Siemens RS485 (CP341)

userxyz · Jul 5, 2007

I have a CP341 card for RS485.

I need to connect a device called TDS (temparature meters).

How can I connect it:

This is what I found of the CP341 and the TDS box:

Is it just like: pin 4 to D+, pin 11 to D- and pin 8 on the ground ?

And can I use a profibus cable to do this ?

JesperMP · Jul 5, 2007

Not sure what to do but in the diagram from Siemens is shown RS485 half-duplex. That means: You use the same 2 wires for send and recieve data.
Notice how the are jumpers inside the CP341 between 2-4 and 9-11.
Not sure if the CP341 supports RS485 full-duplex.

The references in the TD595 diagram for "RS485/input" and "RS485/output" seems to indicate that the device needs RS485 full duplex.

userxyz · Jul 5, 2007

Full Duplex

For Full Duplex it should be something like this then ? :

JesperMP · Jul 5, 2007

Exactly.

userxyz · Jul 5, 2007

so

So:

Connecting these connections should work:

CP341 / pin 9 = => = TDS-RS485-Input / D+
CP341 / pin 2 = => = TDS-RS485-Input / D-

TDS-RS485-Output / D+ = => = CP341 / pin 11
TDS-RS485-Output / D- = => = CP341 / pin 4
GND = = = CP341 / pin 8

like this ?

And when other devices are added, other TDS boxes have to come on the same serial bus, each one has an adress...

like this:

So, I think we will have to go for 2-wire or half duplex

?

userxyz · Jul 5, 2007

half

it will be half I think

And there the internal connections are made, no ?

JesperMP · Jul 5, 2007

If you are going to loop to further devices, then you are right that you have to use half-duplex.
If you select half-duplex it looks like the TDS95 device connects the "input" and "output" terminals internally.

userxyz · Jul 9, 2007

Rs232 - Rs485

As you know, RS232 is easy to test with hyperterminal,

but what about rs485... how can I test this, because I don't receive anything in the s7-300 cpu

userxyz · Jul 9, 2007

Command to RS485 device

maybe it's because I first need to send a command, to receive data, so see the attachments about the PLEVA device if you want please, and here is what I've tried in S7:

Combo said:
As you know, RS232 is easy to test with hyperterminal,

but what about rs485... how can I test this, because I don't receive anything in the s7-300 cpu

ALU · Jan 5, 2009

Combo said:
So:

Connecting these connections should work:

CP341 / pin 9 = => = TDS-RS485-Input / D+
CP341 / pin 2 = => = TDS-RS485-Input / D-

TDS-RS485-Output / D+ = => = CP341 / pin 11
TDS-RS485-Output / D- = => = CP341 / pin 4
GND = = = CP341 / pin 8

like this ?

And when other devices are added, other TDS boxes have to come on the same serial bus, each one has an adress...

like this:

So, I think we will have to go for 2-wire or half duplex

?

Dear JasperMP,
I also have the same query...I have five Displays with 2wire RS485 port returning ASCII string, each Display can be addressed. How can I collect data from five display to one S7-300. If I connect a network like your above drawing. How to programme in S7-300?
Thanks so much for help!
BR,
MHA

JesperMP · Jan 5, 2009

Hi MHA.

I answered the questions in the previous posts regarding the electrical connections, because I know generally how RS232/RS422/RS485 works.

About the programming of the CP340 or CP341 I have no specific knowledge. And you have also not told anything about your application.
I suggest you locate the manuals and sample programs for the CP340 or CP341.

ALU · Jan 5, 2009

Dear JesperMP,
Thanks so much for your reply,
Yes, I'll refer to these doccuments/progams as your advice.
About my application is as follows:
-I use five(05) Kobold Encoders (14Bits Gray) connected to five PM4BC displays (from AIC, Australia) to supervised the aperture of Radial Gates at Spillway in one Hydropower Plant. The displays are place at local and now running well.
-Now I want to collect data from five local displays to Control room using PLC S7-300. The display has 2wire RS485 port return ASCII string, its also can be address assigned. However, I have no experiment on this so I come here and hope someone can help me.
Once again, thanks for your help. If you have more sugestion, it helpful to me!
BR,
MHA

Siemens RS485 (CP341)

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