David Just as a point of reference, we are running RS485 on a pair, and have +24V= DC on one pair, GND on another pair, and have not seen any issues at over 1= 00 feet. I think the issue you need to be aware of is how much current you= r pushing down the cable, and what the IR drop is going to be such that you= r device hanging out there can still function. --- On Thu, 9/10/09, David Duffy (AVD) wr= ote: > From: David Duffy (AVD) > Subject: [EE] CAT5E pairing with RS485 > To: "Microcontroller discussion list - Public." > Date: Thursday, September 10, 2009, 7:17 PM > I am planning to deploy a network of > (approx 70) remote devices via > CAT5E cabling. It will carry 24Vdc as well as RS485 data at > a low speed > (2400 baud at a guess). > = > I've selected the low baud rate so that I can get away with > a mixed > topology (part daisy, part star) that the building layout > imposes. The > longest cable run from the central controller should be > less than 300 > metres. > = > All of the terminations are via 'Phoenix style' 0.2" > plug-in connectors. > To lessen the voltage drop on the 24Vdc wires, I plan to > double them up. > = > It got me thinking that since there is still a spare pair > in the cable, > should I double up on the comms as well? What are the > implications of > having two balanced pairs in parallel, bearing in mind the > low data rate? > David... > = > -- = > ___________________________________________ > David Duffy=A0 =A0 =A0 =A0 Audio Visual Devices > P/L > Unit 8, 10 Hook St, Capalaba 4157 Australia > Ph: +61 7 38235717=A0 =A0 =A0 Fax: +61 7 38234717 > Our Web Site: www.audiovisualdevices.com.au > ___________________________________________ > = > -- = > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > = = -- = http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist