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Old March 8th, 2018, 10:49 AM   #1
AustralIan
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Multidrop RJ45 RS485 connectors

What do you guys use for connecting several Modbus RS485 devices with a single RJ45 port in the one panel? and terminating resistors?
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Old March 8th, 2018, 01:04 PM   #2
kolyur
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I've used these in the past:
http://www.redlion.net/accessory/rj4...llel-connector

If you download the datasheet they have a similar product that has a RJ45 breakout terminal block, looks like a nice way to add a terminating resistor.
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Last edited by kolyur; March 8th, 2018 at 01:07 PM.
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Old March 8th, 2018, 01:32 PM   #3
geniusintraining
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I use a lot of Winford products.... great quality, prices are better than anyone else in the market, great supply of different **** that we need and they normally ship the same day or the next

https://www.winford.com/products/brk8p8csj4b.php
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Old March 8th, 2018, 03:44 PM   #4
swimmy67
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I have used these type of connectors. They work good for RS485 Modbus RTU.

https://www.amazon.com/C2G-Single-37...70_&dpSrc=srch
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Old March 8th, 2018, 04:15 PM   #5
BITS N BYTES
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Quote:
Originally Posted by geniusintraining View Post
I use a lot of Winford products.... great quality, prices are better than anyone else in the market, great supply of different **** that we need and they normally ship the same day or the next

https://www.winford.com/products/brk8p8csj4b.php
+1 for Winford Engineering. Great resource, good quality and reasonably priced.
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Old March 8th, 2018, 06:31 PM   #6
danw
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I would have concerns about either module creating a standing wave which reflects energy back that creates false bits because I see either as more of a star topology where each RJ connector is the beginning of 'stub' exiting from a common point.



Yes, the connectors are physically separated by mm or inches of tracing, but daisy chaining puts devices in parallel. each of which is at some distance from each other, there is a clear end on each end, unlike a star that does not have two ends.

One of the 'rules' of RS-485 is to limit stub or star wiring.

It might be that reflections are not a problem at internal-to-the-panel distances. But it goes against conventional wisdom in 485 networking.
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Old March 8th, 2018, 07:01 PM   #7
lfe
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+1 danw

What makes RS-485 more resistant to noise is to work by current, circulating an appreciable intensity through the cable, and this is only fulfilled with a daisy chain connection and the resistors at the ends.
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Old March 8th, 2018, 09:20 PM   #8
Geoff White
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I'm totally going to try the red lion product on DSI multidrop if I am ever forced to use it again. The Powerflex 523/525 rj45 connectors are utter garbage to try and terminate as a daisy chain.
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