| poe1a2 | passive POE adapter |
| Status | active |
| Part numbers | poe1a2 = POE adapter, RoHS compliant |
| Use with |
ac18veur
ac18vuk |
| 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. |
| Manufacturer | PC Engines |
| Origin | Taiwan |
| Schematics |
