The present work aims to present the operation mode, both theoretically and practically, of an automatic monitoring and control system of the water circuit in a system with thermosolar panels, as well as the main advantages that it constitutes as an automated system of this kind, both in industry and in the everyday life of each of us.

The assembly formed by a pn semiconductor homojunction together with the metal contacts necessary to connect the junction to the external circuit is a diode. The article aims to analysed and determine the internal parameters of a pn homojunction using the Octave software.