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

Thomas Laus lausts at acm.org
Thu Oct 18 13:22:53 UTC 2012


On 2012-10-18, Thomas Laus <lausts at acm.org> wrote:
> Ron:
>
> I am also using this same board and made a discovery a few years ago
> that this backup battery discharges over a period of time, normally
> less than a year and is not available when 'really' needing it.  There
> is a battery charging current available on Pin 3 of your Oncore that
> can be used to charge a 1.5F 5.5V Gold Capacitor.  I used the Digikey
> part P11063-ND for mine.  It will mount in the same loacation as the
> coin cell.  You will need to jumper out R2 (820K) and just connect the
> high Farad capacitor between pins 1 & 3 on your Oncore.  Watch the
> polarity!  The charging circuit in the Oncore is current limiting and
> it will take about 12H for enough charge to hold the almanac between
> powerups.  When the capacitor is fully charged, the almanac stays for
> about a month.
>
> You really can't do without a battery.  Your almanac information and
> current date and time is stored in the Oncore RAM.  Your GPS location,
> and other parameters get saved in Flash, but the Oncore will require
> about 30-40 minutes to recover from a power outage before it can serve
> up time again. 
>
Correction!!!!!!

The battery backup charging current is on Pin 1 of the Oncore
receiver instead of Pin 3.  Pin 3 is tied to ground, but Pin 1 has a
current limited 5V available.

Tom


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