GSM modem at a distance

[AdamEMC]

Hi

I am using a Vision 130-33-TR6 and a GSM KIT 41J and I wish to allow remote access to the PLC using this kit.

However there is no phone signal at the PLC location so I was considering running a cable to another location with signal and placing the modem here. The location with phone signal is 400m away from the PLC location. I have been told that at high baud rates I cannot transfer data that distance but at a baud rate of 2400 I would be able to go up to 900m. Is this correct and if so would I still be able to access the PLC remotely at this baud rate? I assuming if so the project scan time would have an impact on this? Are there any other ways I could solve this problem?

Thanks

Adam

[Emil]

Hi Adam,

Modem's interface to PLC is RS232. according to standard, the distance there is 15 meters. You will need to use RS485, which is up ot 1200 meters. This means, that in PLC you will use RS485 port and in modem side you will need to put RS232/485 converter. I'll recommend Unitronics M90-19-R4 unit.

With this scheme, built properly, you can transfer signal with 9600, which is default for the modem, without any problems up to 1200 meters. Again - with properly built system... which is another story.

[AdamEMC]

Thank you for your help. I assume if I wanted to connect straight to a broadband router at someones house I could apply the same principle?

Also would an RS232 to RS485 converter on the PLC side work in the same way or does the port need to be changed to a dedicated RS485 port?