Any specialist engaged in the repair of electronic equipment or its development must know the element base. The focus of the electronics courses should be given to principle of interaction of electronic devices:
In addition to studying these devices, it is important to know and put into practice the basic laws of electrical engineering: Ohm’s Law, Kirchhoff’s Rules. As well as various types of connection of electronic components (serial, parallel, mixed).
Electronics courses teach the laws of interaction of charged particles with electromagnetic fields.
Regardless of the types of electronic equipment, they all have the same electronic components, but differ in circuitry and design. In the field of electronic engineering, there are passive and semiconductor elements.
Passive elements include:
Semiconductor devices include:
Interpretation of Ohm’s Law for a circuit section, in electronics courses:
Current is directly proportional to voltage and inversely proportional to resistance
Fuse – an element of an electrical circuit that performs a protective function. It protects the electrical circuit from a short circuit in the circuit and the flow of high current. In electrical circuit diagrams, it is denoted by the letter “F”, “FL”.
Graphically indicated by a rectangle with a solid line in the center. Fuses are made in glass, ceramic, integral cases. Designed for a certain rated current, the value of which is indicated on the fuse body.
A test point is a place in an electrical circuit that is used to measure or control the operation of an electronic circuit, diagnose it during repair, or tune it. The values of electrical parameters in it are indicated by the manufacturer or developers of electronic equipment.
When measuring values at control points and their discrepancy with the given ones, it can suggest search paths, which is convenient when repairing, debugging, and setting up any electronic equipment. TP is marked on electronic boards.
An electrical circuit node is a point (place) where three or more elements of an electrical circuit are connected. The resistance in the node is negligible. The node is necessary for the analysis of the electrical circuit. It has branching currents. The largest node in electrical circuits is a node with zero potential (usually this is a negative potential).
Resistors are the most common elements of electronic circuits. They are designed for:
Electronics courses include the study of circuit diagrams of the most common electronic devices. In the diagrams, the resistor is denoted by the letter R, measured in ohms. There are different types of resistors: general purpose, high-resistance, high-voltage, precision.
In turn, resistors have a certain power dissipation. In modern electronics, SMD resistors (surface mount) are more often used. The above resistors are fixed. Their value is always constant, and differs in instrument error.
In electronics courses, in addition to constants, they study variables and tuning resistors. These devices can change their values with the help of constructive solutions. With the help of tuning resistors, electrical modes are adjusted, and with the help of variables, multiple adjustments are made.
There are the following types of connection resistors:
To calculate all types of connections, Ohm’s law is applied for the circuit section I=U/R.
Resistors have basic parameters:
The marking of resistors can have a full designation or be coded in the form of colored stripes, or 3-4 numeric characters and having an additional letter.
In practice, in addition to linear and variable resistors, temperature-dependent and non-linear resistors are used. Thermistors heat up when an electric current flows through them. If their resistance increases, then they are called posistors. And if their resistance decreases, then they are called – thermistors.
Non-linear resistors whose resistance depends on voltage are called varistors. They are most often used to protect against overvoltage in power supplies. In electronic devices, they are used together with fuses.
Passing electronics courses, you will learn the purpose of a capacitor, methods for identifying faulty “capacities”.
Capacitor – a device capable of accumulating and storing an electric charge for a long time. It consists of two plates separated by a dielectric. When a voltage is applied to these plates, an electrical charge accumulates on them.
The charge is denoted by the letter “q”. Capacitor on electrical diagrams is indicated by the letter “C” and the capacitance of the capacitor is measured in Farads (F). Since the Farad value is very large, in practice much smaller values are used:
Accordingly, the amount of charge is determined by the capacitance of the capacitor and the applied voltage: q=C*U
Capacitors are widely used in electrical circuits. They are:
Capacitors conduct electrical alternating current, but do not conduct direct current. AC resistance is given by:
where f- AC frequency
Capacitors can be connected in series, parallel or mixed. This is necessary to obtain the required capacitance and applied voltage. They have full and abbreviated symbols.
There are also SMD capacitors. They do not have an inscription and encoding. The value of their parameters can only be determined by measuring with a device, which greatly complicates the repair of equipment in the absence of technical documentation for the device.
Capacitors have the following main parameters:
Inductive elements are capable of accumulating electromagnetic energy when an electric current passes through them. These include inductors. Unlike capacitors, they are less common in electrical circuits. They are used strictly for the manufacture of certain equipment, they have the parameters necessary for specific devices.
Coils have large dimensions and weight, so their area of definition is limited. But when developing electronic equipment, it is impossible to do without them. By design, they have a cylindrical or spiral shape of turns. Can be wound in one or more layers.
Inductance is denoted by the letter L, measured in Henry H. Since this value is large, in practice a smaller value is used – millihenry and microhenry. To increase the inductance of the coil, a magnetic circuit is used. Coils can be fixed and adjustable. Adjustment is carried out using the core.
These devices can operate at high and low AC frequencies. Accordingly, the resistance of the coil to alternating current is determined by the formula
f – AC frequency
The most important parameter of the coil is the quality factor. This is the ratio of reactance to resistive.
This value depends on the AC frequency. At direct current, the resistance of the coil is small. Varieties of the coil are chokes. They provide high AC resistance and low DC resistance. Work at low and high frequencies.
Inductors have the main parameters:
After completing the electronics courses, you will learn how to troubleshoot transformers on electronic circuit boards. Transformer – a device for converting the parameters of alternating voltages and currents. Transformers allow you to match the resistance of the signal source and load, separate the circuits by direct current, change the form of alternating voltage and current.
The principle of operation of the transformer is based on the conversion of the energy of an electric field into a magnetic field and vice versa. In the design of the transformer, there are two types of windings: primary and secondary.
There are many transformers:
An important parameter of the transformer is the transformation ratio, which determines how the voltage and current at the output have changed relative to the voltage and current applied to the input. Denoted by Ku and determined by the formula:
The main parameters of transformers are: