Atomic Clock & Frequency Counter

Thread Starter

Art

Joined Sep 10, 2007
806
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:



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:

Wendy

Joined Mar 24, 2008
23,415
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.
 

Thread Starter

Art

Joined Sep 10, 2007
806
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:

but I had a dream about it viewing it completed from behind.
 
Last edited:

bance

Joined Aug 11, 2012
315
Well, it certainly looks impressive! What's the plumbing for? Is it part of the frequency standard?
I think that's the 'enclosure.'
Nice project, only thing that would improve it for me would be a nixie display!
 

Thread Starter

Art

Joined Sep 10, 2007
806
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

 

Thread Starter

Art

Joined Sep 10, 2007
806
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.

 

bance

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

Thread Starter

Art

Joined Sep 10, 2007
806
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.
 

Thread Starter

Art

Joined Sep 10, 2007
806
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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