Oscilloclock.com

Handcrafted Scope Clocks with circle graphics

Tag: Circle Graphics

  • Z Core makes Blanking easy!

    Z Core makes Blanking easy!

    Here at the Oscilloclock lab there’s nothing more pleasurable than helping put a cherished vintage oscilloscope back into action. A new lease on life!

    That’s why when [Chris] reached out about his early 1970’s Conar 255 oscilloscope, wanting to convert it into a Vectrex gaming machine, we were naturally excited!

    The Conar 255 – “space age technology” per NRI Journal Nov/Dec 1973
    Beautiful vector graphics! Image by When Chemists Attack

    The original Vectrex was an incredibly cool device. Instead of the pixelated, blocky graphics of the time (anyone remember Pac-Man?), the system used vector graphics to draw smooth line-art images. Each vector was a straight line, or a smooth arc, connecting point A to B. Vectrex games were true works of art, and the original hardware is quite rare (and $$$)!

    Scopetrex

    The Scopetrex

    Well, [Chris] caught the vector graphics bug. But he decided to build a Scopetrex – a hardware emulator that allows you to run Vectrex games on an oscilloscope! He would theoretically just connect this to the Conar 255’s existing X, Y, and Z (blanking) inputs.

    We like this “minimum invasion, maximum re-use” approach. We’ve gone down this route numerous times to craft Oscilloclocks out of still-usable hardware. (The alternative? Install a full set of modern boards that drive the CRT directly.)

    Sample specimens of “minimum invasion, maximum re-use”

    [Chris] got down to planning. He could interface the X and Y inputs easily. But he faced a problem with the Z (blanking, or intensity modulation) signal, which instructs the scope when to turn the beam on and off:

    • The Scopetrex outputs a 5V DC digital blanking pulse.
    • The Conar requires at least 20V peak-to-peak blanking signal – and employs analog AC coupling.

    We’ve solved this mismatch problem before using various non-standard Oscilloclock board setups and complex hook-ins to the existing circuits. Always on a case-by-case basis, always unique.

    But now, at last, it was time to standardise the process. To make it easy. To adapt any vintage oscilloscope for digital blanking from a microcontroller! We proudly announce the next member of the Core family: The Z Core!

    The Z Core (in this case, a Z Core 2 Ex) …

    … joins the Oscilloclock Core family!

    How to install it

    Believe it or not, the minimal installation requires just 3 steps. For almost any oscilloscope! The Z Core effectively sits in series between your device’s blanking supply and the CRT grid.

    1. Snip the wire connecting to CRT grid.
    2. Connect the orange wire from the Z Core to the circuit side of the cut wire.
    3. Connect the green/yellow wire to the CRT grid.
    Snip.
    Connect!

    Visit the Z Core Support Page for lots more detail, including the obligatory warnings about high voltage. There are also details on how to connect the Z Core to your controller, detailed specifications, and some fun Q&A to help answer your most burning questions!

    The Z Core 2 Ex!

    We’ve wanted to develop a dedicated, built-for-purpose Z Core product for a very long time. This would consist of a single, miniaturised, low-power board called (ingeniously) a “Z Core Board”, and a few harnesses.

    But [Chris] didn’t want to wait for Oscilloclock labs to work through its ever-growing bucket list. Could we deliver within 2024?

    Yes!

    In past retrofits such as the Kikusui 537, we’ve taken spare boards that were originally designed for fully-featured Oscilloclocks, and partially populated them with only the necessary components to serve the blanking purpose.

    Partially populated Oscilloclock Power Board

    For [Chris], we found an almost fully-populated new-old-stock Power Board v2.27 and compatible CRT Board v1.21 lying around, just dying to be used and loved by someone. Older revision boards do tend to be set aside, as folks want the latest and greatest.

    With just a few minor modifications, this assembly shipped – and is now branded as the Z Core 2 Ex. The “2” refers to the Power Board’s major revision, and the “Ex” stands for “external blanking amplifier” (the function of the CRT Board). The Power Board rev2.2x series boasts an on-board blanking amplifier, but this section wasn’t already populated. What a great opportunity to use up a stock CRT Board!

    [Chris] will be happy. And we’ll keep up this spirit of minimising waste. You’ll see some other Z Core assemblies popping up in future: a Z Core 1 Ex, a Z Core 2, and potential variations of Z Core 3’s.

    And finally, one day, a genuine dedicated Z Core will be born!

    Why your scope needs a Z Core …

    Many old oscilloscopes simply don’t have any input for Z blanking, Z axis, intensity modulation, or cathode modulation. (Look carefully – it goes by many names!) Or, the input may be there, but it’s not compatible with a microcontroller. Why couldn’t the designers offer a decent interface?

    Well, it all has to do with high voltage! To get there, let’s cover how CRTs work in just three short sections:

    Gun

    A cathode-ray tube (CRT) has an electron gun that shoots electrons at the phosphor molecules on the screen. The electron beam is deflected by putting positive and negative voltages into electrodes placed in the CRT’s neck, and this is how patterns are drawn on the screen.

    This is how a CRT works. It’s awesome.

    But the electron beam has to be turned on and off, to break the pattern and make meaningful images on screen. This is known as blanking.

    Blanking

    Oscilloscopes, particularly, have to blank the beam when it goes back (retrace), from the right to the left again. If there were no blanking, you’d see a retrace line – wickedly cool for us artists, but devastatingly distracting for engineers who want to focus on the waveform itself!

    Retrace lines – arty but not desirable

    Oscilloclocks also rely on blanking. In Circle Graphics, where all figures are composed of lines and circles, blanking is crucial to creating meaningful segments. For example, a “C” is readily created from an ellipse “O”, simply by blanking the beam at just the right place!

    A blanking pulse kills the beam to get a ‘C’

    Grid

    CRTs are designed for blanking. There’s a valve-like electrode called a grid that sits inside the gun, just in front of the cathode where the electrons are spat out. If you inject a negative voltage into the grid (compared to the cathode), it repels those electron babies and sends them back where they came from. They don’t bombard the screen, and no more light is emitted. Blanking in action!

    Titillating! Electron field density is reduced when a negative voltage is applied to the grid!
    A fuller explanation – from The Bible
    The bible

    A change in grid voltage influences the field distribution of the first lens, and in so doing controls the emission from the cathode. For any fixed value of voltage applied to anode 1, it influences the number of electrons which pass through the cross-over point. Let us see how this comes about. In Fig. 5-17 is shown the field distribution in the first lens for two values of grid bias, O and -30 volts, and a fixed value of voltage on the plate.? It is clearly evident that with zero bias, the area adjacent to the cathode, between the cathode and the control-grid aperture, has a comparatively high positive potential as the consequence of the field between the control grid and the first anode. Under such conditions of zero grid voltage, it has been found that the area of the cathode which is emitting corresponds approximately to a projection of the area of the grid aperture; the maximum number of electrons are passing through the grid opening and the beam-current density is high.

    When the control grid is made negative by an increase in the bias, —30 volts in the illustration, the field distribution in the vicinity of the cathode is altered so that only the center of the emitting surface is behaving as an emitter. The other areas are influenced by the space charge and effectively are not emitting. The result is a reduction in beam density and several other related effects.

    High voltage

    So – back to the high voltage aspect. The cathode and grid are usually about 2kV (that’s right – 2,000 volts!) negative compared to the rest of the circuits. If you connected an external input signal directly to the grid, something would fry.

    Old-school oscilloscope designers took a very easy (read: cheap) solution: they stuck a high voltage capacitor between the grid (or cathode) and the external signal. This is called AC coupling because the capacitor blocks the DC voltage (2kV), and only couples through the AC (the fluctuating blanking) component of the signal.

    AC coupled external intensity modulation in the Conar 255 (L) and the Trio CS-1554 (R)

    This method of intensity modulation was fine for the regular, repeating signals observed in old TVs and radios. But it isn’t what [Chris], or so many millions out there like him, needs! They need to send through an irregular, sometimes not-fluctuating-at-all (i.e., DC) signal. They need DC coupling! And it has to be isolated – standing off more than 2kV!

    And there’s another voltage related problem: the grid has to go substantially negative with respect to the cathode, in order to completely block the electron flow. We’re talking 20-50V typically. This is not a voltage that a modern microcontroller board will deliver! This requires an amplifier.

    Summing it up

    So that’s it! Just three(?) words. We need an isolated DC-coupled amplifier. And it needs 2kV isolation with a 10x amplification factor.

    Welcome to the Z Core!

    Demo

    No assembly can leave our lab without being fully tested, and without a demonstration to ensure the customer’s utmost satisfaction. Here’s how the demo went:

    The host device: Trio CS-1554

    This venerable Trio (also branded as Kenwood) hails from around the same era as the Conar 255. It was attractive, had fairly good specifications, and a low(-ish) price tag, making it very popular both in Japan and overseas. Documentation is freely available and… more importantly, I had one lying around!

    Look carefully – it’s bulging and leaking!

    Of course this device is full of high voltage oil capacitors. These were effective in their day, but they break down over time, and things get very nasty. One particular HV capacitor in this unit was overheating to the point that the metal case had warped, and oil was even leaking out! Ick.

    A few modern-day capacitors hacked together replaced the leaky unit and saved the day. Onwards!

    The controller: Oscilloclock Connect

    Oscilloclock Connect

    As mentioned on the Availability page, one lovely Oscilloclock Connect unit is in stock. What better controller to verify the Z Core’s performance?

    The demo

    1. Connect Connect X output to Trio EXT HORIZ input at rear 1
    2. Connect Connect Y output to Trio CH1 vertical input
    3. Connect Connect Z output to Z Core input 2
    4. Connect Z Core outputs to Trio CRT grid and grid circuit (as shown in earlier section)
    1. Incompatibility! The Trio’s horizontal input seemed to want 10V peak-to-peak for maximum deflection (this is way off its original specs of 250mV/cm. I think it’s broken!) The Connect by default has only a 3V peak-to-peak output signal. The image is going to be small… ↩︎
    2. Trickery! The Connect by default is designed for a display device with a high-impedance Z input. The Z Core 2 Ex has a low-impedance input and 15mA drain at 5V. A temporary mod was needed in the Connect – which was promptly reversed after the test. ↩︎

    The result? A relatively clean image, albeit small! But the blanking works well. [Chris] was okay with the jagged edges and other blemishes; these are attributable to the Trio’s rough condition.

    Performance testing

    The Oscilloclock cave is not a precision testing laboratory. But we do have a significant collection of equipment, and every piece plays its part. In this case, we deployed a Hewlett Packard 1901A Pulse Generator.

    Choosing amongst a plethora of delightful old oscilloscopes, we stayed with the HP theme and used a venerable but still digital HP54615B.

    Yes! This HP has an undocumented Tetris game built in!

    The setup was simple:

    1. Set up the pulse generator for 100kHz square wave
    2. Set rise and fall times to minimum (around 10ns)
    3. Set output to 5V and connect to the Z Core’s input
    4. Connect a 20pF capacitor across the Z Core’s output, via the standard 200mm 22AWG harness
    5. Connect Ch1 of the scope to the input, Ch2 of the scope to the output

    Results

    MeasurementAssembly: Z Core 2 Ex
    Waveform base voltage-46V
    Rise time130 ±10 ns
    Fall time180 ±10 ns
    Propagation delay120 ±10 ns
    Effective bandwidthDC to 3 MHz
    (limited by rise/fall time)

    These results were satisfactory. But at some point, we’ll try the same with a Z Core 1 and a Z Core 3. And one day – a purpose-built pure Z Core. Stay tuned!

    In conclusion

    Well, that’s a wrap! The tested assembly has now shipped, and soon [Chris] will be able to try out a Scopetrex on his minimally-modified Conar oscilloscope. Fingers crossed!

    For more technical info, fun facts and Q&A, check out the Z Core Support page. And for a peek at our range of gadgets, be sure to check out the Gallery.

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  • Zork on an OscilloTerm!

    Zork on an OscilloTerm!

    Today’s story began with a mail from [Eric], who’d read up on the Oscilloclock 3-inch VGA Assembly and wondered if it could be used to create an old-school serial terminal display on a vintage oscilloscope CRT.

    Yes it could! In fact, the Oscilloclock Lab did one better. Instead of just a VGA display controlled by an external device, we developed native terminal firmware that accepts DEC VT52 compatible commands over a serial port, and renders all text and graphics using beautiful, curvy Lissajous figures.

    The stuff of dreams. The OscilloTerm Exo B7S4.

    Demonstrating basic terminal features, connecting to a PC via serial cable
    Oh, did I mention? It’s a clock as well!

    Zork, anyone?

    Ultimately, [Eric] just wanted to play Zork. And together we made it happen.

    The CRT. The Case.

    [Eric] wanted a sleek ‘skeleton’ look. His choice of a gorgeous B7S4 CRT, mounted in custom-machined cast acrylic supports, exposes all glassware and allows for a titillating rear viewing experience.

    CRT rings and supports – originally introduced for the Oscilloblock “Summer Dusk” edition

    And with a high-transparency cast acrylic case housing the electronics, the OscilloTerm Exo can be enjoyed from every angle!

    Astute readers may wonder about the 2.1 kilovolts of high voltage coursing through their innocent-looking device. Rest assured! All internal wiring is sealed off, and Oscilloclock CRT harnesses are hand-crafted with heavy insulation and precautions taken against dust, prying fingers, rats, and even salivating cats.

    Safety in action! Mil-spec connector (left); custom-designed acrylic cap on the CRT connector (right)
    An O-ring blocks dust from entering the CRT/socket gap (picture from the Oscilloblock)

    This case and CRT mounting variation is branded the Oscilloclock Exo, and has proven its wow-factor at several public exhibits to date. We certainly love it, and [Eric] did too!

    The Terminal.

    This post would never be complete without showing you what real serial terminals from the 1970’s looked like, and explaining what they actually did! Here goes…

    DECscope VT52 (1974)
    ClickRick, CC BY-SA 3.0, via Wikimedia Commons
    ADDS Regent 40 (1979)

    Terminals such as the above were physical input/output console devices, back when computers were the size of massive refrigerators, and the operator would sit remotely – at a desk in a separate area, or even a different room.

    Gregory Lloyd, CC BY 2.0, via Wikimedia Commons

    The terminal and the remote computer were connected via a cable, and would communicate each other by sending data back and forth across the cable; mainly terminal commands and ascii encoded text. Most commonly, a serial communication protocol was used to get the data safely from one end to the other – and hence the devices were known as serial terminals or even serial consoles.

    Amusingly, they were also called dumb terminals, because they had no computing power of their own; they were only extensions of the computer to which they were connected.

    The OscilloTerm Terminal.

    [Eric] wanted a special Oscilloclock that he could also operate as a terminal, connecting it to a remote computer via cable. The remote computer would control the display, using the same serial protocol and commands as an ancient dumb terminal.

    But an Oscilloclock is anything but dumb. [Eric] wanted to keep all the standard exciting screens and features of his Oscilloclock active, and only display the special Terminal screen when the remote computer started to send commands. Then, when the commands stopped, the Oscilloclock should go back to the screen it was on!

    His wish was our command! Here’s a demo of smart screen switching in the final product:

    Some technical Comments

    Naturally, the terminal emulator firmware was written entirely in assembly language.

    PIC18F2680 – the Oscilloclock workhorse.

    We use assembly mainly because the minimalist PIC microcontroller used in the current Control Board revision has only 64K ROM, and an unbelievable 3328 bytes (yes, BYTES!) of RAM. To squeeze all the lovely Oscilloclock features in, while driving Circle Graphics real-time processing, the code and memory space has to be clean, tight, and heavily optimized at the machine code level.

    Assembly. It’s the ONLY way to squeeze it all in!

    For even more technical details, such as the list of VT52 (and VT100) commands supported by the OscilloTerm, and the various configuration parameters that can be tweaked to make the terminal emulator more ‘friendly’ when connecting to a specific device, check out the Support page. Worth a visit!

    Why Zork? And HOW?

    Zork is an interactive adventure game. But it’s old. And it’s text-based, because it was run on computers long before fancy graphics capabilities were widely available. The player explores mysterious locations, solves puzzles, and collects treasures while avoiding various hazards and creatures. All by reading text and typing commands and responses!

    [Eric] was able to play Zork by loading the game’s Z-code into a Z-machine interpreter known as Frotz, on a PC connected to the OscilloTerm. But there was trickery involved!

    1. He had to recompile a version of dfrotz (the dumb terminal version of frotz) to remove the status bar and audio from the game.
    2. He needed to wrap the dfrotz output with a custom Python script to support the OscilloTerm’s 16×8 screen and simulate the required baud rate.

    But now that’s done, he can play any Infocom game that runs in dfrotz on his OscilloTerm!

    What’s next?

    Readers would probably agree that adding a generative AI feature would be incredibly cool. For example, the War Games feature is great, but the text on the screens is all pre-programmed. What if you could interact more naturally with your Oscilloclock?

    Another one for the list!

    Are you a serial serial terminal collector? Do you want to play Zork on the oddest device imaginable? Or, you fancy a clock in the Oscilloclock Exo range? Contact us and let us know!

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  • Building the Astro Clock

    Building the Astro Clock

    In the last post, we took a look at a funky new sidereal clock from the Oscilloclock Lab. Now let’s take a look at what fanciness went into it!

    The Hardware

    [Alan], our astronomer protagonist, wanted to install all the electronics inside his Tektronix 620 X-Y Monitor. He didn’t need a nice fancy case.

    Demonstration of a Lissajous circle
    No pixels here! Circle Graphics

    No problem! We supplied the Oscilloclock Bare – our stand-alone controller board that generates images and text rendered in smooth and silky Lissajous figures.

    The board ships on a cast acrylic mount to make it easy to test externally, prior to installation into the host piece of equipment.

    Next, we added the Oscilloclock Wave. This is a Wi-Fi adapter that allows an Oscilloclock to pull (Solar) time from NTP servers over the internet, keeping accurate time indefinitely.

    Bare-bones Wave Core module

    For [Alan], we left the cabling and aesthetics options open, and shipped the basic Wave Core module instead of the stand-alone type pictured above.

    Finally, we included a decent quality power pack, to allow running the assembly prior to installation.

    This would eventually be eliminated by powering the unit from the Tek 620’s internal supply itself.

    The software – Sidereal time enhancements

    To transform the Oscilloclock Bare into the astronomically great Astro Clock that it is today, we needed sidereal time.

    Querying the sidereal API. Easy as pie!

    Easy! The US Naval Observatory Astronomical Applications Department provides a publicly available API for querying sidereal time, given a location.

    The Oscilloclock Wave already had features to pull earthquake data from a similar API and push it to the Oscilloclock for display. Extending this for another API wasn’t astronomically difficult.

    The Wave sports a bunch of advanced settings for particularly tweak-loving oscillofans out there. We just needed to add a few more! These are to enable querying and sending sidereal time to the Oscilloclock, and to set the location.

    Setting up for sidereal time

    But why not just calculate sidereal time?

    Some readers may have guessed that formulae and code libraries for calculating sidereal time are readily available. Why didn’t we just implement the calculation in code, and avoid depending on an external API?

    Our minimalist PIC 18F2680 even had a terrible bug at one point…

    Well, I’ve mentioned before that the current revision Oscilloclock Control Board uses a minimal-specification microcontroller with very limited capabilities, and is heavily optimized by coding in assembly language.

    Sadly, this chip was already jam-packed to the hilt, and there simply wasn’t any more space left for the code and run-time memory needed to calculate sidereal time internally.

    And writing the necessary floating-point calculations in assembly would be no mean feat!

    Why Assembly Code?

    Because We Can.

    But, it sure ain’t easy…

    So NO – we couldn’t easily calculate sidereal time, and it was API Option full steam ahead!

    Astro Screens!

    Even with its minimalist microcontroller chip, we’ve managed to squeeze some amazing stuff into the Oscilloclock Control Board firmware.

    For more of the weird and wacky, see Screens & Things!

    For this build, we needed yet more screens.

    First, we used our trusty Figure Creator software to render a rudimentary telescope into Circle Graphics sprite code.

    From a sketch … to … assembly code! Voila!
    Astro Clock splash screen

    We then crafted a simple Astro Clock splash screen, by adding some random circles for stars and laying out basic text around the telescope.

    Finally, we added some basic digital and analog clock screens, using the same telescope figure as a centrepiece. This was mostly straightforward, but the existing clock hand drawing code did need some tweaking, to reference either solar time or sidereal time depending on the active screen.

    Done!

    Invoiced. Paid. Shipped. Received. Treasured forever. Right?

    Wrong!

    Sidereal really sidelined…

    A year after [Alan] received his lovely Astro Clock, the unhappenable happened. The Astronomical Applications API was taken down!

    “undergoing modernization”… a harbinger of API death! Jan 2020 snap courtesy archive.org

    The site was taken offline for a planned six months, for “modernization”. [Alan]’s sidereal clock was relegated to a normal solar Oscilloclock, albeit temporarily.

    Astro Clock features relegated. Utter sidereal sadness

    But as lovers of electron beams striking phosphor, we always look at the bright side! Six months is still relatively short in astronomical terms! We resignedly marked “X” on the calendar, and bided our time.

    But then… the unfathomable fathomed. The COVID-19 pandemic struck. The USNO site modernisation was completely halted – very likely deprioritised in the midst of indiscriminate illness, clinical chaos, and staff shortages.

    Halted… 2 years later, still no luck… Mar 2022 snap courtesy archive.org

    We waited, and waited, and waited. There were no fingernails remaining to chew when, after two and a half years, a revised API was finally made available at the end of 2022. Hooray! Thank the stars!

    API resurrected

    Fresh API documentation in hand, we set about modifying the Wave to use the fresh fruits of the USNO modernisation machine.

    Fortunately, there were only minor changes to the API – a few more mandatory data fields, a change in date format and such. These required a relatively small amount of rework in the Wave’s firmware.

    And … we were back in the amateur astronomy business.

    Almost like a big Christmas present from Santa!

    Was this [Alan]’s Christmas present? – Santa in your Clock

    Do we regret taking the API approach?

    It’s a good question. API death could happen at any time – possibly rendering the Astro Clock lifeless, listless, or lethargic yet again.

    But, no. The decision not to calculate internally was valid, based on the known constraints. And we did our veritable utmost to revive poor [Alan]’s Astro Clock as soon as possible.

    By the way, we at the Oscilloclock Lab certainly can’t complain about USNO’s API shutdown. We, too, have been heavily impacted by pandemic and other worldly events. As of this posting, our formal activities, too, remain on pause…

    … for now!

    Curious about other Oscilloclocks that use APIs? Check out the AfterShock Clock, which taps into an earthquake API to display earthquakes in (almost) real-time on a lissajous-rendered map!

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  • Astro Clock

    Astro Clock

    “Metropolis Time“

    A few years ago, we introduced Metropolis Time, a time system based on the 20-hour, two-shift days featured in Fritz Lang’s iconic movie Metropolis.

    Since then, we’ve received a few requests to craft clocks that display some other calendar and time systems – from the ancient and archaic, to the religious, to the scientific.

    That’s Astronomical!

    Today’s exciting story began with a request from [Alan], a prominent amateur astronomer. He happened to have a lovely Tektronix 620 X-Y Monitor lying around, and wanted to turn it into a clock.

    Well, that would be easy – the Oscilloclock Bare is a bare-bones controller assembly that can be used to drive an oscilloscope or XY monitor that meets certain requirements (for the techies: a DC coupled Z-axis amplifier). And the Tek 620 is perfect – wonderfully performant, and perfectly compatible. Job done! Right?

    Oscilloclock Bare + Tek 620 + scientific passion = Astro Clock!

    No way! [Alan] didn’t want just any old clock. The custom splash screen above was pretty cool, but could his clock display something called “sidereal time“?

    Yes! Anything is possible, and here’s what we ended up delivering: several custom clock faces showing sidereal time (in both analog and digital formats), in addition to all the standard screens that are based on solar time.

    The shipped Astro Clock assembly!

    But what is sidereal time?

    A Solar day

    Well, most normal human beings and their clocks like to measure a 24 hour day by using the Sun as a reference point. One solar day is the time it takes for the Earth to spin on its axis enough and see the Sun at the same height in the sky as the previous day.

    For example, let’s say it’s 1 May 2023. It’s lovely weather out, and you happen to notice that the Sun reached its highest point in the sky at 12:30 pm. The next day, 2 May, you would find the Sun at its highest point at — you guessed it! — 12:30 pm. And if you ignore man-made tweaks such as daylight savings, you find the Sun is always at its highest point at 12:30 pm*, year-round, looking from the same location.

    *This is not quite true – because every day is slightly shorter or longer. But it averages out over the year.

    A sidereal day

    Sidereal time, on the other hand, uses the distant stars as a reference point to measure 24 hours. One sidereal day is the time it takes for the Earth to spin on its axis enough to see the same distant star at the same height in the sky as the previous day.

    Because the Sun is so close, and a distant star is so (relatively) far, there is a difference in the length of a sidereal day compared to a solar day. A sidereal day turns out to be approximately 23 hours, 56 minutes, and 4.0905 seconds.

    Confused? I don’t blame you. This video should help:

    History and Sidereal clocks

    According to this brilliant post, the concept and utility of sidereal time has been around a very long time. The length of a sidereal day was even calculated to a surprisingly high level of accuracy some 1,500 years ago!

    Here are two surviving sidereal clocks that were made “recently” – just a few centuries ago.

    But who on Earth would use sidereal time?

    Astronomers would.

    Most people don’t look at the boring old Sun all the time. We look out to the stars and galaxies far, far beyond our solar system. If an astronomer wants to track the position of Betelgeuse day after day, she can record the sidereal time that she saw it, and know that it’ll be at the same ascension at the same sidereal time the following day. Brilliant!

    Mariners and Astronauts would.

    They can fix their location even when the Sun is not visible, by observing the position of the stars and calculating their position back from the current sidereal time. Life-saving!

    Oscilloclock Labs would.

    Because we can.

    In the next post, we’ll take a look at the build. What hardware went into this Astro Clock? How on earth does it tick? Can you figure it out?

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  • Screens & Things

    Recently I had an enquiry from [Frank], who had just begun a life-long love affair with scope clocks by purchasing one on eBay. The clock was great – but he felt that the two available screens (simple analogue and digital clock faces) lacked a certain oomph.

    He then stumbled across Oscilloclock.com, and in his smitten state immediately reached out with his number one question: just what screens are available on an Oscilloclock?

    Well, let me save Frank’s time trawling through years of blog posts. Right here in one place are most of the Oscilloclock screens and features created to date.

    Enjoy the show!

    Standard Time Screens

    These stock-standard analogue and digital time screens may be quite simple, but they do evoke the ‘retro’ look that most people appreciate.

    Oscilloclock Model 1-S at Tokyo Maker Faire 2013
    Heathkit OR-1 Oscilloclock

    And you can flip a menu setting to display days, months, years in Japanese:

    There are also some ‘random’ screens that add in a bit of dynamic visual entertainment:

    • Random number screen
    • Random letter sequence screen
    • Random four letter word screen (clean words only, by default!)
    • Random phrase screen (the phrase list is typically customized to a theme)

    And of course the mesmerizing Timedrops screen:

    Themed Screens and Features

    … These themed features were developed more recently, and can be added for a small fee to help cover development costs!

    Astroclock (Sidereal Time)

    External XY input

    OscilloTerm (serial terminal)

    Oscilloblock (lego)

    Metropolis

    Aftershock Clock (Earthquake display)

    Unbirthday Clock

    War Games

    Logo screens

    Over the years many folks have requested that I render custom logos in Circle Graphics. Here are some examples:

    Toshiba ST-1248D - Brass bezel

    “Seasonal Treats”

    Up next are some fun, mildly interactive animation features. Not exactly screens per se, these animations pop up after a predefined period of inactivity – but only during certain months of the year. Can you guess which months?

    Boo!
    Santa in your Clock!

    Menu screens

    There are far too many configuration menu and test screens to present here. Fiddle to your heart’s content!

    Various arcs that can be made by blanking out circles

    Q. How are screens switched?

    Screens are switched simply by rotating the control knob in one direction or other.

    There is also a configurable auto-switch feature; the screen is changed every 90 seconds in a predefined order (with the exception of some animation screens). The display time is configurable, and the auto-switch feature can also be turned off for those who prefer to switch screens manually.

    Q. How are screens selected & configured?

    Customers can request screens to include and/or specify the switching order. The configuration is done here in the lab before clocks are delivered.

    Oscilloclock also provides a firmware upgrade kit, which allows the customer to upload a revised version of the firmware into the clock themselves. Using this, updates to screens and other features can be uploaded without shipping the clock back to the lab.

    Q. What is the process for rendering a custom screen or logo?

    We typically prepare a mock-up based on the customer’s description, sketch, or image file. This is tweaked as needed until the screen looks just right to the customer.

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