From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lb0-f171.google.com (mail-lb0-f171.google.com [209.85.217.171]) (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 9672F201AF7 for ; Wed, 9 May 2012 11:35:08 -0700 (PDT) Received: by lbom4 with SMTP id m4so1033740lbo.16 for ; Wed, 09 May 2012 11:35:05 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; bh=tQ0VA3v7arPyA8CJlvygEadzXEQ67KHEq2CUTTFFkLE=; b=Grl6FmkwilwH7uVvRwpNpSMdiCVXYiRRIWsdOpXwFUgPd+Bj+HmDogSdpbxzqO2cVX 25LHu100Bf2v8xNvLq+e5VQaOgDw8eipbLru8vlNjt+3kmcnMdKfnW8uzboVHscD0p5S qMXraf91pRZwnED83sS8ZdHCp2pioVIYCcsbe3qEayqXkN2abts84qaqlfyybFObxyHe jYWpK1VaUVXD+qclemKRlOOCd/TbOohblOgqLqLXRTWlBItAweRmx1B4WT8D7O6UCjxO Z7SHkbVi9x5DFCmFDAQNkSyYdE0yOZj75edWSo4pTpFQlnwj7wIlZADe/OEFB2v1x1IS LT2A== MIME-Version: 1.0 Received: by 10.152.103.11 with SMTP id fs11mr844766lab.23.1336588505698; Wed, 09 May 2012 11:35:05 -0700 (PDT) Received: by 10.112.132.98 with HTTP; Wed, 9 May 2012 11:35:05 -0700 (PDT) In-Reply-To: References: <02af01cd2daf$05b24bb0$1116e310$@navisys.com.tw> <20120509164726.GA2102@thyrsus.com> <4FAAAE4F.80409@techstarship.com> Date: Wed, 9 May 2012 11:35:05 -0700 Message-ID: From: Dave Taht To: tz Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable 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 18:35:09 -0000 jeeze guys, all I asked for was an estimate as to the change to the BOM. Could be a Macx-2, might not be worthwhile at all. My concern was that there are 6+ short power flickers a day - forcing a reboot - in places like Nicaragua. These events are *interesting* from a network analysis perspective, as flickers like this cause massive network disturbances. I don't care about battery life longer than about 30 seconds, although a case could be made for 24 hours. Just wanted the analysis of what it would really take, given how little power this thing sucks... and I hate ANYTHING that needs a user-replaceable component, 5 years after manufacture. So I'd prefer the actual analysis based on power draw, etc, before making any decisions. On Wed, May 9, 2012 at 11:21 AM, tz wrote: > It doesn't work that way.=A0 Microampere DC-DC converters?=A0 That isn't = a swap, > it is a redesign, if microamp converters are possible - the base losses a= re > high so you won't hit a high efficiency.=A0 You get high efficiencies whe= n > dealing with lots of amps.=A0 For it to last overnight you would need a v= ery > large (physically) cap. > > There would be no booting problem.=A0 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.=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, then= a > supercap might be better, but then it is probably a large engineering cha= nge > since the caps and batteries usually have vastly different footprints. > > 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 But do y= ou > want to add $5-$10 to the cost of the unit to make a cheap ($30-$50) GPS > last over a decade?=A0 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.=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 Fin= d a > more optimal chipset.=A0 Maybe a coin-cell port so the battery can be > replaceable.=A0 But the point was to be as cheap as possible so in this c= ase > 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) > 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 amateu= r >> 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 >> A good high efficiency dc-dc converter chip should allow you to drain al= l >> but the last bit of energy from the cap while maintaining whatever worki= ng >> voltage you need.=A0 I cannot speak to size issues, as I have never desi= gned a >> circuit board with one.=A0 The GlobalSat BU-353 that I have has a superc= ap, I >> believe.=A0 Exact backup time is not stated, but I believe it's a few da= ys. >> >> 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 T= his >> usually means hours, not days of backup. >> >> A good rechargeable lithium will last several years, maybe longer as the= re >> will be no charge/discharge, maintains voltage until it is nearly exhaus= ted, >> 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 switc= h >>> >> 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= 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 list >> Thumbgps-devel@lists.bufferbloat.net >> https://lists.bufferbloat.net/listinfo/thumbgps-devel >> >> >> >> -- >> >> (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 > > > > _______________________________________________ > Thumbgps-devel mailing list > Thumbgps-devel@lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/thumbgps-devel > --=20 Dave T=E4ht SKYPE: davetaht US Tel: 1-239-829-5608 http://www.bufferbloat.net