Passive POE adapter POE1A2
POE Passive Power over Ethernet injector
- Status: active
- Part numbers: poe1a2 = POE adapter, RoHS compliant
- 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
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