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sdm120 kwh meter modbus how to add


  • i have a Kwh meter SDM120 i would like to add to Mango.

    http://www.flanesi.it/blog/download/sdm120c/SDM120-Modbus_protocol_V2.1.pdf?dl=0

    also found some code which might be helpfull for someone how needs it.
    https://github.com/gianfrdp/SDM120C

    the rs485-modbus of the sdm120 is connected via rs485-usb to my Mango server.

    under datasource i can add ( /dev/ttyUSB0 2400 8N1 ) and i can scan nodes and it will find 1 node.

    Then i have to enter some data i cant find. i cant figure out how things are working with Hex, registers, offset etc.
    should be simple protocol. but i need a hint in the right direction ( good tutorial about offsets, bits, Hex and stuff )

    Readup for starters like me,
    http://www.simplymodbus.ca/FAQ.htm

    it appeared that , the settings that worked for me where taking the register address minus x_0001 : ( so for Total Kwh. 30343 minus 30001 = offset address is 342 )

    0_1477573484703_upload-8f442fef-14ea-4dfa-ab94-30ab57053fef


  • Try this to read a point, like the Voltage from your meter. You can get here from the Data Sources page. See my picture below:

    Oh, your modbus settings have to match the meter, of course, like the bit rate, parity, etc.

    0_1477517327314_read register test.png

    One more thing, you have to turn off the serial data source to do the test, or else i'll throw an error because it's busy.


  • Thanks Mihai!

    @hengst Hello and welcome!

    Many of these things (offset, bits) are described in the help document available through the blue help (?) near the top of edit page for a data source or its points.

    if you're going to be adding a lot of devices and points, you can also experiment with the CSV importer once you get a point working, then export the CSV through the data source's row on the data sources page, and importing it or rows like it on the import/export page.


  • This post is deleted!

  • Well i had some coffee ...

    to get the Kwh total .....

    0_1477572714719_upload-cf8cec07-bd89-402d-88c3-abfa181cbeca

    to get the Volts ...

    0_1477572782136_upload-05653e39-5daa-4b68-9356-f93f5b408e4a

    and so on..

    so i got it working, but more by gamble than by knowledge.
    it looks like i have to put in the register address from the manual , minus 30001 for every register i want to read.

    maybe someone can explain a little further.


  • Hi hengst,

    I cannot think of a good reason to have an IP posted like that with the implication it has the default password, so I have removed it. Definitely not a secure thing to do.

    The subtraction of 30001 would be a result of two things,

    1. 30000 is the INPUT_REGISTER range in the Modbus spec, and you've selected that as your Register range (bereik?)
    2. Your literature is probably 1 offset, meaning the first address is 1. We use a 0 offset. I was pleased to see Mihai included this consideration in his image!

  • Many thanks for all the Help. i think this topic is SOLVED ( if need to close ). i'am on to the next device i want to add.


  • It's a forum, no need to close things. With regard to the question in the post you've removed about making it more readable, every data point has a text renderer that governs its display. There's a description of the four text renderers for a Numeric data point in the help popup from the blue (?) in the text renderer section of the edit point page. You can also specify the units, or a custom suffix for the value. The units for kWh is kW*h, whereas you can put " kWh" in the suffix.