ABSTRACT

The control of irregular voltage supply with fluctuation so as to become stable is carried out using this voltage stabilizer. Most stabilizers make use of mechanical relays which have a slow switching period. This stabilizer is designed and constructed in a way that it makes use of silicon controlled rectifier which helps in reducing instability in the system and as well as having an increased switching period. This project demonstrates the use of Microcontrollers in power devices. The Micocontroller allows for accurate monitoring of the mains voltage and display on a seven-segment display. Depending on the voltage level of the mains, the Microcontroller triggers the appropriate TRIAC connected to an auto-transformer in order to stabilize the output voltage fed to the loads or appliances.

MODE OF OPERATION

From the circuit diagram, The Mains voltage is stepped down to a very low voltage of around 15V. This voltage is rectified by a bridge rectifier. This rectified voltage in its form is high in ripple content. It is fed to an input pin of the Micrcontroller for zero crossing detection. Zero crossing detection is necessary in applications involving a TRIAC as this allows us accurately trigger the TRIAC at a required AC phase angle. The rectified voltage also passes through a diode before it is filtered by some electrolytic capacitors. The diode ensures that the filtered voltage does not reach the voltage linked to the Microcontroller input for zero-crossing detection. After filtration, a fixed voltage regulator regulates the voltage to a clean and stable 5v used to power the rest of the circuit. The Microcontroller drives the seven segment displays using the principles of multiplexing. Driving of the TRIACS is achieved through an integrated circuit chip MOC3021. This chip provides the required isolation required when driving AC devices from logic devices like the Microcontroller. The auto-transformer has been designed with tappings that ensure that for mains voltage levels withing the regulation range, an output of 220v +- 5% is provided to the loads.