A controller (100) for mounting onto a socket (20) of an outdoor device (10) is disclosed. The controller comprises an inner body (110) comprising a first bottom surface from which an annular arrangement of electrical connection pins (102) for engaging with said socket extends, said inner body further housing control circuitry (132) for said outdoor device, said control circuitry being electrically connected to at least some of said electrical connection pins; and an outer body (120) rotationally mounted around the inner body, the outer body comprising a further bottom surface (122) around the first bottom surface and an outer cover (105) extending from said further bottom plate covering the control circuitry, the further bottom surface carrying an annular compressible gasket (104) for providing a weatherproof seal between the further bottom surface and the socket by rotational displacement of the outer body relative to the inner body. Also disclosed is an outdoor electrical device (10) comprising such a controller (100) and method of mounting such a controller (100) onto an outdoor electrical device (100).