The document describes an AC power control system using pulse width modulation. It uses a microcontroller and TRIAC to adjust the firing angle and control the power delivered to a load. The user enters a desired percentage of power on a keypad, which is then displayed on an LCD screen. The microcontroller automatically adjusts the TRIAC firing angle to maintain the load power at the set level. The system steps down household AC voltage to 12V AC, rectifies it to DC, filters it, and regulates it to the +5V needed to power the microcontroller and other components.

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AC power control using efficient PWM method
ABSTRACT
The principle of firing angle control of thyristors, one can control the ac power. A display unit
displays the full power or any percentage and one can enter the desired percentage to reduce the
power to the load.
The firing angle would be automatically adjusted to maintain the load power. The project uses a
lamp such that the entered power matches the required one. The above operation is carried out by
using a TRIACinseries withtheACload.(Optionally twono’s of SCRsconnectedinbackto
back can also be used)
It uses microcontroller from 8051 family. The input is given to the Microcontroller using a
keypad and ZVS is given as reference. A 16X2 LCD is used for display purpose.
The power supply consists of a step down transformer 230/12V, which steps down the voltage to
12V AC. This is converted to DC using a Bridge rectifier. The ripples are removed using a
capacitive filter and it is then regulated to +5V using a voltage regulator 7805 which is required
for the operation of the microcontroller and other components.