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Comment by magicalhippo | Hacker News Reader

Not quite the same, but I picked up a cheap GPS module with PPS output and an external antenna from AliExpress and hooked it up to a Raspberry Pi 3 running chrony.

Currently it's just set as the time server via DHCP for my computers, but I'm making a nixie clock which will use an ESP8266 running SNTP.

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Almost ten years ago I recycled/converted Topfield to show time with an arduino-like board and a network adapter. Basically, it listens to NTP broadcast messages and "keeps" time in between.

Its timekeeping will suck though if it won't receive the messages periodically, but in practice it's quite fine. Except once when the ethernet board somehow broke down; fixed it by replacing it.

Here's a short writeup I did for hackaday: https://www.modeemi.fi/~flux/projects/TopfieldClock/

Yeah, that's on my bucket list too. I love the looks of Nixie clocks, but I think I've read that they generate a lot of heat. Is that accurate?

No it is not. You can touch them, no problem.

Nixie tubes are cold-cathode discharge tubes.

I've got some IN-14's, they can't handle more than 2.5mA. Operating voltage is ~150V, so that's at most 0.38W per tube.

So no, they won't get hot.

This is unlike vacuum tubes, used for amplifiers and similar, which are hot-cathode and needs a heating filament. They can get quite hot indeed.

Out of curiosity, have you analyzed how different/better your setup is compared to just using something like time.google.com?

I admit it was more for the geek factor than anything else, and I'm no expert in the field. Here are the source stats[1] from chrony:

Pi with GPS

    $ chronyc sourcestats
    210 Number of sources = 7
    Name/IP Address            NP  NR  Span  Frequency  Freq Skew  Offset  Std Dev
    ==============================================================================
    PPS1                        8   6   112     -0.018      0.020   -105ns   336ns
    GPS1                        7   6    95    +55.685    111.018   +126ms  1058us
    GPS2                        8   6   112     -0.018      0.021    -89ns   341ns
    2a01:79a:408::250          18  10  310m     -0.057      0.080  -1364us   522us
    time.cloudflare.com        19  13  344m     -0.068      0.038  -1274us   258us
    ntp.coreless.net            6   3   85m     -0.343      0.706  -2355us   354us
    anduin.net                 21   8  379m     -0.020      0.051   -835us   388us

Debian VM running on Bhyve(FreeBSD) in same LAN

    $ chronyc sourcestats
    210 Number of sources = 5
    Name/IP Address            NP  NR  Span  Frequency  Freq Skew  Offset  Std Dev
    ==============================================================================
    timepi.localdomain         13   7   64m     +0.001      0.031   +328ns    28us
    79.161.39.253.static.lys>   8   6  120m     -0.002      0.184  -2122us   189us
    125.51-174-177.customer.>  22  13  464m     +0.287      0.117   -839us  1201us
    time.cloudflare.com         6   5   85m     +0.009      0.472  -1615us   277us
    c1EE4653E.static.as2116.>  10   7  155m     -0.146      0.603  -3315us  1256us

So on the VM it seems to "just" be an order of magnitude better. But that should be worst-case.

[1]: https://chrony.tuxfamily.org/doc/3.3/chronyc.html

Nice!

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