In the making of this assignment more complex entities were processed. The construction of an automatic light intensity control assembly is described in detail. The automatic control method performed by the PID controller is explained, as is the manual control method. All signals were measured in a laboratory with an oscilloscope and displayed with images taken directly from the oscilloscope. Two PCBs were designed and explained in this work, with the associated schemes. All types of controls used in the automatic light intensity control system and the components necessary for its operation are described. The whole assembly is placed in the housing and the pictures show the exterior of the finished assembly as well as its interior. The main controller, that is, the main microcontroller, is the Arduino, whose role is automatic control, which is programmed in the Arduino IDE environment. The program code is explained through the flowchart. Critical parts of the program code are also provided through code snippets and related explanations for ease of understanding. Finally, all the results are analysed and explained, and a conclusion is drawn.