In this paper an automation system for controlling industrial and building plant using voice commands, spoken in natural language, will be described. This system uses cloud computing services to process spoken sentences and to identify the user's desired request, i.e. it converts voice commands in electronic commands. It also presents a software and hardware architecture that allows the system to be connected to several different Automation Plants, enabling this voice control feature for a larger number of devices without requiring the development of a new control system. Thus, the proposed structure is presented and later it is shown the first prototype that uses this system.