Abstract: Automatic control device for the slats of a venetian blind which responds to ambient radiation and which includes at least one reversible electric motor connected to rotate the slats between open and closed conditions, a sensing device indicating the level of ambient radiation of light and/or heat, two switches connected to the motor to determine its direction of rotation, an electrical control circuit responding to the sensing device to operate either one of the two switches, and limit switches to halt the motor in predetermined condition of the slats.