## 5 Conclusions  
In this paper, a UVB LED general lighting system based on a UV exposure calculation algorithm that allows the user to meet the required UV dose per day is proposed. The proposed system was composed of an IoT UV measurement device that measures the UVI of outdoor natural light, a smartphone that provides information related to UV and vitamin D, a control function of UVB LED lighting, and UVB LED general lighting that provides a safe UVB dose to the user indoors. First, the IoT UV measuring device calculated the intensity of the _EUVout_ by measuring the UVI outdoors in real time, and then sending the result to the smartphone. The smartphone then calculated the cumulative UV dose of the user who was irradiated outdoors based on the EUV value received from the IoT UV measuring device, comparing the cumulative _DUV_ dose and the _RVULD_ for the user for one day. If the cumulative UV dose outdoors did not reach the _RVULD_, then the indoor UVB LED lighting provide the deficient UV dose. In this case, the _RVULD_ by individual was calculated by reflecting individual characteristics such as age, skin type, and exposed area, and then, based on the outdoor UV exposure amount, the control time of the indoor UVB LED lighting was calculated. After that, the control information of the lighting was constituted as packets and sent to the UVB LED lighting, thereby realizing the function of providing the UV dose through the indoor UVB LED lighting. At this time, UVB LED general lighting was developed by applying four UVB LED light sources of 20 mW radiant flux and a current of 201 mA. In order to evaluate the performance of the proposed lighting system, a comparative experiment using a spectrometer was performed. Experimental results of natural light UVI showed the MAPE could be decreased to about 11.1% compared with the spectrometer. In addition, in the experiments conducted in the lighting box to which external lighting was blocked, UVB LED lighting was estimated to be 0.9969 and 1.4885 mW/m\({}^{2}\) for AUV and NUV, respectively, which satisfied the safest level (exempt) when it was evaluated with the risk to the ultraviolet region of the photobiological safety standard. In the simulation for confirming the operation performance of the proposed lighting system, the users of all age groups with skin types 2 and 3 could be provided the daily required UV dose when the outdoor activities are performed for 0-30 min on a day when the average UVI is 3.  
In the future, additional experiments for service in consideration of multiple users in the same space and for operation in different regions and climatic conditions are needed for the commercialization of the proposed lighting. In addition, for users who want to meet the appropriate UV exposure for a short period of time, additional research is needed to develop UVB LED special lighting for therapeutic purposes other than the general lighting type and to develop a lighting system linking to UVB LEDspecial lighting. Furthermore, animal experiments are planned to check the supporting function of vitamin D synthesis through the proposed lighting.  
Methodology and writing of the original draft: D.-H.P. Investigation and writing of the original draft: S.-T.O. Conceptualization and supervision: J.-H.L.  
This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (No. 2017R1A2B2005601). The research was supported by the International Science and Business Belt Program through the Ministry of Science and ICT (2015-DD-RD-0068-04).  
The authors declare no conflict of interest.