From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lpp01m010-f43.google.com (mail-lpp01m010-f43.google.com [209.85.215.43]) (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 DE3672004D7 for ; Wed, 9 May 2012 13:59:34 -0700 (PDT) Received: by lagr15 with SMTP id r15so1287284lag.16 for ; Wed, 09 May 2012 13:59:32 -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=87u8dkwsaNJsa4VDMqNkh9XBxZqEfrjudbGlPtVs/Zg=; b=RfouvFym1khDSD1ucpofCt5v7w5EP+7/4CXLsXPeRDlsOSseV/Wbp9WSAJcgtkOeiF 7Ff7qv0B2bbRZUU4p0oFcUz7WoNpTs/R70FNz/+4Dfv/aTpPgTNZaidjbkJQ7LMjODMm 1q6XcrVEysz5rusfGORDiI2viiOtV3EwDH+sVOTYkT7LVmNlS334jz5by9lGXNgpzWek n5jmpakooe8uTqrXAbQZ6znXILidE/mmq5a21VKJzqoi5Zl9o+WV7vU/S7iWzw1SXLA0 nVLd6RfOnEKiVRvaQjp8079FiI/lob7bnPdGebW0Mx/LYGwHUqY89BEsc7kGOuBFjvas INwA== MIME-Version: 1.0 Received: by 10.152.103.11 with SMTP id fs11mr1267182lab.23.1336597172638; Wed, 09 May 2012 13:59:32 -0700 (PDT) Received: by 10.112.132.98 with HTTP; Wed, 9 May 2012 13:59:32 -0700 (PDT) In-Reply-To: <4FAADA61.9060202@techstarship.com> References: <02af01cd2daf$05b24bb0$1116e310$@navisys.com.tw> <20120509164726.GA2102@thyrsus.com> <4FAAAE4F.80409@techstarship.com> <4FAAD66F.3090405@techstarship.com> <4FAADA61.9060202@techstarship.com> Date: Wed, 9 May 2012 13:59:32 -0700 Message-ID: From: Dave Taht To: "Ron Frazier (NTP)" 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 20:59:35 -0000 On Wed, May 9, 2012 at 1:58 PM, Ron Frazier (NTP) wrote: > I'm just an interested third party. =A0You guys are running the show. =A0= Use the > ideas as you see fit. =A0Just give me some credit if you end up using my > ideas. absolutely. Got another fictional character you resemble? And I'm totally into discussing this stuff, later, but right now I'm too busy with codel.... > > Sincerely, > > Ron > > > > On 5/9/2012 4:46 PM, Dave Taht wrote: >> >> A lot of that stuff I'd want to reserve for the Macx-2. Can I keep our >> request of navisys limited to merely the supercap and silkscreen? >> >> On Wed, May 9, 2012 at 1:41 PM, Ron Frazier (NTP) >> =A0wrote: >> >>> >>> Hi guys, >>> >>> I do see the point TZ was making about the problems of increasing the >>> design >>> and production costs. =A0However, if the supercap turned out to be >>> potentially >>> feasible, I have some Circuit Cellar magazines and such that I could >>> rummage >>> through for info on micro power conversion components. =A0I know they >>> exist. >>> =A0I have no idea about specs and efficiency. =A0How much amperage and = at >>> what >>> voltage is the unit expected to draw if disconnected from the USB power >>> source? =A0Is it expected to continue tracking? =A0I assume this will c= hange >>> if >>> an external antenna is attached. =A0How long should it be maintained? >>> >>> =A0From a user perspective, I'd recommend the following features, if yo= u >>> have a >>> viable choice: >>> >>> * Hi sensitivity internal antenna / chipset that can be used indoors in= a >>> residential type structure. >>> * External antenna port in case you're in a steel building or basement = or >>> something with no signal. =A0Use commonly available, generic, possibly >>> powered, antennas. >>> * GPS status led. =A0(My BU-353 slowly flashes when it has a fix, shows >>> steady >>> with power but no fix.) =A0The led should be synchronized to the pps. >>> * Supercap preferably, or battery which is easily user replaceable and = a >>> common part number, such as CR2032 for example. =A0That battery may be = too >>> big, but you want something readily available. >>> * If a battery is involved, a small flashing led to indicate a weak >>> battery >>> alert, kind of like what is on a smoke alarm. >>> * My BU-353 has a magnetic base. =A0Something like that might be useful= for >>> positioning the antenna. >>> * May or may not be relevant, but, would 5 - 10 Hz position sensing >>> improve >>> accuracy and stability for your purposes? >>> * You may wish to expose the pps signal on a screw terminal or connecto= r >>> in >>> case you want to attach other instrumentation to that signal. >>> >>> Here's a possible alternative to providing an external antenna port, an= d >>> all >>> the hassles of piping RF around. =A0With my BU-353, the "puck" device >>> contains >>> both the electronics and the antenna. =A0The only cord coming from it i= s >>> the >>> USB cable. =A0So, it might be preferable to have a sealed weather proof >>> unit, >>> and just use extension cords for USB rather than extending the RF >>> section. >>> =A0I know you can easily extend USB 10 feet or so. =A0I think you can g= o much >>> further with powered hubs and such. =A0Just a thought. >>> >>> Here's a wild idea, maybe not practical, but, you could attach a solar >>> cell >>> to the external antenna and / or the thumb-gps case. =A0This could feed >>> power >>> back to the GPS board and prolong the life of the battery or slow the >>> drain >>> of the supercap while powering the antenna if the antenna is in the sun= . >>> =A0You could even draw some energy from ambient indoor lighting. =A0I h= ave a >>> solar powered "atomic" watch from Casio that does this. =A0It never nee= ds a >>> battery, never needs charging, and never needs setting. =A0Very handy. = =A0I >>> also >>> have two "atomic" wall clocks that do the same thing. =A0I think they u= se a >>> rechargeable battery instead of a supercap. >>> >>> Here's another idea, which may or may not have already been discussed. >>> =A0Do >>> you want to have an on board RTC, which can keep outputting valid time >>> for a >>> while, if the satellites are not available due to weather, jamming, >>> interference, etc.? >>> >>> Sincerely, >>> >>> Ron >>> >>> >>> >>> >>> On 5/9/2012 2:35 PM, Dave Taht wrote: >>> >>>> >>>> jeeze guys, all I asked for was an estimate as to the change to the BO= M. >>>> 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 =A0 =A0wrote: >>>> >>>> >>>>> >>>>> It doesn't work that way. =A0Microampere DC-DC converters? =A0That is= n't a >>>>> swap, >>>>> it is a redesign, if microamp converters are possible - the base loss= es >>>>> are >>>>> high so you won't hit a high efficiency. =A0You get high efficiencies >>>>> when >>>>> dealing with lots of amps. =A0For it to last overnight you would need= a >>>>> very >>>>> large (physically) cap. >>>>> >>>>> There would be no booting problem. =A0It would merely lose the real-t= ime >>>>> 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 on= ly >>>>> needed to make the startup faster, e.g. cycling power on the computer >>>>> or >>>>> router. =A0USB 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. >>>>> =A0It >>>>> is a matter of cost, both in redesign, size, and reliability. =A0But = do >>>>> you >>>>> want to add $5-$10 to the cost of the unit to make a cheap ($30-$50) >>>>> GPS >>>>> last over a decade? =A0Buy 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. =A0Use a USB 2.0 chip to get 125uS jitter. >>>>> =A0Allow >>>>> for >>>>> a detachable or external antenna (which can be run to the window). >>>>> =A0Find >>>>> a >>>>> more optimal chipset. =A0Maybe a coin-cell port so the battery can be >>>>> replaceable. =A0But 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 t= he >>>>> 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) >>>>> =A0 =A0wrote: >>>>> >>>>> >>>>>> >>>>>> 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. =A0I h= ate >>>>>> the >>>>>> idea of devices having batteries that I have to worry about failing = in >>>>>> 5-10 >>>>>> years. =A0I've had the cmos batteries fail in a few computers, somet= imes >>>>>> preventing them from booting. =A0It can get really ugly trying to re= vive >>>>>> them >>>>>> A good high efficiency dc-dc converter chip should allow you to drai= n >>>>>> all >>>>>> but the last bit of energy from the cap while maintaining whatever >>>>>> working >>>>>> voltage you need. =A0I cannot speak to size issues, as I have never >>>>>> designed a >>>>>> circuit board with one. =A0The GlobalSat BU-353 that I have has a >>>>>> supercap, I >>>>>> believe. =A0Exact backup time is not stated, but I believe it's a fe= w >>>>>> 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. >>>>>> =A0This >>>>>> 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 >>>>>> =A0wrote: >>>>>> >>>>>> >>>>>>> >>>>>>> On Wed, May 9, 2012 at 9:47 AM, Eric S. Raymond >>>>>>> =A0wrote: >>>>>>> >>>>>>> >>>>>>>> >>>>>>>> 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? >>>>>>> >>>>>>> >>>>>>> >>>>>>>> >>>>>>>> -- >>>>>>>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0Eric S. >>>>>>>> Raymond >>>>>>>> >>>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> -- >>>>>>> Dave T=E4ht >>>>>>> SKYPE: davetaht >>>>>>> US Tel: 1-239-829-5608 >>>>>>> http://www.bufferbloat.net >>>>>>> >>>>>>> > > > > -- > > (To whom it may concern. =A0My email address has changed. =A0Replying to = former > messages prior to 03/31/12 with my personal address will go to the wrong > address. =A0Please 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. =A0I don't always see new messages very quickly. =A0If you need a > reply and have not heard from me in 1 - 2 weeks, send your message again.= ) > > Ron Frazier > timekeepingdude AT techstarship.com > --=20 Dave T=E4ht SKYPE: davetaht US Tel: 1-239-829-5608 http://www.bufferbloat.net