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Re: Patch-panel fabrication (POE)

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On a sunny day (Sun, 7 May 2017 13:29:15 -0700) it happened Don Y
<blockedofcourse@foo.invalid> wrote in <oenvrv$8g9$1@dont-email.me>:

>The PSE applies a low voltage (~3 then 10V) and checks to see if there is a
>nominal ~25K resistance detected in the PD.
>
>If so, the PSE (typically) applies another "classification" voltage (~18V) and
>verifies that the PD represents a particularly sized load (250-4000uA for the
>default class 0; 9-12mA for class 1; 17-20mA for class 2 and 26-30mA for
>class 3 -- beyond that, you're looking at PoE+, etc.).
>
>[The classes determine how much power the PSE will allow the PD to consume
>before signalling an overload.  This allows the PSE to budget its power
>availability (cuz it often has less than enough power to supply ALL ports
>at the maximum limit)]

OK.


>At any time, if the PD consumes more power than allowed, the PSE disconnects
>the device -- usually within 100ms of the fault level being exceeded.
>
>If the PSE senses the device becoming unplugged (or, its current drain
>dropping below a ~5mA keep-alive level), it will also disconnect the
>device.
>
>How the system handles the power and data is up to the system; do you
>deliberately stop talking to a device when it stops drawing power?  etc.
>
>>> This is how you prevent things like (analog!) telephones misplugged into PoE
>>> jacks from wreaking havoc.
>>
>> I am worried about house guest finding an ethernet socket and plugging in their 2K$ laptop,
>> hey even my own.
>> You can check though, with an ohm meter, 7,8 to 4.5 if it is infinite it is probably OK.
>
>Then your power sourcing equipment (the midspan injector you mentioned) has to
>have the smarts in it to realize that the attaching device (AS it is plugged
>in) is not behaving like a "genuine PD" *should* behave.  And, limit the
>impact you have on that device to the "detection voltages" that are
>applied at the start of the process.
>
>Likewise, when you sense <whatever> being unplugged, you have to reset the
>process so you can replace a PD with a non-PD, then the non-PD with a PD,
>etc.
>
>The good thing is that the PD (and PSE) controller chips handle most of the
>analog processing AND the signalling protocols.  So, you slap one in your
>design and then figure out how to coerce it to behaving as you'd like.
>
>>>> Yes, OK, I use these selectively to places where I am sure there is only my own equipment connected:
>>>>  http://www.ebay.com/itm/151643358383
>>>> with my own power supply of course.
>>>
>>> Yes, Cisco has a little device that impresses 48V on the unused pairs
>>> for their (older) AP's.  But, it's literally just an adapter from
>>> 48VDC wall wart "barrel connector" to midspan injector.  Plug one
>>> of the devices you're worrying about, above, into it and it
>>> will gladly deliver 48V @ 380mA to the "load".
>>
>> Yes that is what this thing is, but price is good.
>
>The Cisco device is considerably larger -- about the size of half a pack
>of (American) 100mm cigarettes -- and only handles one device.   It
>relies on the inherent current limiting of the wall wart AND the user's
>best practices to protect the downstream device.
>
>You can, no doubt, design a little midspan injector that is more
>compliant.  But, at a fair bit more cost (for low quantities).
>I suspect there are also fully compliant midspan injectors (as
>well as endspan switches) available OTS.  I just can't budget
>for the number I'd need!
>
>As I needed a "custom" switch, it made sense to design the PSE facility
>in addition to the PD devices.  Hence my comment in my previous reply
>stating that I exploit the components that are designed for this "standard"
>way of doing things -- but apply them with my own "twists".

Understood.

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Patch-panel fabrication Don Y <blockedofcourse@foo.invalid> - 2017-05-03 12:54 -0700
  Re: Patch-panel fabrication Lasse Langwadt Christensen <langwadt@fonz.dk> - 2017-05-03 13:23 -0700
    Re: Patch-panel fabrication Don Y <blockedofcourse@foo.invalid> - 2017-05-04 00:10 -0700
      Re: Patch-panel fabrication Lasse Langwadt Christensen <langwadt@fonz.dk> - 2017-05-04 11:27 -0700
        Re: Patch-panel fabrication Don Y <blockedofcourse@foo.invalid> - 2017-05-04 11:43 -0700
        Re: Patch-panel fabrication Clifford Heath <no.spam@please.net> - 2017-05-05 08:57 +1000
          Re: Patch-panel fabrication Lasse Langwadt Christensen <langwadt@fonz.dk> - 2017-05-06 05:47 -0700
        Re: Patch-panel fabrication krw@notreal.com - 2017-05-04 19:37 -0400
      Re: Patch-panel fabrication Neon John <no@never.com> - 2017-05-04 17:56 -0400
        Re: Patch-panel fabrication Lasse Langwadt Christensen <langwadt@fonz.dk> - 2017-05-06 05:46 -0700
      Re: Patch-panel fabrication Jasen Betts <jasen@xnet.co.nz> - 2017-05-11 05:57 +0000
        Re: Patch-panel fabrication Don Y <blockedofcourse@foo.invalid> - 2017-05-11 10:37 -0700
  Re: Patch-panel fabrication Martin Riddle <martin_ridd@verizon.net> - 2017-05-03 20:32 -0400
    Re: Patch-panel fabrication Don Y <blockedofcourse@foo.invalid> - 2017-05-03 23:59 -0700
  Re: Patch-panel fabrication Jasen Betts <jasen@xnet.co.nz> - 2017-05-04 06:34 +0000
    Re: Patch-panel fabrication Don Y <blockedofcourse@foo.invalid> - 2017-05-04 01:45 -0700
  Re: Patch-panel fabrication whit3rd <whit3rd@gmail.com> - 2017-05-04 01:52 -0700
    Re: Patch-panel fabrication Don Y <blockedofcourse@foo.invalid> - 2017-05-04 11:42 -0700
      Re: Patch-panel fabrication whit3rd <whit3rd@gmail.com> - 2017-05-04 21:22 -0700
        Re: Patch-panel fabrication Don Y <blockedofcourse@foo.invalid> - 2017-05-04 23:04 -0700
          Re: Patch-panel fabrication whit3rd <whit3rd@gmail.com> - 2017-05-04 23:24 -0700
            Re: Patch-panel fabrication Don Y <blockedofcourse@foo.invalid> - 2017-05-05 00:19 -0700
              Re: Patch-panel fabrication whit3rd <whit3rd@gmail.com> - 2017-05-05 00:45 -0700
                Re: Patch-panel fabrication Don Y <blockedofcourse@foo.invalid> - 2017-05-05 02:17 -0700
  Re: Patch-panel fabrication jrwalliker@gmail.com - 2017-05-04 08:40 -0700
    Re: Patch-panel fabrication Don Y <blockedofcourse@foo.invalid> - 2017-05-04 10:12 -0700
      Re: Patch-panel fabrication jrwalliker@gmail.com - 2017-05-04 10:27 -0700
        Re: Patch-panel fabrication Don Y <blockedofcourse@foo.invalid> - 2017-05-04 11:01 -0700
          Re: Patch-panel fabrication makolber@yahoo.com - 2017-05-04 11:18 -0700
            Re: Patch-panel fabrication Don Y <blockedofcourse@foo.invalid> - 2017-05-04 11:27 -0700
      Re: Patch-panel fabrication Don Kuenz <g@crcomp.net> - 2017-05-06 05:33 +0000
        Re: Patch-panel fabrication Don Y <blockedofcourse@foo.invalid> - 2017-05-06 15:40 -0700
          Re: Patch-panel fabrication whit3rd <whit3rd@gmail.com> - 2017-05-06 20:15 -0700
            Re: Patch-panel fabrication Don Y <blockedofcourse@foo.invalid> - 2017-05-06 23:47 -0700
              Re: Patch-panel fabrication whit3rd <whit3rd@gmail.com> - 2017-05-07 03:51 -0700
                Re: Patch-panel fabrication Don Y <blockedofcourse@foo.invalid> - 2017-05-07 05:20 -0700
          Re: Patch-panel fabrication (POE) Jan Panteltje <pNaOnStPeAlMtje@yahoo.com> - 2017-05-07 17:30 +0000
            Re: Patch-panel fabrication (POE) Don Y <blockedofcourse@foo.invalid> - 2017-05-07 11:49 -0700
              Re: Patch-panel fabrication (POE) Jan Panteltje <pNaOnStPeAlMtje@yahoo.com> - 2017-05-07 18:58 +0000
                Re: Patch-panel fabrication (POE) Don Y <blockedofcourse@foo.invalid> - 2017-05-07 12:24 -0700
                Re: Patch-panel fabrication (POE) Jan Panteltje <pNaOnStPeAlMtje@yahoo.com> - 2017-05-07 19:48 +0000
                Re: Patch-panel fabrication (POE) Don Y <blockedofcourse@foo.invalid> - 2017-05-07 13:29 -0700
                Re: Patch-panel fabrication (POE) Jan Panteltje <pNaOnStPeAlMtje@yahoo.com> - 2017-05-07 20:54 +0000
  Re: Patch-panel fabrication Allan Herriman <allanherriman@hotmail.com> - 2017-05-07 10:35 +0000
    Re: Patch-panel fabrication Don Y <blockedofcourse@foo.invalid> - 2017-05-07 05:26 -0700

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