A generator for use with a train wheel is provided, which has a housing having a mounting surface for fixedly mounting the housing to a train wheel, a stator fixedly attached to the housing, a rotor rotatably mounted to the stator, a counterweight attached to the rotor with its centre of gravity offset from the axis of rotation of the rotor, the weight of the counterweight acting to maintain the rotor in a stationary position as the stator rotates with the housing. The movement of the stator relative to the rotor generates a potential difference and at least one of a light and a bearing monitoring system is connected to the generator and is powered by the potential difference.
