Abstract :

The project is aimed to design a system to control the speed of an AC motor using an efficient method of PWM technique, using TRIAC which will be very much useful in many applications.

 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.

Here we use two input switches to obtain different speeds, the speed of AC motor can be varied rapidly through TRIAC. The main advantage of using a TRIAC to vary the speed of an AC motor is the TRIAC as it reduces the energy flow to the motor and TRIAC works very well for alternating currents.

A buzzer is provided for audio indication of AC motor speed variation. Whenever the speed is increased / decreased, the system acknowledges by a short beep. This buzzer is driven by transistor driver circuit. 16X2 LCD is connected to display the speed level of the motor. 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

AC motor                   

TRIAC                         :           BT136

Buzzer

Switches

Power supply

Transformer                :           12V step down 

Filter                           :           1000uf/25V

Voltage Regulator      :           7805

SOFTWARE:

Keil micro vision

Proteus

UC flash

APPLICATIONS:

• AC motor drives
• Spinning mills

Industrial applications