Author Topic: Slightly overengineered nixie clock  (Read 15026 times)

0 Members and 1 Guest are viewing this topic.

Offline marshallh

  • Supporter
  • ****
  • Posts: 1459
  • Country: us
  • Country: us
    • retroactive
Slightly overengineered nixie clock
« on: August 24, 2015, 01:16:54 am »
I wanted an alarm clock to use for the next 20 years.

  • FPGA powered with 32bit CPU, 128kx16 SRAM
  • Hardware MPEG decoding
  • 13W audio amp
  • 802.11n Wifi, SD
  • Mains or 12v brick powered
  • 544x tube compatible
  • Regulated HV








Isolation slots did not show in 3d so I exported to the flexible CAD tool "MSPaint"



Buttons/switches are on a separate sub-board over 1wire.
I will update as I build it
« Last Edit: August 25, 2015, 01:12:28 am by marshallh »
Verilog tips
BGA soldering intro

11:37 <@ktemkin> c4757p: marshall has transcended communications media
11:37 <@ktemkin> He speaks protocols directly.
 

Offline Richard Head

  • Frequent Contributor
  • **
  • Posts: 682
  • Country: 00
  • Country: 00
Re: Slightly overengineered nixie clock
« Reply #1 on: August 24, 2015, 11:22:45 am »
Probably best to move C26 (electrolytic cap) away from the heatsink to ensure a longer cap lifetime.
 

Offline ajb

  • Super Contributor
  • ***
  • Posts: 1671
  • Country: us
  • Country: us
Re: Slightly overengineered nixie clock
« Reply #2 on: August 24, 2015, 02:17:44 pm »
No battery backup? 
 

Offline dr.diesel

  • Super Contributor
  • ***
  • Posts: 2118
  • Country: us
  • Country: us
  • Cramming the magic smoke back in...
Re: Slightly overengineered nixie clock
« Reply #3 on: August 24, 2015, 02:20:39 pm »
Is wifi for NTP sync or media only?

Offline Melt-O-Tronic

  • Regular Contributor
  • *
  • Posts: 212
  • Country: us
  • Country: us
  • Brilliant with a slaughtering iron in my hand!
Re: Slightly overengineered nixie clock
« Reply #4 on: August 24, 2015, 02:31:14 pm »
What's the local time base?

Related sub-question; how good will holdover be when an NTP source is unavailable?

Related sub-sub-question; how resilient will timekeeping be to power failures?



Edited to add my appreciation for over-engineering, especially on personal projects.   :-+
« Last Edit: August 24, 2015, 02:34:12 pm by Melt-O-Tronic »
 

Offline alexanderbrevig

  • Frequent Contributor
  • **
  • Posts: 582
  • Country: no
  • Country: no
  • Musician, programmer and EE hobbyist
    • alexanderbrevig.com
Re: Slightly overengineered nixie clock
« Reply #5 on: August 24, 2015, 07:38:55 pm »
This is totally awesome! Nice work man  :-+

Offline deephaven

  • Frequent Contributor
  • **
  • Posts: 783
  • Country: gb
  • Country: gb
  • Civilization is just one big bootstrap
    • Deephaven Ltd
Re: Slightly overengineered nixie clock
« Reply #6 on: August 24, 2015, 07:58:46 pm »
That is INSANE  :scared: Love it  :-+
 

Online tautech

  • Super Contributor
  • ***
  • Posts: 15649
  • Country: nz
  • Country: nz
  • Taupaki Technologies Ltd. NZ Siglent Distributor
    • Taupaki Technologies Ltd.
Re: Slightly overengineered nixie clock
« Reply #7 on: August 24, 2015, 08:41:43 pm »
Beautiful work so far, thanks for sharing.  8)  :-+

Avid Rabid Hobbyist
 

Offline rsjsouza

  • Super Contributor
  • ***
  • Posts: 3316
  • Country: us
  • Country: us
  • Eternally curious
    • Vbe - vídeo blog eletrônico
Re: Slightly overengineered nixie clock
« Reply #8 on: August 24, 2015, 08:52:35 pm »
marshallh, you should be using one of these as your main clock timebase... :)
Vbe - vídeo blog eletrônico http://videos.vbeletronico.com

Oh, the "whys" of the datasheets... The information is there not to be an axiomatic truth, but instead each speck of data must be slowly inhaled while carefully performing a deep search inside oneself to find the true metaphysical sense...
 

Offline marshallh

  • Supporter
  • ****
  • Posts: 1459
  • Country: us
  • Country: us
    • retroactive
Re: Slightly overengineered nixie clock
« Reply #9 on: August 24, 2015, 09:00:52 pm »
marshallh, you should be using one of these as your main clock timebase... :)
Someone turned me onto these...
http://www.microsemi.com/campaigns/atomic-clocks/


I have a 32khz and 50mhz quartz oscillator for timebase. Battery backup is nonexistent though I supose you could wire a 12v SLA to the jack and it would be a crappy UPS. Wifi is for NTP though it could be for streaming.

Added a photocell forming a RC circuit on a FPGA pin. Should let me sense ambient light and dim the tubes that way. Shunt the voltage then see how long it takes to reach Vhth with the pin tristated.
Verilog tips
BGA soldering intro

11:37 <@ktemkin> c4757p: marshall has transcended communications media
11:37 <@ktemkin> He speaks protocols directly.
 

Offline rsjsouza

  • Super Contributor
  • ***
  • Posts: 3316
  • Country: us
  • Country: us
  • Eternally curious
    • Vbe - vídeo blog eletrônico
Re: Slightly overengineered nixie clock
« Reply #10 on: August 25, 2015, 12:29:51 am »
marshallh, you should be using one of these as your main clock timebase... :)
Someone turned me onto these...
http://www.microsemi.com/campaigns/atomic-clocks/
Nice part; thanks for sharing.

I have a 32khz and 50mhz quartz oscillator for timebase.
One detail I am genuinely curious: on a base-2 processor, how can you accurately obtain 1 second timebase out of 50ms by using a binary divider on your CPU? 
Vbe - vídeo blog eletrônico http://videos.vbeletronico.com

Oh, the "whys" of the datasheets... The information is there not to be an axiomatic truth, but instead each speck of data must be slowly inhaled while carefully performing a deep search inside oneself to find the true metaphysical sense...
 

Offline JoeN

  • Frequent Contributor
  • **
  • Posts: 984
  • Country: us
  • Country: us
  • We Buy Trannies By The Truckload
Re: Slightly overengineered nixie clock
« Reply #11 on: August 25, 2015, 01:23:25 am »
It needs an OCXO in there somewhere.   O0
Have You Been Triggered Today?
 

Offline marshallh

  • Supporter
  • ****
  • Posts: 1459
  • Country: us
  • Country: us
    • retroactive
Re: Slightly overengineered nixie clock
« Reply #12 on: August 25, 2015, 01:28:19 am »
One detail I am genuinely curious: on a base-2 processor, how can you accurately obtain 1 second timebase out of 50ms by using a binary divider on your CPU?

http://www.microchip.com/forums/m410159.aspx

If you need to generate an arbitrary frequency you can do so with a fractional-N counter. You will get good long term stability as long as you don't truncate the numbers, at the cost of increased jitter. I've done that to generate I2S clocks off a 74.25mhz clock. An analyzer showed the clock was in spec and with acceptable jitter.

For longer term things you want to stick to old fashioned quartz. There are now lots of MEMS devices that are very cheap (I use them for base clocks and digital stuff) but they have poor long-term drift. They are more resilient for rugged environments since they don't exhibit piezo effects. A MEMS oscillator is basically a fixed output buzzing structure with loads of compensation circuitry to correct for PVT.
They're sold under various frequencies by burning internal PLL settings.
These oscillators have only recently become practical and they are quickly getting better.

Another good way to get accurate time... just read the line frequency of the AC input.
Verilog tips
BGA soldering intro

11:37 <@ktemkin> c4757p: marshall has transcended communications media
11:37 <@ktemkin> He speaks protocols directly.
 

Offline JoeN

  • Frequent Contributor
  • **
  • Posts: 984
  • Country: us
  • Country: us
  • We Buy Trannies By The Truckload
Re: Slightly overengineered nixie clock
« Reply #13 on: August 25, 2015, 02:03:41 am »
Another good way to get accurate time... just read the line frequency of the AC input.

Do they really keep it that stable?  I mean, for all applications other than clocks trying to tell time off the mains it doesn't matter one bit if it is off 1%, no other applications would ever notice it being off even that much, but that would kill basing a clock on it.  If they are keeping it accurate it must be on purpose.  Which begs the question, what timebase is the power company using?
Have You Been Triggered Today?
 

Offline c4757p

  • Super Contributor
  • ***
  • Posts: 7805
  • Country: us
  • Country: us
  • adieu
Re: Slightly overengineered nixie clock
« Reply #14 on: August 25, 2015, 02:28:12 am »
Many old-style plug-in clocks use mains as a time reference, and they generally keep fairly good time, so while I don't know the details, it's clearly accurate enough for household-use timekeeping.
No longer active here - try the IRC channel if you just can't be without me :)
 

Offline marshallh

  • Supporter
  • ****
  • Posts: 1459
  • Country: us
  • Country: us
    • retroactive
Re: Slightly overengineered nixie clock
« Reply #15 on: August 25, 2015, 02:32:34 am »
Do they really keep it that stable?  I mean, for all applications other than clocks trying to tell time off the mains it doesn't matter one bit if it is off 1%, no other applications would ever notice it being off even that much, but that would kill basing a clock on it.  If they are keeping it accurate it must be on purpose.  Which begs the question, what timebase is the power company using?

The short answer is although the frequency does vary, it averages out by design.
https://en.wikipedia.org/wiki/Utility_frequency#Stability

http://www.intersil.com/content/dam/Intersil/documents/an13/an1342.pdf

http://boards.straightdope.com/sdmb/showthread.php?t=446800
« Last Edit: August 25, 2015, 02:34:29 am by marshallh »
Verilog tips
BGA soldering intro

11:37 <@ktemkin> c4757p: marshall has transcended communications media
11:37 <@ktemkin> He speaks protocols directly.
 

Offline JoeN

  • Frequent Contributor
  • **
  • Posts: 984
  • Country: us
  • Country: us
  • We Buy Trannies By The Truckload
Re: Slightly overengineered nixie clock
« Reply #16 on: August 25, 2015, 04:05:13 am »
The short answer is although the frequency does vary, it averages out by design.
https://en.wikipedia.org/wiki/Utility_frequency#Stability

That's more or less what I figured.  It doesn't matter a bit if the jitter makes some ticks off, as long as there are 5,184,000 in a day, and the next day, and the next.  They can let it drift for a bit and then drift it the other way until the count comes back.  I get that.

Still, to do even this this you need an accurate timebase.  I wonder what it is.  I guess they have some sort of a feed from the national atomic clock.

Thanks for the links.
Have You Been Triggered Today?
 

Offline dr.diesel

  • Super Contributor
  • ***
  • Posts: 2118
  • Country: us
  • Country: us
  • Cramming the magic smoke back in...
Re: Slightly overengineered nixie clock
« Reply #17 on: August 25, 2015, 10:21:18 am »
The short answer is although the frequency does vary, it averages out by design.
https://en.wikipedia.org/wiki/Utility_frequency#Stability

That is interesting, I'd heard that rumor before, but as the principal software engineer for two 550MW units I can say there was absolutely no logic to accomplish the above.  Frequency was calculated by rotor RPM, no correction was made between 3597 and 3603 and is fairly cyclic between those limit.  So it will average, think I'll set my old Heathkit power line clock with my GPSDO later today.

This might also be surprising, but there is no "standard" software suit for generation units historically, although some are starting to adopt control system manufacture standards.  Which also don't included this correction.

(trying to ponder if a couple specific units with control logic to attempt correction could be enough to influence the entire grid a few PPM.....)

I will inquire further.

Offline deephaven

  • Frequent Contributor
  • **
  • Posts: 783
  • Country: gb
  • Country: gb
  • Civilization is just one big bootstrap
    • Deephaven Ltd
Re: Slightly overengineered nixie clock
« Reply #18 on: August 29, 2015, 01:27:47 pm »
What chips are you using to drive the Nixies? I'm guessing they're Microchip (nee Supertex) but which one?
 

Offline marshallh

  • Supporter
  • ****
  • Posts: 1459
  • Country: us
  • Country: us
    • retroactive
Re: Slightly overengineered nixie clock
« Reply #19 on: August 29, 2015, 06:16:57 pm »
I think it was supertex HV5122

Verilog tips
BGA soldering intro

11:37 <@ktemkin> c4757p: marshall has transcended communications media
11:37 <@ktemkin> He speaks protocols directly.
 

Offline deephaven

  • Frequent Contributor
  • **
  • Posts: 783
  • Country: gb
  • Country: gb
  • Civilization is just one big bootstrap
    • Deephaven Ltd
Re: Slightly overengineered nixie clock
« Reply #20 on: August 29, 2015, 07:52:49 pm »
I think it was supertex HV5122

Thanks. I'm thinking of doing a layout using those but at the other end of the technology scale, just using a small PIC. Pain they need 12V logic levels!
 

Offline marshallh

  • Supporter
  • ****
  • Posts: 1459
  • Country: us
  • Country: us
    • retroactive
Re: Slightly overengineered nixie clock
« Reply #21 on: August 31, 2015, 08:41:32 pm »


Verilog tips
BGA soldering intro

11:37 <@ktemkin> c4757p: marshall has transcended communications media
11:37 <@ktemkin> He speaks protocols directly.
 

Offline Melt-O-Tronic

  • Regular Contributor
  • *
  • Posts: 212
  • Country: us
  • Country: us
  • Brilliant with a slaughtering iron in my hand!
Re: Slightly overengineered nixie clock
« Reply #22 on: August 31, 2015, 09:32:48 pm »
Oh boy!  I can't wait to see it populated.   :popcorn:
 

Online Circlotron

  • Super Contributor
  • ***
  • Posts: 1576
  • Country: au
  • Country: au
Re: Slightly overengineered nixie clock
« Reply #23 on: September 01, 2015, 02:52:43 am »
Many old-style plug-in clocks use mains as a time reference, and they generally keep fairly good time, so while I don't know the details, it's clearly accurate enough for household-use timekeeping.
The mains frequency does vary a little from moment to moment, but over a 24 hours period they manage to have a more or less exact number of cycles. An interesting thing to do is to trigger your scope on the mains while watching a 5MHz or 6MHz signal. Someone starts pulling big power somewhere and as the mains frequency drops ever so slightly the trace slides to the left(?) then finally slows and stops when the steam has been automatically turned up and then it slides to the right(?) to get back to where it was. Entertainment for nerds.
« Last Edit: September 01, 2015, 02:54:38 am by Circlotron »
 

Offline MyElectronsFellOut

  • Regular Contributor
  • *
  • Posts: 70
  • Country: gb
  • Country: gb
Re: Slightly overengineered nixie clock
« Reply #24 on: September 01, 2015, 06:53:23 am »
The boards are looking very nice indeed.
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf