--===============0959819844== Content-Type: text/plain; format=flowed Content-Transfer-Encoding: quoted-printable X-MIME-Autoconverted: from 8bit to quoted-printable by pch.mit.edu id k55EcQ8M013684 Hey there, Darren, >From my understanding of the problem you described, The problem is most likely with the 5v power transmission over such long distances. If you could regulate it back down at the end points, and increase the voltage supplied, that would work. Another option would be to use large capacitors at the end points as a current source to offset the voltage drop when current is drawn through the CAT5 cable. You could easily enough perform tests to verify or eliminate this as your root problem. Good Luck - D. >From: Darren Gibbs >Reply-To: "Microcontroller discussion list - Public." >To: "Microcontroller discussion list - Public." >Subject: [EE] sensor question >Date: Sat, 3 Jun 2006 17:06:38 -0700 > >I wonder if anyone could help with an insight into this situation... >I'm out of my debugging depth at this point. > >I'm working on a project with several remote sensors. On each of 4 >flights of stairs there are mounted two Sharp GP2D12 IR distance >sensors (pointed lengthwise to detect a stepping foot anywhere on the >monitored stair) and a KC7783 IR motion sensor to detect activity at >the doorways. Both of these parts operate at +5V and are connected >to to a 5V 5A power supply. The distance sensors output an analog >voltage (2V range), and the motion sensor TTL. The distance sensors >draw 33mA each and the motion sensor 400uA. > >When the three sensors are all connected near (within a foot of) the >power supply, they all work fine. >When connected at the end of about 60' of CAT5, the motion sensor >refuses to work and I see low frequency noise on all three sensor >outputs. >If I power the motion sensor right at the 5V supply, but leave the >distance sensors at the far end of the long cable, they all work fine. >If I leave the motion sensor at the far end of the cable, but power >the distance sensors right at the supply everything works fine. >If I leave all three sensors at the far end of the cable, power the >distance sensors right where they're mounted using a 9V battery + >LM7805, and power the motion sensor from the 5V supply at the near >end of the cable, all three work fine. > >The only non-working configuration is all three devices at the far >end of the cable, with all three powered through the cable. > >I'm wondering what the distance sensors could be doing to the power >supply from the far end of the cable that would cause the motion >sensor to crap out, but not have that effect on the near end of the >cable. Is there something about running the power to those device >through the 60' of wire that would make such a difference? > >Any suggestions much appreciated! >-- >http://www.piclist.com PIC/SX FAQ & list archive >View/change your membership options at >http://mailman.mit.edu/mailman/listinfo/piclist _________________________________________________________________ Don=92t just search. Find. Check out the new MSN Search!=20 http://search.msn.click-url.com/go/onm00200636ave/direct/01/ --===============0959819844== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Disposition: inline Content-Transfer-Encoding: 7bit -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist --===============0959819844==--