[time-nuts] Motorola Oncore UT+ firmware upgrade & backup power questions
albertson.chris at gmail.com
Sun Mar 15 15:46:37 EDT 2015
I have one of these UT+ receivers. Backup is not a big deal. How long
will the power be off? Certainly not for days and weeks. The backup
battery only has to last a few seconds or maybe an hours or two. The real
problem with batteries is not how much energy they store but shelf life.
You have to change the 2032 over five to eight years or so just because of
shelf life. So some people are using "super capacitors" because these can
handle the few hours or few days of backup power and have a much longer
working lifetime r maybe 20 years or more. F
That said, for a hobby user you can do fine with zero backup. So what the
unit looses it's memory and takes a few hours to do the site survey all
over again. What happens to the OCXO during the power outage? It cools
down. This is just as bad as killing the memory in the UT+. So... if you
are worried about outages you have to backup the 12 volt power the entire
GPSDO is running on and if you back this up you don't technically even ned
the CR2032 on the GPS because it will never loose power. But then
again coin batteries are go easy to use why not use one?
If you are worried about hold over performance during a power glitch, you
need a big 12V gel cell battery that can supply the biggest load which has
to the heater on the OCXO. The coin cell is really for the convenience of
YOU the developer who has to power cycle the controller 1,000 times to make
software changes or whatever and you don't want to wait for the GPS for
each software test. Once it is running the big 12V battery means the
CR2032 is never used.
On Sun, Mar 15, 2015 at 8:05 AM, paul swed <paulswedb at gmail.com> wrote:
> I agree with Atilla from what I have seen. Its actually somewhat difficult
> to measure this level of current. But all is not lost. Even if the unit is
> drawing 1-10ua because something is going wrong. Simply add a battery
> holder and 2 X AAA or AA or ...
> Whatever it takes to keep the unit going.
> If you mount the batteries externally you can easily replace them and check
> the discharge rate.
> Its a way around the problem if you simply can not get a replacement or its
> totally embedded on the board.
> Best of luck
> On Sun, Mar 15, 2015 at 6:27 AM, Hal Murray <hmurray at megapathdsl.net>
> > attila at kinali.ch said:
> > > A CR2032 is a quite huge coin cell. An NVRAM module does not use much
> > power
> > > once Vcc goes to zero. In todays low power modules it's in the order of
> > > 100nA max specified. You can assume it to be somewhere in the range of
> > 10nA
> > > (probably package leakage limited) and 1uA (something has gone wrong or
> > very
> > > old module). ...
> > GPS also needs the time, so add on a 32KHz clock.
> > --
> > These are my opinions. I hate spam.
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