POE Voltage Monitoring

  • Was thinking of fabbing together an POE Current Monitoring Circuit and would like some thoughts.
    End Result:
    I want an POE monitoring and Injection box that mimics the big box routers with advanced POE interface options in pfSense via a package i make.

    I have a grip on the electronic end but need some basic software development advice. Like what would be the simplest way to input analog or digital signal inputs. I am thinking USB. With the Arduino they use GPIO - An interface which i also have access to, but I would prefer a more broad hardware base. Like USB or Serial.. What already exists that i could piggyback on so a custom kernel wouldn't be needed?

    I know this is alot for me to handle but i would like any works of encouragement or discourgement.


    Some of the components i plan on using:
    So i want to feed this to some kind of usb/comm interface..

    Maybe a prototype PCB with 2 sets of ethernet jacks and input power jack and diodes with the above sensor board piggyback.

    Any design or software advice is welcome.

  • So i guess this would do the hardware end without soldering.


    Could do Voltage too.

  • Netgate Administrator

    Do you actually need to monitor voltage? I would have thought current/power is much more important.
    Do you need to able to set power limits per port as shown in the screenshot?


  • No i don't need "power budgeting" just monitoring and power cycling on/off. Was thinking of using usb voltage gauge on the power input side and usb ammeters on the outputs. Maybe just prototype a single Ethernet in-out connection for starters and move to 4 ports if it works out.. All these parts seem way high in cost but i like the opto-isolator method for ampmeter and nice compact size..
    Since these are power monitoring numbers maybe i could use NUT to display values…

  • Got some parts on order for prototype:
    2 breadboards 7x9cm
    4 RJ45 modules

    I like their style..

    Should i use FTDI usb to serial and then Analog to Digital or skip serial altogether and go USB to A/D?

  • So most I am looking at go basically like this:

    Voltage Monitoring chip to A/D chip to PIC controller to USB

    Does this sound right?

  • Netgate Administrator

    Well that will work but I'd try and skip as many steps as possible if you can. You probably want only one USB connections though so some sort of external small processing box is going to be the way to go.
    Unfortunately I'd be surprised if you could do this for less that a mass produced item.  :-\


  • Been working on a parts list and I know your right, that my cost -in the end- will be more but i would like to learn PIC and it might be a good reason to buy a programmer.

    The other alternative is go total shortcut and use Analog Sensor and use a GPIO motherboard. It looks like inputs would show up as I2C or SMBus. Better motherboards/SBC  have good specs and working examples or code snippets i see.
    Then it would be off to learn pfSense at its heart to try and fashion an package and interface.
    That would be after seeing positive results in Windows.

    One Sensor i bought to try.
    ACS712 20A Range Analogue Current Sensor Module Hall Effect ACS712ELC-20A 5V

  • The more i look at my Vecow PE-1004 POE Gigabit PCI-E ethernet adapters I realize all the components are there onboard. I can't waste time building something like this when i have a working sample of what i need and want -Computer Internally- with zero support or documentation. I am just going to wait for the market to catchup. Hopefully somewhere-sometime they do.

    Thanks for your help Steven

    I might pull my pic. Wasn't sure if i was crossing the line there.

  • Netgate Administrator

    Didn't see your PIC so i can't comment on that.
    If you already have the PoE card then might it be possible to write some drivers for it or interegate it in some cruder fashion.


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