This is a multi-part message in MIME format. --------------050708070909000404090800 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Look at this: http://www.enocean.de nice little parts, low power, and they are build for facility-management ! Bob Axtell schrieb: > Mike Harrison wrote: > >>On Wed, 24 May 2006 09:19:03 -0700 (PDT), you wrote: >> >> >> >>>Whats your estimated hardware costs for the WiFi portion? >>> >>>Olin Lathrop wrote: alan smith wrote: >>> >>> >>>>Client has asked....possibility of doing a WiFi with a PIC. Well...the >>>>project in discussion is for a large greenhouse facility and monitoring >>>>temps and other stuff. >>>> >> >>Wifi would probably overkill for this - a more appropriate way may be low cost sensor/transmitters >>on one of the unlicensed UHF bands sending short packets every few minutes to one or more receivers, >>depending on distance - the receiver could either be a PC or a data concentrator that bulks up the >>data to send via wifi/GSM/GPRS etc. >> >> > > I agree. These tiny transceivers operate in the 433Mhz band, and are > quite reliable within 1/4mile. A PIC would provide packeting for > each data transfer (start char + data + CRC + term char) and another PIC > would unwrap the data and stuff it into a host PC through a > serial port. This would be very inexpensive, just a few dollars per > station. You could make it even cheaper by sending the packet only > at random intervals; for example, if the intent was to poll 16 stations > every minute, you could packet data for the last 3 intervals, then > send it at RANDOM intervals once a minute. Its always possible that two > stations would send on top of each other, but since the data > is triplicated, nothing will be lost. The receiving station would simply > receive packets and install them into a database, and toss duplicated > data. To make this work, the packet length has to be short and the > interval must have a lot of dead air. Even more reliable if the interval > is longer, such as 15 minutes. A simple encryption scheme can be > devised, such as substitution cypher, bit rotation, etc. > > I hope I didn't get too far off the subject. > > In general, I am not enthused about PC wireless schemes. I and some > associates looked into these for a police data dump station, and > the results were NOT heartwarming; not one method was free from hacking. > Personally, I think that IEEE803 etc was a plot hatched by > the NSA/IRS/FBI cabal to easily read everybody's computers by simply > parking in the front driveway and hacking in. It is INCREDIBLY > easy to hack. > > --Bob --------------050708070909000404090800 Content-Type: text/x-vcard; charset=utf-8; name="office.vcf" Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="office.vcf" begin:vcard fn;quoted-printable:Bernd R=C3=BCter n;quoted-printable:R=C3=BCter;Bernd org:Promaxx;Entwicklung adr;quoted-printable;dom:;;W=C3=BClferoder Stra=C3=9Fe 10;Hannover;;30539 email;internet:bernd.rueter@promaxx.net title:Dipl.-Ing. tel;work:+49 511 3746207 tel;fax:+49 511 3746208 url:http://www.promaxx.net version:2.1 end:vcard --------------050708070909000404090800 Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist --------------050708070909000404090800--