[Thumbgps-devel] Article -- Macx-1: GPS receiver with standard USB connector and PPS support

[Ron Frazier (NTP)]

Hi all,

(I'm copying this only to the thumb-gps list and to TZ, the most recent 
commenter, as I don't know all the parties in the header of TZ's 
message.  You guys can forward it to whomever else may need to see it.)

Speaking strictly as a potential user of the thumb-gps device and 
amateur interested party, I would rather see a supercap, if feasible.  I 
hate the idea of devices having batteries that I have to worry about 
failing in 5-10 years.  I've had the cmos batteries fail in a few 
computers, sometimes preventing them from booting.  It can get really 
ugly trying to revive them  A good high efficiency dc-dc converter chip 
should allow you to drain all but the last bit of energy from the cap 
while maintaining whatever working voltage you need.  I cannot speak to 
size issues, as I have never designed a circuit board with one.  The 
GlobalSat BU-353 that I have has a supercap, I believe.  Exact backup 
time is not stated, but I believe it's a few days.

Sincerely,

Ron

On 5/9/2012 1:12 PM, tz wrote:
> For a given size (and circuit board footprint) a supercap will have 
> much less capacity and it has an exponential voltage decay curve, so 
> it might have plenty of charge but not at a voltage that will hold the 
> data.  This usually means hours, not days of backup.
>
> A good rechargeable lithium will last several years, maybe longer as 
> there will be no charge/discharge, maintains voltage until it is 
> nearly exhausted, and can hold the data for days or weeks.
>
> On Wed, May 9, 2012 at 12:55 PM, Dave Taht <dave.taht at gmail.com 
> <mailto:dave.taht at gmail.com>> wrote:
>
>     On Wed, May 9, 2012 at 9:47 AM, Eric S. Raymond <esr at thyrsus.com
>     <mailto:esr at thyrsus.com>> wrote:
>     > Dave Taht <dave.taht at gmail.com <mailto:dave.taht at gmail.com>>:
>     >> What would be the change in cost and delay in manufacturing to
>     switch to
>     >> using a supercap, rather than battery?
>     >
>     > Why would a supercap be better?
>
>     Effective lifetime of... forever. no need for replacement. insanely
>     fast recharge. smaller (probably). What's not to like?
>
>     I am not in a huge hurry to get into manufacturing, and I merely
>     wanted to cost out what what it would do to the bom, any changes to
>     the PCB, and get an estimate for the time it would take to do. I think
>     it will bump the unit cost up slightly,
>     but what price, forever?
>
>     > --
>     > <a href="http://www.catb.org/~esr/
>     <http://www.catb.org/%7Eesr/>">Eric S. Raymond</a>
>
>
>
>     --
>     Dave Täht
>     SKYPE: davetaht
>     US Tel: 1-239-829-5608 <tel:1-239-829-5608>
>     http://www.bufferbloat.net
>     _______________________________________________
>     Thumbgps-devel mailing list
>     Thumbgps-devel at lists.bufferbloat.net
>     <mailto:Thumbgps-devel at lists.bufferbloat.net>
>     https://lists.bufferbloat.net/listinfo/thumbgps-devel
>
>
>
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>    

-- 

(To whom it may concern.  My email address has changed.  Replying to former
messages prior to 03/31/12 with my personal address will go to the wrong
address.  Please send all personal correspondence to the new address.)

(PS - If you email me and don't get a quick response, don't be concerned.
I get about 300 emails per day from alternate energy mailing lists and
such.  I don't always see new messages very quickly.  If you need a
reply and have not heard from me in 1 - 2 weeks, send your message again.)

Ron Frazier
timekeepingdude AT techstarship.com

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