|Part numbers||poe1a2 = POE adapter, RoHS compliant|
|Use with||ac18veur |
|Spec||Passive POE (Power Over Ethernet) adapter, uses unused pairs of 100baseT network cable to transmit power to remote device.|
|Pinout||DC jack center positive, 2.1 mm pin. RJ45 pins 4,5 = positive, RJ45 pins 7,8 = negative.|
|Issues||• Passive POE does not comply with the IEEE 802.3af specification. |
• To minimize cable losses, feed the highest allowed voltage, e.g. 18V. Demarc Technology has a nice POE voltage drop calculator- select 1 pair for correct results. Keep in mind that WRAP input power is fairly constant over input voltage - when the input voltage drops, the current goes up. Power = voltage * current.
• To avoid ground loops, ground should be referenced on the receiving end only, that is use a 2 prong (non grounded) AC adapter.
|Why not active POE ?||• Cost - 802.3af compliant solutions require a high component count, and compliant switches are too expensive for small installations such as CPE. |
• Board space - DC-DC isolation transformer takes a lot of space.
• Efficiency - DC-DC converter is required for 802.3af. Typical solution is a flyback inverter, maybe 70% efficiency. Unless you have a very long cable run, passive POE will be more efficient overall.
PASSIVE POE ADAPTER
- Brand: PC Engines
- Product Code: POE1A2