DSLRKIT Raspberry Pi 3B+ Power over Ethernet (PoE) HAT
Raspberry Pis are convenient small Linux servers. True, virtualisation is useful in many cases, but in some cases a Raspeberry Pi (RPi) is the most practical and uncomplicated solution. In my case, I use a RPi for feeding airplane positions (receiving ADS-B signals with a RTL-2832 dongle) and I have a RPi as a Pi-hole server that filters ads at the DNS-level and gives out IP-addresses as a DHCP-server. Here, virtual machines or Docker instances (for DNSCrypt servers or VPNs for example) are not my preferred solution. First of all, the RPi needs to be close the antenna in the attic and it’s quite fiddly to set up a virtualised DHCP-server.
In the past, I used routers running OpenWRT for many small-server tasks. I particularly enjoyed the PowerPC architecture of the TP-Link TL-WDR4900, but slowly they are all dying due to age. Given the price tag of up-to-date routers, RPis are a more logical solution, particularly because they are usually around € 35 each (with out a case though) and therefore present quite good value. My casual observations show the latest RPi 3B+ can push about 35-40 Mbit/s over an OpenVPN connection (and it has a Gigabit ethenet connection that effectively maxes out around 300 MBit). All in all, a RPi 3B+ can be a fine VPN-server for non-critical use from hotels, for geospoofing and so on, without noticing any slowdown - quite a good match for my VDSL connection at home at any rate, its maximum upload is a little under what my RPi can achieve.
While there is no disputing the practicality of the venerable RPi, one aspect I did not like at all: while the USB and Ethernet ports are neatly at the back (or front) of the diminuitive computer, the USB power connector was a the side. This made difficult to make sleek installations, and also it was cumbersome to position power to where the board was needed.
Power over Ethernet for RPi
It was therefore with interest that I watched the Raspberry Pi Foundation’s with interest: they had introduced a ‘HAT’ (Hardware Attached on Top). It is a small add-on board that can be used for various purposes. There are HATs that have audio amplifiers, TV-tuners or just fancy LEDs. The architecture of RPi means that this can be just added on top of any (recent) RPi.
One of them was the PoE HAT, introduced when the RPi 3B+ was introduced. With the 3B+ series, a special connector was integrated on the board, giving the possibilities for a 5V feed from a HAT, as seen here:
Unfortunately, this HAT features a small fan, that is like not to be only noisy, but also may break down over time. Therefore I did not consider it an option, and soon after it actually became available, problems were noted too, prompting a recall by the producer. All in all, not the most viable option.
DSLRKIT Raspberry Pi 3B+ Power over Ethernet (PoE) HAT
However, as another OpenWRT router died (I assume from dried-out capacitors, or perhaps just planned obsolence), I was looking for alternatives. I already have a few devices by GL-iNet with PoE options, and I was attraced to running a RPi through PoE.
The devices that I have (I have been using two for the last few weeks now) were ordered through Amazon Germany, but they can also be found on other Amazon sites and AliExpress and perhaps other sites. I paid € 15.90, so I would consider the price to be quite low for what it offers. The official RPi PoE HAT is widely avaible for € 22.95, for example here. Note that none of the links are referral links 😄
Quality of the product
The product is delivered a small carton box, in an anti-static plastic bag, along with some plastic standoffs. The products itself seems to be of decent quality, only some of the soldering seems to be of poor quality. For sure, it is not how products that I am involved in look when they are sent to the customer. However, the product works and does not run overly hot, which was a concern of mine (seeing as the Raspberry Pi Foundation’s product has a fan.
The product is very easy to install - just mount it on top of any RPi 3B+ and it will work, no software support is necessary. DSLRKIT includes some nylon standoffs which are not the nicest, but they work. Unfortunately, it is not possible to acutally mount the whole device in a standard case, the RPi with the HAT on top are just too high. I resorted to mounting them in the bottom part of the plastic cases that are available, see the picture below.
The stacking cases that are available do not appeal to me, because they require the board mounted on another board, which seems superfluous. I may try a minimalistic approach with studs, bolts and wire ends, I also find this stacking Cloudlet case by C4Labs very attractive, although as far as I can see it’s not readily available in Europe. Something to cover in a follow-up article I guess…
Once installed, the product performed without any issues. The 5 Volt rail is rated for 2.5A, meaning that you could easily run a few laptop harddisks off it, and there is also a handy 5V outlet with screw terminals provided. Here is a picture of two side by side, installed in my attic.
Unfortunately I noted hefty radio interference from the HAT, particularly on mediumwave from 800 to 1500 kHz (up to 45 dB on a small portable). This must be due to the switched power supply that is used for down conversion of the 48V DC PoE current to 5 Volts needed to run the RPi itself. I remedied this interference by moving the RPi next to the switch, so the wire would not act as an antenna (despite the twisted wire which should shield, too). This has reduced the interference markedly. I am planning to move both RPi in a small metal case before too long, in an attempt to tidy my attic.
During the pandemic of 2020, further analysis showed that the switch itself was also a major source of interference. Therefore I decided to replace the switch and start feeding the RPis again by traditional USB-power. No interference has been noted since.
Compatibility with RPi 4 series
In June 2019, the RPi Foundation announced the RPi 4 series, featuring more memory, a faster CPU, USB-C connector, genuine Gigabit Ethernet and much more improvements under the hood. This new series comes with the same PoE connector, so in principal this HAT should be ready for the RPi 4 too. I am somewhat cautious because all in all, the RPi 4 will probably draw more current, and it remains to be seen if this HAT can cope with the higher demand in current. I will test it as soon as I have one of the new RPis! :)
Conclusion (updated May 2020)
From my experience, the DLSRKIT Raspberry Pi PoE HAT is a solid product for those who want to experiment with Raspberry Pis, albeit with the caveat of interference on mediumwave. With this HAT, a long-standing niggle of having to feed an extra cable for power is gone, it does make all the solution look neater. Mine have been running without fault for a while already. As with any HAT on top of a Raspberry Pi, it is not easy to find a proper solution for mounting them.
In the end, interference on mediumwave made me opt for another solution. If this is not a concern for you, and nor the absence of a truly elegant case, then I can truly recommend this product.