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monkeyboy
11-16-2004, 01:41 PM
I was trying to figure out a way to provide some DC voltage for an enclosure fan for a WRAP board running on PoE. I checked all the pins on the WRAP board and the most I could come up with was about 3.2 vDC. I figured that would not be enough to run most fans.....so a tinkering I went.

I finally came up with a short piece of CATv cable that is terminated with an RJ45 connection on one end and terminated with a female AMP RJ45 wall jack insert on the other. I cut the ethernet pairs when I punched them to the connector, but I left the brown and blue pairs long, and punched them into the connector.

here are the pics:

http://www.eoni.com/~mike/wireless/wrappics/

I then connected the brown and blue pairs to a 12vDC 80mm fan that pulls .15A. I measured the voltage on the pairs before and after plugging everything in. The lowest voltage I reached after putting in two CM9 cards and running the fan was 16.8 vDC.

It seems like this would work great for pulling air through a box without having a direct AC or DC source. I wanted to ask all of you if you see any major faults that are not immediately apparent from first glance.

We are having a custom box fabricated that this would go in. Aluminum, with a vent chase that runs down the side from top to bottom. Has anyone had something like this made before? Seems like they are a pretty good price @ $150.00

Thanks!

Mike

szern
11-16-2004, 02:19 PM
As I understand it (based on the WRAP's manual), you can "steal" power from the WRAP board via the DC Jack, IF you are powering it via POE.
The related cut/paste from the WRAP manualPower over Ethernet

WRAP implements a passive power over Ethernet scheme, using the unused pairs of LAN1 for power. Power can be injected using a passive POE splitter such as PC Engines POE.1A.

When power is fed in through POE, it is possible to “steal” unregulated power through the DC jack. Please note that this port is not fused. The POE input diode is rated for a current of 3A.
Please keep in mind that any EMI injected on this port will go out through the Ethernet cable without further filtering.
If yes, then you can just fashion the appropriate DC jack to PC Fan connector and get power?

Hope this helps...

- Szern