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 Post subject: Re: RS485 - Overview
PostPosted: Tue Nov 20, 2012 1:05 pm 

Joined: Tue Nov 20, 2012 11:17 am
Posts: 10
we have a morley zx5e facp, connected to it are 2 485 comm cards. problem is those devices connected to this cards are now non existing so this cards gives us a comm fault for these 2 485 cards. we tried to loop the wires from out to in, connect eol but still the fault will not reset. please help as we need to remove these comm faults from the panel. also, we do not have the higher level passwords for this panel so we cannot delete the cards from the system. thanks in advance for the help.


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 Post subject: Re: RS485 - Overview
PostPosted: Thu Nov 22, 2012 10:45 pm 
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Joined: Thu Dec 11, 2008 7:52 am
Posts: 739
that comm fault is not going anywhere with out putting the 2 devices back on the RS485 data line.
this panel is addressed number 2 and it is looking for panels 1 and 3


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 Post subject: Re: RS485 - Overview
PostPosted: Fri Nov 23, 2012 8:35 am 

Joined: Tue Nov 20, 2012 11:17 am
Posts: 10
thanks for the reply sir leo...
but, is there a way we could retrieve the level 3 password so we could just delete/erase the other panels from the program?


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 Post subject: Re: RS485 - Overview
PostPosted: Sun Nov 25, 2012 7:45 pm 
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Joined: Thu Dec 11, 2008 7:52 am
Posts: 739
I have never heard of a "morley zx5e" panel.


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 Post subject: RS485 - Overview
PostPosted: Thu Aug 26, 2010 8:27 pm 
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Joined: Thu Dec 11, 2008 7:52 am
Posts: 739
RS485 allows multiple devices to communicate at half-duplex on a single pair of wires, at distances up to 4000ft
Up to 32 electrical drops, not necessarily 32 addresses some panels uses more then one addresses.

plus a ground wire?? - http://www.chipkin.com/articles/rs485-c ... wire-rs485
SHIELDING - http://www.circuitcellar.com/library/cc ... c79bp5.htm


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PostPosted: Thu Aug 26, 2010 9:07 pm 
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Joined: Thu Dec 11, 2008 7:52 am
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RS485 in the alarm world uses Master-Slave Systems
All the systems that I have seen use RS485 is a Master-Slave System or Polling.

IE. The computer's com port (RS232) is converted to RS485. The PC polls panel 1 and waits for a response there panel 2 and so on.
The panel can not send data until it is polled by a PC or master panel/controller.


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PostPosted: Thu Aug 26, 2010 8:51 pm 
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Joined: Thu Dec 11, 2008 7:52 am
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120 Ohm terminating resistance between the RS-485 + and RS-485 - signal lines.

http://www.maxim-ic.com/app-notes/index.mvp/id/763
Termination resistors should always be placed at the far ends of the cable.

As a general rule moreover, termination resistors should be placed at both far ends of the cable. Although properly terminating both ends is absolutely critical for most system designs, it can be argued that in one special case only one termination resistor is needed. This case occurs in a system when there is a single transmitter and that single transmitter is located at the far end of the cable. In this case there is no need to place a termination resistor at the end of the cable with the transmitter, because the signal is intended to always travel away from this end of the cable.

How can I tell if I'll need termination on my RS485/RS422 connections?
Lantronix - So for cables 2000ft or less termination is not needed at 9600bps
http://ltxfaq.custhelp.com/app/answers/ ... equired%3F


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