Abstract : With the continuous development of society, automobiles have gradually become an important means of transportation in modern society. Vehicle lights are essential for driving safety, serving not only illumination but also warning functions such as turning and braking. Turn signals and warning lights are indicators of the vehicle's direction of movement and vehicle status, directly impacting safety. Therefore, the design of a microcontroller-based automotive turn signal controller has always been a crucial area in automotive electronics design. This design uses a microcontroller to control the turn signals. Microcontrollers offer high reliability, precise timing, and can withstand certain temperature variations, remaining largely unaffected by the surrounding environment. This not only achieves precise control but also significantly extends the vehicle's lifespan. This paper details the hardware and software design processes of the automotive turn signal controller, including the main hardware circuits for power drive and fault detection, and the software flowchart. Keywords : Automotive electronics; Microcontroller; Power drive; Fault detection 1. Introduction 1.1 Introduction Vehicle lights are essential for driving safety, serving not only illumination but also warning functions such as turning, meeting oncoming traffic, and braking for pedestrians and other vehicles. The control of automotive turn signals is one such example. Turn signals and warning lights in automobiles indicate the direction of a vehicle's movement and its status, directly impacting vehicle safety. Therefore, microcontroller-based turn signal controllers have always been a crucial area in automotive electronic design. (Full text available for download: Microcontroller-based automotive turn signal controller design)