OVER VOLTAGE INDICATOR ALARM 2

Second part of project

For complete project go to

http://electronicsforengineers.blogspot.com/search/label/OVER%20VOLTAGE%20INDICATOR%20ALARM%20PROJECT

WORKING

The electric power is almost exclusively generated , transmitted and distributed in the form of ac because of economic consideration,but for operation of this device , dc supply is required.in this device for obtaining dc supply ,bridge rectifier is used.

For both positive and negative swings of the transformer, there is a forward path through the diode bridge. Both conduction paths cause current to flow in the same direction through the load resistor, accomplishing full-wave rectification. While one set of diodes is forward biased,the other is reversed baised and effectively eliminated from the circuit.

The simplest voltage regulator uses just a resistor and a zener diode. In the circuit diagram you can see a resistor (R1) and a zener diode (CR1) connected across a power supply. The resistor is connected to the positive (+ve) supply wire and the zener diode anode is connected to the zero volt (ground) wire. At the junction of these two components the voltage is clamped by the zener diode to its specified voltage .This method is OK for low currents but the resistor becomes too hot if larger currents are needed. To cope with this problem we can add the NPN transistor. Now the transistor passes the current required at the output.

The limiting factors are the amount of heat generated by R1, CR1 and Q1 since all excess voltage must be shed as heat. Let the supply voltage increases which will cause the output voltage Eout to increase. An increase in output voltage Vout will result in decrease of V-be (base- emitter voltage) will reduce the level of conduction. This will lead to increase in collector- emitter resistance of transistor causing an increase in collector to emitter voltage as a result the output voltage will be reduced, thus output voltage will remain constant.As the preset voltage is given to the zener diode then this voltage(Eout) is regulated and remains constant by zener diode. As the AC voltage increases, it increases the rectified voltage. Thus this new voltage (over voltage) differs from Vz. Net difference of these two voltages is given to relay which thus beeps the buzzer and therefore can protect our appliances from being damaged by over-voltage.

RESULTS

as this instrument beeps on over voltage ,so when the preset voltage is lesser then 220 volts ,and it is connected to a home ac supply ,then it beeps ,which indicates that the input voltage is greater than the preset voltage. we can set any value of preset voltage ,thus can detect the over voltage corresponding to preset voltage by sound of beep.

COMPARISON BETWEEN THE PRACTICAL AND THEORETICAL LAYOUT

Theoretically we have assume voltage (Eout) across voltage regulator at constant, means which does not vary during whole operation. But practically it varies with change in temperature due to change in transistor currents.

ADVANTAGES

· It has very less cost.

· Its working range is high.

· As in the voltage regulator , resistor is replaced by transistor so it can work at high currents.

DISADVANTAGES

Zener breakdown voltage andtransistor voltage Vbe depends on temperature , thus regulated voltage Vout varies.

APPLICATIONS

· It can be used as a voltage regulator circuit.

· It is used in electrical appliances to protect from high voltages.

· It can be used as warning alarm in industries.