Welshhobo
Posts: 4
Joined: Sun Jun 14, 2020 9:27 am

PoE hat?

Sun Jun 14, 2020 9:36 am

Not sure if this is the correct board but i figured networking is close enough.

I have an RPi 4B, and would like to power it over ethernet cable. I'm also using the 7" touchscreen with the board so i'm concerned with power consumption. I've taken a look at https://www.raspberrypi.org/products/poe-hat/ and was wondering if someone can confirm whether this product also allows you to send data through the same cable. Also, the RPi 4 requires 3a and 5v power, but i've seen some things that say that the PoE Hat doesn't give this - could that be a problem? The cable run itself may be up to 30m long so could i have problems with voltage drops?

plugwash
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Joined: Wed Dec 28, 2011 11:45 pm

Re: PoE hat?

Sun Jun 14, 2020 9:41 am

If you are just powering the Pi4 and some low current perhipherals then the current PoE hat should be ok, but if you load it down with power-hungry peripherals then you may have problems.

Volt drop on the supply cable shuoldn't be an issue, PoE operates at 48V and the hat converts that to the 5V needed by the Pi in a regulated (and isolated) manner.

Welshhobo
Posts: 4
Joined: Sun Jun 14, 2020 9:27 am

Re: PoE hat?

Sun Jun 14, 2020 10:33 am

Brilliant, thank you. I've noticed that the PoE hat also blocks the GPIO pins - one solution is to get GPIO extensions but i've found this:
https://thepihut.com/products/mini-powe ... i-4-no-fan

Looking at that - would you have any reservations?

PiUser10
Posts: 42
Joined: Mon Dec 30, 2013 9:20 am

Re: PoE hat?

Sun Jun 14, 2020 11:06 am

I use the official POE hat on my Pi 4b 8GB and also these extenders
https://thepihut.com/products/4-40-pin- ... oe-hat-set
I have added longer standoff fixing as well which allows the heat sink
https://thepihut.com/products/xl-raspbe ... 4-heatsink
to also be fitted below the POE fan due to the additional clearance of the underside components.
Overclocked to 2.1GHz and when stressed tested temperature does not rise above 55-58 C even with the little POE fan.
I do not use any case with the Pi but if you did it would need to be a tall version.
I then attach a 40 pin ribbon cable from the pins now protruding from above the POE hat to a breakout board
which runs an RTC and 4x20 LCD display.
I have usb mouse and keyboard connected to the usb 2.0 ports and boot from M.2 SSD connected via usb 3.0 port and all is powered OK.
I am using a D-Link DGS-1008p switch for the POE supply.
Hope this is useful information for you.

plugwash
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Re: PoE hat?

Sun Jun 14, 2020 11:35 am

Welshhobo wrote:
Sun Jun 14, 2020 10:33 am
Brilliant, thank you. I've noticed that the PoE hat also blocks the GPIO pins - one solution is to get GPIO extensions but i've found this:
https://thepihut.com/products/mini-powe ... i-4-no-fan

Looking at that - would you have any reservations?
My immediate reservation is it appears to be a non-isolated converter (the visible clue being it has an inductor rather than a transformer). Depending on the particular application this could be problematic.

fruitoftheloom
Posts: 24041
Joined: Tue Mar 25, 2014 12:40 pm
Location: Delightful Dorset

Re: PoE hat?

Sun Jun 14, 2020 12:09 pm

plugwash wrote:
Sun Jun 14, 2020 11:35 am
Welshhobo wrote:
Sun Jun 14, 2020 10:33 am
Brilliant, thank you. I've noticed that the PoE hat also blocks the GPIO pins - one solution is to get GPIO extensions but i've found this:
https://thepihut.com/products/mini-powe ... i-4-no-fan

Looking at that - would you have any reservations?
My immediate reservation is it appears to be a non-isolated converter (the visible clue being it has an inductor rather than a transformer). Depending on the particular application this could be problematic.

There have been a couple of posts this year about similar PoE Hardware to what PiHut sell, but bought on Amazon, which caused various issues, caveat-emptor !!
Thinking outside the box is better than burying your head in the sand...

PiUser10
Posts: 42
Joined: Mon Dec 30, 2013 9:20 am

Re: PoE hat?

Sun Jun 14, 2020 12:56 pm

Just a quick follow up note:-

The official POE hat appears to be mostly out of stock at this time from most of the main suppliers
but I was able to get one from
https://www.newit.co.uk/shop/PI_POE_HAT
less than a week ago where they are currently still listed as in stock should you be looking to order one.
I think going with the raspberry Pi authorised one over others is possibly a safer choice and it has my vote.

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