brucek <bru...@valinet.com> wrote: >If you have an extra pair in the wiring, you could use one pair in and >one >pair out so that the star is functionally a liner network >bk > >-----Original Message----- >From: ekgnkb3d >Sent: Saturday, September 17, 2011 7:05 PM >To: owfs-developers@lists.sourceforge.net >Subject: [Owfs-developers] increase OW reliability in bad topology > > >Hi all, >my problem is a little bit off-topic (because not specific to owfs), >but >maybe in this forum are the experienced 1-Wire net experts ;-) > >I want to replace in an existing building the 12 analog temperature >sensors >by 1-Wire DS18B20 temp sensors. The used cables are standard telephone >twisted pair which are shielded together. They are in star-topology, so >each >of the 12 cable come from a different room (10m to 50m length each) to >the >central controller. So the complete net have a "weight" of approx 350m. >The cables shall be reused, because it would be a hell a lot of effort >to >replace them too. > >As mentioned in http://www.maxim-ic.com/app-notes/index.mvp/id/148 >Maxims >application note 148 and >http://docs.google.com/viewer?url=http%3A%2F%2Fwww.1wire.org%2FFiles%2FArticles%2F1-Wire-Design%2520Guide%2520v1.0.pdf >1-Wire.org Design Guides , the star is the most critical topology for >1-Wire >nets. But what can I do, especially with OWFS, to increase the >reliability >of such a net? I've thought of the following already: > >- Using active pull-up bus masters, e.g. DS2482 with FET >- If using 4 bus-masters, each one have to drive 3 sensors only and >therefore reduce the weight to approx. 100m each. >- Slowing down the net to 16kBit/s Standard Mode (how to do this on >DS2482 >with OWFS?) >or even go slower down, to 8 or 4 kBit/s?? (The temperature is only >needed >each minute) >- Problems usually look like the devices are lost, the search algorithm >occasionally can't find some devices. > Is there a way to configure OWFS to retry let's say 100 times until it >really gives up? >- Connecting each DS18B20 with 3 wires (+5V and 100nF Capacitor each) >- Ensuring that the GND and OW-Data wire is a twisted pair of the cable >- No termination resistor at the end of the cables > >any more constructive ideas? > >Thanks > Achim > >-- >View this message in context: >http://old.nabble.com/increase-OW-reliability-in-bad-topology-tp32487173p32487173.html >Sent from the OWFS - Dev mailing list archive at Nabble.com. > > >------------------------------------------------------------------------------ >BlackBerry® DevCon Americas, Oct. 18-20, San Francisco, CA >http://p.sf.net/sfu/rim-devcon-copy2 >_______________________________________________ >Owfs-developers mailing list >Owfs-developers@lists.sourceforge.net >https://lists.sourceforge.net/lists/listinfo/owfs-developers > > >------------------------------------------------------------------------------ >BlackBerry® DevCon Americas, Oct. 18-20, San Francisco, CA >http://p.sf.net/sfu/rim-devcon-copy2 >_______________________________________________ >Owfs-developers mailing list >Owfs-developers@lists.sourceforge.net >https://lists.sourceforge.net/lists/listinfo/owfs-developers
+1 That is what I do in my house, where I have structured wiring. Currently have 12 ds18b20. Have not had a problem. I use parasitic power. Just make sure you do not leave Vdd floating (ground it). Cheers! -- Eloy Paris ------------------------------------------------------------------------------ BlackBerry® DevCon Americas, Oct. 18-20, San Francisco, CA http://p.sf.net/sfu/rim-devcon-copy2 _______________________________________________ Owfs-developers mailing list Owfs-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/owfs-developers
