Electronics Laboratory Activity: Half-wave Rectification

8/11/2019 Electronics Laboratory Activity: Half-wave Rectification

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LAB ACTIVITY 2:

HALF-WAVE RECTIFIER

I.Objectives

The objectives of this activity are to know what a rectifier is and to study and analyse theprocess of how a half-wave rectifier works.

II.Basic Concepts

Rectification is the process of turning an AC input into DC usually with the help of a diode.

During this process, the diode is referred to as a rectifier. (Boylestad, Nashelsky, 1998)

The Alternating Current

The alternating current (AC) is a stream of charges that periodically changes directionwhereas the direct current (DC) only goes in one direction (Andrew Rader Studios, 1997-2014).

From this, we can see that an AC voltage source creates current that changes polarity over a

period of time across a circuit. The most basic of all AC is the sinusoidal wave since all the other

types of waves are just derivatives of the sine wave using the Fourier transform. The period oftime where the AC voltage source completes one shift of polarity is called one full cycle and it is

divided into two parts, the positive half cycle, where the voltage input is positive, and the

negative half cycle, where the voltage input is negative. Other components to take note for anAC are its amplitude and its frequency. The amplitude is the range of voltage that an AC is

capable of making and the frequency determines how fast or, as its name suggests, how

frequently one full cycle occurs.

Half-wave Rectification

Half-wave rectification is a process where half of the full input AC cycle is used whenconverting AC to DC

[1]. A basic setup of this rectification process can be seen on Figure 2-1.

Figure 2-1. A Basic Circuit Setup for Half-wave Rectification.

The rectification process starts after an AC voltage input is applied across the given setup.

During the positive half cycle, the AC inputs polarity causes the given diode to become

forward-biased, thus allowing current to flow across the circuit. Ideally, this causes the loadresistance to have the same voltage as the AV input, but if the diode has a voltage drop, the


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loads voltage then becomes the input minus the voltage drop of the diode, that is, only for the

positive half cycle. Now during the negative half cycle, the polarity of the AC input reverses,

causing the given diode to become reverse-biased. As discussed in the previous activity, when adiode is in reverse-bias, it blocks all current going through it causing the load resistors voltageto become zero, thus effectively eliminating the negative half of the AC and causing the output

voltage to only have one polarity, which is the positive half in this case. This process can be seenon Figure 2-2.

Figure 2-2. The Half-wave Rectification Process[4]

The DC value of the rectified AC input is given by the equation: VDC = VL / , where VLis thevoltage across the load resistor. This is taken from the average of the net area of VLin one full

cycle[1]

.

Some characteristics and parameters of a half-wave rectifier that should be taken note of areits forward current, peak inverse voltage and ripple factor. The forward current and peak inverse

voltage are the current and voltage values that the rectifier can be able to withstand before

breaking. As for the ripple factor, it is defined as the amount of AC content in the DC output.

The less the ripple factor, the performance of the rectifier is more. (Administrator, 2013) To

lessen the ripple factor during rectification and to smoothen the output, a filter must be addedacross the load. This filter is usually in the form of a capacitor.

III.Materials and Equipment

Diode: 1N4001 (Table 2-1 for datasheet)

Resistors: 500 , 1000 , 10000 Connectors

Breadboard

Oscilloscope

Function Generator

IV.Procedure

Half-wave Rectification[2]

1. Construct the circuit shown in Figure 2-1.

2. Switch on the oscilloscope.3. Switch on the function generator and set the amplitude to 5Vp, 50Hz, sinusoidal.


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Figure 2-4. Output of a 5Vp, 50Hz input at 5V/div and 5ms/div with a load resistor value of 500

Figure 2-5. Output of a 5Vp, 50Hz input at 5V/div and 5ms/div with a load resistor value of

100.


10000.


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Figure 2-7. Output of a 2 Vp, 50 Hz input at 5V/div and 5ms/div with a load resistor value of

1000

Figure 2-8. Output of a 10Vp, 50Hz input at 5V/div and 5ms/div with a load resistor value of1000

Figure 2-9. Output of a 5Vp, 50Hz at 5V/div a5ms/div with a load resistor value of 1000where

the diodes polarity is reversed.


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1000


VI(Peak), V Frequency, Hz Vo(Peak), V VI-Vo, V Resistor,

5 50 4.352 0.648 500

5 50 4.506 0.494 10000

5 50 4.388 0.612 1000

5 25 4.388 0.612 1000

4.982 500 4.370 0.612 1000

2 50 1.445 0.555 100010 50 9.348 0.652 1000

Table 2-2. Data of a Sinusoidal Wave Input


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Triangle Wave Input


500


1000.


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Figure 2-14. Output of a 5 Vp, 50 Hz input at 5V/div and 5ms/div with a load resistor value of

10000.


1000


1000


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1000where the diodes polarity is reversed.


1000

Figure 2-19. Output of a 5Vp, 500 Hz input at 5V/div and 5ms/div with a load resistor value of

1000


4.981 50 4.333 0.648 500

4.981 50 4.487 0.494 10000

4.981 50 4.369 0.612 1000

4.981 25 4.369 0.612 1000

4.735 500 4.127 0.608 1000

1.992 50 1.438 0.554 1000

9.962 50 9.311 0.651 1000

Table 2-3. Table of a Triangle Wave Input

Square Wave Input


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500



10000


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1000


1000


1000where the diodes polarity is reversed


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1000


1000


5 50 4.352 0.648 500

5 50 4.506 0.494 10000

5 50 4.388 0.612 10005 25 4.388 0.612 1000

5 500 4.388 0.612 1000

2 50 1.445 0.555 1000

10 50 9.349 0.651 1000

Table 2-3. Data of a Square Wave Input


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VI.Conclusion

After the activity was conducted, it is concluded that the semiconductor diode, which is alsoknown as a rectifier, is a device used to convert AC to DC. During this experiment it was used as

a half-wave rectifier, in which it converted the given AC input into DC, through the use of the

rectifier diode, with only half of the given AC input. Only half was used because in AC, thepolarity changes over a period of time where one full alternation of its polarity is called a fullcycle. During half of this cycle, its polarity causes the diode to be in forward-bias, while on the

other half it causes the diode to be in reverse-bias. From this, we can see that on one half of the

cycle there is voltage on the load , while on the other half it is equal to zero since no currentpasses through it. This gives the load a voltage equivalent to the input voltage wherein its

polarity of causes the diode to be in forward bias minus the voltage drop across the diode. Since

the voltage across the load has only one polarity, we can now see that the AC input voltage has

been successfully converted into DC.From the data that was gathered, it can be seen that the difference between the input voltage

and the output voltage is across its peaks is the voltage drop of the diode. In this activity, the

diode that was used was a silicon based diode which has an average voltage drop of 0.7V whichcan also be seen in the data in the tables. However, the voltage difference can be affected if, the

input voltage is change or if the value of the load resistor is changed.

Another application of the rectifier diode is to be able to convert the full wave of the AC

input, that is, the Full-wave Rectification process, which will be further discussed in the nextlaboratory activity.

VII. References

1. Boylestad, R. &Nashelsky L. (1998).Electronic Devices and Circuit Theory.Prentince

Hall, Upper Saddle River, New Jersey.

2. Awad N., Al-Khawaldeh S.,Electronics Lab. Electrical Engineering Department,

University of Jordan.

3. Diodes Incorporated.1N4001 - 1N4007.http://www.diodes.com/datasheets/ds28002.pdf

4. Storr, Wayne. (2014).Power Diodes and Rectifiers. http://www.electronics-

tutorials.ws/diode/diode_5.html

5. Phyiscs4kids.com.Electricity & Magnetism Alternating Current.

http://www.physics4kids.com/files/elec_ac.html

6. Administrator. (Sept. 12, 2013). Characteristics and Working of Half-wave Rectifier.

http://www.electronicshub.org/characteristics-and-working-of-half-wave-rectifier/

Electronics Laboratory Activity: Half-wave Rectification

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