From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ob0-f171.google.com (mail-ob0-f171.google.com [209.85.214.171]) (using TLSv1 with cipher RC4-SHA (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority" (verified OK)) by huchra.bufferbloat.net (Postfix) with ESMTPS id D710B201AF7 for ; Wed, 9 May 2012 11:21:34 -0700 (PDT) Received: by obfk16 with SMTP id k16so1342336obf.16 for ; Wed, 09 May 2012 11:21:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:sender:in-reply-to:references:from:date :x-google-sender-auth:message-id:subject:to:cc:content-type; bh=j3lpJpM+FwtrB9GT+2gUTCEO0oxFGbFwwW6xiiRncnw=; b=xvV4tINc1JoAQ1AvFtYlf+UbmMW1/UG08IE1rs4KLcZnDNKz7fbtPeZb5F2qEuJUkw vsU6JjrRxEQfquL4UBp3xrlNB8BMNyLXzrN0nfXGb3i/AH0bmTIl+1RHgdJMZwRT/LaW eqTzTIgH49e9IwVGeNw4Vb3dgKllG0y3w3xpuIc5ndrtc8P8llj2zTQ5POyF5WFYZYM5 9SYFGEZm3Xs/tjr+wuaChI9ZywneKzZtcRiGYDCO7Tf06czTXQYx7+5LVmJ6R09fGgkf 04yfabwwjrNnT53j7+PzXejVhMhM2Kf1HlMT1Z8jr9INDlOSVTXTPdq5aaedhvyqGZIe EJxw== Received: by 10.182.183.73 with SMTP id ek9mr1593827obc.15.1336587692213; Wed, 09 May 2012 11:21:32 -0700 (PDT) MIME-Version: 1.0 Sender: tz2026@gmail.com Received: by 10.182.113.40 with HTTP; Wed, 9 May 2012 11:21:12 -0700 (PDT) In-Reply-To: <4FAAAE4F.80409@techstarship.com> References: <02af01cd2daf$05b24bb0$1116e310$@navisys.com.tw> <20120509164726.GA2102@thyrsus.com> <4FAAAE4F.80409@techstarship.com> From: tz Date: Wed, 9 May 2012 14:21:12 -0400 X-Google-Sender-Auth: NcDO8PYhC949E5IDJjcyMI9JXxw Message-ID: To: "Ron Frazier (NTP)" Content-Type: multipart/alternative; boundary=f46d04478a319b05ec04bf9e92dc Cc: thumbgps-devel@lists.bufferbloat.net Subject: Re: [Thumbgps-devel] Article -- Macx-1: GPS receiver with standard USB connector and PPS support X-BeenThere: thumbgps-devel@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 09 May 2012 18:21:35 -0000 --f46d04478a319b05ec04bf9e92dc Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable It doesn't work that way. Microampere DC-DC converters? That isn't a swap, it is a redesign, if microamp converters are possible - the base losses are high so you won't hit a high efficiency. You get high efficiencies when dealing with lots of amps. For it to last overnight you would need a very large (physically) cap. There would be no booting problem. It would merely lose the real-time clock and/or location backup so would take a bit longer starting. The battery (or cap) only kicks in when the power goes away and is only needed to make the startup faster, e.g. cycling power on the computer or router. USB should be constantly providing 5V 99.9% of the time. I could argue that if surviving only a short power disconnect is ok, then a supercap might be better, but then it is probably a large engineering change since the caps and batteries usually have vastly different footprints. Good batteries can last decades - even Supercaps have a finite lifetime. It is a matter of cost, both in redesign, size, and reliability. But do you want to add $5-$10 to the cost of the unit to make a cheap ($30-$50) GPS last over a decade? Buy a second, seal it hermetically, and put it in your freezer. If you want to add a few thousand in NRE costs, there are a lot of other things I would redesign. Use a USB 2.0 chip to get 125uS jitter. Allow for a detachable or external antenna (which can be run to the window). Find a more optimal chipset. Maybe a coin-cell port so the battery can be replaceable. But the point was to be as cheap as possible so in this case it is adding one wire. You can always break yours open and if you can find a supercap with the specs (Sparkfun has a 3.3v available, but don't put more than 3.3v on it), you can swap the part. On Wed, May 9, 2012 at 1:50 PM, Ron Frazier (NTP) < timekeepingntplist@techstarship.com> wrote: > ** > 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 dra= in > 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 ther= e > 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 wrote: > >> On Wed, May 9, 2012 at 9:47 AM, Eric S. Raymond wrote: >> > Dave Taht : >> >> 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? >> >> > -- >> > Eric S. Raymond >> >> >> >> -- >> Dave T=E4ht >> SKYPE: davetaht >> US Tel: 1-239-829-5608 >> http://www.bufferbloat.net >> _______________________________________________ >> Thumbgps-devel mailing list >> Thumbgps-devel@lists.bufferbloat.net >> https://lists.bufferbloat.net/listinfo/thumbgps-devel >> > > > _______________________________________________ > Thumbgps-devel mailing listThumbgps-devel@lists.bufferbloat.nethttps://li= sts.bufferbloat.net/listinfo/thumbgps-devel > > > -- > > (To whom it may concern. My email address has changed. Replying to form= er > 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 > > --f46d04478a319b05ec04bf9e92dc Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable It doesn't work that way.=A0 Microampere DC-DC converters?=A0 That isn&= #39;t a swap, it is a redesign, if microamp converters are possible - the b= ase losses are high so you won't hit a high efficiency.=A0 You get high= efficiencies when dealing with lots of amps.=A0 For it to last overnight y= ou would need a very large (physically) cap.

There would be no booting problem.=A0 It would merely lose the real-tim= e clock and/or location backup so would take a bit longer starting.

= The battery (or cap) only kicks in when the power goes away and is only nee= ded to make the startup faster, e.g. cycling power on the computer or route= r.=A0 USB should be constantly providing 5V 99.9% of the time.

I could argue that if surviving only a short power disconnect is ok, th= en a supercap might be better, but then it is probably a large engineering = change since the caps and batteries usually have vastly different footprint= s.

Good batteries can last decades - even Supercaps have a finite lifetime= .=A0 It is a matter of cost, both in redesign, size, and reliability.=A0 Bu= t do you want to add $5-$10 to the cost of the unit to make a cheap ($30-$5= 0) GPS last over a decade?=A0 Buy a second, seal it hermetically, and put i= t in your freezer.

If you want to add a few thousand in NRE costs, there are a lot of othe= r things I would redesign.=A0 Use a USB 2.0 chip to get 125uS jitter.=A0 Al= low for a detachable or external antenna (which can be run to the window).= =A0 Find a more optimal chipset.=A0 Maybe a coin-cell port so the battery c= an be replaceable.=A0 But the point was to be as cheap as possible so in th= is case it is adding one wire.

You can always break yours open and if you can find a supercap with the= specs (Sparkfun has a 3.3v available, but don't put more than 3.3v on = it), you can swap the part.

On Wed, May 9= , 2012 at 1:50 PM, Ron Frazier (NTP) <timekeepingntplist= @techstarship.com> wrote:
=20
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.=A0 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.=A0 I hate the idea of devices having batteries that I have to worry about failing in 5-10 years.=A0 I've had the cmos batteries fail in a few computers, sometimes preventing them from booting.=A0 It can get really ugly trying to revive them=A0 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.=A0 I cannot speak to size issues, as I have never designed a circuit board with one.=A0 The GlobalSat BU-353 that I have has a supercap, I believe.=A0 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.=A0 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@gmail.com> wrote:
On Wed, May 9, 2012 at 9:47 AM, Eric S. Raymond <esr@thyrsus.com> wrote:
> Dave Taht <dave.taht@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?

> --
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0<a href=3D"http://www.catb.org/~esr/"&g= t;Eric S. Raymond</a>



--
Dave T=E4ht
SKYPE: davetaht
US Tel: 1-239-829-5608
http://www.buf= ferbloat.net
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Thumbgps-devel mailing list
Thumbgps-devel@lists.bufferbloat.net
https://lists.bufferbloat.net/listinfo/thumbgps-devel


_______________________________________________
Thumbgps-devel mailing list
T=
humbgps-devel@lists.bufferbloat.net
https://lists.bufferbloat.net/listinfo/thumbgps-devel
  

--=20

(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 conc=
erned.
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 te=
chstarship.com

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