---- START NEW MESSAGE --- Received: from cherry.ease.lsoft.com [209.119.0.109] by dpmail10.doteasy.com with ESMTP (SMTPD32-8.05) id AC95119001FA; Fri, 30 Jan 2004 12:20:37 -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 <11.00CC527B@cherry.ease.lsoft.com>; Fri, 30 Jan 2004 14:50:21 -0500 Received: from MITVMA.MIT.EDU by MITVMA.MIT.EDU (LISTSERV-TCP/IP release 1.8e) with spool id 4609 for PICLIST@MITVMA.MIT.EDU; Fri, 30 Jan 2004 14:50:14 -0500 Received: from MITVMA (NJE origin SMTP@MITVMA) by MITVMA.MIT.EDU (LMail V1.2d/1.8d) with BSMTP id 8356; Fri, 30 Jan 2004 14:48:58 -0500 Received: from pd2mo2so.prod.shaw.ca [24.71.223.10] by mitvma.mit.edu (IBM VM SMTP Level 430) via TCP with ESMTP ; Fri, 30 Jan 2004 14:48:58 EST X-Comment: mitvma.mit.edu: Mail was sent by pd2mo2so.prod.shaw.ca Received: from pd3mr2so.prod.shaw.ca (pd3mr2so-ser.prod.shaw.ca [10.0.141.178]) by l-daemon (iPlanet Messaging Server 5.2 HotFix 1.18 (built Jul 28 2003)) with ESMTP id <0HSB003BGIUVA4@l-daemon> for PICLIST@MITVMA.MIT.EDU; Fri, 30 Jan 2004 12:44:55 -0700 (MST) Received: from pn2ml3so.prod.shaw.ca (pn2ml3so-qfe0.prod.shaw.ca [10.0.121.147]) by l-daemon (iPlanet Messaging Server 5.2 HotFix 1.18 (built Jul 28 2003)) with ESMTP id <0HSB00IO6IUV8V@l-daemon> for PICLIST@MITVMA.MIT.EDU; Fri, 30 Jan 2004 12:44:55 -0700 (MST) Received: from UALBERTA.ca (h24-65-14-55.ed.shawcable.net [24.65.14.55]) by l-daemon (iPlanet Messaging Server 5.2 HotFix 1.18 (built Jul 28 2003)) with ESMTP id <0HSB00H5GIUVYR@l-daemon> for PICLIST@MITVMA.MIT.EDU; Fri, 30 Jan 2004 12:44:55 -0700 (MST) MIME-version: 1.0 X-Mailer: Mozilla 4.76 [en] (Win98; U) Content-type: text/plain; charset=us-ascii Content-transfer-encoding: 7BIT X-Accept-Language: en References: <401A9A93.20071.28A7C0C@localhost> <006201c3e75d$14b7f200$0301a8c0@user88l53zxzyb> <008101c3e767$6673d1e0$0301a8c0@user88l53zxzyb> Message-ID: <401AB450.90D8D861@UALBERTA.ca> Date: Fri, 30 Jan 2004 12:45:20 -0700 Reply-To: pic microcontroller discussion list Sender: pic microcontroller discussion list From: Robert Rolf Organization: U of Alberta Subject: Re: [EE]: Challenge for keen minds To: PICLIST@MITVMA.MIT.EDU Precedence: list X-RCPT-TO: Status: U X-UIDL: 371856561 Properly arranged, there should be NO glitches in a reed switch caused by truck movement. Have two sensors. One obvious, to be disabled/bypassed. One hidden, that logs the 'real' activity. If the box is normally dark, a light sensor (CdS cell) hooked to one of the self contained Dallas data logger chips should work with minimal effort. The crooks are going to need light to see what they're stealing. And if they think they've disabled the detector, they're more likely to turn on the lights. And you could always put a floor switch at the entrance, hidden under under a mat. And why not put a disposable camera in a box over the door or shooting through a hole in the side wall. Easy enough to have it snap an image when the door opens (with a 1 sec delay), which presumably happens only at the final destination. Autowinding is fairly easy too. Rubber hobby tire and small gear head motor timed to wind many minutes AFTER the door closes. R Pedro Drummond wrote: > > Yes, but the problem here is someone that, when opening the gate, > immediately recomposes the sensor (for example, puting a second magnet close > to the reed switch). If he takes, say, 2-3 secs to do it, it will be > analyzed afterwards as a glitch, probably caused by truck movement. The > ideal would be some kind of sensor not easily or quickly "recomposed" when > opening the gate. > > ----- Original Message ----- > From: "James Nick Sears" > To: > Sent: Friday, January 30, 2004 2:50 PM > Subject: Re: [EE]: Challenge for keen minds > > > In this case couldn't you just use a switch mounted inside the door > > somewhere where it can't be feasibly reached from the outside until the > door > > has already opened and the time of intrusion has already been logged? > > > > > > ----- Original Message ----- > > From: "Pedro Drummond" > > To: > > Sent: Friday, January 30, 2004 12:12 PM > > Subject: Re: [PICLIST] [EE]: Challenge for keen minds > > > > > > > Thank you all for the help and interest. > > > > > > Ok, time for more data: > > > > > > The space being protected is a metallic box, the size of an elevator, > that > > > will be towed by small trucks. Its metallic "door" (actually a double > > door) > > > is the gate I mentioned. During long trips, these boxes are commonly > moved > > > from truck to truck, with long periods waiting for the next one, with no > > > guards nearby. Although there is a very strong lock, theft was detected > at > > > final destination in locked boxes (i.e., someone opened it, took some > > goods, > > > and somehow relocked it). A redesign of the metal box is being made, but > > it > > > will be a long time until all of them are replaced. It is enough for now > > to > > > help the insurance company in detecting WHEN and for HOW LONG it was > > opened, > > > so the responsible will be known. > > > I do not mind reading its information only when the gate is open, and I > > > cannot modify the gate, only add some small device close to the door. > > > > > > > > > To comment some of the group ideas: > > > > > > Using a contact method for data transfer - I am afraid of dust, grease, > > etc. > > > But maybe. > > > RFID - cheap tag, but expensive sensor (I guess). > > > Gyro/acceleration sensors - can't do, since it will be towed by a truck. > > > Hinge sensored - can't alter the hinge. > > > > > > > > > BTW, special thanks to Russel ! > > > > > > -- > > > 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 > > > > -- > 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 .