Abstract—Automatic controls play an ever-increasing role in a human way of life. Automatic control is vast technological area whose central aim is to develop control strategies that improve performance when they applied to a system. the distinct characteristic of automatic control is that it reduces the human operator. One such gadget is the fan. The fans are generally available with speed control, depending on the requirement the speed is set. Usually, when the temperature is high the fan set at high speed and at lower temperatures the fan is operated with lower speed. This is done manually using human. In this paper, an automatic control solution is suggested to control the fan speed. A circuit with LM35DZ temperature sensor, PIC16F877A microcontroller, brush less DC motor and few of electronic components is designed and implemented to control the fan speed automatically. As an additional feature LCD is used to present the temperature and the fan speed. Finally, the designed system circuit is tested in many times and performed very well. Keywords— Fan speed, microcontroller, LM35DZ, BLDC motor and circuit design. I. INTRODUCTION LECTRIC fan is one of the most popular electrical devices due to its cost effectiveness and low power consumption advantages. It is a common circuit and widely used in many applications. It is also one of the most sensible solutions to offer a comfortable and energy efficient. In fact, the fan has been long used and still available in the market. Nowadays, the demand for accurate temperature control and air freshening control has conquered many of industrial domains such as process heat, automotive, industrial places or office buildings where the air is cooled in order to maintain a comfortable environment for its occupants. One of the most important concerns involved in heat area consist in the desired temperature achievement and consumption optimization [1]. Fan can be controlled manually by pressing on the switch button. where in this method, any change in the temperature will not give any change in the fan speed. except the usage change the speed of the fan which is manually. So, an automatic temperature control system technology is needed for the controlling purpose in the fan speed according to the temperature changes. Mustafa Saad is with the College of Electronic Technology/ Bani-walid. Libya (e-mail: mustafasaad9@yahoo.com). Hossam Abdalghader is with the College of Electronic Technology/ Bani- walid. Libya. Muammer Mohamed is with the College of Electronic Technology/ Bani- walid. Libya. Many researches focusing on automatic temperature control system application in different fields will gain the benefits. For examples, an automatic temperature controller for multi element array hyperthermia systems [2], multi-loop automatic temperature control system design for fluid dynamics [3], design of automatic temperature- control circuit module in tunnel microwave heating system [4], the automatic temperature system with Fuzzy self-adaptive Proportional- Integral-Derivative (PID) control in semiconductor laser [5]. This paper will show how PIC16F877A microcontrollers can be used and applied in a real-world application. One practical use is to integrate a microcontroller in a temperature control system that can be used for automatically controlling a room temperature. II. 1BFAN SPEED CONTROL SYSTEM COMPONENTS The microcontroller PIC16F877A, is the heart of the system. It accepts inputs from the temperature sensor, LM35 which allows for the measurement of the current room temperature, then the controller will give the action to maintain the required fan speed. LCD is used to display the fan speed and room temperature. All of these can be summarized in a diagram as shown in Fig. 1. Fig. 1 Block diagram of fan speed control system A. 5BPIC16F877A Microcontroller A microcontroller is a computer control system on a single chip. It has many electronic circuits built into it, which can decode written instructions and convert them to electrical signals. The microcontroller will then step through these instructions and execute them one by one. As an example of this a microcontroller could be used to control the fan speed according to the temperature of the room. Microcontrollers are now changing electronic designs. Instead of hard wiring a number of logic gates together to perform some function we now use instructions to wire the gates electronically. The list of these instructions given to the microcontroller is called a program. There are different types of microcontroller, this research focus only on the PIC16F877A Microcontroller Automatic Fan Speed Control System Using Microcontroller Mustafa Saad, Hossam Abdoalgader, and Muammer Mohamed E 6th Int'l Conference on Electrical, Electronics & Civil Engineering (ICEECE'2014) Nov. 27-28, 2014 Cape Town (South Africa) 86