[ntp:questions] Motorola Oncore GPS as Stratum 1 source
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:
>> 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.
> 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.
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.
Ron Hahn, CISA, CISSP
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