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Networking Power

Ask Slashdot: Affordable Hardware For Remote-Booting USB Devices? 81

Posted by timothy from the should-exist dept.
phlawed writes: USB ports are everywhere. It is very convenient for powering low-power devices, and by using a run-of-the-mill phone charger you can easily get 10+ watts or so. In other words: everyone already has the generic power supply and power cable. No issue with voltage or polarity. Perfect for the hobbyist market.

Another ubiquitous power source (in the enterprise environment) is Power over Ethernet. Active PoE splitters for 12V output are available for ~6-7 USD and up on eBay. With PoE you get networking and power over the same wires, and booting your (possibly borked) PoE device is a matter of instructing the PoE source to cycle the power on that port. (Also, USB chargers with 12V input are available for less than 1 USD on eBay. They are likely all crap, though.)

I am looking for the combination of these two concepts in a compact, affordable, quality product. I found one product offering USB power from PoE. That product appears to have left out Ethernet and has a MSRP of 30 USD. Otherwise, I find PoE wall sockets for a MSRP of USD 100 or more. It appears excessive, given the cost figures of the pieces listed above.

So, if it does not already exist... anyone feel like running with this on your favorite crowdsourcing platform? Any experienced electronics people who can do a back-of-the-envelope calculation for cost of parts and assembly?
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Ask Slashdot: Affordable Hardware For Remote-Booting USB Devices? More

Ask Slashdot: Affordable Hardware For Remote-Booting USB Devices?

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  • The summary suggests that POE is a "ubiquitous power source", but the suggests that we have to go to the bay of thieves to take a chance on getting one. Which is it?

    • POE is very common. It is the type of device that combines POE with USP that the submitter is asking about that is rare. Read the summary again.

      • As far as I'm concerned, if you have to go to the bay of thieves to try to get one then it doesn't exist. That place is too vile and evil for me.
        • While I sympathise with distrusting "the Bay of Thieves", it does have the useful property that if you can find it on The Bay, then you can probably find it on a more reliable website. You might even get manufacturer's names, model numbers etc from which you can plough through more conventional suppliers (e.g. Radio Spares, Farnell) or less conventional (e.g. Alibaba).

          Wading through the Bay doesn't mean you are going to buy there.

          (Personally I've only had a couple of percent of my purchases off the Bay go

      • The submitter mentioned "USB chargers with 12V input are available for less than 1 USD on eBay. They are likely all crap, though" which sounds like a UBEC [wikipedia.org], I wouldn't get a $1 one but the ones for a couple of dollars are fine, we use a ton of them, they take anything around 12V in and output 5V via various connectors (we use flying leads in, micro-USB out).

        • Re: (Score:3, Informative)

          by Anonymous Coward

          Voltage drop becomes quite a problem on Ethernet when it used as power over medium to long distances. The expensive gear runs higher voltage (56v) and then the PoE devices to suit the standard regulate the power at the other end. This is necessary. The higher voltage also keeps the amps down for efficiency on the thin cat5e/6 cable. This is the same reason mains power is the voltage that it is for delivery in to your home/office.

          I have attempted to run a Wifi AP with homebrew PoE mounted in the roof of my p

          • Also, be aware the gigabit ethernet does use all pairs. If you liven up the unused pins for your 10/100 (especially at higher voltages) dont accidentally plug it in to a gigabit port. Damage to the port will likely follow.

            If you read the PoE spec [wikipedia.org], you'll see that the power is sent on both wires of at least two pair, and because the electrical spec calls for transformers on the receive end, the power will cause no issues. Since there's no voltage difference between the wires in the same pair, there's no prob

      • PoE is not in any sense 'ubiquitous', and where it is common it is used to power devices like VoIP phones or network devices like access points, and I'm not sure you can just 'Tap' into PoE and power your cellphone/tablet AND the VoIP phone...

        PoE can supply at most 36 watts - https://en.m.wikipedia.org/wik... [wikipedia.org]

    • The summary suggests that POE is a "ubiquitous power source", but the suggests that we have to go to [redacted] to take a chance on getting one. Which is it?

      Just because someone names one possible place a thing can be bought doesn't preclude it being massively available via other channels.

      But you knew that. You just wanted to spew a buzz-word you made up. Twice in one thread. Well, sorry, you're getting called on it.

  • It seems like you just need to combine your POE adapter with a USB "lipo" adapter.
    The latter are meant to attach to a lipo battery (7.4V - 22.2V) and provide 5V for USB charging.
    (Of course, you can use any DC power source as input, not just lipo batteries.)
    You can search Ebay for "usb lipo mobile charger" to find them, starting at $5 for basic ones.

  • If you use the cheapest-possible PoE injector/splitters, which are just over a dollar, they give you a barrel jack out the side. Then you just plug your cables in. So all you need is a way to get that barrel jack out to your 5V power supply, and an appropriately high-voltage wall wart to feed it power over the PoE wires. You're overcomplicating this problem. Do not use 12V, though, if you can avoid it. Use something higher, like 17V. 17VDC wall warts and bricks are readily available, and virtually all of th

    • There's a lot of POE "standards" some ranging up to 57V - make sure you know what you're getting into when you start plugging and playing:

      https://en.wikipedia.org/wiki/... [wikipedia.org]

      • There's a lot of POE "standards" some ranging up to 57V - make sure you know what you're getting into when you start plugging and playing

        Yeah, miraculously everything I have is either dumb as hell and I know to keep it together, or it's 802.3af. I looked it up before I plugged it in for just that reason.

      • The cheap ones do not conform to PoE as a standard. They just run some volts over the 2 unused pairs and limit the connection to 100Mbps. You supply whatever power you want.

    • If you're looking at higher wattage, like the mentioned 10W, also use higher voltage like the mentioned 24V. Trying to push higher wattage through ethernet-cable-gauge wires at 5v could end up burning your house down.
  • You mean something like this? http://www.vidabox.com/kiosks/... [vidabox.com]
    • OP: "Otherwise, I find PoE wall sockets for a MSRP of USD 100 or more. It appears excessive, given the cost figures of the pieces listed above." Linked item = $80... would count as "excessive" in my book.

  • Dafuq? (Score:4, Informative)

    by Anonymous Coward on Sunday January 24, 2016 @07:01PM (#51362839)

    What dafuq are you actauloly looking for. You spent so much time describing supposedly unwanted stuff, that I can;t figure out what you want.

    It sounds like you want a PoE device that provides USB power, but you're a cheap bastard and $30 is too high for you. So...
    $19 http://www.ebay.com/itm/iDocx-iPower-POE-to-USB-Converter-/181992770079?hash=item2a5f9d4a1f:g:eioAAOSwqrtWmVbu

    $21 http://amzn.to/1nIeoNw

  • Zwave (Score:2)

    by shuz ( 706678 )

    The http://www.z-wave.com/ [z-wave.com] protocol might work. There are a lot of remote hardware/switch options out there. You could wire in a zwave switch to your power supply. Then set the bios to autoboot on power.

  • Not the cheap as cheap can be use the spare wires in 10/100 but the 1000bt ones like a TL-POE10R. 12/9/5v handles 10w 15 bucks. Getting a 2.1mm barrel jack to usb is easy enough.

  • what the hell do you want? (Score:3)

    by Gravis Zero ( 934156 ) on Sunday January 24, 2016 @07:54PM (#51362995)

    you've mentioned PoE, USB and 12V power sources. what you failed to mention is what the hell you actually want. do you want PoE to 12V? do you want PoE to USB? do you want an SBC powered by PoE that boots off a USB stick? what the hell do you want?

    • I don't even think the editor knows. Something about "remote booting" a USB device, but then they talk about power over ethernet and unrelated concepts. Truly boggles the mind.

      • Re: (Score:2, Insightful)

        by JustAnotherOldGuy ( 4145623 )

        Bingo. Honestly, I read the post 5 times and I'm still unsure.

        I *think* he wants a USB widget that attaches to an ethernet line and plugs into a PC so he can reboot it, but hell if I know.

        Why can't people just say, "I need a thingy that does (whatever thingy is supposed to do)" and be done with it?

        • Re: (Score:1)

          by Mondragon ( 3537 )

          I *think* he wants a USB widget that attaches to an ethernet line and plugs into a PC so he can reboot it, but hell if I know.

          Oh, I thought they wanted a USB power source that they could remotely cycle for a "reboot" of something powered via USB. Of course, you could just as easily be right.

          Horray for clarity.

        • Re: (Score:3)

          by gl4ss ( 559668 )

          i think he wants to plug a raspberry pi to ethernet.
          and to provide power through the ethernet wire to the raspberry.
          and to remote reboot the raspberry when it fails something.

          this is the only thing that would make any sense at all. because it mentions poe adapters, but without "internet".

          all he needs really is a network connected wall wart at the point where he is going to be injecting the poe into the ethernet cable because he is too cheap for the proper solutions and really it does just what he seems to w

    • Re: (Score:2, Informative)

      by drinkypoo ( 153816 )

      He wants PoE to 5V with a female USB A or perhaps a mini USB male, with ethernet passthrough, and apparently with remote power cycling.

      Realistically, he's gonna have to get the power cycling on the supply side, because anything else would require just as much money in hardware as what he's trying to power cycle, most likely. You could do it with any Arduino or similar, but none of the ones that are staggeringly cheap have ethernet. WiFi is actually cheaper. You can get a ESP8266 module for the same money as

      • Re: (Score:3)

        by amorsen ( 7485 )

        The slickest thing would be to get a PoE switch which lets you cycle power on its ports. I have no idea if such a thing even exists, but I would have to bet it does.

        Every managed PoE switch that I have seen supports disabling PoE per port. Some offer true power cycling support with just one command/one click, with others you have to turn the port off then on again, but they all have a way of doing it.

    • Re: (Score:2)

      by phlawed ( 29334 )

      I would like to be able to powercycle a USB-powered device in Farawayland, while sitting in my comfy office. By instructing my switch to cycle the PoE power on the relevant port.

      A device which accepts regular PoE via an RJ45 in one end, and supplies USB power and RJ45 in the other end would facilitate that.

      • I would like to be able to powercycle a USB-powered device in Farawayland, while sitting in my comfy office. By instructing my switch to cycle the PoE power on the relevant port.

        A device which accepts regular PoE via an RJ45 in one end, and supplies USB power and RJ45 in the other end would facilitate that.

        what you want is a PoE "splitter" - http://www.amazon.com/TP-LINK-... [amazon.com]
        it provides a standard barrel for which there are USB adapters - http://www.amazon.com/s/ref=nb... [amazon.com]

  • How about just using a simple 5V power regulator? Ground on 0v on both cables vin on 12v from poe and vout on 5v usb. Just add a dissipador if you guna use it on high load. https://www.sparkfun.com/produ... [sparkfun.com]

  • Perfect for the hobbyist, my ass! (Score:3)

    by Opportunist ( 166417 ) on Sunday January 24, 2016 @08:02PM (#51363029)

    Are you kidding? A device standard that supplies 5V but needs VERY precise 3.6V on its data lines? A device standard where the protocol is VERY picky with its timing and pretty much requires you to either use silicon that can talk USB out of the box (which then requires a bunch of very funky additional bits and pieces and you may hope that it's not only available as BGA, you may dream about getting a DIL chip) or requires you to write very well timed assembler code and STILL would require its own chip if you dare to clock it at less than 20MHz... provided USB 1.1 is enough for your needs. You want more? You better have a way to pump 50+MHz out of that chip.

    USB may be much. It's very user friendly and "plug and play" and whatnot, but one thing it ain't: A hobbyist's wet dream.

    • Bit-banging a USB interface is about as smart as bit-banging an Ethernet interface. Sorry, but both were architected to be implemented in hardware. Once you accept that, both are perfectly fine hobbyist interfaces.

      If you choose a micro without the requisite hardware support, your life will be very, very difficult.

    • Re: (Score:1)

      by Mondragon ( 3537 )

      It's clear that what the OP meant was the ubiquitous bricks for power delivery.

      Of course, nothing else is clear, so who the hell knows what they actually want...

  • Not that hard of a problem to solve... (Score:3)

    by Lumpy ( 12016 ) on Sunday January 24, 2016 @08:11PM (#51363065) Homepage

    POE is massively less common than 12V and you can build a 12V wifi controlled switch for less than $5.00 Anything commercial will be a very very niche device and will cost a lot.

    What is more common, 120-240V AC. That is the absolute most common power on this planet. and Ethernet controlled AC switches are plentiful and easy to get.

    Stop being a cheap bastard and buy one. $79.00 on amazon.

    http://www.amazon.com/gp/produ... [amazon.com]

    If that is too expensive, then build one from a MSP8266 or get a better job.

  • What the hell are you talking about? (Score:1)

    by Anonymous Coward

    How the hell did this story get posted? I'm not even sure what this guy wants, what he's trying to do etc? I talks about powering devices yet the headline is about remote booting devices? Huh?

    What the hell is this crap?

  • Dear Timothy... (Score:4, Insightful)

    by Anonymous Coward on Sunday January 24, 2016 @08:14PM (#51363073)

    How the hell did this rambling incoherent question get posted to the FRONT PAGE of Slashdot?

  • $17 Bucks (Score:4, Informative)

    by stinkydog ( 191778 ) <sd@s t r angedog.net> on Sunday January 24, 2016 @08:20PM (#51363089) Homepage

    http://www.amazon.com/WT-AF-5v... [amazon.com]

    Did not take much google fu to find this sucker. 5v output from POE and passthrough to boot.

    SD

  • This Kickstarter project: https://www.kickstarter.com/pr... [kickstarter.com], which has just announce that it's shipping (with the usual delays hopefully over), seems like it's already solved the major issues, and just needs a hardware refactoring to produce the USB connection you're looking for.

    I'd recommend getting in-touch with the creators and see if they'd be interested in developing this. This is their second Kickstarter project (at least), so they've already learned a lot, so could be positioned well to run with

  • Just decouple the onboard shard-frame from a USB-bearing-spindle and then re-couple it to the lookup table with a multivariate demodulator powered from the blinker fluid reserve tank next to the Turbo Encabulator girdle spring. But don't use the ones made of Amulite, use the old-style ones with the tremi pipe.

  • Ubiquiti mPower 8-Port Power Strip Ethernet WiFi. Turn on or off any device from anywhere in the world. $98 for 8 devices = $12.25 per device.

    http://www.ebay.com/itm/121863... [ebay.com]

  • I have wanted an easily power-controllable port to hook up USB lights to. There are several good ones, as well as cheap ones; I have mostly GoalZero. Right now, I use an Insteon switching module with an Apple USB power supply driving the lights. Goofy solution, and $50 if you have an extra power supply laying around.

    What I wish I had was a power outlet with built-in zigbee controlled USB charging ports.

  • Try making your own PoE Splitter. 1. Send pins 4,5,7 and 8 to a PoE USB Splitter of your choice for USB power and then send pins 1, 2, 3 & 6 for 100BASE-TX Ethernet. 2. PXE Boot will still work. 3. USB power can be cycled in software. You'll need: 1x RJ45 Cat5 Network Lan Cable Crimpers 1x RJ45 Female Connector 2x RJ45 Male Connectors 5 or 6 feet of CAT5 or 6 LAN cable or as little as 12" for smaller splitters.

  • Dangle an LM7805 linear regulator off the PoE. Done.

  • This should be easy. Controller could be Raspberry Pi, Arduino with HC-05, ESP wifi etc. Say $5.
    12V, 10A relay is $0.50
    buck converter, step down, 3A is $0.70.
    Then you need a power supply. Modern PC power supplies are able to deliver all as 12V (PoE standard). The buck converter will accept 5.7V -> 20V or so. So voltage drop on line no issue. Or get a 12V, 6A PSU for $10.
    10 pairs of JST connectors $2.49
    So if you want 4 ports, the cost would be $5 + $2 + $2.8 + $10 + $2.49 + little time = $23 - with the P

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