attila@kinali.ch said:

GPS also needs the time, so add on a 32KHz clock.

--
These are my opinions.  I hate spam.

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
Paul
WB8TSL

On Sun, Mar 15, 2015 at 6:27 AM, Hal Murray hmurray@megapathdsl.net wrote:

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@gmail.com wrote:

--

Chris Albertson
Redondo Beach, California

Hi

For a one off / home use application - enter the local “position hold” info into your
code. Let the micro send it up to the Oncore ….You will be hitting the “compile”
button enough times already that one more isn’t going to slow you down much.

Bob

On Sun, 15 Mar 2015 03:27:06 -0700
Hal Murray hmurray@megapathdsl.net wrote:

Oops.. right. I totally forgot that. Then it's somewhere in the
range of 0.2uA (modern RTC's with NVRAM) to 10uA (really old ones).
RTCs do not use that much current as one might think. I "recently"
did a MSP430FR5736 based system that had its RTC running and was
powered by two SR48 coin cells (~80mAh). Total expected lifetime
was 1.5y with all the stuff it had to do. IIRC minimum current
consumption we measured was 2.6uA(+/-0.5uA measurement accuracy,
total of the whole device).

		Attila Kinali

--
< av500> phd is easy
< av500> getting dsl is hard

On 3/15/2015 8:46 PM, Chris Albertson wrote:

True, it's not a huge deal. The receiver would be in position-hold mode
anyway, so I would have NTPd configured to send the receiver its known
position and a few other configuration options. Everything else is
easily retrievable from the GPS signal given a few minutes.

Backups of several years are overkill for me, particularly because the
ephemeris and almanac are only good for so long. Backup power in the
minutes-to-hours range would be perfectly fine for me.

My question was prompted mainly because I was seeking clarity as to the
proper use of pin #1: I didn't want to connect a non-rechargeable
battery if pin #1 was only intended for rechargeable batteries, as that
might cause damage. If that were the case I could use a supercapacitor,
but I wanted to be sure the pin (a) could supply power, which the manual
didn't mention, and (b) was current-limiting, otherwise the
supercapacitor would draw enormous currents and possibly cause damage.

Fortunately, it seems that a coin-cell battery will work perfectly. Once
the boards arrive I'll do some tests with the supercapacitor.

Many thanks to all for your help.

Cheers!
-Pete

On Sun, 15 Mar 2015 11:05:53 -0400
paul swed paulswedb@gmail.com wrote:

It's not that difficult. You just need a good DMM. Standard ones
will not work as they have resolution limits in the range of 10-100uA.
A semi-decent Fluke handheld gets you already to 0.5uA. If you get
a reall DMM, then you will start worrying about the surface currents
on your device (FR4 has a quite low surface resistance of 10-100Mohm,
depending on humidity and whether you have any finger prints on it)
and anything you have in your setup (finger prints, small residues
of oily stuff, dirt,...)

The bigger problem is, that you have to make sure you have no floating
inputs anywhere (inputs are not clearly 0 or 1, will have more input leakage
current, additionally to the "shot trough" they cause inside the chip).
If you use diodes for decoupling parts of circuitry, you need those with
extremely low reverse current (in the low nA) and those will have high
forward voltages (>1V, the ones we used had iirc 2V). etc pp
Ultra low power electronics is probably as messy a field as ultra low
noise electronics.

Please be aware that AA and AAA cells have a much higher self discharge
than coin cells. A CR2032 is usually of LiMnO2 chemistry, while AA/AAA's
are usually ZnMnO2. Also coin cells are optimized for long life times,
with very little current drawn, while most AA/AAA are not, or not as much.
Ie, i wouldn't expect an AAA cell, and much less an AA cell to last 10 years.

		Attila Kinali

--
< av500> phd is easy
< av500> getting dsl is hard

Atilla
Nor do I expect them to last 10 years, more like 1-2 years if the units
drawing the currents mentioned. Being external they are easy to change and
measure. Also cheap.
Only do this on boards that can't be replaced etc.
Regards
Paul

On Sun, Mar 15, 2015 at 6:40 PM, Attila Kinali attila@kinali.ch wrote:

Attila wrote:

The Energizer AA and AAA lithium primary batteries (Li/FeS2) have a
shelf life exceeding 10 years, as do their 9v batteries (Li/MnO2).  I
have been mightily impressed with their performance on all counts.

Best regards,

Charles