been a while since we featured a programmable guitar pedal, so we hope this tool enables others to rock out.

You want Retro? We did, when we started our retrocomputing challenge. [Peter] decided that transistors weren’t retro enough, and sent us this lovely homebrew relay computer, complete with 16- bit CPU, which is rather more bits than one normally associates with clicky clacky contacts.

The architecture is very simple– it just uses an accumulator register, ACCU, and goes from there. All mathematics and save/load operations go through ACCU. There whole instruction set is only 19 commands, and he’s used that set to program such lovely things as calculating 3 digits of Pi– which only took 8 minutes of glorious clicking. There’s a demo video of that embedded below. [Peter] has even implemented a display by hooking his computer to a 32×32 LED matrix, but don’t expect it to relay updates really quickly.

If this computer looks familiar, it’s because its earlier incarnation was one of the more “extra” entries in last year’s one-hertz challenge, where it was used to blink an indicator lamp. Yes, even relay computers apparently get started with the “blinky” sketch.

If you want in on the fun, our retrocomputer challenge runs until October 27th, so there’s lots of time left to turn back the clock.

Although building a table saw out of LEGO is probably not the first thing that comes to mind when you look at those colorful bits of plastic, [Jamie] has been on a bit of a search for more applications of his LEGO-based air-powered motors. Naturally this led to the idea of doing something useful with it, like making a table saw you can actually use for real wood.

Starting off with a basic prototype using only regular LEGO pieces to get the mechanism figured out, [Jamie] then builds this up into said air-powered table saw featuring an actual metal blade. Suffice it to say that this isn’t something that you want your children to do with their LEGO while unsupervised.

The star of the show is of course the air-powered turbine that spins the blade. This is something that [Jamie] has been working on for a while, going through a number of prototypes to figure out a 3D printed geometry for the turbine blade that helps to convert as much of the high-pressure air into rotation.

Along the way it was also discovered that 3D printing saw blades is pretty hard, probably due to the lack of a sharp edge. This is definitely an area where it’s hard to beat a real table saw blade, with the added caveat that anything that’s good at cutting up boards of wood and sausages will just as happy slice through careless primate fingers.

In terms of safety features, the air supply is cut automatically with a sort of dead-man switch that requires you to keep one hand on it while using the final table saw design. There also an auto-feeding system added that tries to guide the board into the saw, but this turned out to be finicky. Suffice it to say that an air compressor and a handful of non-LEGO-approved components created a pretty convincing table saw.

[Andy Huot] has a fantastic-looking infinity mirror digital clock that really raises the bar. It uses high quality components, smart use of RGB LED animations, and a clever “stacked diffuser” vertical design to the 7-segment display elements that really enhances the infinity mirror effect. It needs to be seen in action, so check it out.

The end result is expressly portal-like, with the smooth animations of the LEDs really playing into the effect. The size helps, too. It’s 24 inches in diameter, giving it considerable presence.

A basic infinity mirror design consists of lit elements sandwiched between a reflective back surface and a partially-reflective, partially-transmissive top cover. That same basic principle is used here, but with great care given to ensure nothing so much as a fingerprint spoils the illusion. For example, the top cover is a disk of acrylic with a 90% reflective film affixed to the inside surface. That’s easy enough to DIY with some car tint, but [Andy] found that for the very best results it was worth having high-quality film professionally applied.

We like the use of 3D-printed custom jigs for soldering the segments of RGB LED strips, and holding the pre-measured wires in place with some putty is a great way to keep them in place while working. In case you’re wondering, the mirrored acrylic making up the back wall has holes in it for mounting each segment’s LED strip in a holder, and running the wires to the rear.

The video (embedded below) documents every step of the assembly, and it’s a serious build. While the design files for the 3D-printed parts are not free, there’s certainly enough detail for an enterprising hacker to replicate the design in their own way.

Apple hardware has always been proprietary, sometimes to an extreme. But that’s not to say that it’s impossible to make something that does the same job, which is what [DosFox1] appears to have done with the OSHintosh. It’s an open source PCB that implements a Mac 512k. Is it a 68k Hackintosh? You decide.

While it boots into a classic Mac OS image, it’s not quite a Mac. For a start, there are no disks, and no SCSI. Instead it boots from a disk held in ROM, which we guess will be a lot faster than the floppy from back in the day. They’ve even managed to do it on a 2-layer board, which means that despite its size, it shouldn’t be too expensive to have made.

We’re not sure quite what the legality of dumping a Mac ROM image to the ROM on this board would be, but assume for a moment that you own a copy in a defunct original Mac. This board can’t yet replace the original due to the disk issue, but given that original Macs are now long in the tooth, a modern replacement for those who must have hardware rather than an emulator sounds like a good idea. Perhaps for some people it will join the FPGA Amiga.