Daisy Chaining the fin, a plan of action

support
#1

Hello,
Fellow people that are limited by the sometimes multi-thousand dollar cost of long cable runs rejoice! For with this design you may be able to power up to 5-8 (or more if you are crazy) on one cat7 ethernet cable.

Design goals:
-As many fins on one cat 6 dc power bus as possible
-Not burning down a building by over amping wires
–By extension not making anything run too hot as to avoid shortening lifespans
-There doesn’t have to be data connections via these wires (there is 100% no way to do this with data)

Constraints queue to me:
-Managed active POE switch (client requirement)
-Nothing that involves custom crimping of rj45 connectors (I get around that)

Links to buy this stuff:
The blue triangle
The red triangle
The green thing
The active to passive converters

If I could though I would cut off converters and replace them and the switch with two of these injectors to really pack in the wattage. I would be worried about putting more than 8 fins on cat6 cable though. 801.3bt says the cable can get up to 10 C warmer under that kind of load, maybe use cat7 shielded for that kind of thing.

POE_fin_chain

What I have tested:
The blue and red triangle pattern works, I need more green things to test the rest.

I would love some feedback from anyone. @chrisys @ntzovanis if you have a second for your thoughts.

What do you think I should watch out for as I test this? What is my greatest risk of failure? Any improvements you would make?

Thanks
-Thomas

#5

@tacLog

Hi Thomas, that’s an interesting setup! Here’s my two cents.

I would try to make sure the upstream “blue triangles” can handle that amount of current, especially on the single-ended side, without getting too hot. Have you peeked inside one of those to see how they are assembled?

Cheers,
Nico

#7

Hey @tacLog, glad to see you’ve got a plan together.

Personally I’d be trying to remove the green thing, it seems superfluous. As you’re running on 24V passive PoE, have you tested taking a jumper cable from the 4 pin header and feeding it straight into the Phoenix connector or barrel jack?

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#8

Hey @chrisys

That is a great idea!, it works!

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#9

To be clear to everyone, this will only work with 24v passive POE.

For POE type B, the kind used by ubiquity and other injectors you need to connect pins 3, 4 with 4 being (+) to ether the barrel or the Phoenix jack.

Refer to the schematics on the last page for why it works.

-Thomas

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#10

@ntzovanis

That is a great thing to test for and think about. I haven’t had any spares I can take a knife to yet, but next week I will take one apart.

I also plan on doing some kind of load test for 24 hours to see if anything gets hot.

Also using a multimeter to test resistance? This is not my field.

-Thomas

#11

That’s cool that works OK! It should be OK with the 12V passive injectors that are available too.

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#13

@tacLog

Those two tests should be enough to get a sense of how the connector would behave. If the resistance is low enough and it doesn’t get hot under a decent load it should be ok. Just make sure that you measure the resistance with cables connected at both ends, something like probe -> cat 6 cable -> connector -> cat 6 cable -> probe.

Cheers,
Nico