latest mad scientist project (nixie clock)
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Author:  WeaselSqueezer [ Sat Mar 29, 2014 8:32 pm ]
Post subject:  latest mad scientist project (nixie clock)

I always wanted a nixie clock, and recently I've been building one. Here's a picture of the first ignition test:

File comment: IN-18 ignition test
in18-ignition-test.jpg [ 57.21 KiB | Viewed 4446 times ]

Left: Raspberry Pi, center: custom daughterboard for Raspberry Pi, right: two IN-18 nixie vacuum tubes (from the Gazotron Tube Factory, Rovno, Ukraine) in custom driver board

Author:  MightyMouser [ Sun Mar 30, 2014 12:07 am ]
Post subject:  Re: latest mad scientist project (nixie clock)

Awesomesauce, Weas; I've always wanted to build one of these...

Author:  Fed [ Sun Mar 30, 2014 2:17 am ]
Post subject:  Re: latest mad scientist project (nixie clock)

Party like its 1999? Cool stuff wease. :)

Author:  icanbeurhero [ Mon Mar 31, 2014 5:36 am ]
Post subject:  Re: latest mad scientist project (nixie clock)

Nice! I like how people are getting creative with a cheap raspberry pi. I used to do stuff like this on some of the parallax basic stamp boards, PIC microcontrollers, then eventually moved over to the AVR microcontrollers and boards. I might get back into it with a raspberry pi :)

Author:  WeaselSqueezer [ Thu Apr 10, 2014 4:49 pm ]
Post subject:  Re: latest mad scientist project (nixie clock)

The big advantage of working with Pi is that you can use a full linux stack (Raspbian is Debian) with a constantly updated distribution, or something else if you prefer. This clock already has the 'heartbleed' patch. If I actually ran CAT5 to this, I could use it as a wireless access point, but I just want it to tell me what time it is, and be really goshdarn sure about that time.

gazotron_top.jpg [ 50.63 KiB | Viewed 4393 times ]

From the top: two high voltage DC-DC converters on the left, small audio amp, custom Pi power supply and expander PCB, Raspberry Pi (model B from UK), round blue 'Chronodot' RTC module, and three double custom tube drivers (BCD logic) along the front.

gazotron_side.jpg [ 67.86 KiB | Viewed 4393 times ]

Side shot showing speaker and proximity/ambient light module. Anybody else get "Hillbilly Bread" in their regional market?

gazotron_frontq.jpg [ 64.81 KiB | Viewed 4393 times ]

Author:  icanbeurhero [ Thu Apr 10, 2014 7:09 pm ]
Post subject:  Re: latest mad scientist project (nixie clock)

Damn that looks sweet! If you want accurate time, I guess you're gonna have to sync it with NTP servers - so you might as well add the whole network stack to it :P

Author:  AssemblerManiac [ Fri Apr 11, 2014 8:42 am ]
Post subject:  Re: latest mad scientist project (nixie clock)

Nice looking clock.

Did you use glass, lexan, or plexi for the clear stuff? Looks like glass, but can't tell.

Copper frame looks nice. Hard as heck to keep it all steady and square while you were doing it I bet.

Haven't played with Ras Pi, but can definitely think of cool applications for it. Just don't have the time to play with it.

Author:  WeaselSqueezer [ Mon Apr 14, 2014 12:54 pm ]
Post subject:  Re: latest mad scientist project (nixie clock)

Hey AssemblerManiac, long time no see!! It's actually 'low iron' glass, 1/4" thick. If you look at regular glass from the edge, it looks green, this stuff is much clearer. I did a lousy job making it, it was not intended to be particularly well done, but it came out a little better than expected. Stained glass soldering is a breeze if you're used to electronics. All of the solder on the outside is no-lead, and Kester NXG1 for the surface mount parts on the custom PCBs, but I used 60/40 leaded on the through-hole parts.

Yes, it runs an NTP daemon, and uses an Adafruit "Chronodot" RTC (DS3231) with thermally compensated crystal to set the date on boot. Easiest way to make sure that was working was to take out the battery :-) If I disable networking for the NTP daemon, it should only gain/lose a couple of minutes over a year.

I'm running the tubes way below nominal, it's supposed to need 200V to ignite and 4ma to shine, I'm seeing it ignite at 150V and almost running okay at 3.2ma. Some of the numbers have faded spots at that amperage.

ntpq -pn:
     remote           refid      st t when poll reach   delay   offset  jitter
*    3 u  732 1024  377   18.102   29.015  16.858
ntpdc -c kerninfo:
pll offset:           0.0242662 s
pll frequency:        -14.983 ppm
maximum error:        0.605618 s
estimated error:      0.020737 s
status:               2001  pll nano
pll time constant:    10
precision:            1e-09 s
frequency tolerance:  500 ppm
ntpdc -c loopinfo localhost:
offset:               0.029015 s
frequency:            -14.983 ppm
poll adjust:          30
watchdog timer:       732 s
ntp_gettime() returns code 0 (OK)
  time d6f68b46.dafdeb00  Mon, Apr 14 2014 12:28:54.855, (.855437716),
  maximum error 605618 us, estimated error 20737 us, TAI offset 0
ntp_adjtime() returns code 0 (OK)
  modes 0x0 (),
  offset 24266.211 us, frequency -14.983 ppm, interval 1 s,
  maximum error 605618 us, estimated error 20737 us,
  status 0x2001 (PLL,NANO),
  time constant 10, precision 0.001 us, tolerance 500 ppm,
cat /var/lib/ntp/ntp.drift:

Hmm, the offset is a little high today. I think it takes the inner loop 65ms to execute, so the amount of error is still faster than the speed at which the tubes are updated.

Anybody know what the real "Big Ben" sounds like? Right now, I have it chiming good resolution recordings of Big Ben in London ("Westminster"), but I don't know the amount of time between the cadence and the strikes. The recordings I have (from the UK Parliament web site) play out the final ring of the last note of the top of the hour, and I assume that the strikes follow that immediately. It seems to be a little longer between the first strike and the top of the hour cadence than it should be. I'll have to spend a little more time on YouTube trying to find a combined/full cadence with strikes.

Most importantly, my wife likes it. This is extremely important for glass objects that will be in your living room for the next 30 years.

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