Dear All,

i have a project about to communicate the PLC (Micrologix 1200) to PC (which is installed with RSView 32) via modem.

i have an external modem 3COM US ROBOTICS connected with Micrologix 1200 while the remote side is a pc which is installed SCADA RSView 32 and also installed with PCI modem. this toplogy would be modem to modem communication.

kindly help for it that how can we initialize the modem with PLC. while the remote pc dial the number of the modem on other side connected with plc.

i have made null modem cable plc to modem.

so help for these issuse.

waiting for your prompt reply

When connecting to a modem your cable should be straight thru( not a null modem) ( see link below for additional help on setup)

http://www.mrplc.com/kb/index.php?page=ind...p;id=9&c=11

Mickey's post and link is good information. The one piece of advise I would give is once you decide the speed of the Micrologix Com port {say 19200 for example} whatever commands or switch settings it takes force the modem/s to operate at this speed and do not allow auto-negotiate of speed. This will result in fewer issues in the long term.

Thanx for your cooporation but i have all it done that u discribe above but fial to communication.
will you please tell the any point that may be i bypass of that.

and one more think that u explain me that are we need to make a program in plc to communicate with modem. is it necessory or void it.

let me please explain this thing or any point that u think, could be skip by me let me also explain of that.


thanx for your coordination
waiting for your reply

Since you are having so much trouble with the modem and it appears English is not your first language let's take this slow and step by step.

Use a serial cable and connect your PC to the PLC. Once you can connect RSLogix to the PLC and write your program post the Baud rate and Protocol settings of the DF-1 Driver and we'll proceed with modem connection. A screenshot of your RSlinx Driver config would be great if you ahve the capability.

Please Find the attched images for channel configuration in RS logix. and Driver Configuration in SCADA PC.

(if those settings are wrong then send me the actual settings for Micrologix 1200 C series)

i have download the program in to PLC, after that i unplug the serial cable from the PC and connect with modem's serial cable, which is 25-pin connected with modem and 9-pin connect with PLC cable. (8-pin MINI DIN pluged in PLC and other side D-Sub 9-pin connect with modem cable, this is null modem cable PLC to modem)

after that on other PC installed with RSView 32 and having a internal modem i configure the driver in RS Linx with RS-232 DF1 Devices and configure the driver parameters along with modem configurations.

when all of those have to be done, and PC modem dail the number of PLC modem, and goes to connect.

but in RS Linx we unable to monitor the connected PLC,

now tell me where is the actually problem creates, whether are we using wrong cable for PLC to modem, if yes then, how can we make our modem cable that we could successfully connected with modem and use the PLC in scada software.


further information will be provided on request

waiting for your reply.

The posting of your settings all look good and the fact that the remote modem can answer and connect with the local modem is a good sign. I am beginning to think that the cable from Remote Modem to PLC may be your issue. I have two thoughts to address.

Test #1 - Connect a Hyperterminal Capable PC to the remote modem and connect to modem. Next Open a Hyperterminal Session on your SCADA PC and dial the remote modem. If and I suspect they will the two Hyperterminal Sessions can communicate we have narowed it down to the Remote Modem to PLC cable.

Test #2 - Since we know that the DIN 8 to DB9 cable works when connecting a PC try the following.
First determine which pins of Din8 connect to pins 2 & 3 of the DB 9. Then using the following chart see if the pin that goes to DB9 pin2 is conencted to DB25 pin 3. Also confirm that the Din8 Pin which went to DB9 pin 3 goes to DB25 Pin 2. IF not then you'll need to remove or insert a null modem to get the wiring straight.

If the above two checks yield no joy then I am stumped and others will need to review and suggest.

here is one more point which i ask abt it,
can we use the office internal extensiones instead off dail-up lines for both sides?

As long as the modem can detect a dial tone and dial use of internal office extensions should not affect the operate or not operate state. In fact internal office extensions will probably operate at a higher baud rate than dial up lines due to fewer switches and less wire length between the modems.

This comes via e-mail:
PS: it's best to post all questions direct to the forum, most moderators will all tell you the same. Thanks for reading this reminder.....

Dear sir,

I have a problem in communication with Micrologix 1200 C serise to Remote RSView 32 Scada PC via modems, by using the outsided lines or office internal externtions followings are equipments that in used for modem to modem communication.

1. PLC (Micrologix 1200 C series FRN5)
2. U.S Robotics modems
3. PC (Installed with RSView 32 Scada software)
4. modem cable
5. PLC Programming Cable (1761-CBL-PM02 Series C)
6. Office internal Extentions (or have been used landlines)

System topology:

We have a Scada system from the distance of about 300km from remote side PLC control system, both are communicating via external modems.

I have tried to query in forum and followed the replies against my querys. but could not successfull to send or recieve the data with SCADA.

Otherwise the modem dial the number of other modem connected with PLC and handshake but did not recive or transmit any data. while we have try our best and approch to made every possiblity.

In general case as reply from the Forum, i have to chage the settings accordingly but fail.

In RSLogix 500 we Configuration of Channel in PLC:

We have only Channel 0 in ML1200
Driver: DF1 Full Duplex Source ID: 1
Baud: 9600
Parity: NONE

Control Line : Full Duplex Modem (RTS on)
Error Detection: BCC
Embedded Responses: Auto Detect
Duplicate Packet Detect: CHEKED
ACK Time: 50
NAK Retries: 3
ENQ Retries: 3

After these download the program and channel configuration.

IN RSLINX CLASSIC SETTINGS:

We have configure the Device Driver as bellow:
Device Name: AB_DF!-1
Comm Port: COM1
Device: SLC-CH0/Micro/PanelView
Baud Rate: 9600
Station Number: 00
Parity: None
Error Checking: BCC
Stop Bit: 1
Protocol: Full Duplex
Use modem Dialer: Checked and Configure the Dialer

After all configurations the modem dial the number of other side and make handshake and both modem illustrate thier CD led on while did not flashes the RD and SD lights.

we have program the modem by AT commands from the Artical ("How to Connect a Us Robotics External Modem to Allen Bradley DF1 PLC") posted by forum members, but could unable to make communicate both sides.

After study my query if any possibility have been made, then send your best solution for that scenerio,
I would be very much thankfull to you.

Further information could be given as your acknowlegement.
I will wait for your feedback.

Regards
Muhammad Daniyal

Dear Muhammad Daniyal:
Again I am unclear as to your level of success or lack thereof. Could you please answer the following.

1. Have you been able to get two PC's to communicate thru hyperterminal and the modems when on local office extensions?

2. Have you been able to get to PC's to communicate thru hyperterminal and the modems when on actual long distance phone lines?

3. If yes to Question 1, Have you been able to get a PC and your PLC to communicate thru the modems when on local office extensions?

4. If yes to Question 2, Have you been able to get a PC and your PLC to communicate thru the modems when on actual long distance phone lines?

Assuming you can answer yes to 1,2 & 3 but answer no to 4 I'd suggest a slower baud rate. Really need the answers to these four questions to advise further.

BobLfoot

Thanks every one for coordinate with this issue, i have meture that communication, every thing is working fine and in order.

once again thanks.

So that others who might be having the same problem can profit from you experience would you mind posting the root problem and what you did to resolve it. thanks BobLfoot.

Ok bob, i'll provide u all documentaion regarding this issue, the working scenerio is quit diffrent from the available artical on this site.

we have made our AT command sets for Micrologix 1200, this will also i qout those commands. and configuration of PLC channels along with cables used in this communications.