[time-nuts] Motorola Oncore UT+ firmware upgrade & backup power questions

[Chris Albertson]

I don't know about firmware but I do use the CR2032.   The super cap would
work too but an uncharged cap look like a short circuit.

On Fri, Mar 13, 2015 at 1:33 PM, Pete Stephenson <pete at heypete.com> wrote:

> Hi all,
>
>
> 2. The two Oncores I purchased were not factory-equipped with a
> rechargeable battery. The user guide says that one can apply "Externally
> applied backup power (< +5V)" to pin #1 in order to maintain data in RAM
> in case the main power is interrupted.
>
> Can one use a common non-rechargeable coin-cell battery like a CR2032 to
> provide this backup power, or does it need to be a rechargeable battery?
> Will a CR2032 or the Oncore itself be damaged if such a cell is used?
>
> 3. Tom says at
> <http://lists.ntp.org/pipermail/questions/2012-October/034001.html> that
> in addition to being an input for external backup power, pin #1 on the
> Oncore provides current-limited 5V for battery/supercapacitor charging.
>
> Is this true for Oncore receivers that were not factory-equipped with a
> rechargeable battery? If true, what is the maximum current that can be
> safely supplied by the pin? As above, is it safe to use a
> non-rechargeable battery like a CR2032?
>
> If pin #1 can supply power and I wanted to charge a supercapacitor from
> that pin, would I also need to include a current-limiting resistor to
> prevent the Oncore from sourcing too much current?
>
> I could find nothing in the user guide that says that pin #1 can be used
> for charging a battery.
> <
> http://www.synergy-gps.com/images/stories/ShopTalk/9backup_battery_considerations.pdf
> >
> is unclear on whether or not pin #1 can be used for charging batteries,
> or if it's safe to use non-rechargeable cells like a CR2032 coin-cell
> battery.
> 4. The user manual and the battery backup considerations document says
> that the Oncore UT+ draws 5-100 uA (15uA typical) from the backup power
> source. Is this a constant draw, even when the main 5V power is being
> supplied to the unit, or does the unit only draw current from the
> battery when the main power is interrupted?
>
> I'd measure it directly, but none of my multimeters are able to
> accurately measure microamperes.
>
> Thank you all for your time and assistance. If any other time-nuts
> happen to make it to Bern, Switzerland in the next few years, please let
> me know and drinks are on me.
>
> Cheers!
> -Pete
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-- 

Chris Albertson
Redondo Beach, California