-----Original Message----- From: questions-bounces+ron.hahn=fmr....@lists.ntp.org [mailto:questions-bounces+ron.hahn=fmr....@lists.ntp.org] On Behalf Of Thomas Laus Sent: 18 October 2012 14:10 To: questions@lists.ntp.org Subject: Re: [ntp:questions] Motorola Oncore GPS as Stratum 1 source
On 2012-10-17, Hahn, Ron <ron.h...@fmr.com> wrote: > Colleagues, > > I am putting together some Motorola Oncore UT+ boards to replace my > Sure boards in my ntp servers. I am using this > http://www.tapr.org/gps_vpib.html board as the templat for the > interface circuits. The circuit calls for a BR2325 battery which > I cannot find in the local parts store. Is there a person on this > list with experiences of this board design that can tell me what I > can substitute for this part? Or maybe it is not necessary? I am > not even sure if the battery is necessary but from my experiences > the boards go from a cold start whenever power is interrupting. > One of my servers is part of the ntp pool so I am needing the > rapid recovery if the power is interrupted. My systems are on > the UPS so maybe this battery is not required? > 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. Tom Tom, I have already experienced the head aches from accidentally disconnecting the power to the Oncore board! I am looking at the schematic diagram and pin 1 is the battery + and pin 3 is the battery - connections. Are you saying that there is the charge current on pin 1 to charge up this capacitor, to be discharged when the power is interrupting? Thanks for the helping hands, Ron _______________________________________________ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
