Simple modbus network and logging

glideratio · Jun 2, 2009

Hi guys,
I'm looking for a simple and cheap solution to create modbus network, read devices and log data on PC.

I have 5 modbus compatible devices that I have to hook up to the Modbus network and read them from PC.

Can I get some help ? I've no experience with modbus at all.

Thanks
Regards

nettogrisen · Jun 2, 2009

There are different kinds of modbus.
Is the communication going to be serial?

seb · Jun 2, 2009

Check out the OPC server from kepware.com they have a free trial version you can down load. It has drivers for most PLC's a datalogger plugin that will log to a data base like ms access unlimited tags as fast as 10 msec or you can read and write from excel to your device.

glideratio · Jun 3, 2009

Communication has to be RS485.

tragically1969 · Jun 3, 2009

glideratio said:
Communication has to be RS485.

You will need an RS485 card in the PC, a piece of software to read Modbus and your modbus devices, although you probably already know this.

So.....specifically what do you want to know ?

glideratio · Jun 3, 2009

tragically1969 said:
You will need an RS485 card in the PC, a piece of software to read Modbus and your modbus devices, although you probably already know this.

So.....specifically what do you want to know ?

What inexpensive software can you recommend for logging data on PC from Modbus devices.
The logging frequency would be once in 24 hours.

tragically1969 · Jun 3, 2009

glideratio said:
What inexpensive software can you recommend for logging data on PC from Modbus devices.
The logging frequency would be once in 24 hours.

We just read modbus devices from PLC's\SCADA so i have never done this but...

I would suspect there are plenty of options, you could write your own or build something, using custom tools:

http://www.modbustools.com/modbus_activex.asp
http://www.sapia-inc.com/

Or you could buy something cheap and cheerful like this:

http://www.windmill.co.uk/modbus.html

(I have never used any of the above)

glideratio · Jun 4, 2009

tragically1969 said:
We just read modbus devices from PLC's\SCADA so i have never done this but...

I would suspect there are plenty of options, you could write your own or build something, using custom tools:

http://www.modbustools.com/modbus_activex.asp
http://www.sapia-inc.com/

Or you could buy something cheap and cheerful like this:

http://www.windmill.co.uk/modbus.html

(I have never used any of the above)

Thanx for the links.

glideratio · Jun 10, 2009

I just found that RS485 devices are not of the same type. Most are 4 wire type and some are 2 wire type. Is it an issue for installing them in one network ?

thanks

CowDung · Jun 10, 2009

The difference is half duplex (2 wire) and full duplex (4 wire).

Everything on the network should be of the same type.

TimothyMoulder · Jun 10, 2009

Here's a silly question - what are the devices?

Brian123 · Jun 10, 2009

CowDung said:
The difference is half duplex (2 wire) and full duplex (4 wire).

Everything on the network should be of the same type.

Everything on the network should be _wired_ the same way. You can (usually) wire a full duplex device (4 wire) to a half duplex network (2 wire).

Brian

glideratio · Jun 11, 2009

Brian123 said:
Everything on the network should be _wired_ the same way. You can (usually) wire a full duplex device (4 wire) to a half duplex network (2 wire).

Brian

So if wired properly everything should be ok on the same network?
The spec of 4 wire device allows 2 wire network.
Is there any catches?

Simple modbus network and logging

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