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PoE+ (802.3at) Support?

Posted: Sun Mar 18, 2012 8:59 pm
by restlessdesign
I recently purchased an Ethernet Shield, only to find out that my workplace is running PoE+, which supports a much higher power output*. I take it the 8023af Regulator isn't going to be enough? If that's the case, can it be modded or is there another product to ensure that I don't blow up my Arduino? :D

* — From what I've read (I'm pretty new to this), this doesn't necessarily mean that it has to output at a higher voltage—should I test this by plugging the board in and taking a reading with my multimeter?

Re: PoE+ (802.3at) Support?

Posted: Mon Mar 19, 2012 7:17 am
by cef
PoE+ and PoE should be compatible.

PoE+ should refer to 802.3at. 802.3at has 2 types. 802.3at type 1 is equivalent to 802.3af. The max voltage that comes out of 802.3at and 802.3af is still capped at 57 volts, regardless of type.

Note: The end device negotiates the current (and therefore power) that it will get when it is first connected. Some useful notes on this can be found at http://en.wikipedia.org/wiki/Power_over_Ethernet - FYI: This all happens on the regulator.

PS: Of course, this will not be enough if you're using a non-PoE regulator, and could result in the regulator getting fried. I know you said you're using a PoE regulator, but this is just a reminder for others reading this post.

Re: PoE+ (802.3at) Support?

Posted: Thu May 17, 2012 5:14 pm
by anas_ali
There are several ethernet arduino shields available on different sites, some with poE module and some without poE module .
SO, MY question is if i buy ethernet shield without poE module which is going to cost me less then what is it i am loosing or simply not getting or it it that i ultimately have to buy a poE module and join it with the normal ethernet shield.
Will there be some features not compatible in absence of poE module. Or is it that the ethernet board will not get power via its data cable which is very obvious.And if it is the case then will the ethernet shield without poE MODULE WOULD work normally upon hooking it up with arduino boards like uno or mega.????


please help me.....

Re: PoE+ (802.3at) Support?

Posted: Thu May 17, 2012 9:51 pm
by cef
Hi anas_ali,

Simply put, if you buy any ethernet shield without a PoE regulator, then you will not be able to power the shield/arduino over the ethernet cable, and will have to power it via other means (eg: usb, via the power connector on the arduino, etc).

With something like the Freetronics Ethernet shield, the EtherTen or the EtherMega boards, which have a connector for a PoE regulator, you could install one at a later date, should you change your mind and want to power your project using a PoE switch or PoE injector (via the the ethernet cable). Same should apply to any other Ethernet shield that allows you to add a PoE regulator.

If you do want to add PoE to your project later on, make sure you leave enough room for the PoE regulator to fit on the shield when designing/making your project.

Notes:
1) The PoE regulators can only provide a limited amount of current (802.3af specifies a max guaranteed of 12.95W of usable power, some of which gets lost in the conversion process), so if you have project that draws a lot of current (eg: say more than 500mA) it is probably worth it to run a dedicated supply.
2) I would not guarantee that the pinout of the PoE regulator from Freetronics would work on any other brand Ethernet shield, and vice versa (any brand PoE regulator with a Freetronics shield). If someone wants to go down this path, feel free to ask about the specific combination of PoE regulator and shield.

Re: PoE+ (802.3at) Support?

Posted: Fri May 18, 2012 4:53 am
by anas_ali
hi cef
Thank's for the reply ,it is really very kind of you..