Если у вас возникли сложности с курсовой, контрольной, дипломной, рефератом, отчетом по практике, научно-исследовательской и любой другой работой - мы готовы помочь.
Предоплата всего
Подписываем
Diary of Electronics Laboratories
Electronics and Measurements
Degree Program of Information Technology
27.04.2011
Introduction 3
Theory 4
Laboratory work 1 13
Laboratory work 2 15
Laboratory work 3 17
Laboratory work 4 19
Laboratory work 5 21
Laboratory work 6, 7, 8 22
Laboratory work 9, 10 26
Conclusion 28
Purpose of the labs is study of electronics on practice. During these labs we were working with equipments such as Elvis, multimeter, oscilloscope and etc. Also we met with resistors, capacitors and other components. For better understanding we were doing our homeworks.
Resistance is a natural feature of all materials. We have conducting materials and we have insulating materials. Usually all metals are good conductors and non metals are insulators.
The resistance is calculated from the length of the wire (l) divided by the cross sectional area of the wire (A) and multiplied by the material constant, resistivity (ρ):
The parallel resistors can be calculated together by equation:
and series connection can be solved by equation:
The equation which describes the relationships of the current, voltage and resistance is called Ohm’s law. Current (amperes) is voltage (volts) divided by resistance (ohms).
Power can be written in different forms of the equation:
First Kirchoff’s law is: If there is an intersection point in the circuit, the current is divided there in two (or more) branches. The current in those two branches are determined by the resistances which follows the intersection. The current cannot stay in the point.
The second Kirchoff’s law is: The voltage drops or voltage rises equals zero if the whole loop is went around. When we go through the battery from the ground to the positive terminal, we take that as positive voltage rise. The direction of the current is chosen to be clockwise and the voltage drops in each resistor are positive if going to that direction, and negative if coming against that direction. This has a lot of meaning if there are loops in which we have two currents going in both directions.
Capacitors are components which can store charge. How much the capacitor can store charge is a product of the capacitors ability to collect electrons, the capacitance, and the voltage applied between the ends of the capacitor. Usually this is expressed other way, the capacitance (C) is the charge (Q) divided by the voltage (V):
The parallel capacitors can be calculated together by equation:
and series connection can be solved by equation:
Aluminium electrolyte capacitors are cylindrical shape and big in size. The two legs can be attached either on same end or on both ends. They are polarized, which means that you have to insert it correct way into a circuit. The minus leg is usually marked on the side of the capacitor. Their typical values are from 100 nF to 4700 µF. The car stereo systems have even 1 F capacitors to provide big bass boost. These capacitors have also a maximum voltage value, which can be as low as 5 V. Typical values are 12 V, 16 V, 32 V, 64 V. High voltage capacitors are for different purpose, and they can have voltage limits like 600 V. The electrolyte capacitor is made of a long sheet of coated plastic film, which is rolled inside the cylindrical tube. The insulating material inside the capacitor is a non conducting liquid. If the polarized capacitor is connected wrong way into the circuit this liquid will sprout out with a small explosion. The connection is made so that the minus leg is connected to the more negative potential than the positive leg. (It is not necessary ground voltage.) The frequency range for these capacitors is very limited, just few hundred hertz. Also the temperature will change the capacitance value typically of several percents.
Tantalum capacitors are for low-voltage devices. Their capacitance range is from 1µF up to 150 µF. Compared to electrolyte capacitors tantalum capacitors have very stable capacitance and have very low impedance in low frequencies. Tantalum capacitors like electrolyte capacitors do not like voltage spikes and can explode if connected wrong way into the circuit.
There are many different plastics used in capacitor manufacturing. They differ in capacitance range, frequency range, tolerance and price. The typical materials are polystyrene, polyester or Mylar, polypropylene and Teflon. Polystyrene is typically used only in picoFaraday range, but it is very stable signal capacitor. Polyester is cheaper and its frequency range is good for applications in audio frequencies. Its capacitance varies from 1 nF to 50 µF. It is used in signal conditioning and integrator circuits. Polypropylene tolerates higher voltages than other plastic ones and it has a low-loss. It is good for signal purposes, it is more expensive than previous ones. Teflon is best material for signal purposes, and has highest price.
Ceramic materials is once again a long list. Ceramic capacitors have small capacitance values in pico to nano Faraday range. They are very good capacitors for high frequency circuits less than 1 GHz.
Mica is a natural mineral, which cuts itself easily into very thin slices. This material is used as the insulating material in mica capacitors. It has a very high voltage range, very high frequency range and it is very stable against the changes in temperature and moisture of air. These are used in radio transmitters and oscillator circuits.
If the switch of the circuit is closed the power supply is connected to the resistor and the capacitor. At the beginning there is a big current. The current will reduce as the capacitor charges, because the voltage is rising in the capacitor. The current will be zero at the time the capacitor has reached the final state, the same voltage as the power supply has. This usually is defined to take five time constants (5τ). The time constant (τ) can be calculated from resistance and capacitance:
If the switch is then moved back to the original position the capacitor will discharge to the ground through the same resistor as it was charged. So the similar current is expected, now the current will stop when the capacitor has drained all its voltage (read charge). The equations to cover this phenomena come from differential equations of the current, where is called the derivative of charge. The voltage rise during charging the capacitor can be expressed with equation:
and the discharging voltage in time can be calculated from the equation:
Inductor
An inductor (or reactor) is a passive electrical component that can store energy in a magnetic field created by the electric current passing through it. An inductor's ability to store magnetic energy is measured by its inductance, in units of henries. Typically an inductor is a conducting wire shaped as a coil; the loops help to create a strong magnetic field inside the coil due to Ampere's Law. Due to the time-varying magnetic field inside the coil, a voltage is induced, according to Faraday's law of electromagnetic induction, which by Lenz's Law opposes the change in current that created it. Inductors are one of the basic components used in electronics where current and voltage change with time, due to the ability of inductors to delay and reshape alternating currents. Inductors called chokes are used as parts of filters in power supplies or to block AC signals from passing through a circuit.
Types of inductor:
Inductors in a parallel configuration each have the same potential difference (voltage). To find their total equivalent inductance (Leq):
The current through inductors in series stays the same, but the voltage across each inductor can be different. The sum of the potential differences (voltage) is equal to the total voltage. To find their total inductance:
Transformer
A transformer is a static device that transfers electrical energy from one circuit to another through inductively coupled conductors—the transformer's coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core and thus a varying magnetic field through the secondary winding. This varying magnetic field induces a varying electromotive force (EMF) or "voltage" in the secondary winding. This effect is called mutual induction.
If a load is connected to the secondary, an electric current will flow in the secondary winding and electrical energy will be transferred from the primary circuit through the transformer to the load. In an ideal transformer, the induced voltage in the secondary winding (Vs) is in proportion to the primary voltage (Vp), and is given by the ratio of the number of turns in the secondary (Ns) to the number of turns in the primary (Np) as follows:
The voltage induced across the secondary coil may be calculated from Faraday's law of induction, which states that:
where Vs is the instantaneous voltage, Ns is the number of turns in the secondary coil and Φ is the magnetic flux through one turn of the coil.
Diode
In electronics, a diode is a two-terminal electronic component that conducts electric current in only one direction. The term usually refers to a semiconductor diode, the most common type today. This is a crystalline piece of semiconductor material connected to two electrical terminals. A vacuum tube diode (now little used except in some high-power technologies) is a vacuum tube with two electrodes: a plate and a cathode.
Diodes were the first semiconductor electronic devices. The discovery of crystals' rectifying abilities was made by German physicist Ferdinand Braun in 1874. The first semiconductor diodes, called cat's whisker diodes, developed around 1906, were made of mineral crystals such as galena. Today most diodes are made of silicon, but other semiconductors such as germanium are sometimes used.
Types:
Types and coding schemes of semiconductor diodes:
Semiconductor
A semiconductor is a material with electrical conductivity due to electron flow (as opposed to ionic conductivity) intermediate in magnitude between that of a conductor and an insulator. This means a conductivity roughly in the range of 103 to 10−8 siemens per centimeter. Semiconductor materials are the foundation of modern electronics, including radio, computers, telephones, and many other devices. Such devices include transistors, solar cells, many kinds of diodes including the light-emitting diode, the silicon controlled rectifier, and digital and analog integrated circuits. Similarly, semiconductor solar photovoltaic panels directly convert light energy into electrical energy. In a metallic conductor, current is carried by the flow of electrons. In semiconductors, current is often schematized as being carried either by the flow of electrons or by the flow of positively charged "holes" in the electron structure of the material.
Regulator
A voltage regulator is an electrical regulator designed to automatically maintain a constant voltage level. A voltage regulator may be a simple "feed-forward" design or may include negative feedback control loops. It may use an electromechanical mechanism, or electronic components. Depending on the design, it may be used to regulate one or more AC or DC voltages.
Electronic voltage regulators are found in devices such as computer power supplies where they stabilize the DC voltages used by the processor and other elements. In automobile alternators and central power station generator plants, voltage regulators control the output of the plant. In an electric power distribution system, voltage regulators may be installed at a substation or along distribution lines so that all customers receive steady voltage independent of how much power is drawn from the line.
Light-emitting diode (LED)
A light-emitting diode (is a semiconductor light source. LEDs are used as indicator lamps in many devices and are increasingly used for other lighting. Introduced as a practical electronic component in 1962,early LEDs emitted low-intensity red light, but modern versions are available across the visible, ultraviolet and infrared wavelengths, with very high brightness.
When a light-emitting diode is forward biased (switched on), electrons are able to recombine with electron holes within the device, releasing energy in the form of photons. This effect is called electroluminescence and the color of the light (corresponding to the energy of the photon) is determined by the energy gap of the semiconductor. An LED is often small in area (less than 1 mm2), and integrated optical components may be used to shape its radiation pattern. LEDs present many advantages over incandescent light sources including lower energy consumption, longer lifetime, improved robustness, smaller size, faster switching, and greater durability and reliability. LEDs powerful enough for room lighting are relatively expensive and require more precise current and heat management than compact fluorescent lamp sources of comparable output.
Photodiode
Photodiode is a type of photodetector capable of converting light into either current or voltage, depending upon the mode of operation. The common, traditional solar cell used to generate electric solar power is a large area photodiode. Photodiodes are similar to regular semiconductor diodes except that they may be either exposed (to detect vacuum UV or X-rays) or packaged with a window or optical fiber connection to allow light to reach the sensitive part of the device.
A photodiode is a PN junction or PIN structure. When a photon of sufficient energy strikes the diode, it excites an electron, thereby creating a free electron (and a positively charged electron hole). This mechanism is also known as the photoelectric effect. If the absorption occurs in the junction's depletion region, or one diffusion length away from it, these carriers are swept from the junction by the built-in field of the depletion region. Thus holes move toward the anode, and electrons toward the cathode, and a photocurrent is produced. This photocurrent is the sum of both the dark current (without light) and the light current, so the dark current must be minimised to enhance the sensitivity of the device.
Transistor
A transistor is a semiconductor device used to amplify and switch electronic signals. It is made of a solid piece of semiconductor material, with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current flowing through another pair of terminals. Because the controlled (output) power can be much more than the controlling (input) power, the transistor provides amplification of a signal. Today, some transistors are packaged individually, but many more are found embedded in integrated circuits.
Transistors are commonly used as electronic switches, both for high-power applications such as switched-mode power supplies and for low-power applications such as logic gates.
In a grounded-emitter transistor circuit, such as the light-switch circuit shown, as the base voltage rises the base and collector current rise exponentially, and the collector voltage drops because of the collector load resistor. The relevant equations:
VRC = ICE × RC, the voltage across the load (the lamp with resistance RC)
VRC + VCE = VCC, the supply voltage shown as 6V
Transistor can be used as an amplifier also.
The common-emitter amplifier is designed so that a small change in voltage in (Vin) changes the small current through the base of the transistor and the transistor's current amplification combined with the properties of the circuit mean that small swings in Vin produce large changes in Vout.
Various configurations of single transistor amplifier are possible, with some providing current gain, some voltage gain, and some both.
Bipolar junction transistor
A bipolar junction transistor (BJT) is a three-terminal electronic device constructed of doped semiconductor material and may be used in amplifying or switching applications. Bipolar transistors are so named because their operation involves both electrons and holes. Charge flow in a BJT is due to bidirectional diffusion of charge carriers across a junction between two regions of different charge concentrations. This mode of operation is contrasted with unipolar transistors, such as field-effect transistors, in which only one carrier type is involved in charge flow due to drift.
An NPN transistor can be considered as two diodes with a shared anode. In typical operation, the base-emitter junction is forward biased and the base–collector junction is reverse biased.
The Bipolar transistor exhibits a few delay characteristics when turning on and off. Most transistors, and especially power transistors, exhibit long base storage time that limits maximum frequency of operation in switching applications.
A BJT consists of three differently doped semiconductor regions, the emitter region, the base region and the collector region. These regions are, respectively, p type, n type and p type in a PNP, and n type, p type and n type in a NPN transistor. Each semiconductor region is connected to a terminal, appropriately labeled: emitter (E), base (B) and collector (C):
Types of BJT:
Operational amplifier
An operational amplifier is a DC-coupled high-gain electronic voltage amplifier with a differential input and, usually, a single-ended output. An op-amp produces an output voltage that is typically hundreds of thousands times larger than the voltage difference between its input terminals.
The circuit symbol for an op-amp is shown to the right, where:
The power supply pins can be labeled in different ways. Despite different labeling, the function remains the same — to provide additional power for amplification of the signal. Often these pins are left out of the diagram for clarity, and the power configuration is described or assumed from the circuit.
The amplifier's differential inputs consist of a input and a input, and ideally the op-amp amplifies only the difference in voltage between the two, which is called the differential input voltage. The output voltage of the op-amp is given by the equation,
where is the voltage at the non-inverting terminal, is the voltage at the inverting terminal and AOL is the open-loop gain of the amplifier.
1. Multimeter, how does it function?
A digital multimeter is a tool which can measure current (DC, AC), voltage(DC, AC) and resistance.
2. We measured the resistance of the given resistors
green = 5, blue = 6, orange = 103, gold = ± 5 %
So, R1 = 56 · 103± 5 %Ω = 56 ± 5 % kΩ
brown = 1, red = 2, brown = 101, gold = ± 5 %
So, R2 = 120 ± 5 % Ω
The results obtained in both cases are approximately equal.
3. We used five different value resistors in series and did measurements:
Resistors 1 and 2 were too large (77,83 kΩ and 79,116 kΩ) and current through the circuit was too small, so we redid measurements with only three resistors:
V = ± 4,95 V
I = 1,15 mA
|
Resistor |
Resistance, kΩ |
Voltage, V |
|
R3 |
3,2655 |
3,75 |
|
R4 |
1,014 |
1,165 |
|
R5 |
0,0126 |
0,0146 |
|
Voltage, V |
Resistance, kΩ |
Current, mA |
|
1 |
3,2655 |
0,3 |
|
1,5 |
3,2655 |
0,14 |
|
5 |
3,2655 |
1,5 |
|
10 |
3,2655 |
2,8 |
|
12 |
3,2655 |
3,8 |
During this lab we learned to use a digital multimeter. We measured resistance values of some resistors. We compared the color codes and made measurements to get same results with both methods. We learned the resistor color code.
If we measure current we need to put the wire in either small current input or bigger current input. Voltage and resistance use the same input. Also the dial of the meter has to be according to the measurement or we might burn the fuse inside the meter.
Resistors can be connected in series or in parallel and the total resistance can be calculated with the equations.
1. We built the circuit.
We made measurement the voltage at the point A by using oscilloscope.
We calculated the total current through the circuit using R4 and Ohm’s law.
The total resistance of the circuit is:
2. We built the second circuit.
Voltages between points AB and AC are:
We can calculate all currents in the circuit if we know voltage drop on R1. If we don’t know this value, we need to use resistances of R3 and R4. Resistance of only R4 is insufficiently to find all currents, because at the point B it is separated to two smaller currents.
I also did simulation the circuit and saw that my supposition was right.
Today we learned how to measure the dc voltage, built two circuit and calculated total currents of the circuits and total resistance in the first part. Also I tried to simulate the circuit by using Multisim program and got good practice.
We calculated resistance:
, so
We took resistor with resistance 820 Ω
By definition, after 5 τ the signal has reached its final value. Time what we measure with oscilloscope is t. The time constant is measured from oscilloscope screen at the location, where the signal is 1-e-1 or 64 % of the maximum.
We calculated τ:
And our practical results from oscilloscope are almost the same:
During these tasks we learned to measure a transient signal. We build a circuit to charge and discharge a big electrolyte capacitor. In this measurement we needed to adjust also the time setting to see the whole five time constant time on the screen.
The capacitor is said to be fully charged after five time constants, which is also the required to discharge the capacitor. Electrolyte capacitors are polarized and the minus side must be connected towards the ground.
At the beginning we built the following circuit and took some values of frequency and amplitude:
for C1 = 4,7 nF for C2 = 220 µF
|
f, Hz |
A, mV |
f, Hz |
A, mV |
|
|
100 |
593 |
100 |
1000 |
|
|
600 |
123 |
10100 |
419 |
|
|
1100 |
67 |
20100 |
230 |
|
|
1600 |
47 |
30100 |
159 |
|
|
2100 |
36 |
40100 |
123 |
|
|
2600 |
29 |
50100 |
101 |
|
|
3100 |
25 |
60100 |
86 |
|
|
3600 |
21 |
80100 |
67 |
|
|
4100 |
18 |
100100 |
57 |
|
|
4600 |
16 |
150100 |
42 |
|
|
5100 |
15 |
300100 |
27 |
Then we built another circuit and took some values of frequency and amplitude:
for C2 = 220 µF we didn’t take values, because they
for C1 = 4,7 nF were wrong.
|
f, Hz |
A, mV |
|
100 |
593 |
|
600 |
123 |
|
1100 |
67 |
|
1600 |
47 |
|
2100 |
36 |
|
2600 |
29 |
|
3100 |
25 |
|
3600 |
21 |
|
4100 |
18 |
|
4600 |
16 |
|
5100 |
15 |
Now we can draw the graphics.
fc
In this work we measured values of frequency and amplitude, draw these two measurement series on one graph, and saw that the curves of the two measurements cross each other at the frequency fc.
1. We built the circuit with diode and resistor, which were connected in series and measured the peak-to-peak value of the voltage and average value of the voltage:
2. We added a capacitor in parallel of the resistor and again measured the voltage:
3. The next we change capacitor to bigger:
During this work we built the circuit and made some measurements of voltage (Vp-p (AC) and Vaver (DC)). From results we can compare values in different situations. If we add the capacitor our Vp-p is decreases, but average voltage is constant. The higher value of capacitor - the higher value of average voltage.
The labwork is small, because one task with modem could do only one group at the same time. And many tasks which there are in new paper in Moodle we didn’t have, when doing work. The teacher was Osmo Ojamies and so there are some differences in tasks.
1. We built the circuit:
We measured the voltage:
We removed the diodes or LED (only one at a time) and measured the voltage:
a) The diode was removed, V1 = 5,56 V
b) The zener diode was removed, V2 = 11,85 V
c) The LED was removed, V3 = 7,33 V
2. The next we changed the LED from red to green:
V = 5,42 V
a) The diode was removed, V1 = 6,1 V
b) The zener diode was removed, V2 = 12,748 V
c) The LED was removed, V3 = 7,38 V
The threshold voltage depends on the semi conductive materials used to make the component. They are always higher than silicon diode. Use manufacturer’s data sheet for each component to find out. The led lamps has the difficulty that two new batteries connected in series give about 3 V. This is so close the threshold that it has higher dynamic resistance, and after the batteries empty a little the voltage is not over the threshold voltage and the light dies immediately. We need to use 3 batteries and regulators to get adequate voltage.
3. We simulated the transistor switch with Multisim:
But unfortunately I didn’t save the pictures of this work.
4. We built and simulated the circuit with Elvis and Multisim and made measurements:
Our measurements:
|
By using Elvis |
By using Multisim |
|
|
Vin Vout VB VC VE |
978 mV 1,9 V 2,26 V 10,63 V 1,6 V |
399,84 mV 774,87 mV 2,51 V 9,7 V 1,7 V |
5. We measured the Collector-Base and Emitter-Base junctions:
0,5 V
We measured the junctions from Base to Collector and then from Base to Emitter and got similar picture, so everything is working fine.
6. We measured the characteristic current curves of the transistor:
Collector is connecting to DUT+
Base is connecting to BASE
Emitter is connecting to DUT-
∆IB = 15 µA
∆IC = 2 mA
In this lab we were got skills of working with PN-junction devices. Founded out how Zener diode is working, got familiar with a LED.
Also we simulated the transistor switch with Multisim.
We built and simulated the circuit with Elvis and Multisim, made measurements, and compared two results of each value. We measured the characteristic current curves of the transistor, and calculated the value of
1. We simulated the circuit and measured Vin and Vout:
2. We feed the same signal into these inputs, first into one input at a time and then into all at same time and measured Vin and Vout:
a) into one input at a time
b) into all at same time
3. a) Feed the signal into the one of inputs
b) Feed the same signal into the both inputs at the same time
During this laboratory work we made all the circuits. Measured V on the input, calculated its value on the output, and compared theoretical result with the values we’ve measured in practice.
We’ve feed same signal into the inputs, first into one at a time and then into all at same time, and connected the unused inputs to the ground.
Also we were changing frequency, and were looking for the differences in amplitude, and founded out that the amplitude is reducing.
During completing labs we learned a lot of theoretical and practical information about electronics. We got skills of working with special equipment, like Elvis, digital multimeter, oscilloscope, function generator etc. Learned a lot about basics of electronic circuits, their components got used to work with them.
Also, we got skills of measuring wide range of values, practical experience of “hands on” operating with electronic equipment.
During studying theoretical part, we learned about operating principles of different components, like capacitors, transistors, diodes etc, their types, and the way of their practical usage.