INTERNATIONAL ISLAMIC UNIVERSITY ISLAMABAD

SUBJECT

LAB REPORT TO MAKE FULL WAVE BRIDGE RECTIFIER USING FOUR DIODE

SUBMITTED TO

SIR JAVED

SUBMITTED BY

SEHRISH BASHIR

SEMESTER

MSC-I

DATE: 11 MAY 2014

TO MAKE A FULL WAVE BRIDGE RECTIFIER USING FOUR DIODE

COMBINATION

APPARATUS:- Diodes (1N400) Transformer 470(Micro farad) 16V polar capacitor(one side polarized) RL(1 kilo ohm) Connecting wires Cathode ray oscilloscope(CRO) Digital millimeter(DMM) Cutter Bread board/ trainer Narrow plas

OBJECTIVE:- To learn and understand the full wave rectification and filtering the pulsating DC. One method is to improve on this is to use every half cycle of the input voltage instead of other half cycle. The circuit which allow us to do this is called full wave bridge rectifier.

THEORY OF EXPERIMENT:- The full wave bridge rectifier uses four diodes individual rectifying connected in a closed loop “bridge” configuration to produce the desired output. The main advantage of this bridge circuit is that it does not require a special center tapped transformer, thereby reducing its size and cost. The single secondary winding is connected to one side of the diode bridge network and the load to the other side as shown below:

PROCEDURE:-¥ Make a neat and clean circuit on the bread board. TO MAKE A

FULL WAVE BRIDGE RECTIFIER USING FOUR DIODES.

¥ The circuit has a step down transformer. ¥ Now use the DMM to confirm that root mean square voltage is

6V.¥ Diode testing by using DMM to the one side makes it to conduct

now invert the leads then it will not conduct.¥ The four diodes labelled D1 to D2 are arranged in “series pairs”

with only two diodes conducting current during each half cycle.¥ During the positive half cycle of the supply, diodes D1 and D2

conduct in series while diodes D3 and D4 are reverse biased and the current flows through the load.

¥ The one end of the secondary becomes negative and the other end becomes positive during negative half cycle of secondary voltage.

¥ During the negative half cycle of the supply, diodes D3 and D4 conduct in series, but diodes D1 and D2 switch “OFF” as they are now reverse biased.

¥ The current flowing through the load is the same direction as before.

¥ As the current flowing is unidirectional, so the voltage developed is also a unidirectional.

FULL WAVE RECTIFIER WITH SMOOTHING CAPACITOR:- The rectified output of full wave rectifier is not smooth DC. It has some ripples. By using different types of filters these ripples can be removed.

The smoothing capacitor converts the full wave rippled output of the rectifier into the smooth D.C output voltage. Generally for D.C power supply circuits the smoothing capacitor is an Aluminum Electrolytic type that has the capacitance value of 100 Micro Farad or more with repeated D.C voltage pulses from the rectifier charging up the capacitor to peak voltage.

However, there are two important parameters to consider when choosing a suitable smoothing capacitor and these are its Working Voltage, which must be higher than the no-load output value of the

rectifier and its Capacitance Value, which determines the amount of ripple that will appear superimposed on top of the D.C voltage.

Too low a capacitance value and the capacitor has little effect on the output waveform. But if the smoothing capacitor is sufficiently large enough (parallel capacitors can be used) and the load current is not too large, the output voltage will be almost as smooth as pure D.C. As a general rule of thumb, we are looking to have a ripple voltage of less than 100mV peak to peak.

The maximum ripple voltage present for a Full Wave Rectifier circuit is not only determined by the value of smoothing capacitor but by the frequency and load current, and is calculated as:

V(ripple) = I(load)/f*C, Volts

Where: I is the DC load current in amps, f is the frequency of the ripple or twice the input frequency in Hertz, and C is the capacitance in Farads.

PRECAUTIONS:-1. All connections should be verified before clicking run button.2. The range of the resistance should be in range of kilo ohm.3. The best performance is achieved with in the frequency of 50HZ