A collision sensor assembly is attachable to a stationary structure such as a pallet rack, a door frame, the corner of a wall, or the like. The collision sensor is configured to sense when a collision occurs with the stationary structure such as when a piece of movable machinery contacts the stationary structure. The collision sensor assembly includes a sensor operatively connected to a processor which determines when a collision occurs, and produces a signal to an output signal generator to provide an external indication of the collision.