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RS 232 to RS485 converter wiring question

Created by: Fran at: 11/30/2007 1:13 PM (7 Replies)

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11/30/2007 1:13 PM	Rate (1)
Fran Posts: 26 Rating: (1)	Hi all S7-200 users! I have searched FAQ's about this but i couldn't find a convincinganswer, so... I'm a rookie inRSxxx interfaces and maybe I'm trying to do something impossible, or senseless. I have a S7 224XP which i need to connect to an Fargo Maestro GSM Modem. I have a PC/PPI cable and aAten RS232 to RS485 converter (IC 485). I'm using the PPI cable for programming the CPU and the Aten converter to connect the PLC to the GSM Modem. I want to do this way because i want to debug the PLC-MODEM communication with the PC without buying and aditional PPI/PC cable. The Aten converter has a terminal blockwith four pins: R+, R-, T+, T- and an aditional ground i wired from the DB25plug input. Ihave built a cablefor connectingto the PLC port 0. According to the S7200 user's manual and Aten converter manuali wired the R- and T- output to the pin 8 of the PLC port (signal A) and the R+ and T+ output to the pin3 of the PLC port (signal B). The ground signal is wired too. This is Point-to-Point 2 wire half duplex configuration. To test the circuit i tried to communicate the PC to the S7 224 with this fittings (DCE mode for Aten converter). However, when refresh in the "communications" screen i get 127 unknown devices... even if i unplug the PLC (only with the Aten converter). This setting is only testing purpouse only. In the future the PC/PPI wil be used for PLC programming/debuging and the Aten converter for connecting the MODEM to the PLC. The question is i don't know if i built the cable wrong , or the PC/PG configuration. PC/PG interface is set to the same functional settings of the PC/PPI cable. I'm using Step7/MicroWIN V4 + SP4. Any ideas? Thanks in advance!
Fran Posts: 26 Rating: (1)
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11/30/2007 3:03 PM	Rate (0)
Husam Posts: 101 Rating: (11)	Hi Fran, Take a look at this thread: /tf/WW/en/Posts/2120 Also, at these links, they might be of help: http://www.airborn.com.au/rs232.html http://www.airborn.com.au/rs585.html http://interface.centraltreasure.com/rs485.html http://www.commfront.com/RS232-RS485-RS422-Serial-Converters/RS232-RS485-Converter.htm?gclid=CIWqnabdhJACFSdWZwod1S4hrw
Husam Posts: 101 Rating: (11)
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12/4/2007 10:17 AM	Rate (0)
Fran Posts: 26 Rating: (1)	Hi Husam !. Thank you for your answer but I think it ismore a signal/wiring problem than a power management one. My RS485 converter has an external power supply. It doesn't take power from the RS232 port. Here you are the user's manual of the Aten converter. I send you too a screenshot from the communications screenof MicroWIN that i get when trying to communicate the PLC with the PC via the Aten converter and my homemade cable. This result is the same even if i unplug the PLC from the converter. I think the converter (or the cable i made) is working in test mode. Attachment Aten.zip (388 Downloads)
Fran Posts: 26 Rating: (1)
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12/4/2007 12:10 PM	Rate (0)
yming1 Advanced Member Joined: 12/4/2007 Last visit: 10/30/2024 Posts: 8 Rating: (0)	Hi Fran, I think youconfig as the Fig. Attachment GSM-232.JPG (470 Downloads)

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12/10/2007 8:55 AM	Rate (0)
Fran Posts: 26 Rating: (1)	Hi yming1! That'sthe configuration i use to debug the PLC program. To test the Aten converter i plug it betwen the PLC and the PC and try to communicate them with MicroWin. That's whe in get 127 "unknown devices" result.
Fran Posts: 26 Rating: (1)
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4/23/2008 11:40 AM

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nawaz_fly

Posts: 7

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Dear Fran,
I have used the Aten converter for adifferent application which required me to convert RS-232 to RS485. On the RS485 front , I used the following wiring configuration...
For ATEN IC485S RS232 to RS485 Converter

Configuring the converter:

Set the switches on the converter as per the table shown below.

SW1	SW2
DCE mode	TxON,RxON

Connection:

Connect the wires as per the table shown below.

485 device	Pin on IC485S Converter
(A) Data-	2 (T-)
(B) Data+	4 (R+)

If you connect as per the Aten manual it wont work.

12/6/2009 2:33 PM	Rate (0)
pcuser01 Posts: 1 Rating: (0)	following links,hope will help someones : http://www.sintech.cn/en/rs232%20rs485%20converter/rs232%20rs485%20converter.htm and http://www.shopsintech.com/index.php?cPath=3&osCsid=433ac6dd26d2c115a7610a39a74fc0df.
pcuser01 Posts: 1 Rating: (0)
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7/24/2011 1:20 AM	Rate (0)
HansNielsens Posts: 4 Rating: (0)	Sounds like you are using a RS232 to RS422 covnerter instead of a [url=http://www.usconverters.com/index.php?main_page=index&cPath=65]RS232 to RS485 converter[/url], the RS422 converter has 4 wires where the RS485 only has 2 data wires. Check this basic [url=http://www.rs232-to-rs485.com]RS232 to RS485 converter[/url] wiki, it will help you with the basics.
HansNielsens Posts: 4 Rating: (0)
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