Power over ethernet

[funkstar]

I know this has been discussed a lot recently, especially with the interest in having a Touch wall mounted.

Well I was looking for something completely different and came across this:
http://linitx.com/viewproduct.php?prodid=11849

This one especailly caught my interest: http://linitx.com/viewproduct.php?prodid=11849

Personally I would be very tempted to use a handful of these, a modified PC power supply (for the 5v source) and wire up the players in my appartment. I'm sure I could come up with uses for supplying 12v round the place using ethernet as well.

[ShutterShock]

I guess I'm a bit paranoid about using PoE with the Touch. As elegant as the solution is (especially with the Touch wall mounted), the concern I have is the Touch's current draw is rated at 3 amps, and most of the PoE injectors max out at 2 - 2.5 amps.

[SteveEast]

Yeah, but the solution above uses the original equipment power supply rather than a custom one. Passive POE rather than Active POE.

Steve.

[ShutterShock]

Yeah, but the solution above uses the original equipment power supply rather than a custom one. Passive POE rather than Active POE.

So because of DC losses, cable runs must be relatively short - and that's where they get the 30 - 40 meter maximum.

Based on your clarification, PoE is looking really attractive again.

Thanks.

[dean]

I'm using one of these with my Touch right now:

http://www.cisco.com/en/US/products/ps10044/index.html

If you aren't using the USB port, then it should be fine.

[pippin]

Do you have something for power-over-wifi as well?
THAT would be a killer!

[fuzzyT]

I tried that, but it gave me a sunburn.

--rt

pippin wrote:
> Do you have something for power-over-wifi as well?
> THAT would be a killer!
>
>

[seanadams]

I'm using one of these with my Touch right now:

http://www.cisco.com/en/US/products/ps10044/index.html

If you aren't using the USB port, then it should be fine.

I just made an adapter to feed the DC input from the USB port. Works great and saves electricity too.

[iPhone]

I just made an adapter to feed the DC input from the USB port. Works great and saves electricity too.

Care to share what you did in the DIY section?

[seanadams]

Care to share what you did in the DIY section?

I was just kidding. Maybe I need to work on my deadpan delivery. :|

[iPhone]

I was just kidding. Maybe I need to work on my deadpan delivery. :|

It was very good deadpan, to good. I was seating here looking at the USB Spec trying to figure out how that would even be possible. The main thing though was how would it save power? A watt is a watt no matter where it comes from. Maybe a winking smiley at the end might have helped.. ;=}

Anyway good to see you in the Forums......

[fuzzyT]

I think I /almost/ got it on first reading.

Powering the Touch's DC input from it's own USB output?

Electron perpetual motion?

Definitely an energy saver!

--rt

seanadams wrote:
> iPhone;460472 Wrote:
>> Care to share what you did in the DIY section?
>
> I was just kidding. Maybe I need to work on my deadpan delivery. :|
>
>

[radish]

Hey...I got it...I just couldn't think of a witty enough retort ;)

[agillis]

That low cost POE adapter should work fine. You could save self even more money by just splitting out the cat5 brown pair at both ends and connecting power to it. That's all your £7 adapter is doing.

If anybody is interested I could post something in the Wiki about this zero cost PoE option.

[timearp]

If anybody is interested I could post something in the Wiki about this zero cost PoE option.

Go on then! I'm interested.. some pics as well if you could please.

[seanadams]

That low cost POE adapter should work fine. You could save self even more money by just splitting out the cat5 brown pair at both ends and connecting power to it. That's all your £7 adapter is doing.

If anybody is interested I could post something in the Wiki about this zero cost PoE option.

This is a bad idea in general, but especially for Touch. You need regulation at the point of load because CAT5 has a high resistance (3 ohms / 100ft) and Touch draws highish, variable current at only 5V. Even if it appears it to work on a shorter cable run, you could get compromised sound quality (due to clipping and/or noise) or you might even get intermittent crashes when load current increases. You will probably find it gets worse when USB devices are connected. And you can't just increase the source voltage to compensate, because the load is not going to be constant.

If you're going to do POE, use a proper regulated splitter. I would not suggest the "passive" trick for anything more sophisticated or expensive than a light bulb.

[seanadams]

I also should mention that a real (802.3af) POE switch or injector uses a safe automatic detection mechanism to verify that the target device is ready to accept power before switching it on at the source. Without that feature, you run the risk of cooking a conventional device that is accidentally plugged into that port, especially if it's a gigabit device (which actually has all four pairs connected).

[ftlight]

On 9/23/2009 9:25 PM, seanadams wrote:

> This is a bad idea in general, but especially for Touch. You need
> regulation at the point of load because CAT5 has a high resistance (3
> ohms / 100ft) and Touch draws highish, variable current at only 5V.

I was surprised to see that CAT5 is so lossy (having never had a reason
to check it) but I just put my meter on a cheap 100' cable from
Monoprice and it measured 3.2 ohms.

--
Bill Burns
Long Island NY USA
http://ftldesign.com

[Dogberry2]

Powering the Touch's DC input from it's own USB output?

Electron perpetual motion?

Definitely an energy saver!
Unfortunately, it only works with superconductor cables, and the power required to keep them down near zero Kelvin makes it cost prohibitive. ;-)