Back in August 2021, I did a teardown of an Ubiquiti Networks power-over-Ethernet (PoE) injector, following up on the dissection of a TRENDnet PoE-supportive powerline networking adapter set from three years earlier. I did detailed PoE technology overviews in both of those, which I’m not going to substantially replicate here in the interest of brevity. Suffice it to say that:
- There are multiple variants of PoE technology, some multiplexing DC voltage on the same wires that carry AC data transitions and others (specifically for 10/100 Mbps Ethernet) leveraging otherwise-unused wires-and-pins for DC transmission. i.e.:
The means by which power is carried within a 10/100 Mbps Ethernet cable also varies: with so-called “Mode A,” the power delivery takes place over the same 1-2 and 3-6 pairs used for data, whereas “Mode B” uses “spare” pairs 4-5 and 7-8. With Gigabit Ethernet, which employs all four pairs of wires for data, merging data and DC power over the same wires is the only option.
- Even within a particular PoE implementation “flavor” a diversity of input (at source)-and-output (at “sink”) voltage combinations exist in the marketplace, making multi-vendor and (even within a common supplier’s product line) multi-product interoperability difficult at best and more likely a non-starter.
If your PoE injector (or PoE support-inclusive router or switch source device, for that matter) implements one mode and your PoE splitter (or PoE support-inclusive remote device) implements another, your only recourse is a frustrating return of one or both devices to your retailer. Voltage and current incompatibilities between source and destination can also result in a product return (not to mention, potentially “fried” gear).
And regarding network topology node naming, excerpting from that premiere 2018 writeup:
If power is added to the network connection at a PoE-cognizant router, switch, or adapter source, that particular power sourcing equipment (PSE) variant is referred to as an endspan or endpoint. Otherwise, if power is added in-between the router/switch and remote client, such as via an appropriately named PoE injector, that device is known as a midspan. A PoE-cognizant remote client is called a powered device (PD); a PoE splitter can alternatively provide separate power and data connections to a non-PoE-supportive LAN client.
For more background details, please see the earlier powerline-plus-PoE adapter and PoE injector writeups.
What we’re looking at today is another PoE injector, the TP-DCDC-2USB-48 from Tycon Systems:
Here’s the sticker on the baggie my unit came in (absent the USB cables shown in the earlier stock photos):
Why the seeming teardown-device redundancy? Part of the answer comes from the respective product names. The Ubiquiti Networks injector was specifically the model 24-24W-G-US:
As I’ve found is commonly the case with PoE products, the output voltage (for an injector, or alternately the input voltage for a splitter) is embedded within the product name. Specifically, in the Ubiquiti Networks 24-24W-G-US case:
Here’s the “decoder ring” for the product name: The first “24” indicates that it outputs 24 V over the Ethernet connection; the following “24W” means what it says—24 W, alternatively indicating that the unit outputs 1 A max current; “G” means that it supports GbE connections; and “US” means that the power cord has a US-compatible NEMA 5-15 wall outlet connection.
Note, too, that since this device supports GbE (whether it actually delivers GbE over powerline is a different matter), “With Gigabit Ethernet, which employs all four pairs of wires for data, merging data and DC power over the same wires is the only option” applies.
If I apply a “decoder ring” to the Tycon Systems TP-DCDC-2USB-48, conversely, what do I get? Honestly, skimming through the company’ injector (which it also refers to in various places as “inserter”) product line web pages, I can’t discern an obvious pattern. And unlike with Ubiquiti Networks, there isn’t explicit documentation to assist me with the code decipher.
That said, the “DCDC” portion might mean that we have an injector that not only outputs DC voltage but also inputs it (versus, say, an injector with an integrated AC-to-DC power supply, which would conceivably be an “ACDC” variant). Specifically, as you may have already noticed from the stock photos, it takes its input voltage from the dual 5V 1.4A (each) USB-A connectors on one side, presumably explaining the “2USB” portion of the product name. And, unlike the 24V/24W (1A)-output Ubiquiti Networks device, this Tycon Systems one outputs 48V (at 12W, therefore 0.25A) DC, therefore—duh—the “48” in the name. But that all said, both the Ubiquiti Networks and Tycon Systems devices are passive, not active, meaning that they provide a fixed output voltage; there is no upfront negotiation as to what the powered device on the other end of the Ethernet strand needs.
As another key rationale for revisiting the “PoE injector teardown” theme, I’ll in-advance share with you one of the product photos, that of the underside (as usual accompanied by a 0.75″/19.1 mm diameter U.S. penny for size comparison purposes):
Again, recall that the Ubiquiti Networks device was GbE-cognizant, therefore using all eight Ethernet wires for data, so DC voltage multiplexing was a necessity. The even earlier analyzed TRENDnet PoE-supportive powerline networking setup wasn’t GbE-capable, even in theory, so it theoretically had four spare wires available for DC voltage purposes (presumably generated by an AC/DC converter inside the adapter). Nevertheless, it also was a multiplexed data-and-DC device, in this case the earlier discussed 10/100 Mbit Ethernet “Mode A”. In contrast, from the photo you’ll note that this device is “Mode B”, completing the implementation option variety.
The final notable revisit rationale was fundamentally curiosity-fueled. I’d found the Tycon Systems TP-DCDC-2USB-48 for sale used at Lensrentals, a photo (mostly video) gear retailer that I’ve mentioned (and bought stuff from multiple times) before. The device’s listed price was only $22; at the time (November 2023) an additional 15%-off promotion made it even more economical ($18.70 plus tax). But what on earth was a PoE injector doing for sale at a photo equipment retailer’s website? This final TP-DCDC-2USB-48 stock photo provides a clue:
Even more telling, after a bit of revealing research, is the seemingly cryptic “VR – Orah PoE Injector” notation on the Lensrental website product page for the Tycon Systems TP-DCDC-2USB-48. It refers to the Orah 4i, a four-fisheye-camera plus multi-mic setup for live-streaming 360° spherical virtual reality:
The A/V capture module tethers to an Intel- and NVIDIA-based mini-PC “box” that stitches together the various sources’ A/V data before network broadcasting the result. And speaking of networks—specifically, Ethernet cables—some of you have probably already guessed how the mini-PC and cameras-plus-mics module connected…over PoE-augmented Ethernet, via the injector on the “stitching box” side and directly powering the capture module on the other end.
1,000 (hopefully educational) words in, let’s get to tearing down, shall we? You’ve already seen my device’s underside; here are views from other perspectives. Top-side block diagram first; gotta love that “Ethent” spelling variant of “Ethernet”, eh?
The two bare sides:
The input voltage-and-data end:
And the unified voltage-plus-data output end:
The seam along all four sides wasn’t glued down, but something else was still holding the two halves together:
I found it when I peeled away the underside sticker:
That’s better:
Note the sizeable ground plane and other thick traces on the PCB underside, similar to those encountered with the Ubiquiti Networks PoE injector three years back:
The PCB pops right out of the top with no additional screws to be removed first:
At the far right is the power LED, with the Ethernet connector above it and the dual USB power inputs below. Two inductors along the bottom, one of them toroidal. The PoE connector is on the left edge. Two more inductors in the upper left corner (one again toroidal), with two capacitors in-between them. At the top is a Linear Technology (now Analog Devices) LT1619 low voltage current mode PWM controller for DC/DC conversion purposes.
And what of that heat sink to the right of the PoE connector? Glad you asked:
It’s normally held in place by glue (to the PoE connector) to one side and a thermal pad underneath. And below it are two ICs: an On Semiconductor FDS86140 small signal MOSFET and, to one side (and therefore only partially attached to the thermal pad) a chip marked:
CSP
10S100S
citc
and a “D1” mark on the PCB alongside, which I’m guessing is a 3-lead Schottky diode (readers?).
In conclusion, here are some PCB side-view shots for your perusal:
That’s what I’ve got for today. I’m now going to try to meaningfully reattach the heat sink and otherwise return the TP-DCDC-2USB-48 to full functionality. Why? The spec sheet says it best:
This USB powered PoE injector is a must for any technician’s toolbox because it allows powering …Passive PoE products from a laptop’s USB port. The 48VDC passive PoE model is perfect for powering IP Phones, Cameras and other devices that use 48VDC PoE. This allows the technician to quickly test the device by direct connection to his laptop, saving him a lot of time. The TP-DCDC-2USB-xx can also be used in customer premise equipment to power external wireless gear from a customer’s computer USB ports, reducing wiring clutter at the PC and allowing the wireless gear to be powered down when the computer is powered down to conserve energy.
As always, I welcome reader thoughts in the comments!
—Brian Dipert is the Editor-in-Chief of the Edge AI and Vision Alliance, and a Senior Analyst at BDTI and Editor-in-Chief of InsideDSP, the company’s online newsletter.
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- Teardown: Powerline networking plus PoE
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- Simple circuit design tutorial for PoE applications
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