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ianr
2007-12-18, 17:49
Has anyone looked into whether it is possible (or rather what is involved) to have the squeezebox powered off the ethernet cable? Recently I've come to really appreciate how much this simplifies things and cuts down on clutter (installed some Voip phone sets that don't need separate wall warts).

This would be something that I would suggest might be a cool feature for the SB4 (whenever that makes an appearance :)

thoughts?

SuperQ
2007-12-18, 18:27
Normally you get POE support at the ethernet PHY interface. I suppose you could hack something up.

http://en.wikipedia.org/wiki/Power_over_Ethernet#Homebrew

amcluesent
2007-12-19, 01:03
IIRC the POE protocol requires the powered device to present a certain electrical characteristic on the wires so that the powering unit handshakes before switching to full power.

The DIY approach would be run 5V DC down the 2 unused wire pairs in the CAT5, maybe using a variable voltage supply to account for losses depending on the wire length.

radish
2007-12-19, 05:50
Don't forget you can get POE adapters (like this one: http://www.dlink.com/products/?pid=332) which let you retrofit non-POE devices. Not as neat as an all in one, but it works.

ianr
2007-12-19, 19:25
It seems to me that this technique could be useful in isolating the SB from the wall wart thereby eliminating the RF noise problem, no?
The gotcha AFAIK is that POE normally runs +48VDC which means you can either
1) source your own power as described above OR
2) use some manner of DC-DC step down meaning heat (linear/resisitor) or noise (stepper)

Am I missing anything?

seanadams
2007-12-24, 14:03
Nothing special is required of the MAC/PHY. Something like this (5V 2A) should work: http://www.voiplink.com/Linksys_POES5_p/linksys-poes5.htm

As far as EMI is concerned... you're just replacing one power supply with another.

ianr
2007-12-26, 19:59
Nothing special is required of the MAC/PHY. Something like this (5V 2A) should work: http://www.voiplink.com/Linksys_POES5_p/linksys-poes5.htm

As far as EMI is concerned... you're just replacing one power supply with another.

Ah! It seems I was misunderstanding the nature of the problem attributed to the wall wart when I thought it was related to proximity. I figured that having a switcher 50' away would effectively isolate the squeezebox (inverse square law).
Is the problem then noise from the switcher on the power line itself?

For anyone interested in this, it is worth pointing out that simply putting power on the ethernet jack won't work. You'd need to solder some lines from the pins on the jack to the appropriate points on the power connector. I believe this could be done quite cleanly inside the case.

cheers!

seanadams
2007-12-27, 08:14
I'm talking about the supply that gives you 5VDC from 48VDC...

ianr
2007-12-27, 18:56
I'm talking about the supply that gives you 5VDC from 48VDC...

well I guess that would cut down on cables. sort of. If one took the SB out of its casing and recast it, but at the end of the day its one switcher for another. No net EMI improvement.

:-/

Is it your view that POE wouldn't work well for this very reason? (circuit is going to need 5V/12V so cutting from 48 is going to produce more noise as it is closer to the PCB?) I guess its a niche idea anyhow. I really dig the single cable idea though.