MECH-10127 Solid State Electronics
Module 15 - ELEVATING DEVICES MECHANIC
Lab 4
Power Supplies
Rectifiers and Voltage Regulators
MECH-10127 Lab 4
Page 1 of 14
Rev.A - Sep 2021
INTRODUCTION
Most electronic equipment requires DC power to operate. However, it is powered from AC line
voltage. Therefore, an internal conversion process is required, which is typically performed by a
diode rectifier. Once the voltage is converted to DC it still needs to be filtered to reduce ripple
and often regulated to a specific required voltage.
USEFUL FORMULAS:
AC Sine Wave
Average DC Voltage (No Filtering)
Single-Phase Rectifier
Frequency
Time Period
VDC = DMM reading when set to measure VDC
Vavg = Calculated average voltage from the Oscilloscope’s measured Vpeak
PARTS REQUIRED:
1 - Design trainer
1 - Oscilloscope
1 - DMM (Digital Multi-meter)
4 - 1N4004 diodes
1 - LM7805CT Regulator
1 - 100µF capacitor
1 - 0.1µF capacitor
1 - LED
1 - 5.6 KΩ resistor
1 - 1 KΩ resistor
1N4004 Diode
PLEASE READ CAREFULLY
Neatly sketch the specified oscilloscope waveforms on the CRT grids provided. Politely ask your
professor to initial each waveform as completed, before leaving the laboratory area. Please be aware
that once you leave the lab, your professor will not sign off on your waveforms!
*This is a validation that you completed each waveform during the allotted time, and not an
endorsement or evaluation of your work. Failure to follow these instructions will result in a grade of
‘zero’ for your waveforms.
SUBMIT YOUR ORIGINAL WORK ONLY
MECH-10127 Lab 4
Page 2 of 14
Rev.A - Sep 2021
PART A: HALF-WAVE RECTIFIER CIRCUIT
1.
Construct the half-wave rectifier circuit shown in Figure 4-1. Use the 12.6 VAC centre-tapped
transformer on the design trainer to supply power to the circuit. Do not connect the L2 terminal to
the circuit (identified as NC - NO CONNECTION).
Figure 2-1
2.
Turn on your Oscilloscope and set the controls as follows:
Channel 1: 5 Volts/Div., calibrated
Channel 2: 5 Volts/Div., calibrated
Channels 1 and 2 Coupling: GND
Display MODE: CH1
Check Test Probe Attenuation: x1
Sweep Time/Div.: 5 ms, calibrated
Trigger Level: 0 V
Trigger Source: LINE
Reference the trace to the graticule line that is
marked 90%
3.
Connect the ground alligator clip of the Oscilloscope probe to the point C (GND) of your circuit.
Connect CH1 test probe to Point A and the CH2 test probe to point B of your circuit. Have the
instructor check that the circuit is wired correctly before you turn on the design trainer.
4.
Set Channel 1 input coupling switch to DC. A sine wave should appear on the oscilloscope’s CRT.
Measure the time elapsed for 1 full cycle by counting the horizontal number of divisions and subdivisions, starting where the positive slope of the sine wave crosses the "X" axis and ending where
the next positive slope of the following cycle starts crossing the "X" axis again. Then, multiply by the
sweep Time/Div setting. Record your reading in Table 4-1 under the "Oscilloscope" column.
8.
Then, using the same Period in seconds, apply the reciprocal formula to determine the frequency of
the sine wave. Record in Table 4-1 under the "Oscilloscope" column.
MECH-10127 Lab 4
Page 3 of 14
Rev.A - Sep 2021
9.
Measure the peak voltage of the sine wave by counting the vertical divisions and sub-divisions from
your reference line (zero Volts) and then multiply by the attenuator Volts/Div setting. Record in
Table 4-1 under the "Oscilloscope" column.
10. Use the peak voltage of the sine wave and calculate the VRMS (VAC). Record in Table 4-1 under the
"Oscilloscope" column.
11. Use your DMM to measure the VRMS (VAC) of the sine wave from points A to C (GND) and record in
Table 4-1 under the DMM column. Compare the calculated VRMS to the measured VAC. They should
be very close. If your DMM has a frequency counter use it to measure the frequency of the sine
wave and record in Table 4-1 under the DMM column.
AC Sine Wave Input Voltage (Half-Wave Rectifier Circuit)
Oscilloscope CH1
Period (time to complete 1 full cycle) =
DMM
N/A
Frequency =
Volts peak =
N/A
VRMS (VAC) =
Table 4-1
12. Switch display MODE to CH2 and CH2 input coupling switch to GND. Adjust CH2 reference line on
your Oscilloscope’s CRT to the 10% graticule line. The bottom trace (Channel 2) will be your
rectified DC voltage reference line (Zero Volts). Set CH2 input coupling switch back to DC and
display MODE to CHOP. You should have on the top of the screen an AC sine wave before the diode
(Point A) and on the bottom part of the oscilloscope screen the wave form after the diode (Point B):
a DC half-wave positive pulsating signal displayed.
13. For the half-wave positive pulsating DC signal (CH2), determine the time period to complete one
cycle by measuring the time from where the signal starts to rise to the next time the signal starts to
rise again through the bottom X axis. Record in Table 4-2 under the Oscilloscope column.
14. Calculate the frequency of the pulsating DC and record in Table 4-2 under the oscilloscope column.
15. Measure the peak value of the "pulsating" DC by measuring from the reference line "X" axis to the
top of the peak. For more accuracy, you may want to use the horizontal position control to move
the peak, so that it is on the "Y" (vertical) middle axis where the sub-divisions are. Record in Table
4-2 under the oscilloscope column.
16. Use the formula to calculate the "average" DC voltage for the half-wave rectifier. Record in Table 42 under the oscilloscope column.
MECH-10127 Lab 4
Page 4 of 14
Rev.A - Sep 2021
17. Set your DMM on VDC and measure the "average" DC voltage between points A and C. Record in
Table 4-2 under the DMM column. Note that if your reading fluctuates between voltage ranges,
take your meter out of auto range and fix the display to two decimal places. Compare the
calculated Vavg to the measured VDC. They should be very close.
18. If your DMM has a frequency counter, use it to measure the frequency. Record in Table 4-2 under
the DMM column.
Pulsating DC Output Voltage (Half-Wave Rectifier Circuit)
Oscilloscope CH2
Period T (time to complete 1 full cycle) =
DMM
N/A
Frequency =
Volts peak =
N/A
Vavg (average or VDC) =
Table 4-2
19. What is the voltage difference between the AC peak before the diode (Table 2-2) and the DC peak
after the diode (Table 4-2)?
_____________________________________________________________________
20. Neatly draw the waveforms on the CRT grid below – Figure 4-2.
Volts/Div. __________
Time/Div. __________
Coupling AC/DC ?____
Figure 4-2
MECH-10127 Lab 4
Page 5 of 14
Rev.A - Sep 2021
21. Turn off your power supply and reverse the diode. Carefully measure and record the following
measurements.
Pulsating DC Output Voltage (Half-Wave Rectifier Circuit)
Oscilloscope CH2
Volts peak =
DMM
N/A
Vavg (average or VDC) =
Table 4-3
22. Measure the peak value of the "pulsating" DC by measuring from the reference line "X" axis to the
top of the peak. For more accuracy, you may want to use the horizontal position control to move
the peak, so that it is on the "Y" (vertical) middle axis where the sub-divisions are. Record in Table
4-3 under the oscilloscope column.
23. Use the formula to calculate the "average" DC voltage for the half-wave rectifier. Record in Table 43 under the oscilloscope column.
24. Set your DMM on VDC and measure the "average" DC voltage between points A and C. Record in
Table 4-3 under the DMM column. Note that if your reading fluctuates between voltage ranges,
take your meter out of auto range and fix the display to two decimal places. Compare the
calculated Vavg to the measured VDC. They should be very close.
25. Neatly draw the waveforms on the CRT grid below – Figure 4-3.
Volts/Div. __________
Time/Div. __________
Coupling AC/DC ?____
Figure 4-3
MECH-10127 Lab 4
Page 6 of 14
Rev.A - Sep 2021
PART B: FULL-WAVE CENTRE-TAPPED RECTIFIER CIRCUIT
26. Turn off the design trainer. Modify your circuit to Figure 4-4. You're going to use both 6.3 VAC
transformer terminals plus the CT on your design trainer. A short circuit could result if the diodes
D1 and D2 are not installed correctly. Have the instructor check if your circuit is wired correctly
before you turn on the design trainer.
Figure 4-4
27.
Repeat steps 5 to 18. Fill in Tables 4-4 and 4-5 instead of Tables 4-1 and 4-2.
AC Sine Wave Input Voltage (Full-Wave Centre-Tapped Rectifier Circuit)
Oscilloscope CH1
DMM
Period T (time to complete 1 full cycle) =
N/A
Frequency =
Volts peak =
N/A
VAC (VRMS) =
Table 4-4
Pulsating DC Output Voltage (Full-Wave Centre-Tapped Rectifier Circuit)
Oscilloscope CH2
DMM
Period T (time to complete 1 full cycle) =
N/A
Frequency =
Volts peak =
N/A
Vavg (average or VDC) =
Table 4-5
MECH-10127 Lab 4
Page 7 of 14
Rev.A - Sep 2021
28. Neatly draw the waveforms on the CRT grid below – Figure 4-5.
Volts/Div. __________
Time/Div. __________
Coupling AC/DC ?____
Figure 4-5
MECH-10127 Lab 4
Page 8 of 14
Rev.A - Sep 2021
PART C: FULL-WAVE BRIDGE RECTIFIER CIRCUIT
29. Turn off the design trainer and disconnect CH2 test probe from your oscilloscope. Modify your
circuit to Figure 4-6. You're going to use both 6.3 VAC transformer terminals (12.6VAC), without
connecting the CT. A short circuit could result if D1, D2, D3, or D4 are not installed correctly. Have
the instructor check if your circuit is wired correctly before you turn on the design trainer.
30. Adjust CH1 reference line to the centre “X” axis. Repeat steps 5 to 18. Fill in Tables 4-6 and 4-7
instead of Tables 4-1 and 4-2.
For this part of the Lab the AC power supply MUST be ISOLATED from ground, so you
don't have a short circuit thru the oscilloscope’s chassis ground. Disconnect the
oscilloscope’s CH2 probe and make sure the oscilloscope’s GROUND binding post is
not connected to the PB-505 design trainer’s transformer or DC power supply.
Figure 4-6
To fill Table 4-6, measure VAC from point A to point B (Figure 4-6 above)
AC Sine Wave Input Voltage (Full-Wave Bridge Rectifier Circuit)
Oscilloscope
Period T (time to complete 1 full cycle) =
DMM
N/A
Frequency =
Volts peak =
N/A
VAC (VRMS) =
Table 4-6
MECH-10127 Lab 4
Page 9 of 14
Rev.A - Sep 2021
Figure 4-7
To fill the pulsating DC Table 4-7, measure from point C to point D (Figure 4-7 above).
Pulsating DC Output Voltage (Full-Wave Bridge Rectifier Circuit)
Oscilloscope
Period T (time to complete 1 full cycle) =
DMM
N/A
Frequency =
Volts peak =
N/A
Vavg (average or VDC) =
Table 4-7
31. What is the voltage difference between the AC peak before the diode (Table 4-6) and the DC peak
after the diode (Table 4-7)?
___________________________________________________________________________
32. Neatly draw the waveforms on the CRT grid below – Figure 4-8.
NOTE: Do not disassembly your circuit!
MECH-10127 Lab 4
Page 10 of 14
Rev.A - Sep 2021
Volts/Div. __________
Time/Div. __________
Coupling AC/DC ?____
Figure 4-8
PART D: VOLTAGE REGULATOR
WEAR YOUR SAFETY GLASSES
ELECTROLYTIC CAPACITORS MAY EXPLODE IF INSERTED IN A CIRCUIT REVERSED OR IF
THE APPLYED VOLTAGE EXCEEDS THE MAXIMUM ALLOWED.
MECH-10127 Lab 4
Page 11 of 14
Rev.A - Sep 2021
33. Turn off your power supply and modify your circuit to Figure 4-8 connecting a 100μF filter capacitor
in parallel with the resistor. Be careful with the capacitor polarity!
Figure 4-8
34. Turn on the power supply and compare the waveform on the oscilloscope screen with Figure 4-8.
The 100μF capacitor is filtering the DC pulses leaving a small ripple on the DC voltage.
35. Turn off your power supply and modify your circuit removing the resistor RL (5.6KΩ) and connecting
the LM7805 Linear Voltage Regulator according to Figure 4-9.
Figure 4-9
MECH-10127 Lab 4
Page 12 of 14
Rev.A - Sep 2021
36. Turn on the power supply and measure the DC voltage Vout (the regulator’s output voltage across
the 0.1uF capacitor). Vout = ___________________________
37. Turn off your power supply and disassemble the bridge rectifier part of the circuit. Connect the
variable 1-18 VDC power supply from the design trainer to the input of the Figure 4-10 circuit.
Figure 4-10
38. Connect your DMM to the power supply and adjust the voltage to the values below. For each value
of Vin (Input voltage) you adjust, record the output voltage in Table 4-8.
Vin
(Input voltage)
Vout
(Output voltage)
1V
2V
3V
4V
5V
6V
7V
8V
9V
10V
15V
Table 4-8
MECH-10127 Lab 4
Page 13 of 14
Rev.A - Sep 2021
MECH10127 SOLID STATE ELECTRONICS
Lab #4 Professor Approval Sheet
Student Name: __________________________ Student #: ____________________
Student Name: __________________________ Student #: ____________________
Class Day/Time/Date: __________________________________________________
PROFESSOR NOTE: CHECK ONE ONLY
i)
Student was present and completed all required steps.
ii) Student was present but did not complete all required steps.
Notes and Comments
______________________________________________________________________
______________________________________________________________________
______________________________________________________________________
______________________________________________________________________
______________________________________________________________________
Professor Approval: _______________________ Date: ______________________
MECH-10127 Lab 4
Page 14 of 14
Rev.A - Sep 2021