Speed Control Of DC Motor Using MOSFET

Ahmad Mursyid, Ramli (2015) Speed Control Of DC Motor Using MOSFET. Project Report. UTeM, Melaka, Malaysia. (Submitted)

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Abstract

The purpose of this project is to control the speed of DC motor using MOSFET (Metal Oxide Semiconductor Field Effect Transistor), to explore its use and to suggest other areas of application. DC (Direct Current) motors have been widely used in many industrial application due to its precise and continuous control characteristics. In theory, the DC motor speed is directly proportional to the supply voltage, so if the voltage is reduce from 12 to 6 volts the speed decrease by half. In practice, the supply voltage cannot be change all the time to control the motor speed so the MOSFET as the switching device will tum supply ON and OFF, where switching is done so fast that the motor only notices average voltage effect and not the switching operation. This project consists of PWM (Pulse Width Modulation) circuit to control voltage output at the motor and used MOSFET as the switching device. PWM circuit based on timer NE555 as the heart of the circuit is connected as astable multivibrator whose duty cycle can be varied from 0-100% by adjusting the lOOk variable resistor. The output of NE555 is connected to the gate of MOSFET that will drives the motor at demanded speed. The higher the value of duty cycle the higher the voltage across the motor resulting in an increase in motor speed. This control circuit is very cheap and easy to implement and manage to control speed of DC motor smoothly. The application of this project is very useful in industrial nowadays depending on the type of DC motor used such DC shunt and DC series motor. For the DC shunt, it can be use in train and automotive traction application while DC series it can be use in elevators application. It is possible to improve overall performance speed control of DC motor in future work by using microcontroller or micro-processor to gives pulse to the switching device so that the speed variation remain constant. Besides that, IGBT can be use instead ofMOSFET as the switching device so we can drive higher voltage application such as 220 volts DC motor at higher power requirement.

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