Welcome to Russells-World

Rb Time Standard

PROLOGUE



I have an odd obsession with time. It's the one thing we can't control, have a finite amount of, and can never gain back. It's an expense. With that said, I wanted to build a better time standard within my house, and after doing some research, settled on Rubidium time sources. This is my build log of an Rb time source.

Core Components Needed



  1. RaspberryPi 3 with Raspbian


    Let's get it on


For background, here is how a Rb oscillator works:
"http://www.nist.gov/pml/div688/grp40/enc-re.cfm"

  • They can have a time accuracy of 2x10^-11
  • The ones we'll use are recycled from decomissioned cell towers
  • Part number: FE-5680A
  • Beware of the mutliple form factors that exist with the same part number.
  • NOTE: You'll look for a 1PPS and 10MHz output

  • image4.png
    image9.png
    what you will be looking for specifically is this:
    image6.png
    I won't get into how these work here yet, but what you'll need to figure out is how to get the 1PPS pin into the Raspi. I'm finishing a board to do all this for you as a shield. The main issue from just putting it together is that the 1PPS is a very short and powerful burst as seen below:

    This needs to be expanded from 1us to 100ms, and reduced from 5VDC to 3.3VDC.
    You can download the code for the raspi here