Over Current Relay (OCR) is a protection relay used to detect and cut off electric current when there is excess current (fault current). The definite time type OCR has constant trip time characteristics, regardless of the magnitude of the fault current. OCR is widely used in electric power systems to protect equipment from damage due to fault currents. This final report discusses the design of Arduino Uno-based definite time OCR with the use of PZEM sensor components, I2C LCD, relay module, and Arduino Uno. This system is designed to be able to measure the load current, display the current value on the LCD, and cut off the current when the load current exceeds the specified setting value.