Lab 3 Rectifier Circuits Objective: Students

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Name: ______________________________
ECET 242 – Electronic Circuits
Lab 3
Rectifier Circuits
Objective:
Students successfully completing this lab exercise will accomplish the following
objectives:
1. Learn how to construct a full-wave rectifier using both center-tapped
transformer and bridge configurations.
2. Learn how to filter rectified waves to generate a DC source from an AC
source.
3. Learn how to measure ripple effects from a filtered power supply.
Lab Report:
A formal lab report will be required based on your combined results from labs 2,
3 and 4. Retain you results from this lab exercise and combine them with results
from labs 2 and 4. The formal lab report will be due one week after lab 4 has
been performed.
Equipment:
Oscilloscope, 2 kΩ resistor, 1N4004 silicon diodes (4), 1 µF capacitor, 100 µF
capacitor, Digital Multimeter (DMM), Cadet II Lab Trainer Breadboard and Power
Supply.
Procedure 1: Center-tapped Transformer Rectifier
1.
Turn on the oscilloscope.
2.
Follow the basic setup for display and measurement of time-varying signals from Lab 2.
3.
Examine the Cadet II lab trainer. Notice the red, yellow and blue terminals of the 12.6 V
transformer output. The red and blue terminals are connected to the ends of the secondary
winding of the transformer. The yellow terminal is connected to the center tap of the
transformer.
4.
Examine the bread boards on the Cadet II lab trainer. Notice that there are four vertical
columns for power strips per breadboard. Connect the ends of the secondary windings
(red and blue terminals) to the outer vertical columns of one of the breadboards. Connect
the center tap (yellow terminal) to the inner vertical columns.
5.
Set the ground reference to the center tap of the transformer secondary winding. To do
this, use a connecting lead to connect the yellow terminal of the transformer to the ground
(black) terminal of the lab trainer.
6.
Using the oscilloscope, clip the CH1 probe first to the blue terminal, then to the red terminal
to measure the peak-to-peak voltage (with respect to ground) on each half of the secondary
winding. Make sure the switch on the CH 1 probe is set to x1. Record your
measurements in Table 1 below.
Table 1: Transformer winding voltages
Quantity
V1 (P-P)
V1 (P)
V2 (P-P)
V2 (P)
7.
Description
Measured Value
Voltage across left half of winding (Yellow to Red)
Peak value of sine wave of V1 (P-P)
Voltage across right half of winding (Yellow to Blue)
Peak value of sine wave of V2 (P-P)
Construct the center-tapped transformer full wave rectifier shown on page 911 of the
textbook. Use a 2 kΩ resistor as RL.
Page 2 of 5
8.
Using the oscilloscope, connect the CH 1 probe to measure and display the resistor
voltage. The probe should be connected at the 3-way junction of the resistor and the two
diodes. This is the load voltage of the rectifier.
Below, sketch several cycles of the waveform. Include a copy of your sketch in your report.
Label the horizontal and vertical axes and indicate the scale of each. Include a title that
indicates the type of waveform.
Figure 1: Load voltage of a center-tapped transformer full-wave rectifier
SCALES: Vertical ____________ V/Div, Horizontal ____________ s/Div
9.
Using the oscilloscope, measure the peak voltage of the rectified waveform. To obtain an
accurate measurement, be sure to zero out the waveform and adjust the vertical control to
set the ground level to the x-axis.
VL (P) = ________________ V
Notice that the peak value of the load voltage is about 0.7 V lower than the peak value of
the supply voltage.
10.
Using the relationship: Vdc = 0.637 VL(P), calculate the average value of the rectified wave
from the measured peak load voltage, VL (P).
Calculated VL (dc) = ________________ V
11.
Use a DMM to measure the average load voltage. Connect the DMM across the terminals
of the resistor and measure the DC voltage. This is the average load voltage of the
rectifier.
Measured VL (dc) = ________________ V
12.
Add a 1 µF capacitor in parallel with resistor and notice the effects. BE VERY CAREFUL
TO NOTE THE POLARITY OF THE CAPACITOR. (polarized caps can explode in you are
not careful!!) Connect the + side of the capacitor to the HIGH (+) side of the resistor and
the – side of the capacitor to the LOW (-) side of the resistor. This is the filtered load
voltage of a rectifier.
Below, sketch several cycles of the waveform. Include a copy of your sketch in your report.
Label the horizontal and vertical axes and indicate the scale of each. Include a title that
indicates the type of waveform.
Page 3 of 5
Figure 2: Load voltage of a center-tapped transformer full-wave rectifier with a 1 µF filter capacitor
SCALES: Vertical ____________ V/Div, Horizontal ____________ s/Div
13.
Replace the 1 µF capacitor with a 100 µF capacitor. BE VERY CAREFUL TO NOTE THE
POLARITY OF THE CAPACITOR. (polarized caps can explode in you are not careful!!)
Connect the + side of the capacitor to the HIGH (+) side of the resistor and the – side of the
capacitor to the LOW (-) side of the resistor.This is the filtered load voltage of a rectifier.
Below, sketch several cycles of the waveform. Include a copy of your sketch in your report.
Label the horizontal and vertical axes and indicate the scale of each. Include a title that
indicates the type of waveform.
Figure 3: Load voltage of a center-tapped transformer full-wave rectifier with a 100 µF filter capacitor
SCALES: Vertical ____________ V/Div, Horizontal ____________ s/Div
Procedure 2: Bridge Rectifier Circuit
14.
Connect the bridge rectifier using four 1N4004 diodes and a 2 kΩ load resistor as shown on
page 912 of the textbook.
15.
Remove the ground reference from the windings of the transformer. Connect a new ground
reference to the black ground connection on the trainer and wire to one of the vertical
columns. Connect this column appropriately as the to the ground points of your bridge
rectifier circuit.
16.
Connect the oscilloscope to measure resistor voltage.
17.
Adjust the oscilloscope view until you see the full rectified waveform.
Page 4 of 5
Below, sketch several cycles of the load resistor waveform. Include a copy of your sketch
in your report. Label the horizontal and vertical axes and indicate the scale of each.
Include a title that indicates the type of waveform.
Figure 4: Load voltage of a bridge rectifier
SCALES: Vertical ____________ V/Div, Horizontal ____________ s/Div
18.
Add a 1 µF capacitor in parallel with the load resistor. BE VERY CAREFUL TO NOTE THE
POLARITY OF THE CAPACITOR. Measure the Ripple voltage of the load voltage. The
ripple voltage is the peak-to-peak voltage of the waveform.
VRPP = ________________ V
Calculate the Percent ripple (peak-to-peak) where %Ripple = (VRPP / VP) x 100%.
%Ripple = ________________ %
Below, sketch several cycles of the load resistor waveform. Include a copy of your sketch
in your report. Label the horizontal and vertical axes and indicate the scale of each.
Include a title that indicates the type of waveform.
Figure 5: Load voltage of a bridge rectifier with a 1 µF filter capacitor
SCALES: Vertical ____________ V/Div, Horizontal ____________ s/Div
19.
Replace the 1 µF capacitor with a 100 µF capacitor. BE VERY CAREFUL TO NOTE THE
POLARITY OF THE CAPACITOR. The ripple voltage is the peak-to-peak voltage of the
waveform. Sketch the load voltage waveform with the 100 µF capacitor installed.
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Below, sketch several cycles of the load resistor waveform. Include a copy of your sketch
in your report. Label the horizontal and vertical axes and indicate the scale of each.
Include a title that indicates the type of waveform.
Figure 6: Load voltage bridge rectifier with a 100 µF filter capacitor
SCALES: Vertical ____________ V/Div, Horizontal ____________ s/Div
Measure the Ripple voltage of the load voltage. Record your result below.
VRPP = ________________ V
Calculate the Percent ripple (peak-to-peak) where %Ripple = (VRPP / VP) x 100%.
%Ripple = ________________ %
Calculate the theoretical ripple voltage using equations from the textbook.
VRipple = ______________________V
(theoretical)
Calculate the % error between the measured and theoretical ripple voltage.
%Error = ________________ %
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