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Logging Modbus Data

camo200sx

Hi there

 

I am am undertaking a project involving a portable battery powered box that houses 6 modbus sensors. The box is required to collect data for a duration of about 2 - 5min at a time and then the results exported so they can be used to generate a report.

 

I'm wondering what options people would recommend using for such a task? Being battery powered it would want to be as efficient as possible.

 

I initially thought something like an arduino but then decided it needed to be of industrial spec. This lead me to the IOT2040 with onboard RS-485. There are also stand alone dataloggers such as the KTA-287 by ocean controls that would possibly use less power but be a little more simple. The 2040 would allow for further addition of things like wireless connectivity, I'm just not too sure if its over the top

 

Thanks for your help!

 

Cam

  • Hi Cam,

     

    This is an interesting challenge.  The KTA-287 looks like a really nice little unit for what you want to do - I would be very tempted to go for this unit unless you have a requirement for more complex functionality.

     

    There are a number of other ways you could solve this each with their own advantages and disadvantages -

     

    Some options I would consider:

    • Siemens S7-1200 PLCSiemens S7-1200 PLC with RS485 comm boardRS485 comm board.  I know the PLC definitely supports acting as a Modbsu TCP master or slave, however I am not 100% sure if it support Modbus RTU over the RS485 module - my guess is that it will.  You could log the data to a datablock in the PLC.  The challenge would then be to pull the data out of the PLC, depending on the tools you have available and if you planned to connect the PLC to a network, you could use an OPC server and some software to save the data to a DB.  You could probably rule this option out if you didn't have any existing tools such as an OPC server, data historian or even the Siemens Step7 software to program the PLC - unless you are prepared to spend some money and time setting these up!

    imageimage

     

    • MBED board with an RS485 interface converter of some kind - I would recommend the Mikroe RS485 Click boardMikroe RS485 Click board as a converter.  There are a whole host of mbed boards you could use with different features on-board.  The list of boards is here.  With this option, you could use an existing Modbus library such as this one.  You would then need to write your own code to poll the required resisters and save the data to a specified location.  Some boards will have an SD card interface where you could save the data to an SD card.  Alternatively, the mbed interface provides a small amount of mass storage where you can create and save a CSV file.  This is something I have done very successfully using the LPC1768 board.  You then just plug in a USB cable and treat it like a USB drive.

    imageimage

     

    • Use a board such as the Embedded Micro Technology MyPi board with a Raspberry Pi Compute module and RS485 interface card.  They actually provide an example application to do exactly what you want to do.  See this link. This example will take Modbus data and save it into a SQLite DB.  This board could give you an awful lot of extra functionality should you need it as it is effectively a Raspberry Pi.  You would need to speak to Embedded Micro Technology directly to purchase one of these.

    imageimage

     

    • If you can connect to a network and have a PC or server available, you could use a Modbus RTU to TCP converter such as the ADAM 4572ADAM 4572 and then connect the Modbus devices to your network via this.  You would then need some software on a PC or Server to Poll the data from the devices and save it to a specified location.  There are a few Modbus applications available on Sourceforge that may do the job.  I have not had experience using these so cannot comment on which ones would work and which would be best.  Of course if you have any existing SCADA software tools available such as Wonderware, you could use these.

    image

     

    Hope this helps!

     

    I would be very interested to hear what you use in the end and how well it worked.

     

    Cheers

    ---------------------------

    Tony

  • in reply to tonydbeck

    Wow. Thanks Tony

     

    You've certainly given me some food for thought!

     

    Ocean controls also has another one they told me about that is possibly a better option. It can read floating point directly without conversion needed. Apparently the sensor can do this too

    MSD200 Modbus Datalogger :: Data Loggers :: Welcome to Ocean Controls

     

    Like you say, a unit such as this would require less setup. I would then need to focus on a way to use the data obtained to create a nice report. Possibly excel or similar can do this with a template.

     

    I was leaning more towards the 2040 as I like to tinker but the above option is robust and industrial

     

    Keep ya posted!