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Topic: remote sensors - wich (wired) connection is better? (Read 2 times) previous topic - next topic

sotomaior


sonnyyu



Please post new links, those don't work.

true, sorry!
http://www.ebay.it/itm/280992276053?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649
http://www.ebay.it/itm/271083725046?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649
http://www.ebay.it/itm/270984792461?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

RS485 Cable spec;-
2. Only  STP Shielded  cable is compatible, order that type cable only.

may i ask you why? (just to know it)


1. Impedance, It could be fine tune the transceiver resistor to keep match.


you mean it is "enough" or is it only better?


take a look picture, UTP is no shield then out. ScTP is  shield all pairs then have to out. Only  STP Shielded  cable is compatible.

transmission line is require impedance match.  RS485 transceiver IC is designed to work at Impedance: 100-130 ohms, now we feed it Impedance: 85-115 ohms cable, fine tune resistor to keep match.

all above is for keep system run at long distance, for short distance it does not matter.
but question if for short distance why you use RS485 anyway?


sotomaior


all above is for keep system run at long distance, for short distance it does not matter.
but question if for short distance why you use RS485 anyway?


What do you mean by "long distance"? im planning to do a 70 m^2 domotic house, so there isnt any long distance, but 20-30m are  enough to kill my 5v dc signal i think...

im searching the easiest possible way to place sensors and switches into all rooms starting from a single "control box", possibly in a wired way, i understand that for serial communication the rs385 is a good idea, but is it useful and simple also for trasmitting a single 5v dc signal for a deviator for example?

sonnyyu

1200m is max, say few hundred m to 1.2km is long distance.
20-30m, you do not need do anything, even it might work at UTP cable.

sotomaior

do you mean using rs485 data transmission or the "simple" 5v digital signal?

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