Inside A Rubidium Frequency Standard

December 5, 2023 by Al Williams 14 Comments

We think of crystals as the gold standard of frequency generation. However, if you want real precision, you need something either better than a crystal or something that will correct for tiny errors — often called disciplining the oscillator. [W3AXL] picked up a rubidium reference oscillator on eBay at a low cost, and he shows us how it works in the video you can see below. He started with a GPS-disciplined oscillator he had built earlier and planned to convert it to discipline from the rubidium clock.

The connector looks like a D-shell connector superficially, but it has a coax connector in addition to the usual pins. The device did work on initial powerup, and using a lissajous pattern to compare the existing oscillator with the new device worked well.

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Cockpit Instrument Respectfully Retasked As A Clock

December 5, 2023 by Dan Maloney 3 Comments

How do you convert an old cockpit instrument into a clock? Easy: just build a circuit that convinces it it’s in the air, and the rest will take care of itself.

Now obviously, little about [porkfreezer]’s conversion of King KI 266 DME into a clock was actually easy; working with avionics rarely is. DME stands for “Distance Measuring Equipment,” an instrument that’s part of the radio navigation suite of many aircraft. DME measures the line-of-sight distance of a plane to a ground station by measuring the time it takes for a signal to return after the plane interrogates it. The plane-mounted equipment includes a UHF transceiver and a display for the cockpit instrument panel, which accepts an analog voltage signal from the transceiver and translates it into a readout on the nice Panaplex digital display.

Rather than gutting the thing and just driving the display directly, [porkfreezer] decided to build a circuit to generate the proper signals for the DME. The board uses a PIC16 and an MCP47C dual 10-bit digital-to-analog converter to generate the voltages needed, while a USB-powered DC-DC converter provides the ±15 volt supply the DME display expects.

Everything lives on a PCB that fits right on the back of the instrument. Sadly, the connector needed to mate up to the one on the instrument was outlandishly expensive — again, avionics — so [porkfreezer] had to solder the board directly to the DME’s pins. Otherwise, this would have been a completely reversible hack.

Still, it’s an interesting reuse of an unusual piece of gear, and one that respects the original design as much as possible. That counts as a win in our book.

Swatch Internet-Time Clock Doesn’t Miss A Beat

November 27, 2023 by Kristina Panos 21 Comments

The thing about human invention is that occasionally, two or more people think of an idea around the same time, and it’s difficult to determine who was first. Such is the case with Swatch’s Internet time, which is told in something called “.beats”. Rather than using hours and minutes, the solar day in the .beat system is divided into 1,000 parts equal to one minute in the French Revolutionary decimal time system, or 1 minute and 26.4 seconds of standard time.

Swatch came up with .beats to sell their special line of .beats watches. But they weren’t the only ones to divide the solar day this way. A few months before Swatch’s announcement of .beats time, a Argentinian drummer named [Charly Alberti] came up with the same idea and created a website for it to display the current Internet time of day.

The point of all this is that [Roni Bandini] has created an homage to both .beats and [Charly] in the form of a small clock. The main brain is a Seeed Studio Xiao nRF52840, with a Xiao TFT round display to show the time as well as a tribute to [Charly]. The 3D-printed stand incorporates a cylindrical power source. We think the black and white images, which [Roni] created with Dall-e, look fantastic.

Interestingly enough, the Xiao has no Internet connectivity; the time is set manually via hard-coded variable, and then the display’s RTC keeps track of the seconds and convert them to Internet time. Check out the brief build video after the break.

Interested in regular old metric time? Here’s a modern metric clock.

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Analog Wall Calendar Keeps Track Of The Days For You

November 23, 2023 by Lewin Day 4 Comments

[ssh16] had seen some fancy wristwatches with retrograde hands. Wanting to do something similar of their own, they set about creating an analog wall calendar that displays the date and the day of the week.

The build uses a pair of stepper motors to control the hands, a simple choice for accurate and reliable motion control. A Microchip PIC18F24J50 serves as the brains of the operation, chosen for its built-in RTC module and the fact that it has plenty of IO for controlling stepper motors. The built-in RTC is programmed with calendar information for the next 100 years, so there is no need to adjust the clock for leap years on the regular. The top hand of the wall calendar is driven in an arc to show days of the month, from 1 to 31. The bottom hand similarly steps through the 7 days of the week. If you’re unfamiliar with the concept of retrograde hands, they’re simply hands that sweep in an arc instead of moving in a whole continuous circle.

Hackers do love a good clock build, even if this one doesn’t specifically tell the time itself. If you’ve whipped up your own nifty timepiece, know that we’d love to see its fine face on the tipsline!

A Modernized Metric Clock

November 22, 2023 by Bryan Cockfield 60 Comments

Much to the chagrin of many living in North America who still need to do things like keep two sets of wrenches on hand, most of the rest of the world has standardized to a simpler measurement system using metric units exclusively. The metric system is widely adopted worldwide, but we still use a base-60 system for timekeeping that predates the rest of the metric system. The French did attempt to “decimalize” timekeeping as well with the French Republican Calendar at around this same time, but this “metric” timekeeping system never caught on particularly well. It’s still an interesting historical tidbit, and [ClassTech] built this modern metric clock to explore it a little more.

The system itself uses ten-day weeks, ten-hour days, and 100-minute hours which makes it more in line with the base-10 system common to the rest of the metric system. But this means that a second in the French Republican system actually works out to a little less than one and a half SI seconds, meaning that a modern timekeeping computer needs to do a little more math to display the correct time at the correct interval. [ClassTech] is using a Particle Photon IoT processor getting the time from a NTP server, converting it to “metric time”, and displaying the time on a Nextion touch display.

While the device is reported to update the time once per second, we’re not sure if this is every SI second or every French Republican second. Either way, there are plenty of reasons this timekeeping system never gained widespread adoption, and a surprising one is that timekeeping tends to be easier in a base-60 system due to its capability of having more divisors. Many other reasons are less technical and more cultural, and timekeeping tends to be surprisingly difficult to coordinate even among shared numbers systems and languages.

Don’t Look Up, Or You’ll See The Time From This VFD Projection Clock

November 15, 2023 by Dan Maloney 17 Comments

Ceiling clocks were a bit of a thing back in the days when clock radios were a fixture of nightstands. The idea was to project the time onto the ceiling so you’d only have to roll over onto your back and open your eyes to check the time, instead of potentially disturbing your slumber by craning your neck around to see the front of the clock.

As we recall, what sounded like a good idea was iffy in practice, with low-end optics and either weak incandescent bulbs or blazing LEDs. This nifty VFD projection clock by [Thomas Shupfs] seeks to fix those problems, and from the look of it does a pretty good job. It takes advantage of something else that fell out of favor with consumers — analog photography — by tapping into the ready supply of unwanted lenses. He paired that up with an IVL2-7/5 vacuum fluorescent display inside a 3D printed case with a cone-shaped extension to hold the lens at the right distance above the display. [Thomas] says that the STM32 software only supports JSON-RPC over USB at this time, and includes a couple of Python programs with examples of how to set the time and check the accuracy of the clock.

[Thomas] compares the clock head-to-head against his old LED projection clock, as seen in the featured image above; we flipped it for a better idea of what it would look like from bed. We’ve got to say the soft blue glow of the VFD would be a lot more pleasant to wake up to than the bright red LED projection. But this soft white projection clock is nice too.

Thanks to [skymab] for the tip.

Watch Time Roll By On This Strange, Spiral Clock

November 13, 2023 by Donald Papp 15 Comments

[Build Some Stuff] created an unusual spiral clock that’s almost entirely made from laser-cut wood, even the curved and bendy parts.

The living hinge is one thing, but getting the spacing, gearing, and numbers right also takes work.

The clock works by using a stepper motor and gear to rotate the clock’s face, which consists of a large dial with a spiral structure. Upon this spiral ramp rolls a ball, whose position relative to the printed numbers indicates the time. Each number is an hour, so if the ball is halfway between six and seven, it’s 6:30. At the center of the spiral is a hole, which drops the ball back down to the twelve at the beginning of the spiral so the cycle can repeat.

The video (embedded below) demonstrates the design elements and construction of the clock in greater detail, and of particular interest is how the curved wall of the spiral structure consists of a big living hinge, a way to allow mostly rigid materials to flex far beyond what they are used to. Laser cutting is well-suited to creating living hinges, but it’s a technique applicable to 3D printing, as well.

Thanks to [Kelton] for the tip!

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