[ntp:questions] Motorola Oncore GPS as Stratum 1 source

Thomas Laus lausts at acm.org
Fri Oct 19 13:28:27 UTC 2012

On 2012-10-18, Mike S <mikes at flatsurface.com> wrote:
> re: using gold caps
> You may wish to consider rechargeable lithium cells, which will give you 
> a more consistent voltage than a capacitor. I'm not sure how voltage 
> sensitive the Oncore boards are for holding data while powered down, but 
> these are what Motorola used in the ones with the on-board battery option.
The high Farad capacitor will charge to just a little under supply
voltage in about 24H.  My Oncore seems to keep the RTC running and the
almanac valid for about a month after power off.  That part of the
Oncore seems to draw in the very low nano-amp range.  The capacitor
has enough charge after about 3 hours to be useful for short power
blips.  I also thought about Lithium rechargables in searching for
this solution, but found that the high Farad capacitor was a drop in
replacment on my TAPR board.  It fit in the exact footprint of the
coin cell holder and all that I needed to do is replace one resistor
with a jumper wire.


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