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

Ron Hahn ron.hahn at dhco.org
Thu Oct 18 21:09:36 UTC 2012


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On 18/10/2012 14:22, Thomas Laus wrote:
> 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
> 
> 
Tom,

Thank you for this kind advice.  I would have not thought of such a
solution. I will order some of this part from Digi Key instead of
persuing the battery solution.

R

- -- 
Ron Hahn, CISA, CISSP
Rose Hill
Rosslare Strand,
Wexford, IRELAND
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