wiki:poe

Version 16 (modified by Tim Harvey, 13 days ago) (diff)

added PoE classes

Power Over Ethernet (PoE) Notes

PoE works by having a PoE capable injector or network switch. When the switch connects to a device, the switch tries to make a handshake with the device. The device has to have the signature to be able to do the handshake to activate PoE. Some Gateworks boards do not have this signature. If the signature is not detected, then power is not turned on.

PoE has evolved to define several different classes of power requirements:

  • class 0 - (no signature) max device power of 12.95W
  • class 1 - 4.0W available for max device power of 3.84W
  • class 2 - 7.0W available for max device power of 6.49W
  • class 3 - 15.4W available for max device power of 12.95W
  • class 4 (PoE+) - 30W available for max device power of 25.5W
  • class 5 (PoE++) - 45W available for max device power of 40W

Please reference the user manual for the product to learn if it has POE capability at http://www.gateworks.com/usermanuals

Specs:

  • 802.3af-2003 standard provides up to 15.4W of DC power (min 44Vdc and 350mA) to each device. Only 12.95W is assured to be available at the powered device (as some power is dissipated in the cable)
  • 802.3at-2009 standard (PoE+) provides up to 25.5W of power and prohibits a powered device from using all four pairs for power. Some vendors have products that offer up to 51W by utilizing all four pairs.

References:

Gateworks PoE

Gateworks supports a variety of Power-over-Ethernet solutions depending on product family.

Family Board Supported Notes
Newport GW640x 802.3af (J21), Passive3 (J22)
GW630x 802.3af (J19), Passive3 (J20)
GW620x 802.3af (J14), Passive3 (J16)
GW610x Passive3
Ventana GW540x emulated half-rectified3 802.3af (both ports) Jumper1
GW530x emulated half-rectified3 802.3af (both ports) Jumper1
GW52xx emulated half-rectified3 802.3af Jumper1
GW51xx half-rectified3 Passive
GW552x half-rectified3 Passive (both ports)
Laguna GW2388 half-rectified3 Passive (both ports) Jumper2
GW2386 full-rectified emulated 802.3af Jumper2
GW2387 full-rectified emulated 802.3af Jumper2
GW2391 full-rectified emulated 802.3af Jumper2
GW2380 Passive3 (up to 42V) Jumper2
GW2382 Passive3 (up to 42V) Jumper2
  1. Jumper W1 selects passive (install) vs 802.3af (remove) voltage range
  2. Jumper W1 selects passive (ext) vs 802.3af (std) voltage range. See below for details on the 802.3af emulation
  3. Half-rectified or Passive PoE on Gateworks boards assumes positive on blue pair, negative on brown pair. A cross-over cable can be used for devices using the opposite polarity

Passive PoE

Most Gateworks products support what is typically referred to as 'Passive PoE' as power is applied to the same pins defined in 802.3af however the intelligent signalling/detection is not present. We do this because 802.3af DC range is only 37-60V and our customers typically want lower ranges.

See the Gateworks Online Shop for Passive PoE Injectors

802.3af

802.3af is a standard adopted in 2003 for intelligent Power Over Ethernet where a signature is required before the supply turns on voltage. This can be a safer option than passive PoE.

Gateworks boards with true 802.3af support:

  • Newport GW640x/GW630x/GW620x

Emulated 802.3af

Originally, true 802.3af was costly and difficult to co-exist with passive PoE, so Gateworks designed a circuit that emulated it by providing the 'signature' needed to make an 802.3af PoE compliant switch enable power. The circuit used on the boards that use this emulation provides a 'class 0' signature but does not provide a 2-event class and PoE signature which may make it fail to turn-on certain 802.3af power adapters.

While the 802.3 spec calls out the power pins explicitly it does not call out polarity because it also requires full rectification (which makes polarity a moot point). This created the fact that some products use one polarity and others use opposite with regards to + and - voltage rails (see here http://pinouts.ru/Net/poe_pinout.shtml). Some of our emulated 802.3af products do not have this full rectification for space reasons which can make them in-compatible with PoE on some devices without the use of a 'cross-over cable'.

Refer to the table above to find which boards use emulated 802.3af and note in the table that some of the above products feature a jumper 'W1' which enables 802.3af emulation ULVO (under voltage lockout). This jumper needs to be in the correct position (or removed) see above table depending on the board and whether or not you want passive PoE or 802.3af emulation.

The following switch products use the opposite polarity that Gateworks uses and thus requires either a) a fully rectified emulation (see above), b) a crossover cable, c) a GW16090 revB+:

  • D-Link DGS-1008P
  • Cisco SG100D-08P 8-port PoE switch
  • ZyXel GS1910-24HP

GW16090 GigE 802.af/at to GigE passive PoE Adapter

The Gateworks GW16090 (Purchase Here) allows boards that have no 802.3af/at support to be powered by an 802.3af/at switch or boards that only support 802.3af to be powered by an 802.3at switch. The GW16090 uses the Maxim MAX5969B PoE PD Interface Controller which provides both 802.3af and 802.3at signatures to the PSE device. For more info on the controler see: http://www.maximintegrated.com/en/products/power/switching-regulators/MAX5969B.html

The GW16090 is only intended with purely passive PoE Ethernet ports and is not meant to be compatible with ports with emulated 802.3af or ports with true 802.3af/at and using it on those ports would be invalid and may need to unexpected results due to signature resistor conflicts.

For a list of products that the GW16090 has been validated with please see below.

Notes:

  • Prior to revB only half wave 802.3a emulation was supported.
  • Prior to revD only 802.3a emulation was supported.
  • It is critical that any external connections (eth, jtag, serial, etc) to the product being powered by the GW16090 are electrically isolated. Otherwise ground-loops can occur causing power failure at the switch and possible board damage. This is particularly an issue with PoE switches that use Power/Ground polarity opposite of what Gateworks uses for Passive PoE.

Schematic Diagram of GW16090:

GW16090 Schematic

PoE Testing

Product PoE Type Notes
Netgear FS108P 8port 10/100 802.3af PoE Switch 802.3af
D-Link DGS-1008P 8port GigE 802.3af PoE Switch 802.3af Opposite Gateworks Polarity1
Cisco SG100D-08P 8port GigE 802.3af PoE Switch 802.3af Opposite Gateworks Polarity1
ZyXel GS1910-24HP 24port GigE 802.3af PoE Switch 802.3af Opposite Gateworks Polarity1
ANVISION 48V 0.8A 802.3af/at GigE PoE Injector 802.3af/at integrated power supply
TP-LINK TL-PoE150S 802.3af GigE PoE Injector 48V 0.35A 802.3af external supply provided, not compatible with emulated 802.3af2
Brash Networks BN-PE901G 802.3at GigE PoE Injector 52V 30W 802.3af/at integrated power supply
GW10027 Passive PoE Power Injector 24V 0.8A Passive integrated power supply
GW10041 Passive PoE Power Injector 24V 2A Passive integrated power supply
Ubiquiti Networks GP-A240-050G Passive GigE PoE Injector 24V 0.5A Passive integrated power supply
GW10022 10/100 Ethernet Passive PoE Injector Passive requires external power supply
GW10054 GigE Ethernet Passive POE Injector Passive requires external power supply
  1. Requires cross-over cable if using with a Gateworks board on a port that has half-rectified passive PoE (ie Ventana)
  2. This product is not compatible with the emulated 802.3af used on certain Ventana and Laguna products

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