Electronic I (DMT 121)
Laboratory Module
Exp3
EXPERIMENT 3
Diode as Rectifiers
1.
OBJECTIVE:
1.1
1.2
2.
To understand the application of diode.
To demonstrate the characteristics of three different diode rectifier
circuits: half-wave rectifier, center-tapped full-wave rectifier, and full-wave
bridge rectifier.
INTRODUCTION:
Assuming sine wave input with input frequency fin
2.1
Half-wave rectifier
DC voltage output
=
VS ( peak )  VB

(sine wave input)
(3.1)
where: Vs ( peak ) is a transformer’s peak secondary voltage
VB is the peak voltage across 1k resistor
Output frequency
2.2
2.3
2.3
=
fin
(3.2)
Center-tapped full-wave rectifier
Dc voltage output
=
2VS ( peak )  VB 
(3.3)
Output frequency
=
2 * fin
(3.4)
Full-wave bridge rectifier
DC voltage output
=
Output frequency
=

2VS ( peak )  VB 

2 * fin
(sine wave input) (3.5)
(3.6)
Percentage (%) error
In most practical analysis problems, a calculated value is considered to
be accurate enough if it is within ±10% of the actual measured value. The
percentage of error in a given calculation is determined using
X X'
% of error =
X
 100
(3.7)
where X = the measured value
X ' = the calculated value
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Electronic I (DMT 121)
Laboratory Module
Exp3
3.
COMPONENT AND EQUIPMENT:
3.1
3.2
3.3
3.4
3.5
3.6
4.
1 kΩ resistor
1N4001 silicon rectifier diodes(4 units)
Secondary center-tapped transformer(12 Vrms)
Oscilloscope
Multimeter
Breadboard
PROCEDURE:
4.1
Half Wave Rectification:
4.1.1 Assemble the half wave rectifier circuit shown in Figure 3.1.
Figure 3.1 Schematic diagram of half-wave rectifier
(NOTE: Be very careful to make sure that connections to the 240V primary of the
transformer are properly protected. Note that neither of the transformer’s primary
leads is grounded, while the center-tapped secondary lead is not used in this
section.)
4.1.2
4.1.3
Determination of transformer’s peak secondary voltage [VS(peak)]
and the peak voltage [V0(peak)] across the 1kΩ resistor:
Set oscilloscope to the following approximate settings:
Channels 1 & 2:
Time base
:
10 V/division, dc coupling
5 ms/division
Apply 240 VAC (rms) to the transformer’s primary leads.
Connect one scope probe to the anode terminal of the 1N4001
diode (point A)
4.1.6 Connect the other probe to the diode cathode terminal (point B).
4.1.7 Record your results in Table 3.1
4.1.8 Next, we want to measure the dc voltage (VDC) across the 1 kΩ
resistor:
4.1.9 Use your multimeter.
4.1.10 Record your result in Table 3.1.
4.1.4
4.1.5
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Electronic I (DMT 121)
Laboratory Module
Exp3
4.1.11 Compare this result with that obtained from the equation for the
average or dc voltage of a half-wave rectifier (Equation 3.1).
4.1.12 Observe both waveforms. Then, turn off the power to the
transformer.
4.2 Full-wave Rectification:
4.2.1 Then, assemble the center-tapped full-wave rectifier circuit shown
in Figure 3.2.
Figure 3.2
Schematic diagram of full-wave rectifier
(NOTE: Pay careful attention to the polarity of both diodes and the connections to
the 240V primary of the transformer. The center-tapped lead is grounded.)
4.2.2
4.2.3
Determination of transformer’s peak secondary voltage [VS(peak)]
and the peak voltage [V0(peak)] across the 1kΩ resistor:
Set your oscilloscope to the following approximate settings:
Channels 1 & 2
Time base
:
:
5 V/division, dc coupling
5 ms/division
Apply 240 VAC (rms) to the transformer’s primary leads.
Connect one probe to the anode terminal of the 1N4001 diode (point
A)
4.2.6 Connect the other probe to one of the diode’s cathode terminals
(point B).
4.2.7 Record your results in Table 3.1
4.2.8 Then, using your multimeter, measure the dc voltage (VDC) across
the 1 kΩ resistor:
4.2.9 Record your result in Table 3.1.
4.2.10 Compare this result with that obtained from the equation for the
average or dc voltage of a half-wave rectifier (Equation 3.3).
4.2.11 Observe both waveforms. Then, turn off the power to the transformer
4.2.4
4.2.5
4.3 Full-wave Bridge Rectification:
4.3.1
Next, assemble the full-wave bridge rectifier circuit shown in
Figure 3.3.
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Electronic I (DMT 121)
Laboratory Module
Exp3
Figure 3.3
Schematic diagram of full-wave bridge rectifier
(NOTE: Pay careful attention to the polarity of all four diodes and the connections
to the 240V primary of the transformer. The center-tapped lead is grounded for
this section.)
4.3.2
4.3.3
4.3.4
Apply 240 VAC (rms) to the transformer’s primary leads.
Set the channel to dc coupling,
Connect the probe to the ungrounded lead of the 1kΩ (point A).
(NOTE: If everything is working properly, you should obtain the same full-wave
rectified waveform obtained in Step 4.2)
4.3.5
With oscilloscope, measure the peak voltage V0 (peak) across the
1kΩ resistor.
4.3.6 Record your result in Table 3.1.
4.3.7 Then, using your multimeter, measure the dc voltage (VDC) across
the 1kΩ resistor
4.3.8 Record your result in Table 3.1.
4.3.9 Compare this result with that obtained in the equation for the
average or dc voltage of a full-wave bridge rectifier (Equation 3.5).
4.3.10 Observe both waveforms.
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Electronic I (DMT 121)
Laboratory Module
Exp3
Name
:
______________________________
Matric No.:______________________________
5.
Date : ______________
Course : ______________
RESULT:
Table 3.1
Rectifier data
Rectifier
Type
Measured
VS (peak)
V0 (peak)
Expected VDC
% Error
VDC
Half-wave
Full-wave
(center tap)
Full-wave
(bridge)
Instructor Approval :
____________________
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Date : ____________
Electronic I (DMT 121)
Laboratory Module
Exp3
Name
:
______________________________
Matric No.:______________________________
6.
Name
Date : ______________
Course : ______________
CALCULATIONS:
:
______________________________
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Date : ______________
Electronic I (DMT 121)
Laboratory Module
Exp3
Matric No.:______________________________
7.
Course : ______________
DISCUSION:
7.1 PART A:
1.
Answer the question by referring to the Figure 3.4:
a) Calculate the peak output voltage.
b) Sketch the output voltage of rectifier.
c) What type of the rectifier?
+12V
-12V
Figure 3.4
Schematic diagram of circuit
Name :______________________________
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Date : ______________
Electronic I (DMT 121)
Laboratory Module
Exp3
Matric No.:______________________________
2.
Course : ______________
Find the average value of the full-wave rectifier voltage in Figure 3.5.
5V
Figure 3.5 Full-wave rectifier voltage
Name : ______________________________
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Date : ______________
Electronic I (DMT 121)
Laboratory Module
Exp3
Matric No.:______________________________
Course : ______________
7.2 PART B - TROUBLESHOOTING PROBLEM :
Secondary centertapped transformer
1.
Full-wave
rectifier
F
1/4 A
RL
2.2 k
Figure 3.6
Bridge full-wave rectifier circuit
Assume the circuit in Figure 3.6 (shown above) blows the fuse when it is first
plugged in. What should you do (give two possible solutions)?
Name : ______________________________
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Date : ______________
Electronic I (DMT 121)
Laboratory Module
Exp3
Matric No.:______________________________
Course : ______________
2. A student constructs the circuit as shown in Figure 3.7. Determine the peak
output voltage for the bridge rectifier and the PIV rating which required for the
diodes (The transformer is specified to have a 24V rms secondary voltage for
the standard 240 V across the primary).
Figure 3.7
Name
:
Bridge full-wave rectifier circuit
______________________________
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Date : ______________
Electronic I (DMT 121)
Laboratory Module
Exp3
Matric No.:______________________________
8.
Course : ______________
CONCLUSION
Explain in brief how full-wave rectification differs from half-wave rectification.
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