Power from ethernet?
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I suspect I already know the answer, but any chance we can grab enough power from the Ethernet connection to power this thing? It' would be a hack for sure, but would be interesting to just drop it next to my router on a short piece of CAT5 and see it simply take off.
OBC
OBC
Comments
Do a little research first ... hmmm ... all it takes is a web search.
You'll need a switching regulator with a high enough voltage rating, but it's certainly doable.
See here
Rich H
If you fake it and inject whatever you want you can work with lower voltage levels. Just build a cable adapter at one end that allows you to pass through the 4 data lines and input your power to the other 4 lines. At the receiving end, you build an adapter that does the opposite. I have run 9 volts over several hundred feet of cat5 and still had enough headroom at the far end to feed a 5V regulator. I tested with 1000 feet but I forget what the results were.
I don't think it will be easy to build this directly into the Spinneret board, however. You would need a simple adapter (this can really just be a modified cable) at the Spinneret end to break out the power instead. Looking at the schematic for the RJ45 magjack, it doesn't look like it's easy to connect to the 4 unused pins to pull the power out directly from there. You'd have to do it slightly upstream.
This is one of the first things I looked at when the Spinneret was officially released (right after I ordered mine (which arrived yesterday
Yes, I was referring to grabbing some of the power that is there.
I've noticed that there is generally enough power to light a couple LEDs on the jack on a NIC without having power applied to a PC. From your answers, it looks like this isn't enough juice to make things interesting.
Thanks
OBC
Robert
No _way_. Ethernet is transformer isolated. I'll lay a carton of beer and 2 bottles of scotch that you can't get the lights on a NIC to light up with only an ethernet cable attached. In fact, I'll wager another bottle of scotch on the ethernet card being powered from the +5V stby line on the PSU (5 volts, on all the time the PC has a plug in the back of it) to allow the NIC to detect a WOL packet and wake the PC up.
There are 4 differential pairs of wire on Ethernet that are isolated with a transformer that form the total of 8 wires that you see. In order to get POE you need to break that code and have at least two devices ... one designed to send power while the other is designed to receive power. ... in most cases other devices on the Ethernet line that are not POE capable will not be affected if there is power present or not.
I don't drink beer or scotch, but I know that I have witnessed this on more than one occasion. It actually caught my eye because it was so strange. Being in the PC repair business I get all sorts of different PC configurations pushed across my desk for repair. Next time I get one that does this I'll grab my video camera and lay proof that I've seen it.
OBC
Here is a link showing the above configuration and other possibilities.
http://hw-server.com/docs/power_over_ethernet-PoE.html
The maximum allowable amount of power that you can transfer is about 31 Watts (62 Watts if you double up and use the spare pair), but in order to transfer any power at manageable DC voltages, you must use DC-DC converters.
The maximum voltage allowed is about 57V
The maximum current allowed is about 550 mA
57V X 550mA = 31.35 Watts <-- however, read the conclusion at the bottom of the link I posted, about
the amount of true available power due to I/R drop
I'm sure there are cheaper ways to get the Spinnernet power from Cat5, but this is much easier in small quantities.
Newegg.com, Walmart.com, and Amazon.com carry the D-Link, but Amazon has free shipping and no tax.
Product Features
Technical Details
Please note that many cheep "Power over Ethernet" are not Power over Ethernet (802.3af) compliant, but only acts as a connector transmitting power over spare pairs in the tp cable. Those units will not work with other PoE equipments, e.g. switches etc. This D-link is such an example of a non standard unit.
http://en.wikipedia.org/wiki/Power_over_Ethernet
If one is trying to power more Spinnerets or Network equipment, I suppose they would have more money for a compliant unit.
In the meantime, for those who simply want to power up their Spinneret, it might be hard to find a cheaper commercial alternative.
I also noticed that Amazon is probably providing "shipping specifications" or else, this unit may be pretty heavy.
You would still need something at the other end to extract the power.
The D-Link "fake POE" is useful if you only have one device you need to connect.