Cheap Power Over Ethernet For The ESP32

While most projects we see with the ESP32 make use of its considerable wireless capabilities, the chip can be connected to the wired network easily enough should you have the desire to do so. [Steve] liked the idea of putting his ESP32s on the wired network, but found the need for a secondary power connection burdensome. So he took it upon himself to modify some cheap Power Over Ethernet (PoE) hardware and create a single-cable solution (Google Translate).

[Steve] bought a PoE module intended for security cameras and ran a close eye over the board to figure out what kind of hardware it was using to generate the nominal 12 V output. He identified an MP2494 step-down converter, and with the datasheet in hand found how the output voltage is configured by changing the values of resistors in the circuit. Swapping out the stock 21.5 kΩ resistor for a 57.1 kΩ one changed the output of the converter to the 5 V necessary for his electronics.

But of course that was only half of the problem solved; he still had to connect the Ethernet side of the PoE device to the Waveshare LAN8720 board that’s providing Ethernet for the ESP32. So he removed the RJ45 jack from the LAN8720 completely, and wired that directly to the connector on the PoE board. Helpfully, the PoE board had all the pins labeled on the bottom side so this wasn’t nearly as tricky to figure out as you might expect (if only it was always that easy).

We’ve previously covered the Waveshare LAN8720 board for anyone who’s interested in the ins and outs of getting their ESP32 talking Ethernet. If you’re wondering how you can put PoE to work for you, our very own [Jonathan Bennett] has been showing off his home Raspberry Pi infrastructure which makes extensive use of the new PoE hat.

Raspberry Pi PoE Redux

[Martin Rowan] was lucky enough to get his hands on the revised Power Over Ethernet (PoE) hat for the Raspberry Pi. Lucky for us, he wrote it up for our benefit, including inspection of the new hat, it’s circuit, and electrical testing to compare to the original hardware.

You may remember the original release of the PoE hat for the Raspberry Pi, as well as the subsequent recall due to over-current issues. In testing the revised board, [Martin] powered a test load off the USB ports, and pulled over an amp — The first iteration of the PoE hat would often trip the over-current protection at 300 milliamps.

This afternoon, the redesigned PoE board was officially released, and the post mortem of the problem documented in a blog post. It’s a lesson in the hidden complexity of hardware design, as well as a cautionary tale about the importance of thorough testing, even when the product is late and the pressure is on.

The PoE hat converts 48 volt power down to a 5 volt supply for the Pi using a flyback transformer. The problem was that this transformer setup doesn’t deliver clean steady 5 volt power, but instead provides power as a series of spikes. While these spikes were theoretically in spec for powering the Pi and usb devices, some Raspberry Pis were detecting those spikes as too much current pushed through the USB ports. The official solution essentially consists of better power filtering between the hat and the Pi, flattening that power draw.

We’re looking forward to getting our hands on this new and improved PoE Hat, and using it in many project to come.

Rasberry Pi PoE Hat Released

It was announced at the beginning of March, but now the Raspberry Pi Power over Ethernet (PoE) hat is out. Thanks to the addition of a new 4-pin header on the Raspberry Pi 3 Model B+, the Pis can get power from an Ethernet cable, provided you’ve got the setup to deliver PoE.

This is a remarkable bit of engineering, even though it’s just adding Power over Ethernet to a small single board computer. Mechanically, the PoE hat doesn’t increase the 3D bounding box volume of the Raspberry Pi at all. It adds cooling with a fan controlled over I2C. Even more bizarrely, the transformer is mounted in a PCB cutout, and we’re desperate to know how that was specced, designed, and assembled. Yeah, it might just be an add-on for the Raspberry Pi, but there’s some clever work that went into designing it.

The Raspberry Pi gained PoE capability with the introduction of the Raspberry Pi 3 Model B+ last March, a release that did require a slight change to the hardware and pinout of the Raspberry Pi. Compared to the Pi 3 Model B, the Pi 3 Model B+ sports a four-pin header right next to the Ethernet jack and one of the mounting holes. This is the same location of the ‘Run’ header found in the Pi 3 Model B, and probably caused much consternation to anyone who built a hat to take advantage of having a real power button on their Pi.

Nevertheless, what’s done is done, and now we have a real PoE solution for the Raspberry Pi. This is bound to be a boon for anyone who wants to build a Raspberry Pi cluster computer, or anyone who is dropping a few Pis into a server rack that already has PoE hardware.

You can pick up a PoE Pi hat through the usual suspects (Farnell, RS, and other resellers) for $20.

Power Over Ethernet Splitter Improves Negotiating Skills

Implementing PoE is made interesting by the fact that not every Ethernet device wants power; if you start dumping power onto any device that’s connected, you’re going to break things. The IEEE 802.3af standard states that the device which can source power should detect the presence of the device receiving power, before negotiating the power level. Only once this process is complete can the power sourcing device give its full supply. Of course, this requires the burden of smarts, meaning that there are many cheap devices available which simply send power regardless of what’s plugged in (passive PoE).

[Jason Gin] has taken an old, cheap passive PoE splitter and upgraded it to be 802.3af compatible (an active device). The splitter was designed to be paired with a passive injector and therefore did not work with Jason’s active 802.3at infrastructure.

The brain of the upgrade is a TI TPS2378 Powered Device controller, which does the power negotiation. It sits on one of two new boards, with a rudimentary heatsink provided by some solar cell tab wire. The second board comprises the power interface, and consists of dual Schottky bridges as well a 58-volt TVS diode to deal with any voltage spikes due to cable inductance. The Ethernet transformer shown in the diagram above was salvaged from a dead Macbook and, after some enamel scraping and fiddly soldering, it was fit for purpose. For a deeper dive on Ethernet transformers and their hacked capabilities, [Jenny List] wrote a piece specifically focusing on Raspberry Pi hardware.

[Jason]’s modifications were able to fit in the original box, and the device successfully integrated with his 802.3at setup. We love [Jason]’s work and have previously written about his eMMC adventures, repairing windows tablets and explaining the intricacies of SD card interfacing.

Wiring The ESP-32 To Ethernet

Since its introduction years ago, the ESP-8266 has taken over the world. It’s the chip inside thousands of different projects, and the basis for dozens of different IoT thingamadoos. The follow-up to the 8266, the ESP-32, is even more capable. It has a ton of peripherals inside, including an Ethernet MAC. What’s that? Yes, it’s possible to put Ethernet on an ESP-32, and give an IoT board PoE. That’s what [Patrick] is doing for his Hackaday Prize project, and it’s an awesome idea.

This build began as you would expect, with an ESP-32 module attached to one side of a board with some breakouts for the GPIOs and a USB to Serial chip. The tricky part here is the PoE part of the Ethernet, which requires MagJack Ethernet connectors, a flyback transformer, and a PoE-PD controller. These were expensive parts, and the design of such a board requires some thinking — you need isolation across the transformer, and proper ground planes for this mess.

There’s something slightly brilliant about using an ESP-32 in a wired configuration. Far too often, we see these modules used as wireless nodes in a sensor net. The battery consumption is significant, and all those makers are adding USB power input to their fancy WiFi sensor nets. If you’re running wires for power anyway, why not add Ethernet and do away with all that mucking around with WiFi setup. It’s a great project, and one of the better entries in this year’s Hackaday Prize.

Hacklet 94 – Pi Zero Contest Entries

Hackaday and Adafruit have joined forces to present the Raspberry Pi Zero Contest. A great contest is nothing without entries though. This is where the community is proving once again that they’re the best in the world. The contest is less than a week old, yet as of this Thursday evening, we’re already up to 33 entrants! You should submit your own project ideas now for a chance at one of the many prizes. This week on The Hacklet, we’re going to take a look at a few of these early entrants!

controllerWe start with [usedbytes] and Zero Entertainment System [usedbytes] has crammed an entire emulator into a classic Nintendo Entertainment System control pad thanks to the Raspberry Pi Zero. Zero Entertainment System also has something the original NES couldn’t dream of having: An HDMI output. The emulator uses the popular RetroPie front end. We’re happy to say that [usedbytes] knew that hacking up a real Nintendo controller would be sacrilegious, so they grabbed a low-cost USB clone from the far East. A bit of creative parts-stuffing and point-to-point wiring later, ZES was ready to meet the world!

wsprNext up is [Jenny List] with The Australia Project. [Jenny] is a hacker from Europe. She’s hoping to use a Pi Zero to talk to Australia. “Talk” may be pushing it a bit though. The Australia Project will use the Weak Signal Propagation Reporter (WSPR) network to transmit RF straight out of the Pi’s GPIO ports. All that is required is a good filter, an antenna, and a balun. The filter in this case is a 7-pole Chebyshev low-pass filter. The filter keeps the Pi’s harmonic filled square waves from messing up every band from DC to light. [Jenny] normally sells these filters as a kit, but she’s made a special version specifically for the Pi Zero.

tote0[Radomir Dopieralski] has brought his signature walking robots to the Pi Zero world with Tote Zero. Tote Zero is a quadruped walking robot built mainly from 9 gram servos. [Radomir’s] custom tote board interfaces the servos to the Pi Zero itself. The Pi Zero opens all sorts of doors for sensors, vision, and advanced processing. The Arduino board on the original Tote would have been hard pressed to pull that off. Tote is programmed in Python, which will make the code quick and easy to develop. Tote Zero just took its first steps a few days ago, so follow along as a new robot is born!


ethernetpoFinally we have [julien] with PoEPi: Pi Zero Power over Ethernet with PHY. The Raspberry Pi Zero is so tiny, that it’s easy to forget it needs a fair amount of power to run. [Julien] is giving us a way to connect our Pi to a network while ditching the USB power supply using Power Over Ethernet (PoE). PoE has been powering devices like IP cameras for years now. It’s become a standard way of transmitting power and data. For the Ethernet physical interface, [Julien] is using Microchip’s ENC28J60, which has a handy SPI interface. Linux already has drivers in place for the device, so it’s a slam dunk. The “power” part of this system comes with the help of an LTC4267 PoE interface chip, which has a built-in switching regulator.

If you want to see more entrants to Hackaday and Adafruit’s Pi Zero contest, check out the submissions list! If you don’t see your project on that list, you don’t even have to contact me, just submit it to the Pi Zero Contest! That’s it for this week’s Hacklet. As always, see you next week. Same hack time, same hack channel, bringing you the best of!

DIY solution does PoE on the cheap


Depending on the scope of your requirements, Power over Ethernet (PoE) components can get pretty pricey. [Fire] wrote in to share a 4-port PoE solution he put together for under 20 euros (Ignore any SSL errors – we’ve checked it out, it’s safe).

The most expensive part of the build was the 8-port patch panel he purchased for 11 euros. He popped it open, wiring the first four ports for power after drilling spots for an indicator LED and the PSU. He wound the power lines through ferrite beads to hoping to dampen any interference that might occur before reassembling the panel.

In the picture above, you might notice that the panel is being powered via the first Ethernet port rather than through the barrel jack, which [Fire] said was done for testing purposes. When deployed in his network, he plans on using a regulated power supply from a junked laptop to provide electricity.

If you need to provide PoE to devices on your network, this is a great way to go about it. Using a patch panel like [Fire] has gives you the flexibility to easily wire up as many powered ports as you need without much hassle.