There is a circuit called a Bob Smith termination associated with the Ethernet ports. If that termination is facing the world and if they did not put capacitors in it, then it could be a source of ground (via 75-120 ohm resistor) to any of the wires.
From: Mathew Howard Sent: Monday, June 25, 2018 2:28 PM To: AnimalFarm Microwave Users Group Subject: Re: [AFMUG] Fw: -48 vDC to 48 vDC I'd imagine you'd be fine if you just turn poe-out off on all the ports. On Mon, Jun 25, 2018 at 2:38 PM, Mike Hammett <af...@ics-il.net> wrote: I got hEX PoE because they didn't have any hEX S. Now that I figure out that hEX PoE won't work right, they have hEX S in stock. The hEX S has two ports that aren't PoE in or out. *sigh* ----- Mike Hammett Intelligent Computing Solutions Midwest Internet Exchange The Brothers WISP ------------------------------------------------------------------------------ From: "Mike Hammett" <af...@ics-il.net> To: "AnimalFarm Microwave Users Group" <af@af.afmug.com> Sent: Monday, June 25, 2018 10:17:07 AM Subject: Re: [AFMUG] Fw: -48 vDC to 48 vDC Ugh. This device is capable of sending PoE. ----- Mike Hammett Intelligent Computing Solutions Midwest Internet Exchange The Brothers WISP ------------------------------------------------------------------------------ From: ch...@wbmfg.com To: "AnimalFarm Microwave Users Group" <af@af.afmug.com> Sent: Monday, June 25, 2018 10:15:54 AM Subject: Re: [AFMUG] Fw: -48 vDC to 48 vDC No, all ethernet conductors hit a transformer inside the device. Called phy magnetics. That gives you an electrical isolation between the ethernet circuit and the rest of the unit – unless – it is capable of receiving POE over that jack. In that case there is a connection. From: Mike Hammett Sent: Monday, June 25, 2018 9:10 AM To: AnimalFarm Microwave Users Group Subject: Re: [AFMUG] Fw: -48 vDC to 48 vDC Oh, okay, so no concern that some of the Ethernet pins have continuity to negative\ground when I've reversed the polarity coming in to compensate for using a +48 device in a -48 environment? ----- Mike Hammett Intelligent Computing Solutions Midwest Internet Exchange The Brothers WISP ------------------------------------------------------------------------------ From: ch...@wbmfg.com To: "AnimalFarm Microwave Users Group" <af@af.afmug.com> Sent: Monday, June 25, 2018 10:04:12 AM Subject: Re: [AFMUG] Fw: -48 vDC to 48 vDC If you will not be using shielded cables and the plastic case insulates the board ground from the environment, you should be good to go. From: Mike Hammett Sent: Monday, June 25, 2018 8:38 AM To: AnimalFarm Microwave Users Group Subject: Re: [AFMUG] Fw: -48 vDC to 48 vDC Oddly enough, I don't have continuity from the shield around the Ethernet connectors to anything, but the USB and SFP cages as well as the metal around the mounting holes (which do nothing on a plastic case with plastic standoffs) carry through to the outside of the DC jack. I can check what has voltage when I'm back to where I actually have one plugged in. Now, I won't be using shielded cable, just standard cat 5. I don't know what type of isolation there is from standard Ethernet to the negative\ground. I just checked and the solder points on the bottom of the board (eight of them for each Ethernet) do indeed go to negative\ground. Sounds like that idea is out until I can get +48 to the router. I can make do by stacking VLANs on the SFP and using the DSLAM or switch to move the traffic around, but having one port for east and one for west would be nice. ----- Mike Hammett Intelligent Computing Solutions Midwest Internet Exchange The Brothers WISP ------------------------------------------------------------------------------ From: ch...@wbmfg.com To: "AnimalFarm Microwave Users Group" <af@af.afmug.com> Sent: Monday, June 25, 2018 9:12:04 AM Subject: Re: [AFMUG] Fw: -48 vDC to 48 vDC Yes, the shields around the ethernet jacks. I presume they have a little metal tab that would engage with a shielded plug if inserted. I think the USB shield should be connected to internal ground as well. From: Mike Hammett Sent: Monday, June 25, 2018 8:06 AM To: AnimalFarm Microwave Users Group Subject: Re: [AFMUG] Fw: -48 vDC to 48 vDC When you say chassis, I assume the case, but this is a plastic case, so something inside? https://mikrotik.com/product/RB960PGS ----- Mike Hammett Intelligent Computing Solutions Midwest Internet Exchange The Brothers WISP ------------------------------------------------------------------------------ From: ch...@wbmfg.com To: af@af.afmug.com Sent: Monday, June 25, 2018 8:44:01 AM Subject: [AFMUG] Fw: -48 vDC to 48 vDC Hard to answer. Power up the MT with it resting on something that is not conductive. Measure from both sides of the incoming power to the chassis and ethernet shield connection. If there is no voltage between chassis and shield and either side of the power input it is probably a floating load. If it is a floating load you can hook it up to any source of 48 volts. However, if you measure a voltage from chassis to the positive input, then it is a negative ground load and will short out a –48 input. From: Mike Hammett Sent: Monday, June 25, 2018 7:27 AM To: AF Subject: -48 vDC to 48 vDC I have a Mikrotik hEX PoE plugged into a telco -48 vDC plant by reversing the polarity of the power wires. Should I expect a cat 5 connection between the router and the DSLAM to cause issues? ----- Mike Hammett Intelligent Computing Solutions Midwest Internet Exchange The Brothers WISP -- AF mailing list AF@af.afmug.com http://af.afmug.com/mailman/listinfo/af_af.afmug.com ------------------------------------------------------------------------------ -- AF mailing list AF@af.afmug.com http://af.afmug.com/mailman/listinfo/af_af.afmug.com -- AF mailing list AF@af.afmug.com http://af.afmug.com/mailman/listinfo/af_af.afmug.com ------------------------------------------------------------------------------ -- AF mailing list AF@af.afmug.com http://af.afmug.com/mailman/listinfo/af_af.afmug.com -- AF mailing list AF@af.afmug.com http://af.afmug.com/mailman/listinfo/af_af.afmug.com ------------------------------------------------------------------------------ -- AF mailing list AF@af.afmug.com http://af.afmug.com/mailman/listinfo/af_af.afmug.com -- AF mailing list AF@af.afmug.com http://af.afmug.com/mailman/listinfo/af_af.afmug.com -- AF mailing list AF@af.afmug.com http://af.afmug.com/mailman/listinfo/af_af.afmug.com -- AF mailing list AF@af.afmug.com http://af.afmug.com/mailman/listinfo/af_af.afmug.com -------------------------------------------------------------------------------- -- AF mailing list AF@af.afmug.com http://af.afmug.com/mailman/listinfo/af_af.afmug.com
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