Atomic Clock & Frequency Counter

Discussion in 'The Projects Forum' started by Art, Nov 27, 2014.

  1. Art

    Thread Starter Distinguished Member

    Sep 10, 2007
    785
    61
    Hi Guys :)
    I've almost completed my Retro Atomic Clock / Frequency Counter based on one of the
    Rubidium Frequency Standards which are becoming affordable from eBay.

    This has been a three month long project aimed at using digital logic even if a little
    extra programming for the micro could make it redundant.
    I wanted to simulate the way the old HP frequency counters count live in your face :)
    Speech is done with Roman Black's 1 bit algorithm. The main chip queues samples to play
    spoken numbers naturally (ie "eleven, thirteen, thirty-five", etc.) up to 100, which covers the spoken time.
    Larger numbers are spoken like "two-twenty-seven", or "seven-twenty".

    I have yet to implement a reset signal, but know how to do it.
    The least significant digit is a high speed decade counter (up to 50 MHz),
    and the frequency counter is only designed for HF work with absolute count (without any pre scaling).

    YouTube Video:


    [​IMG]

    The following video is a test when I assembled the high frequency RF preamp.
    This is the counter boards counting a 10MHz test signal.


    Cheers, Art.
     
    Last edited: Nov 27, 2014
  2. Wendy

    Moderator

    Mar 24, 2008
    20,765
    2,536
    How to post a project to the collection

    Please review the requirements to post in this forum. You need to have schematics, parts list, and pictures locally hosted on this site, AAC. You tube videos are acceptable, but do not count as proper documentation.

    If this post is not brought in line in a week I'll move it to The Projects forum. We can always move it back when the project is completed. I will also delete this post when that happens.
     
  3. Art

    Thread Starter Distinguished Member

    Sep 10, 2007
    785
    61
    Ah yeah, sorry about that. It's only a "show off" of a completed project.
    No way schematics are happening, there's no ISO 9001 or RoHS here :D

    ps
    At work I have overheard a conversation about the choice of a custom screw.
    This is seriously my only written plan:
    [​IMG]
    but I had a dream about it viewing it completed from behind.
     
    Last edited: Nov 27, 2014
  4. JDT

    Well-Known Member

    Feb 12, 2009
    658
    85
    Well, it certainly looks impressive! What's the plumbing for? Is it part of the frequency standard?
     
  5. bance

    Member

    Aug 11, 2012
    315
    34
    I think that's the 'enclosure.'
    Nice project, only thing that would improve it for me would be a nixie display!
     
  6. Art

    Thread Starter Distinguished Member

    Sep 10, 2007
    785
    61
    The copper was originally for heatsinking because the rubidium standard runs at about 50 deg C,
    and can get hotter than that. I ended up just completing the frame and doing aluminium chassis pan.
    The accuracy is only quoted in datasheets if you can keep it below 50.
    A centre bar was added later, and even after that, it still requires a conventional heatsink :O

    [​IMG]
     
  7. bushrat

    Member

    Nov 29, 2014
    97
    22
    I do not know why I would ask this, but...
    Do you have to go 88 MPH ?
     
  8. Art

    Thread Starter Distinguished Member

    Sep 10, 2007
    785
    61
    You're not the only one who's asked :D I have never got alpha LED digits to play with yet.
    A Human can't set it, so ideally you'd be standing still, provide coordinates to a ublox timing GPS and sync to UTC seconds mark pulse.
    I have a few of these, but have to come up with an antenna.

    [​IMG]
     
  9. bance

    Member

    Aug 11, 2012
    315
    34
    Can I ask where you got the LEA-5T's? I've been thinking of setting up a gpsdo, for a frequency standard.
    Steve.
     
  10. Art

    Thread Starter Distinguished Member

    Sep 10, 2007
    785
    61
    Hi, 6T is recommended for new design now.
    I got a few from work off boards to be scrapped which is why the black part is masked.
     
  11. Art

    Thread Starter Distinguished Member

    Sep 10, 2007
    785
    61
    I got the reset circuit done so at least a finished working frequency counter.


    The reset pulse is sent a little after 900ms into the display hold time so as not to interrupt the 1 second counting time.
     
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