Disclosed herein is a system for detecting rotational speed and early failures of an electronic device. The system includes a rotating disk affixed to a rotating shaft of the electronic device. The rotating disk has projections extending from its periphery. A time of flight ranging system determines distance to the projections extending from the rotating disk. Processing circuitry determines a rotational speed of the rotating shaft from the determined distances to the projections extending from the rotating disk, and detects whether the electronic device is undergoing an early failure from the determined distances to the projections extending from the rotating disk. Rotational speed is determined from the time between successive peaks in the determined distances, and early failures (for example, due to wobble of the shaft) are determined where the peaks vary unexpectedly in magnitude.