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 DEDCF201AF7 for ; Wed, 9 May 2012 13:46:38 -0700 (PDT) Received: by lbom4 with SMTP id m4so1272956lbo.16 for ; Wed, 09 May 2012 13:46:36 -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=SzT10McKk1zerfB5cNdJrMOVHOdtMLm2zjHYSUOQoe4=; b=PNfoCB62zmTSEARS4L8KswdReGEwMqpx6viOJIzHy+rvmeCHzOro2soKX0y2A6s75f mGDb+D6ns/sMkBhEefUWF2kqspt4MvubhtERMOY8lzzvQfQq4IkRPNdQoTIADUNFxdVD qPwwvS3vDjdym+m6N7i4HX9Uv/hdlDgasssyR8DDOIrXWN1RY2zzZ751r3UhUBYiR+Ta EqZ8oW1oakFh59Eae4D9lAPrd0Zx3AOgZuB29+T3W2d/73DpXMlY/ny1FuaQEz+hCO19 0c8LBNYxMpgu4zZVrokE09ET4vNhkwRoSrEl6LQ7oUBgTHwKyZj4BpZgPqQ7133Xr/BB MaUw== MIME-Version: 1.0 Received: by 10.152.114.106 with SMTP id jf10mr1583643lab.16.1336596395044; Wed, 09 May 2012 13:46:35 -0700 (PDT) Received: by 10.112.132.98 with HTTP; Wed, 9 May 2012 13:46:35 -0700 (PDT) In-Reply-To: <4FAAD66F.3090405@techstarship.com> References: <02af01cd2daf$05b24bb0$1116e310$@navisys.com.tw> <20120509164726.GA2102@thyrsus.com> <4FAAAE4F.80409@techstarship.com> <4FAAD66F.3090405@techstarship.com> Date: Wed, 9 May 2012 13:46:35 -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 20:46:39 -0000 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) wrote: > Hi guys, > > I do see the point TZ was making about the problems of increasing the des= ign > and production costs. =A0However, if the supercap turned out to be potent= ially > feasible, I have some Circuit Cellar magazines and such that I could rumm= age > through for info on micro power conversion components. =A0I know they exi= st. > =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 cha= nge if > an external antenna is attached. =A0How long should it be maintained? > > From a user perspective, I'd recommend the following features, if you hav= e 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 s= teady > 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 to= o > big, but you want something readily available. > * If a battery is involved, a small flashing led to indicate a weak batte= ry > alert, kind of like what is on a smoke alarm. > * My BU-353 has a magnetic base. =A0Something like that might be useful f= or > positioning the antenna. > * May or may not be relevant, but, would 5 - 10 Hz position sensing impro= ve > accuracy and stability for your purposes? > * You may wish to expose the pps signal on a screw terminal or connector = in > case you want to attach other instrumentation to that signal. > > Here's a possible alternative to providing an external antenna port, and = all > the hassles of piping RF around. =A0With my BU-353, the "puck" device con= tains > both the electronics and the antenna. =A0The only cord coming from it is = the > USB cable. =A0So, it might be preferable to have a sealed weather proof u= nit, > 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 go = much > further with powered hubs and such. =A0Just a thought. > > Here's a wild idea, maybe not practical, but, you could attach a solar ce= ll > to the external antenna and / or the thumb-gps case. =A0This could feed p= ower > back to the GPS board and prolong the life of the battery or slow the dra= in > 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 hav= e a > solar powered "atomic" watch from Casio that does this. =A0It never needs= 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 use= 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 fo= r 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 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 =A0wrote: >> >>> >>> It doesn't work that way. =A0Microampere DC-DC converters? =A0That 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. =A0You get high efficiencies w= hen >>> 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-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 >>> needed to make the startup faster, e.g. cycling power on the computer o= r >>> 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, 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 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) GP= S >>> last over a decade? =A0Buy a second, seal it hermetically, and put it i= n >>> your >>> freezer. >>> >>> If you want to add a few thousand in NRE costs, there are a lot of othe= r >>> things I would redesign. =A0Use a USB 2.0 chip to get 125uS jitter. =A0= Allow >>> for >>> a detachable or external antenna (which can be run to the window). =A0F= ind >>> 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 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) >>> =A0wrote: >>> >>>> >>>> Hi all, >>>> >>>> (I'm copying this only to the thumb-gps list and to TZ, the most recen= t >>>> 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 hat= e >>>> 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, sometim= es >>>> preventing them from booting. =A0It can get really ugly trying to revi= ve >>>> 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. =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 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 mu= ch >>>> less capacity and it has an exponential voltage decay curve, so it mig= ht >>>> 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 =A0wro= te: >>>> >>>>> >>>>> 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 swit= ch >>>>>>> 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 thin= k >>>>> 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