12 ms·

Precision Clock Mk IV

552 points by ahlCVA 1y ago

djoldman 1y ago
You just have to give the upvote for projects targeting extreme performance hardware by the DIY folks. If I'm not mistaken, this is why HN was made.
- hinkley 1y ago
  I’m still waiting for several guys on YouTube to get their steel ball clock to display seconds. Though their neighbors will kill them. Their prototypes are so goddamned loud.
a3w 1y ago
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- deleted 1y ago
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addaon 1y ago
Beautiful write-up of taking a project from requirements to a shipping product. I wish I had any use for one at all!
brokensegue 1y ago
i love mitxela and i love this project. don't know if i can stomach >250 GBP for a clock though.
- naikrovek 1y ago
  I was about to buy two, but my daughter lost my debit card while running an errand for me and I had to have the card replaced. That will take a few days, but it doesn’t matter, they’re sold out.
reconnecting 1y ago
Hope it's not the case, but... People with photosensitive epilepsy are affected by lights that have different flash or flicker rates from as low as 3 to as high as 60 per second.
- drivers99 1y ago
  What part does this comment refer to? It looks like they're multiplexing each section of the display at 100 kHz rate (500 kHz overall), well outside that range.
  - reconnecting 1y ago
    Thanks for the clarification. I was just raising a general concern about flicker affecting people with photosensitive epilepsy, but if the multiplexing is indeed at 100 kHz per section, that’s definitely outside the problematic range.
- alwa 1y ago
  In fact, this is one of the central design points he mentions within the first two lines of TFA: no point in a clock with a milliseconds place if it doesn’t display each millisecond legibly. > Summary The specifications for the clock were as follows: * Millisecond precision, with no perceptible jitter * Display clearly, without flicker, when filmed at very high framerates (20,000fps or more). The brightness should still automatically adjust, of course, and without the use of PWM
  - reconnecting 1y ago
    This reminded me how in Japan, 700 people were rushed to the hospital after watching pokemon on TV [1] due to 12Hz red/blue flashing frames, but now I understand that’s not the case here. [1] https://www.neurology-asia.org/articles/19991_001.pdf https://www.neurology-asia.org/articles/19991_001.pdf
    - cstrahan 1y ago
      I’m guessing you’ve already realized this, but in case it helps clarify things for someone else: The signals rates mentioned in the article are with respect to how frequently the segments are updated, not the brightness. (With the one exception being the colons being PWM controlled, IIRC). PWM means Pulse Width Modulation. Controlling a (perceived) light intensity of an LED via PWM means (if we pretend for the sake of simplification that the voltage rise and fall is instantaneous, etc) quickly turning the LED fully on and fully off, varying the duty cycle to achieve the desired perceived brightness. This project avoids the flickering inherent with PWM by not using PWM: the voltage itself is set to some fixed value for a given target brightness. (If one then wonders why this wouldn’t be the default approach for such things: microcontrollers often provide a built in means for PWM output, but it’s less common to have built in true, non-PWM analog outputs, requiring additional parts (thus more cost, more complexity) to implement variable voltage control).
drivers99 1y ago
The attention to detail in the assembly instructions was enjoyable to read.
geerlingguy 1y ago
One of the best features of this clock (I have one and have been messing with it a while now) is the up to 100 kHz refresh rate and an analog LCD driver circuit that makes the digits not flicker even a bit, even when dimmed, with a high speed camera. That and the fact it's the highest precision clock display I've ever owned! It is certainly not inexpensive, but it's more of an art piece than a practical instrument, unless your eyes can see in the thousands-of-hertz range!
- newman314 1y ago
  Super random but I seem to remember that you were working on/testing a different time device/prototype recently in a GitHub comment. Can you perhaps refresh my memory? Been trying to find the reference and it's driving me nuts this am. Thanks.
  - geerlingguy 1y ago
    Check my time-pi repository on GitHub: https://github.com/geerlingguy/time-pi https://github.com/geerlingguy/time-pi
- gblargg 1y ago
  Note that it's LED, with each segment driven continuously with a variable voltage for brightness control. Even most LED drivers are multiplexed, with each segment flashing for a short time then going dark. This uses a separate dedicated buffer for every segment. This design is important for working well with high-speed cameras, an obvious use.
airstrike 1y ago
Easily my favorite part > Auto timezone > Possibly the most requested feature, automatically setting the timezone based on the GPS coordinates was essential. However, most people don't realise how complex this process is, at least within the restrictions I'd given myself: no internet or cellular modem, nothing beyond the GPS data, and a USB port for occasional updates. > If we had an internet connection, sure, we could just query an online service. But I don't want my clock to require wifi. > If we had a cellular modem, we could get the time from the cell towers, which is broadcast through a protocol called NITZ. This is how phones auto-update when you enter a different timezone, but it's somewhat unreliable depending on the carrier, and overall worse than using GPS. And I really don't want my clock to have a sim card. > I'd also like, just for the sake of it, for the clock to work anywhere in the world, even at sea. > This means we need to keep a copy of the map data for the country outlines for the whole world. It also means we need a full copy of the timezone database, and have the processing power onboard to make use of all this.
- deleted 1y ago
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Neywiny 1y ago
I'll concede I didn't make it all the way through. I always have respect for people who make a physical product, especially one to sell. I'm not really tracking the MHz signals thing considering there's the 10 MHz oscillator. It would've been interesting to see an EMI/C report. Usually I can see SMPS frequencies as a spur (especially in PFM mode). For the 32K, at least for the H7 they recommended a ring of ground around it for some shielding. Unsure if that would've helped here. There are also micros that can use their internal RC 32K on vbat. And ones that can do USB without a crystal. The best micro is the one you know, the second best is the one you have. Maybe that's in play here. The LED driver variability was nifty. My first reaction to large IO with tight timing would be an FPGA, but I don't know if they'd like the variable bank supply. It would probably be fine bit the solution used is interesting and works.
- LiamPowell 1y ago
  > It would've been interesting to see an EMI/C report. It's a two layer board with no attempts made to keep loop areas small, it's going to be bad. Most of what I read of this seems fine at a glance but that part about EMI sticks out as complete nonsense. Edit: I have nothing against it being a two layer stackup as part of the art of it, I however don't like that they're also claiming that it's designed to have extremely low radiated emissions while doing so.
  - mastax 1y ago
    > no attempts made to keep loop areas small That is not correct, with a charitable reading of the text. Which is not to say it’ll have good EMI characteristics - you never really know until you get it tested. > Artificially confining ourselves to two layers is exactly the kind of challenge I am wont to be engulfed by. The trick, if you want the board to work well, is to work on only one layer, and keep almost the entirety of the other layer as ground. It is almost always possible to do this, if you're willing to put in enough thought. I rather find that designing circuit boards is a lot like Tetris, and once I'm in the swing of it I can route things for hours on end. It can become a multi-day trance, with dreams of signal integrity and current loop area. Though on this subject: > In contrast, said this one PCB designer, a thin track has a higher inductance, so if you make your power supply lines thin, you'll get a free bit of extra filtering. Inductance in your power supply lines is bad, but I don’t have time to get into it right now.
ianbicking 1y ago
"If we had a cellular modem, we could get the time from the cell towers, which is broadcast through a protocol called NITZ. This is how phones auto-update when you enter a different timezone, but it's somewhat unreliable depending on the carrier, and overall worse than using GPS. And I really don't want my clock to have a sim card." Just out of curiosity, what can you do with a cellular modem but no sim card? Can you get the time?
- infthi 1y ago
  One possibility is to call 911 and ask what time is it.
  - accrual 1y ago
    I know this wasn't meant literally, but it does make for an interesting thought experiment - under what circumstances might it be valid to dial 911 to ask for the time? My first thought was something like a nuclear operator - "we need to shut down the core at exactly 19:00, but our clocks are down!" so they call and wait for the operator to advise when the time is reached. Obviously contrived and not realistic, but interesting to think about.
    - mattbee 1y ago
      In the UK they are fine with you calling 999 to test your newly-configured office phone routing. They don't want a chat though.
      - fc417fc802 1y ago
        That's a bit different than asking for the time. That's testing a newly configured emergency system to make sure it works.
    - zzo38computer 1y ago
      > under what circumstances might it be valid to dial 911 to ask for the time? Maybe, if all of your clocks don't work and you went to somewhere else and their clock isn't working either, and it is raining and you cannot use a sundial, and you tried to call everyone else already and they also cannot give you the time for whatever reason, then you might try to call 911 and ask them, because you tried everything else and it didn't work. (I once heard a (fictional) story where this happened. This is an unlikely scenario, but some of the things mentioned here (and other things) might happen, e.g. bad weather so you cannot go out, the television and computers are not working (and maybe the power is out but the telephone uses a separate power), and there are some problems with the telephone too (I have had problems before where some telephone numbers worked and some didn't), etc.)
boricj 1y ago
> I designed this clock years ago, with the intention to incorporate every feature request I ever received for the previous precision clock. My first thought after reading this statement was to add one Ethernet port to run a NTP server and have PoE capability. Completely overkill for the intended purpose, but I can't help but giggle at the thought of hanging this on a wall in a datacenter and have the clock also provide time-keeping for it.
- XorNot 1y ago
  That would actually be really useful though: being able to see at a glance what the network time should be would be incredibly useful. There's other types of environments where you isolated users like SCIFs or really anything airgapped. Hell: that would convince me to buy one that for my house.
  - signal-intel 1y ago
    No GPS in SCIFs. Agree ntp would be great. Also I’d prefer a way to manually switch between a fixed set of time zone, or even just showing UTC always as an option.
    - sneak 1y ago
      How do SCIFs do time? Do they use optoisolated network connections and then do time sync over that? (SIPRnet, is it?)
      - signal-intel 1y ago
        The US Navy maintains NTP servers on a variety of networks, the public internet and SIPR included. https://www.cnmoc.usff.navy.mil/Our-Commands/United-States-Naval-Observatory/Precise-Time-Department/Network-Time-Protocol-NTP/DoD-Customer-Servers/ https://www.cnmoc.usff.navy.mil/Our-Commands/United-States-N...
      - offmycloud 1y ago
        If you have a special project need, you might be able to get one-way IRIG time signal on fiber with guard boxes at both ends. There's really no technical reason why you couldn't do analog GPS baseband over fiber, but you do need approved equipment at both ends for policy reasons. (certified for no backflow)
Scene_Cast2 1y ago
That reminds me of production studio master clocks such as the bronics WCD-530W or the evertz equivalent. I'm more of a fan of the analog style such as the 1275T - https://evertz.com/products/12x5T https://evertz.com/products/12x5T.
sstanfie 1y ago
I use two of these clocks daily at work, to synchronize a high-speed process on video. I'll be buying a couple more.
- Scaevolus 1y ago
  How well synchronized are the updates of the two displays?
  - geerlingguy 1y ago
    Assuming any decent GPS signal at all, they should be well within 1ms of each other, likely a bit better.
    - tverbeure 1y ago
      A cheap GPS module without a disciplined 1PPS output (like the ublox MAX-M8 that's used in this project) typically has a jitter of about a few hundreds nanoseconds, so the potential is there for the precision to be much better than 1ms if the microcontroller on this clock has the 1PPS wired to an interrupt routine.
      - geerlingguy 1y ago
        That it does. Should be within tens of ns if you have good reception and decent antenna placement.
        addaon 1y ago
        In a previous life, with a specific set of hardware, we used a measured value of 70 ns two sigma as the typical skew between two GPS-disciplined clocks. Don’t use these numbers without testing your own system, but confirms order of magnitude estimate.
      - RossBencina 1y ago
        > jitter of about a few hundreds nanoseconds The 1PPS output may have that much jitter (due to it being clocked synchronously with the module's system clock) but I believe there is usually a way to query the device for the error between the 1PPS signal and the actual idealised pulse time. Sylvain Munaut made a project using a high resolution TDC/time of flight converter to discipline another clock against the GPS idealised pusle time. I can't find a link right now unfortunately.
mastax 1y ago
Absolutely fascinating read and design process for something which I thought didn’t seem that hard to do ;)
lokimedes 1y ago
Feature request for Mk V: An onboard committee of three atomic clocks to ensure proper uncertainty estimation when GPS is lost.
- mastax 1y ago
  Finally a good use case for the chip-scale atomic clock. https://www.microchip.com/en-us/product/csac-sa65 https://www.microchip.com/en-us/product/csac-sa65
  - nullhole 1y ago
    Heh, my thoughts exactly! Those chips are also useful for getting better positions from navigation signals. One could imagine using them to help filter out spoofed signals, for example.
- nullhole 1y ago
  They exist[0], but aren't cheap (~$1400 US/chip for the base model). [0] https://www.microchip.com/en-us/products/clock-and-timing/components/atomic-clocks/embedded-atomic-oscillators/mac https://www.microchip.com/en-us/products/clock-and-timing/co...
  - tverbeure 1y ago
    Rubidium oscillators are atomic clocks the way PhDs are doctors! (Don't worry, I know they are considered atomic clocks, I have 2 Rb modules.)
KingOfCoders 1y ago
A philosophical, ontological problem, a clock or a display? (Really nice project)
accrual 1y ago
This is insanely cool. It's a beautifully written article that covers all the major design decisions and issues that affected the final outcome. I'm considering purchasing one for myself and to support the developer. It would be a very cool addition to a homelab or tech/hacker space. I think my own minor issue is the use of a micro-USB port instead of USB-C - I wonder why, I don't see it mentioned in the article. Maybe adding a PD controller would have complicated the already complex dance of components on the board. Standard USB can supply 5V at 1A (5.0W) no problem, so maybe that was just a simpler way to go.
- Kirby64 1y ago
  > I think my own minor issue is the use of a micro-USB port instead of USB-C - I wonder why, I don't see it mentioned in the article. Maybe adding a PD controller would have complicated the already complex dance of components on the board. Standard USB can supply 5V at 1A (5.0W) no problem, so maybe that was just a simpler way to go. You don’t need a PD controller. You need two resistors of a set value to be able to have USB-C supply 5V at up to 3A. No ICs needed on the input side.
  - accrual 1y ago
    Great point! I suppose then it would be trivial to add ones own USB-C port if desired.
- LiamPowell 1y ago
  Most have very small spaces between the pins, they might not have been able to do them reliably on their home setup shown at the end of the post.
  - bsder 1y ago
    Power-only USB-C connectors don't have the same pitch issues as they only need to pin out the power and CC1/CC2 pins. However, the 0.65/0.40 pads required for USB-C are no longer an issue for any of the board houses I have used in the past couple of years.
hinkley 1y ago
Umm.. it’s not time to the millisecond of the 100s and thousandths place smear to “88”. I wonder if there’s some electronics hackers you can do to increase the response time on the last three elements.
- m1el 1y ago
  It's an artifact of the camera. The camera shutter is long enough that it averages the images over 33ms. At some point in the video you can see that a high speed camera can see the correct display.
  - hinkley 1y ago
    In the high speed you can see that they are distinct but you can see the rollover. Maybe mark V could tighten that up.
    - signal-intel 1y ago
      At the 7 minute mark the industrial 14k FPS camera shows essentially zero rollover. The earlier rollover does appear to be an artifact of the cheap consumer grade high speed camera used.
- Bud 1y ago
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WhitneyLand 1y ago
Is it possible to be an engineer and not think this is cool?
IIAOPSW 1y ago
When you're identical twin gets back from their extended space travels with their clock you're going to be in for some hard truths about the nature of precision and time.
- hinkley 1y ago
  They just need to go to IIS. IIRC the astronauts are already milliseconds younger than us. Too bad hard living up there prematurely ages them far faster than milliseconds per day.
hinkley 1y ago
The bike mechanic in the back of my head wants to know if you eventually filed down those bolts so they aren’t as proud of the nuts.
xd1936 1y ago
I've assembled two Mk III kits and they've been a delight each time. Instant impulse buy from me.
matrix2596 1y ago
Best of luck.
matrix2596 1y ago
Really interesting to see the deep dive into PCB design and EMI considerations here. It's a great reminder how much thought goes into balancing cost, manufacturability, and compliance, even for hobbyist products. The point about using one layer as a near-continuous ground plane is especially practical, and it's fascinating how even seemingly minor layout choices can have big implications for signal integrity. Thanks to everyone for sharing their expertise—it's one of the things that makes this community so valuable.
- matrix2596 1y ago
  yes
- deleted 1y ago
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HippoBaro 1y ago
I’m amazed by the ambition, technical brilliance, and relentless dedication behind some personal projects on display here. All of this for a clock! I don’t get it, but I’m in awe.
gregsadetsky 1y ago
When I encourage/cheerlead my extremely technically talented friends to “monetize their hobbies”, I am picturing exactly this. A hyper technical, perfectly executed, fun/whimsical/smart product. You can share all the source code and have build instructions! And sell assembled versions and make a buck! And hopefully make money / thrive/survive doing what… you love? ((The reality, ofc, is that in the hardware biz, getting more orders can just mean a ton of additional problems re logistics of making, assembling and shipping the thing. But I still naively think that’s a good problem..?)) Extraordinary Clock, truly. Cheers, congrats on launching and wishing you all the sales!
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bdz 1y ago
£350, I just realized I'm poor
- layer8 1y ago
  It’s cheaper than an Apple Watch Series 10. ;)
- SimonAllen 1y ago
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bubblethink 1y ago
Cool project, but with this sort of power and area budget, can't we use chip scale atomic clocks ? Also, the quartz accuracy is listed as 1000 seconds to drift 1 millisecond. So that's 31 secs a year ? That's less than HAQ quartz watches (+- 5 secs a year) and definitely less than Citizen 0100 (+-1 sec a year).
- layer8 1y ago
  The clock is synchronized to the GPS time signal. So the quartz accuracy is only for when you have no GPS signal, or between synchronizations.
  - bubblethink 1y ago
    Yes, I get that, but that is less interesting. Any clock can sync to GPS or NTP. It would be cooler to have an autonomous accurate clock if you are making a giant device with an ARM chip, flash storage etc.
    - layer8 1y ago
      I wouldn’t know how to obtain a clock that synchronizes to GPS. I’ve had situations in the past where it would have been useful to have such a clock for checking at a glance if the NTP server is screwing me up, or when you’re offline.
      - bubblethink 1y ago
        If you want a commercial GPS wall clock, Seiko makes several models. I have one - GP502W. They make others too. They are JDM models though, so you'll have to order one from Japan.
        layer8 1y ago
        Thanks. Do you know if it automatically adjusts to the local time zone?
layer8 1y ago
How well does the GPS work indoors?
- geerlingguy 1y ago
  I've been testing various GPS/GNSS antennas indoors for the past year, and unless you're in a multistory building or have a full metal roof, there's a good chance you'll pick up 4+ satellites, good enough for a decent time. But it can come and go, especially as there are other sources of interference in the 1-1.5 GHz range indoors, and reflections off various surfaces and objects make the signal way harder to distinguish. But for by far the best chance of success, you should have the antenna outside, ideally with a clear view of most of the sky. If inside, you could put it near a window or exterior wall, but a lot of modern construction materials can block things pretty badly.
- petee 1y ago
  I have an older garmin gps18x I use for ntp and it gets fantastic reception from a window shaded by trees. I wanted to test a monitor script so I stuffed it in a metal can, capped with a thick plate, and used excessive tinfoil to seal...If i recall it only dropped 2 satellites near the horizon, leaving 4+ with good signal. I suspect the signal was leaking in through the cable. During past year running i don't believe its lost 3d fix once (not in the can)
jiveturkey 1y ago
Damn. Out of Stock. Wish the 2 ports were on the rear.
timewizard 1y ago
> Timezone and offset should be determined automatically from the GPS coordinates, no customisation or user interaction needed Are there no good reasons why I might want to display time for a timezone other than the one I am currently in?
PicassoCTs 1y ago
Wouldn't be- a oscillator display, showing the quartz crystal oscillating, be the final display of precision? Like a pendulum, but for the digital age?
sneak 1y ago
I thought about doing precisely something like this, with a tcxo and an fpga! I’m happy to see someone else has already taken it to its logical conclusion. The only other thing I’d add is NTP support, and perhaps I2C for driving external displays (such as a few other time zones).
lgats 1y ago
feature request: wifi and ntp server
DrNosferatu 1y ago
Make the clock ETERNAL with solar power to charge a small battery ;)
Tabular-Iceberg 1y ago
To work at sea it would rather need a way to manually enter an offset, since customarily the local time on board is entirely at the discretion of the master.
- Jolter 1y ago
  Maybe a feature request for mk V?
schobi 1y ago
What a beautiful execution. He seems to have included all requests and written about every detail. Going to this kind of resolution, the only practical use case is with cameras. You record some frames and later want to check the exact timestamp. This is even useful for a single image, not just high speed cameras. But taking images is not just a single point in time. There is an exposure time and it is hard to measure absolute timings on start and end of exposure. With a segment clock display, the numbers will blur. For this a row of LEDs is fine - just light up one at a time. In the image you will see multiple leds on at once, giving you verification of start and stop. But again, I needed just one clock and built it already.
1120 1y ago
any chance that this clock wwould dbe available by Christmas 2025 Thanks Susan Morris USA
dtgriscom 1y ago
I ordered one of these the same day (5/31). Arrived yesterday, built this morning in about two hours, came right up and worked. Very, very cool. Great design, great instructions.

552 points by ahlCVA 1y ago

You just have to give the upvote for projects targeting extreme performance hardware by the DIY folks. If I'm not mistaken, this is why HN was made.

hinkley 1y ago
I’m still waiting for several guys on YouTube to get their steel ball clock to display seconds. Though their neighbors will kill them. Their prototypes are so goddamned loud.

a3w 1y ago

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addaon 1y ago

Beautiful write-up of taking a project from requirements to a shipping product. I wish I had any use for one at all!

brokensegue 1y ago

i love mitxela and i love this project. don't know if i can stomach >250 GBP for a clock though.

naikrovek 1y ago
I was about to buy two, but my daughter lost my debit card while running an errand for me and I had to have the card replaced. That will take a few days, but it doesn’t matter, they’re sold out.

reconnecting 1y ago

Hope it's not the case, but... People with photosensitive epilepsy are affected by lights that have different flash or flicker rates from as low as 3 to as high as 60 per second.

drivers99 1y ago
What part does this comment refer to? It looks like they're multiplexing each section of the display at 100 kHz rate (500 kHz overall), well outside that range.
- reconnecting 1y ago
  Thanks for the clarification. I was just raising a general concern about flicker affecting people with photosensitive epilepsy, but if the multiplexing is indeed at 100 kHz per section, that’s definitely outside the problematic range.
alwa 1y ago
In fact, this is one of the central design points he mentions within the first two lines of TFA: no point in a clock with a milliseconds place if it doesn’t display each millisecond legibly. > Summary The specifications for the clock were as follows: * Millisecond precision, with no perceptible jitter * Display clearly, without flicker, when filmed at very high framerates (20,000fps or more). The brightness should still automatically adjust, of course, and without the use of PWM
- reconnecting 1y ago
  This reminded me how in Japan, 700 people were rushed to the hospital after watching pokemon on TV [1] due to 12Hz red/blue flashing frames, but now I understand that’s not the case here. [1] https://www.neurology-asia.org/articles/19991_001.pdf https://www.neurology-asia.org/articles/19991_001.pdf
  - cstrahan 1y ago
    I’m guessing you’ve already realized this, but in case it helps clarify things for someone else: The signals rates mentioned in the article are with respect to how frequently the segments are updated, not the brightness. (With the one exception being the colons being PWM controlled, IIRC). PWM means Pulse Width Modulation. Controlling a (perceived) light intensity of an LED via PWM means (if we pretend for the sake of simplification that the voltage rise and fall is instantaneous, etc) quickly turning the LED fully on and fully off, varying the duty cycle to achieve the desired perceived brightness. This project avoids the flickering inherent with PWM by not using PWM: the voltage itself is set to some fixed value for a given target brightness. (If one then wonders why this wouldn’t be the default approach for such things: microcontrollers often provide a built in means for PWM output, but it’s less common to have built in true, non-PWM analog outputs, requiring additional parts (thus more cost, more complexity) to implement variable voltage control).

drivers99 1y ago

The attention to detail in the assembly instructions was enjoyable to read.

geerlingguy 1y ago

One of the best features of this clock (I have one and have been messing with it a while now) is the up to 100 kHz refresh rate and an analog LCD driver circuit that makes the digits not flicker even a bit, even when dimmed, with a high speed camera. That and the fact it's the highest precision clock display I've ever owned! It is certainly not inexpensive, but it's more of an art piece than a practical instrument, unless your eyes can see in the thousands-of-hertz range!

newman314 1y ago
Super random but I seem to remember that you were working on/testing a different time device/prototype recently in a GitHub comment. Can you perhaps refresh my memory? Been trying to find the reference and it's driving me nuts this am. Thanks.
- geerlingguy 1y ago
  Check my time-pi repository on GitHub: https://github.com/geerlingguy/time-pi https://github.com/geerlingguy/time-pi
gblargg 1y ago
Note that it's LED, with each segment driven continuously with a variable voltage for brightness control. Even most LED drivers are multiplexed, with each segment flashing for a short time then going dark. This uses a separate dedicated buffer for every segment. This design is important for working well with high-speed cameras, an obvious use.

airstrike 1y ago

Easily my favorite part > Auto timezone > Possibly the most requested feature, automatically setting the timezone based on the GPS coordinates was essential. However, most people don't realise how complex this process is, at least within the restrictions I'd given myself: no internet or cellular modem, nothing beyond the GPS data, and a USB port for occasional updates. > If we had an internet connection, sure, we could just query an online service. But I don't want my clock to require wifi. > If we had a cellular modem, we could get the time from the cell towers, which is broadcast through a protocol called NITZ. This is how phones auto-update when you enter a different timezone, but it's somewhat unreliable depending on the carrier, and overall worse than using GPS. And I really don't want my clock to have a sim card. > I'd also like, just for the sake of it, for the clock to work anywhere in the world, even at sea. > This means we need to keep a copy of the map data for the country outlines for the whole world. It also means we need a full copy of the timezone database, and have the processing power onboard to make use of all this.

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Neywiny 1y ago

I'll concede I didn't make it all the way through. I always have respect for people who make a physical product, especially one to sell. I'm not really tracking the MHz signals thing considering there's the 10 MHz oscillator. It would've been interesting to see an EMI/C report. Usually I can see SMPS frequencies as a spur (especially in PFM mode). For the 32K, at least for the H7 they recommended a ring of ground around it for some shielding. Unsure if that would've helped here. There are also micros that can use their internal RC 32K on vbat. And ones that can do USB without a crystal. The best micro is the one you know, the second best is the one you have. Maybe that's in play here. The LED driver variability was nifty. My first reaction to large IO with tight timing would be an FPGA, but I don't know if they'd like the variable bank supply. It would probably be fine bit the solution used is interesting and works.

LiamPowell 1y ago
> It would've been interesting to see an EMI/C report. It's a two layer board with no attempts made to keep loop areas small, it's going to be bad. Most of what I read of this seems fine at a glance but that part about EMI sticks out as complete nonsense. Edit: I have nothing against it being a two layer stackup as part of the art of it, I however don't like that they're also claiming that it's designed to have extremely low radiated emissions while doing so.
- mastax 1y ago
  > no attempts made to keep loop areas small That is not correct, with a charitable reading of the text. Which is not to say it’ll have good EMI characteristics - you never really know until you get it tested. > Artificially confining ourselves to two layers is exactly the kind of challenge I am wont to be engulfed by. The trick, if you want the board to work well, is to work on only one layer, and keep almost the entirety of the other layer as ground. It is almost always possible to do this, if you're willing to put in enough thought. I rather find that designing circuit boards is a lot like Tetris, and once I'm in the swing of it I can route things for hours on end. It can become a multi-day trance, with dreams of signal integrity and current loop area. Though on this subject: > In contrast, said this one PCB designer, a thin track has a higher inductance, so if you make your power supply lines thin, you'll get a free bit of extra filtering. Inductance in your power supply lines is bad, but I don’t have time to get into it right now.

ianbicking 1y ago

"If we had a cellular modem, we could get the time from the cell towers, which is broadcast through a protocol called NITZ. This is how phones auto-update when you enter a different timezone, but it's somewhat unreliable depending on the carrier, and overall worse than using GPS. And I really don't want my clock to have a sim card." Just out of curiosity, what can you do with a cellular modem but no sim card? Can you get the time?

infthi 1y ago
One possibility is to call 911 and ask what time is it.
- accrual 1y ago
  I know this wasn't meant literally, but it does make for an interesting thought experiment - under what circumstances might it be valid to dial 911 to ask for the time? My first thought was something like a nuclear operator - "we need to shut down the core at exactly 19:00, but our clocks are down!" so they call and wait for the operator to advise when the time is reached. Obviously contrived and not realistic, but interesting to think about.
  - mattbee 1y ago
    In the UK they are fine with you calling 999 to test your newly-configured office phone routing. They don't want a chat though.
    - fc417fc802 1y ago
      That's a bit different than asking for the time. That's testing a newly configured emergency system to make sure it works.
  - zzo38computer 1y ago
    > under what circumstances might it be valid to dial 911 to ask for the time? Maybe, if all of your clocks don't work and you went to somewhere else and their clock isn't working either, and it is raining and you cannot use a sundial, and you tried to call everyone else already and they also cannot give you the time for whatever reason, then you might try to call 911 and ask them, because you tried everything else and it didn't work. (I once heard a (fictional) story where this happened. This is an unlikely scenario, but some of the things mentioned here (and other things) might happen, e.g. bad weather so you cannot go out, the television and computers are not working (and maybe the power is out but the telephone uses a separate power), and there are some problems with the telephone too (I have had problems before where some telephone numbers worked and some didn't), etc.)

boricj 1y ago

> I designed this clock years ago, with the intention to incorporate every feature request I ever received for the previous precision clock. My first thought after reading this statement was to add one Ethernet port to run a NTP server and have PoE capability. Completely overkill for the intended purpose, but I can't help but giggle at the thought of hanging this on a wall in a datacenter and have the clock also provide time-keeping for it.

XorNot 1y ago
That would actually be really useful though: being able to see at a glance what the network time should be would be incredibly useful. There's other types of environments where you isolated users like SCIFs or really anything airgapped. Hell: that would convince me to buy one that for my house.
- signal-intel 1y ago
  No GPS in SCIFs. Agree ntp would be great. Also I’d prefer a way to manually switch between a fixed set of time zone, or even just showing UTC always as an option.
  - sneak 1y ago
    How do SCIFs do time? Do they use optoisolated network connections and then do time sync over that? (SIPRnet, is it?)
    - signal-intel 1y ago
      The US Navy maintains NTP servers on a variety of networks, the public internet and SIPR included. https://www.cnmoc.usff.navy.mil/Our-Commands/United-States-Naval-Observatory/Precise-Time-Department/Network-Time-Protocol-NTP/DoD-Customer-Servers/ https://www.cnmoc.usff.navy.mil/Our-Commands/United-States-N...
    - offmycloud 1y ago
      If you have a special project need, you might be able to get one-way IRIG time signal on fiber with guard boxes at both ends. There's really no technical reason why you couldn't do analog GPS baseband over fiber, but you do need approved equipment at both ends for policy reasons. (certified for no backflow)

Scene_Cast2 1y ago

That reminds me of production studio master clocks such as the bronics WCD-530W or the evertz equivalent. I'm more of a fan of the analog style such as the 1275T - https://evertz.com/products/12x5T https://evertz.com/products/12x5T.

sstanfie 1y ago

I use two of these clocks daily at work, to synchronize a high-speed process on video. I'll be buying a couple more.

Scaevolus 1y ago
How well synchronized are the updates of the two displays?
- geerlingguy 1y ago
  Assuming any decent GPS signal at all, they should be well within 1ms of each other, likely a bit better.
  - tverbeure 1y ago
    A cheap GPS module without a disciplined 1PPS output (like the ublox MAX-M8 that's used in this project) typically has a jitter of about a few hundreds nanoseconds, so the potential is there for the precision to be much better than 1ms if the microcontroller on this clock has the 1PPS wired to an interrupt routine.
    - geerlingguy 1y ago
      That it does. Should be within tens of ns if you have good reception and decent antenna placement.
      - addaon 1y ago
        In a previous life, with a specific set of hardware, we used a measured value of 70 ns two sigma as the typical skew between two GPS-disciplined clocks. Don’t use these numbers without testing your own system, but confirms order of magnitude estimate.
    - RossBencina 1y ago
      > jitter of about a few hundreds nanoseconds The 1PPS output may have that much jitter (due to it being clocked synchronously with the module's system clock) but I believe there is usually a way to query the device for the error between the 1PPS signal and the actual idealised pulse time. Sylvain Munaut made a project using a high resolution TDC/time of flight converter to discipline another clock against the GPS idealised pusle time. I can't find a link right now unfortunately.

mastax 1y ago

Absolutely fascinating read and design process for something which I thought didn’t seem that hard to do ;)

lokimedes 1y ago

Feature request for Mk V: An onboard committee of three atomic clocks to ensure proper uncertainty estimation when GPS is lost.

mastax 1y ago
Finally a good use case for the chip-scale atomic clock. https://www.microchip.com/en-us/product/csac-sa65 https://www.microchip.com/en-us/product/csac-sa65
- nullhole 1y ago
  Heh, my thoughts exactly! Those chips are also useful for getting better positions from navigation signals. One could imagine using them to help filter out spoofed signals, for example.
nullhole 1y ago
They exist[0], but aren't cheap (~$1400 US/chip for the base model). [0] https://www.microchip.com/en-us/products/clock-and-timing/components/atomic-clocks/embedded-atomic-oscillators/mac https://www.microchip.com/en-us/products/clock-and-timing/co...
- tverbeure 1y ago
  Rubidium oscillators are atomic clocks the way PhDs are doctors! (Don't worry, I know they are considered atomic clocks, I have 2 Rb modules.)

KingOfCoders 1y ago

A philosophical, ontological problem, a clock or a display? (Really nice project)

accrual 1y ago

This is insanely cool. It's a beautifully written article that covers all the major design decisions and issues that affected the final outcome. I'm considering purchasing one for myself and to support the developer. It would be a very cool addition to a homelab or tech/hacker space. I think my own minor issue is the use of a micro-USB port instead of USB-C - I wonder why, I don't see it mentioned in the article. Maybe adding a PD controller would have complicated the already complex dance of components on the board. Standard USB can supply 5V at 1A (5.0W) no problem, so maybe that was just a simpler way to go.

Kirby64 1y ago
> I think my own minor issue is the use of a micro-USB port instead of USB-C - I wonder why, I don't see it mentioned in the article. Maybe adding a PD controller would have complicated the already complex dance of components on the board. Standard USB can supply 5V at 1A (5.0W) no problem, so maybe that was just a simpler way to go. You don’t need a PD controller. You need two resistors of a set value to be able to have USB-C supply 5V at up to 3A. No ICs needed on the input side.
- accrual 1y ago
  Great point! I suppose then it would be trivial to add ones own USB-C port if desired.
LiamPowell 1y ago
Most have very small spaces between the pins, they might not have been able to do them reliably on their home setup shown at the end of the post.
- bsder 1y ago
  Power-only USB-C connectors don't have the same pitch issues as they only need to pin out the power and CC1/CC2 pins. However, the 0.65/0.40 pads required for USB-C are no longer an issue for any of the board houses I have used in the past couple of years.

hinkley 1y ago

Umm.. it’s not time to the millisecond of the 100s and thousandths place smear to “88”. I wonder if there’s some electronics hackers you can do to increase the response time on the last three elements.

m1el 1y ago
It's an artifact of the camera. The camera shutter is long enough that it averages the images over 33ms. At some point in the video you can see that a high speed camera can see the correct display.
- hinkley 1y ago
  In the high speed you can see that they are distinct but you can see the rollover. Maybe mark V could tighten that up.
  - signal-intel 1y ago
    At the 7 minute mark the industrial 14k FPS camera shows essentially zero rollover. The earlier rollover does appear to be an artifact of the cheap consumer grade high speed camera used.
Bud 1y ago
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WhitneyLand 1y ago

Is it possible to be an engineer and not think this is cool?

IIAOPSW 1y ago

When you're identical twin gets back from their extended space travels with their clock you're going to be in for some hard truths about the nature of precision and time.

hinkley 1y ago
They just need to go to IIS. IIRC the astronauts are already milliseconds younger than us. Too bad hard living up there prematurely ages them far faster than milliseconds per day.

hinkley 1y ago

The bike mechanic in the back of my head wants to know if you eventually filed down those bolts so they aren’t as proud of the nuts.

xd1936 1y ago

I've assembled two Mk III kits and they've been a delight each time. Instant impulse buy from me.

matrix2596 1y ago

Best of luck.

matrix2596 1y ago

Really interesting to see the deep dive into PCB design and EMI considerations here. It's a great reminder how much thought goes into balancing cost, manufacturability, and compliance, even for hobbyist products. The point about using one layer as a near-continuous ground plane is especially practical, and it's fascinating how even seemingly minor layout choices can have big implications for signal integrity. Thanks to everyone for sharing their expertise—it's one of the things that makes this community so valuable.

matrix2596 1y ago
yes
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HippoBaro 1y ago

I’m amazed by the ambition, technical brilliance, and relentless dedication behind some personal projects on display here. All of this for a clock! I don’t get it, but I’m in awe.

gregsadetsky 1y ago

When I encourage/cheerlead my extremely technically talented friends to “monetize their hobbies”, I am picturing exactly this. A hyper technical, perfectly executed, fun/whimsical/smart product. You can share all the source code and have build instructions! And sell assembled versions and make a buck! And hopefully make money / thrive/survive doing what… you love? ((The reality, ofc, is that in the hardware biz, getting more orders can just mean a ton of additional problems re logistics of making, assembling and shipping the thing. But I still naively think that’s a good problem..?)) Extraordinary Clock, truly. Cheers, congrats on launching and wishing you all the sales!

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bdz 1y ago

£350, I just realized I'm poor

layer8 1y ago
It’s cheaper than an Apple Watch Series 10. ;)
SimonAllen 1y ago
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bubblethink 1y ago

Cool project, but with this sort of power and area budget, can't we use chip scale atomic clocks ? Also, the quartz accuracy is listed as 1000 seconds to drift 1 millisecond. So that's 31 secs a year ? That's less than HAQ quartz watches (+- 5 secs a year) and definitely less than Citizen 0100 (+-1 sec a year).

layer8 1y ago
The clock is synchronized to the GPS time signal. So the quartz accuracy is only for when you have no GPS signal, or between synchronizations.
- bubblethink 1y ago
  Yes, I get that, but that is less interesting. Any clock can sync to GPS or NTP. It would be cooler to have an autonomous accurate clock if you are making a giant device with an ARM chip, flash storage etc.
  - layer8 1y ago
    I wouldn’t know how to obtain a clock that synchronizes to GPS. I’ve had situations in the past where it would have been useful to have such a clock for checking at a glance if the NTP server is screwing me up, or when you’re offline.
    - bubblethink 1y ago
      If you want a commercial GPS wall clock, Seiko makes several models. I have one - GP502W. They make others too. They are JDM models though, so you'll have to order one from Japan.
      - layer8 1y ago
        Thanks. Do you know if it automatically adjusts to the local time zone?

layer8 1y ago

How well does the GPS work indoors?

geerlingguy 1y ago
I've been testing various GPS/GNSS antennas indoors for the past year, and unless you're in a multistory building or have a full metal roof, there's a good chance you'll pick up 4+ satellites, good enough for a decent time. But it can come and go, especially as there are other sources of interference in the 1-1.5 GHz range indoors, and reflections off various surfaces and objects make the signal way harder to distinguish. But for by far the best chance of success, you should have the antenna outside, ideally with a clear view of most of the sky. If inside, you could put it near a window or exterior wall, but a lot of modern construction materials can block things pretty badly.
petee 1y ago
I have an older garmin gps18x I use for ntp and it gets fantastic reception from a window shaded by trees. I wanted to test a monitor script so I stuffed it in a metal can, capped with a thick plate, and used excessive tinfoil to seal...If i recall it only dropped 2 satellites near the horizon, leaving 4+ with good signal. I suspect the signal was leaking in through the cable. During past year running i don't believe its lost 3d fix once (not in the can)

jiveturkey 1y ago

Damn. Out of Stock. Wish the 2 ports were on the rear.

timewizard 1y ago

> Timezone and offset should be determined automatically from the GPS coordinates, no customisation or user interaction needed Are there no good reasons why I might want to display time for a timezone other than the one I am currently in?

PicassoCTs 1y ago

Wouldn't be- a oscillator display, showing the quartz crystal oscillating, be the final display of precision? Like a pendulum, but for the digital age?

sneak 1y ago

I thought about doing precisely something like this, with a tcxo and an fpga! I’m happy to see someone else has already taken it to its logical conclusion. The only other thing I’d add is NTP support, and perhaps I2C for driving external displays (such as a few other time zones).

lgats 1y ago

feature request: wifi and ntp server

DrNosferatu 1y ago

Make the clock ETERNAL with solar power to charge a small battery ;)

Tabular-Iceberg 1y ago

To work at sea it would rather need a way to manually enter an offset, since customarily the local time on board is entirely at the discretion of the master.

Jolter 1y ago
Maybe a feature request for mk V?

schobi 1y ago

What a beautiful execution. He seems to have included all requests and written about every detail. Going to this kind of resolution, the only practical use case is with cameras. You record some frames and later want to check the exact timestamp. This is even useful for a single image, not just high speed cameras. But taking images is not just a single point in time. There is an exposure time and it is hard to measure absolute timings on start and end of exposure. With a segment clock display, the numbers will blur. For this a row of LEDs is fine - just light up one at a time. In the image you will see multiple leds on at once, giving you verification of start and stop. But again, I needed just one clock and built it already.

1120 1y ago

any chance that this clock wwould dbe available by Christmas 2025 Thanks Susan Morris USA

dtgriscom 1y ago

I ordered one of these the same day (5/31). Arrived yesterday, built this morning in about two hours, came right up and worked. Very, very cool. Great design, great instructions.