a full wave rectifier.final

7/31/2019 A Full Wave Rectifier.final

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INTRODUCTIONA full wave rectifier is a device which is usedto rectify all the alternating currentcomponents in an alternating supply andmake it purely a direct current. The twoalternating halves of an alternation current arerectified in a full wave rectifier which is anadvantage over a half wave rectifier. Most ofelectronic devices cannot withstand very highvoltage or alternating current due to its intensehigh power. The use of batteries in alldevices is not practical as their replacement anddurability is a huge problem as the device has tobe dismantled each time for such a replacement.So these rectifiers are used in most of theelectronic devices like TVs, Radios, Chargers and

Lightings etc.

There are several stages in a rectifier. Basedon their rectification they are classified intotwo:-The single staged & multi staged. In the multistaged rectifiers, more than two diodes are

used and these are used in the above-mentioneddevices. The singled staged rectifier has only 2diodes, the one we are to discuss in this project.

The multi diode rectifier has only 2 diodes, theone we are to discuss in this project. Themulti diode rectifiers has an efficiency ~ 94.6%while that of the single is only 81.2%.


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THEORY INVOLVED:-

The input transformer steps down the A.C

mains from 220V to 9V between the centretap and either of the two ends of thesecondary winding. The transformer hasa capability of delivering a currentOf 500mA.

The 9V A.C appear ing across the second

ary is the RMS value of the waveform andpeak value would be .4826 volts=x

The diodes rectify the A.C waveform appearingacross the secondary with the help of alternateforward and reverse biasing. The capacitor furtherfilters 99% of the resident components and this isleft to pass through the resistance and emerges

out as +ve and ve. The bulb connected verifiesthe output as it works on Direct Current and ifused on an Alternating Current, the fluctuationwill burn out the bulb.

MATERIALS REQUIRED IN THE CONSTRUCTION :-

Connecting wires, a plug, single lead wire -2m, ca rd board , a t rans fo rmer , af i l t e r , a r e s i s t o r ( 1 K ) ,P - N j u nc t i o n d i o d e s , Insulation tape,Blades, soldering wax, soldering lead and solderingiron.


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Details of the materials used:-

i) Connecting Wires and a Plug.

ii) A normal insulated copper wire able towithstand 220-250V is required.

iii) Single Lead wire-Thin wire with one singlestrand of copper well insulated and able toconduct a current of 1 ampere or a D.C current

efficiently.

iv) A card Board.

v) Soldering wax & lead.(The wires are to besoldered firmly to make the connection tight sofor this a thin lead wire is required to affix the

connections and wax to make the lead to holdon when soldered).

vi) L.E.D It is called light emitting diode(L.E.D).It is used to test the output voltage whether Director not. It glows on as we get a rectified directcurrent as an output.

v i i ) S t ep Down T r ans f o rmer -A 9- 0 -9 t r an sf or me r Transformer is adevice used to change the voltage of analternating current. The transformer whichconverts low voltage to high voltage is called astep up transformer whereas the one which

converts high voltage to low voltagei s c a l l e d a s t e p d o w n t r a n s f o r m e r .


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I t c o ns i s t s o f laminated core consisting of twocoils, a primary & a secondary coil. In a step upthe number of turns in the secondary is

greater that of the primary and the reverse in astep down transformer. Here we use a stepdown transformer which steps down 220V to 9Vbetween the secondary terminals and the centretap.

viii) Filter - It is used to filter the the ripples,

which is present in the output of the diode to anextent. Here we have used 1000MFD25V filter.

ix) A Resistor- A resistor is electroniccomponents whose resistance value tells usabout the opposition it offers to the flow of electriccurrent.Resistance is measured in ohms ().We determinethe value of a resistor using the colour coding onthe rings of the resistor.

x)P-N junction Diode :-When one side of a semiconductor crystal(Germanium or silicon) is doped withacceptor impurity atoms and the others ide with donor i m p u r i t y a t o m s a P -N j u n c t i o ni s f o r m e d . I t i s a l s o c a l l e dS e miconductor or crystal diode. When diffusion ofthe two regions occur a resultant potentia lbarrier is created between the twosides due to migration of electrons and holes.


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When the diode is connected with P side to positiveterminal of a battery & N side to ve terminal it issaid to be forward biased & reverse biased when

reversed. In forward biasing the appliedpositive potential repels the holes and turnsa current is made to flow overcoming theinternal potential Barrier. While in reversebiasing the ve electrons 1st attract the holes andwiden the Barrier and then only the repulsionbetween

inner electrons occur and current flows. Sotheoretically no current flowsthrough due tothe widening of the Potential barrier but practicallya very small current does flows through. Differenttypes of diodes are present :1.Zener diode, 2.P-N junction diode, 3.Led ,4.Lad, 5.Solar Cell,

Here we use a P-N junction diode. The greyishring indicated the N side and the Black colourationthe P side.

x ii )Final ly , smal l equipments such as asoldering iron to solder the lead, Blades,holders, insulation tapes to insulate the

wire from shocking and sand paperto rub theoxidized wire ends are used.


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CIRCUIT DIAGRAM :-

Connection details :-

Connections are done as in the circuit. TheA.C. supply is given to bot h the inpu t wiresof the transformer and the two ends o f the secondary coil is given to the P side of thetwo diodes and the N side of the diodes aretwined and then connected to the

one end of the capacitor and the other end


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to the centre tap lead and to the resistor.Further, the other end of Filter with thediode connect ion is connected to the other

end of the resistor. Connect 2 leads on boththe ends of the resistor to measure the output andthis is connected to the +ve & -ve terminals of thebulb

WORKING :-

First when the A.C. is supplied to thetransformer, it steps down the 220V mainsupply to 9 volts. It has a capability of delivering aCurrent Of 500mA. The 9 volts A.C.appearing across the secondary is the RMSvalue and the peak value is 26 or 8.4 volts.

During the 1st

half cycle of the A.C. input DiodeD1 is forward biased and a current flows in thecircuit in the direction S1D1ABEOS1.During this time diode D2 is reverse biased.So it does not conduct any electric current.During the next half cycle the diode D2 is forwardand D1 is reversed. Hence D2 conducts current

in the direction S2D2ABEOS2and D1 does notconduct any current. In subsequent half cycles ofthe A.C current the above processes arerepeated. In both the half cycles,it is clear thatcurrent flows through the resistor in only onedirection ABE. Even though the voltage across RLis unidirectional it will still contain a few A.C

components. This is filtered and madesmooth using a capacitor filter, which filters


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99% of the A.C current. A resistor is thenused to adjust the output vo l tage. Wecan then test the o/p Voltage using a multi-

meter.Efficiency of Rectification - = D.C power output.

Total A.C input power For a half wave rectifier, ~0.406 = 40.6 %For a full wave rectifier, the oneused here is ~ 0.812 = 81.2 %By the use of morenumber of diodes the efficiency can be increase toa maximum of 94.6%. Here we only use 2 diodes.

The use of multiple capacitors also nearly filters allA.C components from the supply and resistanceis adjusted for the required output. As thisis a simple circuit, only one capacitor and aresistance is being used. But there will beslight factor of A.C. current still left in theoutput but it is negligible.


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WAVEFORMS :-

RESULT :- A full Wave rectifier is constructed & a

rectified d.c voltage is obtained as a output.


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BIBILIOGRAPHY:-

1 ) E l e c t r o n i c p r o j e c t s f o r

b e g i n n e r s b y A . K M a n i n i

2 ) S c r i b d . c o m

a full wave rectifier.final

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