---- START NEW MESSAGE --- Received: from cherry.ease.lsoft.com [209.119.0.109] by dpmail10.doteasy.com with ESMTP (SMTPD32-8.05) id AFAB31010116; Thu, 29 Jan 2004 22:54:35 -0800 Received: from PEAR.EASE.LSOFT.COM (209.119.0.19) by cherry.ease.lsoft.com (LSMTP for Digital Unix v1.1b) with SMTP id <12.00CC43C1@cherry.ease.lsoft.com>; Fri, 30 Jan 2004 1:54:22 -0500 Received: from MITVMA.MIT.EDU by MITVMA.MIT.EDU (LISTSERV-TCP/IP release 1.8e) with spool id 1738 for PICLIST@MITVMA.MIT.EDU; Fri, 30 Jan 2004 01:54:16 -0500 Received: from MITVMA (NJE origin SMTP@MITVMA) by MITVMA.MIT.EDU (LMail V1.2d/1.8d) with BSMTP id 8264; Fri, 30 Jan 2004 01:52:52 -0500 Received: from mail011.syd.optusnet.com.au [211.29.132.65] by mitvma.mit.edu (IBM VM SMTP Level 430) via TCP with ESMTP ; Fri, 30 Jan 2004 01:52:51 EST X-Comment: mitvma.mit.edu: Mail was sent by mail011.syd.optusnet.com.au Received: from jake (c211-30-161-191.farfl1.nsw.optusnet.com.au [211.30.161.191]) by mail011.syd.optusnet.com.au (8.11.6p2/8.11.6) with SMTP id i0U6qp130977 for ; Fri, 30 Jan 2004 17:52:51 +1100 MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook IMO, Build 9.0.6604 (9.0.2911.0) X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1165 Importance: Normal Message-ID: Date: Fri, 30 Jan 2004 17:54:06 +1000 Reply-To: pic microcontroller discussion list Sender: pic microcontroller discussion list From: Jake Anderson Subject: Re: [EE]: Challenge for keen minds To: PICLIST@MITVMA.MIT.EDU In-Reply-To: <02b301c3e6fb$2ee56070$1308a8c0@Daniel> Precedence: list X-RCPT-TO: Status: U X-UIDL: 371856449 Analogs sample system is really top notch. problem you might have is picking the difference between the gate rattling in the wind and the gate opening. take a look at their digital PWM 10G or 2G sensor might work if you sum and average etc over a period of time. though if sombody opened it *really* slowly your screwed. magnetic compas? bringing a magnet near it should cause it to screw up enough that it will trigger. > -----Original Message----- > From: pic microcontroller discussion list > [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Daniel Imfeld > Sent: Friday, 30 January 2004 4:35 PM > To: PICLIST@MITVMA.MIT.EDU > Subject: Re: [EE]: Challenge for keen minds > > > ----- Original Message ----- > From: "Pedro Drummond" > > Hi, all. > > > > I have to implement a gate opening detector. It will log date and time > each > > time the gate is open and for how long. Must be battery-driven, battery > must > > last as much as possible, must be rugged and robust, and tamper-proof. > > People WILL try to defeat it. > > > > What I have already thought: > > > > 1) It will be all enclosed in a box with no openings, time of day > > programming will be done with an IR remote, data will be > collected from it > > the same way. > > Aside from these operations, battery consumption must be minimum. > > > > Any ideas to improve this number 1 ? > > > > 2) How to detect gate openings ? Well, if I use a regular reed switch, > > people will defeat it inserting a flexible magnet close to the sensor > before > > opening the gate. The same applies for metal (induction) sensors, > proximity > > (capacitive) sensors. I thought of having a second device on the moving > door > > sending IR data to the main device, but another battery consumption here > is > > out of the question. Last idea was to have a sequence of magnetized and > > non-magnetized surfaces, similar to a bargraph, only much larger, that > will > > match the reed (or HAL) sensors in the device. Much harder to fool and > > easier to save battery, yet not the elegant solution we all pursue... > > > > Any ideas here ? > > > > Thanks a lot, > > > > > > Pedro > > > > -- > > http://www.piclist.com hint: The PICList is archived three different > > ways. See http://www.piclist.com/#archives for details. > > > > If you can put the entire device on the gate itself, how about an > accelerometer? If a quiescent current consumption of 400 uA is all right, > Analog's ADXL311 should work well. It goes for $8.50 in single quantities > from Digikey, and Analog seems to have a good samples program too. You'll > have to read the value with a comparator or A/D, but if 600 uA consumption > is ok, you can use the ADXL202, which has a duty cycle output. The URL is > incredibly long > > http://tinyurl.com/2agpf > > or if you want the long URL: > http://www.analog.com/Analog_Root/sitePage/mainSectionResource/0,2 131,level4%253D%25252D1%2526level1%253D212%2526level2%253D213%2526level3%253 D%25252D1% 2526resourceWebLawID%253D13,00.html -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body .