Abstract :
The aim of this project is providing efficient and simple method to control speed of DC motor using pulse width modulation.
Here in this project we use the PWM technique to control the speed of the motor. The average voltage supplied to the load should be varied to obtain different speeds, which can be achieved by setting an appropriate duty cycle. The term duty cycle describes the proportion of ‘ON’ time to the regular interval or ‘period’ of time. A low duty cycle corresponds to low power, because the power is OFF for most of the time. Duty cycle is expressed in percent, 100% being fully ON. The main advantage of PWM is that power loss in the switching devices is very low. When a switch is off there is practically no current, and when it is on, there is almost no voltage drop across the switch. Power loss, being the product of voltage and current, is thus in both cases close to zero. PWM also works well with digital controls, which, because of their ON/OFF nature, can easily set the needed duty cycle.
Two push-to-on switches are provided for increasing / decreasing the speed of the motor. 16X2 LCD is connected to display the speed level of the motor.
A buzzer is provided for audio indication of DC motor speed variation and change in direction. Whenever the speed is increased / decreased, the system acknowledges by a short beep. This buzzer is driven by transistor driver circuit.
This project uses regulated 5V, 500mA power supply. 7805 three terminal voltage regulator is used for voltage regulation. Full wave bridge rectifier is used to rectify the ac output of secondary of 230/12V step down transformer.
TECHNICAL SPECIFICATIONS:
HARDWARE:
Micro controller : AT89x series
Crystal : 11.0592 MHz
LCD : HD44780
DC motor : 100 R.P.M gear motor
Driver IC : ULN 2003
Switches
Power supply
Transformer : 12V step down
Filter : 1000uf/25V
Voltage Regulator : 7805
SOFTWARE:
Keil micro vision
Proteus
UC flash
APPLICATIONS:
- Consumer electronics
- Office machines
- Toys
- Motor driven gadgets