Dimmable LED reading light unit, arrangement of power supply and dimmable LED reading light unit, method of operating a dimmable LED reading light unit in a power supply system, and method of replacing a dimmable light unit by a dimmable LED reading light unit

A dimmable LED reading light unit (8), in particular for a passenger transportation vehicle, such as an airplane, a bus or a ship, comprises an input (10) which is connectable to a potentiometer (6) that outputs a direct voltage having a voltage intensity corresponding to a selected potentiometer position; a load current source (12) being configured to generate a predetermined load current; a current controller (16) providing an operating current for operating at least one LED (18); and an electronic measuring and control unit (14); wherein the load current source (12) and the current controller (16) are connected to the input (10) in parallel; wherein the electronic measuring and control unit (14) is configured to measure the voltage when no load current is generated by the load current source (12); to drive the load current source (12) to generate a predetermined load current and to measure the voltage when the predetermined load current is generated; to determine the position of the potentiometer (6), based on the measured voltages, based on the load current, and based on a predetermined nominal resistance value of the potentiometer (6); and to control the current controller (16) to supply driving current to the at least one LED (18) necessary to emit light with a luminous flux corresponding to the position of the potentiometer (6).