24V Passsive PoE for Raspberry Pi

Discussion in 'Embedded Systems and Microcontrollers' started by Christian McDonald, Jul 23, 2015.

  1. Christian McDonald

    Thread Starter New Member

    Jul 23, 2015

    I'm working on making a shield for the raspberry pi that will accept passive 24V PoE and output 5v to power the Pi along with providing 12V/24V rails to power an HID iClass reader and electronic door strike. At 12V, the reader under load pulls a max of 116 mA (1.39W). At 24V the strike pulls a max of 255mA (6.12W). Raspberry Pi should only pull max 3-4 watts under load. So we are looking at ~10W.

    I'm looking at using LM2596's for both the 24-12 and 24-5 step down.

    Would perfboard traces be acceptable here to distribute the 24V?
  2. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    Sure you can carry 24V on protoboards all day long.. and WAY more than that..
  3. Christian McDonald

    Thread Starter New Member

    Jul 23, 2015
    I've decided to attempt to build my own Pi Hat. I've also decided to attempt to implement 802.3at Type 2.

    There are plenty of options here:

    Texas Instruments makes PoE controllers that are pretty trivial to implement
    SilverTel produces SiL packages that include 802.3at controller + DC/DC on one board (sexy)
    Molex produces PDJacks which incorporates PoE controller, rectifiers, and isolation transformers into the RJ45 socket

    I'd really prefer to just use the TI controller as they are cheap. The SilverTel and Molex produces are $20-25 a piece.

    My biggest set back is actually finding parts that are easily accessible in low (minimum of 1) orders... ugh