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Multiple ethernet devices off a single PoE?

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    Multiple ethernet devices off a single PoE?

    Our house is scaffolded now including our chimney which is hard to reach via a regular ladder (unless you are a roofer). I was thinking about putting a camera and/or weather station up there with a simple PoE setup - a single cable probably via the loft. But if I have two devices is that feasible? I don't really want multiple cables but it's a fairly exposed situation.

    I can just about wire a CAT cable but it's not really my area. Is there an easy solution, do I need a roof-top hub or something?

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    Originally posted by MaryPoppins
    I'd still not breastfeed a nazi
    Originally posted by vetran
    Urine is quite nourishing

    #2
    Yes you can run multiple devices, but it depends on how much power they require in total.
    IEEE 802.3bt Type 4 from 2018 is rated at 100W total, but probably better to say 70W.
    So as long as your camera & weather station are less than that, then you're laughing.
    …Maybe we ain’t that young anymore

    Comment


      #3
      I think the challenge is maintenance, given the inaccessibility. Is there a skylight from which you could access the devices?

      In practical terms, I’d be using UV stabilised outdoor quality Ethernet cable, one cable per device, and power injected from a PoE switch in an upstairs room. I agree that in power terms you can share a cable, but then you need to split the connections, which need to be waterproof.
      I’d avoid electronic devices in lofts where there are temperature extremes.
      Personally, I have lost devices to lightning induced surges with exposed Ethernet cables and would not be keen to run these outdoors. Whether that is a risk rather depends on where you live.
      Wireless devices may be advantageous in which case you may only need power supply cabling. Again, I would not install the power supplies in the loft on grounds of fire hazard.
      Last edited by Protagoras; 20 July 2022, 17:32.

      Comment


        #4
        Originally posted by Protagoras View Post
        I think the challenge is maintenance, given the inaccessibility. Is there a skylight from which you could access the devices?
        No not really. There are skylights in the middle of the roof but the scale in the photo may not show quite how high it is. Even when you get up to the top scaffold lift, the chimney stack is still taller than me (not even counting the pots). We're 40-50 feet up - my big 3-section ladders can reach the gutter but that's about half the height!
        A roofer would probably have a ladder to get up there but I'm realistically thinking this might be something we do and enjoy until it fails, or maybe it fails and we wait until next time we have roof work done and get the guy to swap a faulty unit.
        My thought is maybe to mount a pole to the stack (like for a TV aerial) that things can be clamped to but there's no realistic way to make this easily accessible. Plus, it's terrifying enough being up there on a proper scaffold let alone a ladder!

        In practical terms, I’d be using UV stabilised outdoor quality Ethernet cable, one cable per device, and power injected from a PoE switch in an upstairs room. I agree that in power terms you can share a cable, but then you need to split the connections, which need to be waterproof.
        I’d avoid electronic devices in lofts where there are temperature extremes.
        Personally, I have lost devices to lightning induced surges with exposed Ethernet cables and would not be keen to run these outdoors. Whether that is a risk rather depends on where you live.
        Thanks for that. I had been thinking on grounds of neatness a single cable is nice, but for reliability and weather-protection you may be right. I can always rout them in a conduit to keep it neat.
        The loft is actually mostly converted and we have our boiler up there too so I can safely have stuff there although access via the first floor (notice that window) would be OK too.

        Wireless devices may be advantageous in which case you may only need power supply cabling. Again, I would not install the power supplies in the loft on grounds of fire hazard.
        Initially I was thinking WiFi but then wasn't sure if my signal reaches that high - and if I ever have to change my WiFi or the device needs re-pairing (not unknown) I'm screwed. Since I need power anyway PoE seemed the obvious answer to both and perhaps preferable to trailing a long flimsy USB cable.


        Cheers for the thoughts.
        Originally posted by MaryPoppins
        I'd still not breastfeed a nazi
        Originally posted by vetran
        Urine is quite nourishing

        Comment


          #5
          Originally posted by WTFH View Post
          Yes you can run multiple devices, but it depends on how much power they require in total.
          IEEE 802.3bt Type 4 from 2018 is rated at 100W total, but probably better to say 70W.
          So as long as your camera & weather station are less than that, then you're laughing.
          I'm not sure you can.

          You can have 2 devices communicating using the same switch port. That's basically want an uplink is.
          But you cannot connect 2 devices to the same port on the same switch. Ethernet is a baseband protocol not a broadband protocol.

          *Showing my age now, but you could use 10base-2 (thin ethernet) and run just one cable for many devices, but that won't be POE and good luck finding any devices newer than 20 years old with that connection.*

          What you would need (and I'm not sure they exist) is a POE switch that is powered by PoE. If you can't get one of them you're going to need 2 cables, or 1 cable and power to run another switch. As it's on a roof you could feasibly use solar/battery/inverter for power and use just the one cable, but that might struggle through winter and maintenance will be a headache.

          See You Next Tuesday

          Comment


            #6
            What sort of camera were you thinking of getting?
            Is it for the view over other properties, or looking around your own?
            A stationery one, or one you can remotely control?

            I would probably put camera(s) lower down - maybe outside windows or under the eaves.
            …Maybe we ain’t that young anymore

            Comment


              #7
              Originally posted by Lance View Post

              I'm not sure you can.

              You can have 2 devices communicating using the same switch port. That's basically want an uplink is.
              But you cannot connect 2 devices to the same port on the same switch. Ethernet is a baseband protocol not a broadband protocol.

              *Showing my age now, but you could use 10base-2 (thin ethernet) and run just one cable for many devices, but that won't be POE and good luck finding any devices newer than 20 years old with that connection.*

              What you would need (and I'm not sure they exist) is a POE switch that is powered by PoE. If you can't get one of them you're going to need 2 cables, or 1 cable and power to run another switch. As it's on a roof you could feasibly use solar/battery/inverter for power and use just the one cable, but that might struggle through winter and maintenance will be a headache.
              I was thinking more in terms of power.

              But I've seen this as well...
              https://ellipsesecurity.com/product/...s-one-1-cable/
              …Maybe we ain’t that young anymore

              Comment


                #8
                Originally posted by WTFH View Post

                I was thinking more in terms of power.

                But I've seen this as well...
                https://ellipsesecurity.com/product/...s-one-1-cable/
                that's handy....
                It must have some sort of switch/bridge on a chip. And this will then run as an uplinked 2 port switch.

                The power is easy enough to split, it's getting the ethernet frames onto 10-baseT without them causing issues that's the hard part. CSMA/CD is very much a shared ethernet component (thinnet, thicknet, hubs, etc).
                But for £17 that's a great device.
                Last edited by Lance; 21 July 2022, 11:53.
                See You Next Tuesday

                Comment


                  #9
                  Originally posted by d000hg View Post
                  Thanks for that. I had been thinking on grounds of neatness a single cable is nice, but for reliability and weather-protection you may be right. I can always rout them in a conduit to keep it neat.
                  The loft is actually mostly converted and we have our boiler up there too so I can safely have stuff there although access via the first floor (notice that window) would be OK too.

                  Initially I was thinking WiFi but then wasn't sure if my signal reaches that high - and if I ever have to change my WiFi or the device needs re-pairing (not unknown) I'm screwed. Since I need power anyway PoE seemed the obvious answer to both and perhaps preferable to trailing a long flimsy USB cable.
                  Some further thoughts; most weather data can be collected at ground level, so probably the only weather sensor you really need up there at chimney height is for wind speed and direction. If you're feeling plush, an ultrasonic sensor with no moving parts should work reliably for a long time and be visually unobtrusive. Traditional anemometers will eventually need the bearings replaced. Mr Google came up with this by way of example (I have not tried this unit), but to some extent choice of sensor depends on how you want to get the data. Many devices will provide NMEA0183 protocol which is readable via a serial port.

                  If you go with @WTFH's advice re camera location, then you only need one device up there. A camera on a pole at the height of your chimney could well move around annoyingly in the wind.


                  Comment


                    #10
                    Originally posted by Lance View Post

                    that's handy....
                    It must have some sort of switch/bridge on a chip. And this will then run as an uplinked 2 port switch.

                    The power is easy enough to split, it's getting the ethernet frames onto 10-baseT without them causing issues that's the hard part. CSMA/CD is very much a shared ethernet component (thinnet, thicknet, hubs, etc).
                    But for £17 that's a great device.
                    It is clever. I hadn't noticed initially that you need two of them as it still requires two ports on your network. I'm wondering why - if it's a teeny 2-port hub why would you need to split it back instead of just plugging it in like any other hub?
                    Originally posted by MaryPoppins
                    I'd still not breastfeed a nazi
                    Originally posted by vetran
                    Urine is quite nourishing

                    Comment

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