Title:
SPEED AND DIRECTION CONTROL OF DC ELECTRIC MOTOR USING H-BRIDGE DRIVER

Authors:
Engr. Obi, Fortunatus Uche , Makinjuola, Peter and Asso. Prof. Atuchukwu John

Abstract:
The speed of a DC motor depends on the amount of current entering the armature coil and the direction of rotation depends on the direction of current flow. The essence of this research is to implement the most economic and reliable way of varying the speed and changing the direction of rotation of DC motor by electronic means rather than the usual contactor design and use of external resistor for the speed control which is not only bulky in design but also less effective. The methodology employed was the consideration of the fact that the amount of current flowing into the armature of the DC motor determines the speed of the motor and the H- bridge driver could be modeled with transistors for switching and for change of direction of current flow which automatically brings about the change in the rotation of the motor. A multifunctional NE556 timer which can be used to achieve to achieve a lot of electrical designs was used to generate the pulses. These various factors were considered in the design for the control of speed and direction of a DC motor. In this work, A 14 pin 556 DUAL Timer was used to generate the square wave (pulse). Under proper biasing, for simulation purpose, in the Proteus software, this IC is contained in two different pin configurations which are combined to get all the desired pins. Using a variable resistor to vary the duty cycle of the pulse width modulated signal, an H- Bridge driver and a two-pole switch were used to change the direction of the current flow through the armature of the DC motor. Various speeds at different duty cycles were recorded. The system was simulated using proteus software environment and various table generated were plotted using Microsoft Excel. The relationships between the duty cycle / voltage were proportional and that of duty cycle/ speed was also proportional from a certain point above 40% of the rated voltage.

Keywords:
H-Bridge Driver, Pulse Generation, Pulse Width Modulation, Timer Circuit, Duty Cycle

DOI: