2B-OVER VOLTAGE PROTECTOR
THE SPECIALITIES OF PROJECT
This project cuts the main supply to the equipment in case supply voltage exceeds the limit. This avoids burning of equipment from main supply. This project is made keeping in view of the above problem.
TECHNICAL DESCRIPTION AND WORKING OF THE PROJECT
This project has been developed and tested by our readers and sent to the “T.V.Engineers Technical lab” for publication in the book. The spare parts and PCB of the projects published in the series of our book publication or available in the market. The information of project code is given in the first and last page of the books.
The working of the project depends upon the operational amplifier 741 and IC7812. 5V DC reference voltage are given to the Pin No.1 of IC741. The supply voltage is connected to the Non-Inverting Pin No.3 of IC741. Its adjustment is done with the preset VR1(10k). When voltage on Pin No.3 is less than 5.1V then transistor T1 does not contact. The relay RL1. is put on by the transistor T2. The load is connected to the relay. When main supply is more then 240V then transistor T1 conducts and transistor T2 stops conducting. It puts the relay in OFF position. The load connected to the relay is protected.
The preset VR2 is connected to adjust the voltage to the transistor T1 BC547. The circuit is given a regulated supply through IC2 7812. The unregulated voltage are obtained from the step down transformer and bridge rectifier.
PRECAUTIONS WHILE MAKING THE PROJECT
- Check all components as per the list.
- While connecting transformer take care of primary and secondary winding.
- Check the cathode and anode terminals of the diode.
- Check positive and negative of the capacitor C1 & C2.
Take care of base, collector & emitter of the transistor.