Abstract: Control apparatus 1 for photovoltaic modules 3 which can be connected to one or more photovoltaic modules 3. The control apparatus is able to check for the proper working of the solar modules, and also to collect all electrical data like voltage, current, power, energy in order to calculate also the efficiency of the plant. Up to 16 modules can be used (including a master controller, temperature measurement modules, output modules, input modules) and they are interconnected by using a bus system which does not require any wire. A base level consist of one master controller module and one or more input modules. An extended system includes also additional modules, like measurement of temperatures or relay outputs.