Power over Ethernet (POE) injector combines d.c. power supply with LAN data and injects it into the 4 unused cores of the ethernet cable which are not carrying data. If used with WRAP boards, or other boards whose ethernet connector is designed to collect power off the unused cores, the other end of the etherenet cable can be pluigged straight into the connector.
In other cases a second POE injector can be used at the other end of the ethernet cable to separate dc power and data, enabling these inexpensive units to be used as POE for many different devices.
Because there is a voltage drop over ethernet cable - the longer the cable the more the voltage drop - cables should not exceed 10 metres for 12v systems (this is a very broad rule of thumb), less for 5v systems, more for 18, 24 and 48v systems.
You are advised to calculate the voltage and current drops if in any doubt. |