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auto reset over under voltage cut out by using relay
#1

give the presentation/doc/ppt on the tittle
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#2
This over/under voltage cut-outwill save your costly electricaland electronic appliances fromthe adverse effects of very high andvery low mains voltages.The circuit features auto reset andutilises easily available components. Itmakes use of the comparators availableinside 555 timer ICs. Supply is tappedfrom different points of the power supplycircuit for relay and control circuitoperation to achieve reliability. The circuit utilises comparator 2for control while comparator 1 output(connected to reset pin R) is kept lowby shorting pins 5 and 6 of 555 IC. Thepositive input pin of comparator 2 isat 1/3rd of Vcc voltage. Thus as long asnegative input pin 2 is less positivethan 1/3 Vcc, comparator 2 output ishigh and the internal flip-flop is set,i.e. its Q output (pin 3) is high. Atthe same time pin 7 is in high impedancestate and LED connected to pin 7 is thereforeoff. The output(at pin 3)reverses (goeslow) when pin2 is taken morepositive than1/3 Vcc. At thesame time pin7 goes low (asQ output of internalflip-flopis high) andthe ED connectedto pin 7is lit. Both timers(IC1 andIC2) are configuredto function in the same fashion.Preset VR1 is adjusted for undervoltage (say 160 volts) cut-out by observingthat LED1 just lights up whenmains voltage is slightly greater than160V AC. At this setting the output atpin 3 of IC1 is low and transistor T1 isin cut-off state. As a result RESET pin4 of IC2 is held high since it is connectedto Vcc via 100 kilo-ohm resistor R4.Preset VR2 is adjusted for overvoltage (say 270V AC) cut-out by observingthat LED2 just extinguisheswhen the mains voltage is slightlyless than 270V AC. With RESETpin 4 of IC2 high, the output pin 3 isalso high. As a result transistor T2conducts and energises relay RL1,connecting load to power supply viaits N/O contacts. This is the situationas long as mains voltage is greaterthan 160V AC but less than 270V AC.When mains voltage goes beyond270V AC, it causes output pin 3 ofIC2 to go low and cut-off transistor T2and de-energise relay RL1, in spite ofRESET pin 4 still being high. Whenmains voltage goes below 160V AC,IC1’s pin 3 goes high and LED1 isextinguished. The high output at pin 3results in conduction of transistor T1.As a result collector of transistor T1as also RESET pin 4 of IC2 are pulledlow. Thus output of IC2 goes lowand transistor T2 does not conduct.As a result relay RL1 is de-energised,which causes load to be disconnectedfrom the supply. When mains voltageagain goes beyond 160V AC (butless than 270V AC) the relay againenergises to connect the load to powersupply.

Download full report
http://pecworld.zxqAssets/SOURCE/PDF_fun..._under.pdf
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#3
i need full operation about
over-under-voltage-cut-off-circuit-using-ic-555
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#4
to get information about the topic "auto reset over under voltage cut out by using relay" related topic refer the link bellow

https://easystudy.info/Thread-auto-reset...sing-relay
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#5
Auto Reset Over/Under Voltage cut-out


.docx   1Auto Reset Over.docx (Size: 1.3 MB / Downloads: 73)

INTRODUCTION

Our project is to develop a circuit which will protect our costly home appliances from over/under voltage cut-out (i.e voltage fluctuations) and prevent them from damage.
This document describes about the power supply unit which consists of transformer, bridge rectifier,78xx voltage regulator and these are responsible for converting AC voltage into constant DC voltage.
Also,the 555Timer plays an prominent role which is used for comparing the applied voltage with the constant 1/3 Vcc.To serve the purpose it consists of a comparator and RS-flipflop elements.We describe about the preset adjustment(i.e potentiometer )to make changes in the applied voltage to the 555Timer.LED is used to indicate the variations in accordance with the applied voltage.
Transistor is in on state when there is sufficient base voltage and the relay is energized and connects the load to the power supply.When there is no sufficient base voltage transistor is in off state which makes relay de-energised and disconnects the load from power supply.
Thus, in ideal condition(i.e greater than under voltage but less than over voltage) load is connected to the power supply.

WORKING PRINCIPLE

This over/under voltage cut-out will save your costly electrical and electronic appliances from the adverse effects of very high and very low mains voltages. The circuit features auto reset and utilises easily available components. It makes use of the comparators available inside 555 timer ICs. Supply is tapped from different points of the power supply circuit for relay and control circuit operation to achieve reliability. The circuit utilizes comparator 2 for control while comparator 1 output (connected to reset pin R) is kept low by shorting pins 5 and 6 of 555 IC. The positive input pin of comparator 2 is at 1/3rd of Vcc voltage. Thus as long as negative input pin 2 is less positive than 1/3 Vcc, comparator 2 output is high and the internal flip-flop is set, i.e. its Q output (pin 3) is high.
At the same time pin 7 is in high impedance state and LED connected to pin 7 is therefore off. The output (at pin 3) reverses (goes low) when pin 2 is taken more positive than 1/3 Vcc. At the same time pin 7 goes low (as Q output of internal flip-flop is high) and the LED connected to pin 7 is lit. Both timers (IC1 and IC2) are configured to function in the same fashion.
Preset VR1 is adjusted for under voltage (say 160 volts) cut-out by observing that LED1 just lights up when mains voltage is slightly greater than 160V AC. At this setting the output at pin 3 of IC1 is low and transistor T1 is in cut-off state. As a result RESET 4 of IC2 is held high since it is connected to Vcc via 100 kilo-ohm resistor R4.Preset VR2 is adjusted for over voltage (say 270V AC) cut-out by observing that LED2 just extinguishes. when the mains voltage is slightly less than 270V AC. With RESET pin 4 of IC2 high, the output pin 3 is also high. As a result transistor T2 conducts and energises relay RL1, connecting load to power supply via its N/O contacts. This is the situation as long as mains voltage is greater than 160V AC but less than 270V AC.

TRANSFORMER

A transformer is an electro static device which transfers electrical energy from one place to another without change in frequency, which is electrically isolated and magnetically coupled. It is a device that transfers electrical energy from one circuit to another through inductively coupled conductors—the transformer's coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core and thus a varying magnetic field through the secondary winding. This varying magnetic field induces a varying electromotive force (EMF), or "voltage", in the secondary winding. This effect is called inductive coupling.
If a load is connected to the secondary, current will flow in the secondary winding, and electrical energy will be transferred from the primary circuit through the transformer to the load.

BRIDGE RECTIFIER

A diode bridge is an arrangement of four (or more) diodes in a bridge circuit configuration that provides the same polarity of output for either polarity of input. When used in its most common application, for conversion of an alternating current (AC) input into direct current a (DC) output, it is known as a bridge rectifier. A bridge rectifier provides full-wave rectification from a two-wire AC input, resulting in lower cost and weight as compared to a rectifier with a 3-wire input from a transformer with a center-tapped secondary winding.
When four diodes are connected as shown in figure2.2, the circuit is called a BRIDGE RECTIFIER. The input to the circuit is applied to the diagonally opposite corners of the network, and the output is taken from the remaining two corners.

RELAYS

A relay is an electrical switch that opens and closes under the control of another electrical circuit. In the original form, the switch is operated by electromagnet to open or close one or many sets of contact, because of the relay is able to control an output circuit higher power than the input circuit. It can be considered to be, in a broad sense, a form of an electrical amplifier.
An electrical current through conductor will produce a magnetic field at right angles to the direction of electron flow. If that conductor is wrapped into a coil shape, the magnetic field produced will be oriented along the length of the coil. The greater the current, the greater the strength of the magnetic field, all other factor being equal. Relays are extremely useful when we have a need to control a large amount of current and/or voltage with small electrical signal. The relay coil which produces the magnetic field may only consume fractions watt of power, while the contacts closed or opened by that magnetic field may be able to conduct hundreds of times that amount of power to a load. In effect, a relay acts as a binary (on or off) amplifier. Just as with transistors, the relays ability to control one electrical signal with another misapplication in the construction of logic functions. For now, the relay’s “amplifying” ability will be explored.
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