Eastern Mediterranean University
Department of Mechanical Engineering
Laboratory Handout
COURSE: Mechatronics Components and Instrumentation (MECT 361)
Semester: Fall (2014-2015)
Name of Experiment: Introduction to mechatronic components
(Power Filter/Regulator Circuits)
Instructor: Prof. Dr. Majid Hashemipour
Assistant: Alireza Kazemeini
Submitted by:
Student No:
Group No:
Date of experiment:
Date of submission:
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EVALUATION
Activity During Experiment & Procedure 30 %Data , Results & Graphs 35 %
Discussion, Conclusion & Answer to Questions 30 %
Neat and tidy report writing 5 %
Overall Mark
INTRODUCTION:
What are AC and DC?
A representation of an Alternating Current (AC) supply is shown in figure 1. The voltage (and current) alternates between positive and negative over time and the resulting waveform shape is a sine wave. In the case of the UK mains supply, the frequency of this sine wave is 50Hz, or 50 cycles per second.
Figure 1. An Ac waveform
A Direct Current (DC) supply, shown in figure 2, stays at a fixed, regular, voltage all of the time, like the voltage from a battery. A DC supply is needed by most circuits as a constant reference voltage. Also, some components would be damaged by the negative half-cycles of an AC supply.
Figure 2. A DC waveform
Parts of a Power Supply
Figure 3 shows a block diagram of a power supply system which converts a 230V AC mains supply (230V is the UK mains voltage) into a regulated 5V DC supply.
Figure 3. Block diagram of power supply system
1. The Rectifier
THEORY:
The purpose of a rectifier is to convert an AC waveform into a DC waveform. There are two different rectification circuits, known as 'half-wave' and 'full-wave' rectifiers. Both use components called diodes to convert AC into DC.
A diode is a device, which only allows current to flow through it in one direction.
The Half-wave Rectifier
The half-wave rectifier is the simplest type of rectifier since it only uses one diode, as shown in figure 4.
Figure 4. Half-wave rectification
While the output of the half-wave rectifier is DC (it is all positive), it would not be suitable as a power supply for a circuit,because for half the time there is no output at all.
The Full-wave Rectifier
The circuit in figure 5 shows this time four diodes are arranged, so that both the positive and negative parts of the AC waveform are converted to DC. The resulting waveform is shown in figure 6.
Figure 5. A full-wave rectifier
Figure 6. Full-wave rectification
When the AC input is positive, diodes A and B are forward-biased, while diodes C and D are reverse-biased. When the AC input is negative, the opposite is true - diodes C and D are forward-biased, while diodes A and B are reverse-biased.
PROCEDURE:
1. Use a transformer to provide the desired voltage in alternative current.
2. Connect this power to blue and red rows of your breadboard.
3. Connect one side 2 diodes to blue line in opposite sides, and also connect 2 diodes to red line in opposite sides.
4. Connect the other side of diodes 2 by to in order to have same heads of diodes together (positive heads together).
5. Connect positive heads to column 10 of your breadboard and negative heads to column 15.
6. Set your multimeter on (AC Voltage 700) and measure and record the city voltage which is input to transformer.
7. Set your multimeter on (AC Voltage 20) and measure and record the output of transformer in lines blue and red.
8. Set your multimeter on (AC Voltage 20) and measure and record the output of diodes in columns 10 and 15.
9. Set your multimeter on (DC Voltage 20) and measure and record the output of diodes in columns 10 and 15.
RESULTS:
Input voltage to transformer / Output voltage from transformer / AC voltage after rectifier / DC voltage after rectifierCONCLUSIONS:
1) What is the reduction ratio of your transformer?
2) How much is your DC output?
3) Is your output a DC electricity?
2. Smoothing
THEORY:
Most circuits will require 'smoothing' of the DC output of a rectifier, and this is a simple matter since it involves only one capacitor, as shown in figure 7.
Figure 7. Asmoothing capacitor
The output waveform in figure 8 shows how smoothing works. During the first half of the voltage peaks from the rectifier, when the voltage increases, the capacitor charges up. Then, while the voltage decreases to zero in the second half of the peaks, the capacitor releases its stored energy to keep the output voltage as constant as possible. Such a capacitor is called a 'smoothing' or 'reservoir' capacitor when it is used in this application.
Figure 8. Smoothing
PROCEDURE:
1. Select a capacitor with a voltage above your working voltage and 1000 mf for maximum 2 ampere output.
2. Connect the capacitor to columns 10 and 15, considering correct positive and negative sides.
3. Set your multimeter on (DC Voltage 20) and measure the voltage of columns 10 and 15 again.
RESULTS:
Output voltage from transformer (AC) / Voltage after rectifier(DC)
CONCLUSIONS:
1) Is the DC voltage the same as AC voltage? If not what is the reason?
3. The Regulator
THEORY:
There are many types of regulator IC and each type will have different pin-outs and will need to be connected up slightly differently. negative regulation voltages for circuits that require them.
The 78xx Series of Regulators
Type Number / Regulation Voltage / Maximum Current / Minimum Input Voltage78L05 / +5V / 0.1A / +7V
78L12 / +12V / 0.1A / +14.5V
78L15 / +15V / 0.1A / +17.5V
78M05 / +5V / 0.5A / +7V
78M12 / +12V / 0.5A / +14.5V
78M15 / +15V / 0.5A / +17.5V
7805 / +5V / 1A / +7V
7806 / +6V / 1A / +8V
7808 / +8V / 1A / +10.5V
7812 / +12V / 1A / +14.5V
7815 / +15V / 1A / +17.5V
7824 / +24V / 1A / +26V
78S05 / +5V / 2A / +8V
78S09 / +9V / 2A / +12V
78S12 / +12V / 2A / +15V
78S15 / +15V / 2A / +18V
Ripple Voltage
If you are using a regulator after the smoothing block of the power supply, then you shouldn't need to worry about the ripple voltage, since the whole point of using a regulator is to get a stable, accurate, known voltage for your circuits! However, if the ripple voltage is too large and the input voltage to the regulator falls below the regulated voltage of the regulator, then of course the regulator will not be able to produce the correct regulated voltage. In fact, the input voltage to a regulator should usually be at least 2V above the regulated voltage.
78xx Pin-out
The 78xx, 78Mxx, and 78Sxx regulators all have the pin-out shown in the left of figure 9. They are all connected to the rest of the power supply in the same way, as shown in figure 10.
Figure 9. Pin-out diagram of the 78xx series of regulators ICs
Figure 10. Wiring up a regulator IC
PROCEDURE:
1. Use a 12-volt regulator and connect pins following pin-out diagram of regulator.
2. Set your multimeter on (DC Voltage 20) and measure the voltage before and after regulator.
RESULTS:
Output voltage from transformer (AC) / Voltage after rectifier(DC) / Voltage after regulator
(DC)
CONCLUSIONS:
1) What is the benefit of using regulator when we can reduce the voltage from transformer?