Excessive exposure to the sun brings harm such as skin cancer, premature aging, burns, among others. However, correct sun exposure brings benefits that reflect on the quality of muscles, bones and organs, in addition to promoting the synthesis of vitamin D, a vitamin related to the functioning of the brain, which may be related to depressive disorders. The present study aims to create a mathematical calculation that expresses the time each individual needs to be exposed to the sun without risking health, as well as to create an accessory (physical and digital part) that performs the calculation and counts the time of sun exposure performed. . The work methodology was based on a literature review on vitamin D synthesis and sun exposure, to list which variables interfere in vitamin D synthesis and the creation of an accessory that will calculate and account for the correct and performed time of sun exposure. To produce the accessory, the GoGo board and its light sensor will be used together with the Raspberry Pi 3 board. An application will be created, connected to the programming boards from the cell phone with it, through the Android Studio software using the language of Java programming. In order for the light sensor to differentiate sunlight from artificial ones, tests will be carried out with different filters (fabrics with different threads). As partial results, variables such as amount of exposed skin, daily ultraviolet rays index and age are the main factors for vitamin D synthesis, and these factors are included in the calculation. The filter made from the fabric of fine threads was the one that best assisted the sensor in distinguishing sunlight from artificial light. The programming on the Gogo Code website is complete and the app is under construction. Over time, society has been combining sun exposure solely with possible skin problems that excessive exposure can cause, however, problems related to low exposure are increasingly affecting a greater number of people, such as depression and bone problems. We conclude that knowledge of the sun exposure time is necessary, both to avoid psychological and physical illnesses.