Electrical circuit diagrams

The main purpose of the fundamental electrical diagrams is a reflection with sufficient completeness and clarity of the mutual connection of individual devices, automation equipment and auxiliary equipment that are part of the functional units of automation systems, taking into account the sequence of their operation and the principle of operation. serve to study the principle of operation of the automation system; they are also necessary in.

Circuit diagrams are the basis for the development of other project documents: wiring diagrams and tables of switchboards and consoles, external wiring diagrams, connection diagrams, etc.

When developing automation systems technological processes usually they carry out schematic electrical diagrams of independent elements, installations or sections of the automated system, for example, a valve control diagram, an automatic and remote control pump, tank level signaling circuit, etc.

Schematic electrical diagrams are drawn up on the basis of automation diagrams, based on specified algorithms for the functioning of individual control, alarm, automatic regulation and control units and general technical requirements requirements for the automated object.

Schematic electrical diagrams depict devices, devices, and communication lines between individual elements, blocks and modules of these devices in a conventional form.

In general, circuit diagrams contain:

1) conventional images of the operating principle of one or another functional unit of the automation system;

2) explanatory notes;

3) parts of individual elements (devices, electrical devices) of a given circuit, used in other circuits, as well as elements of devices from other circuits;

4) diagrams of switching contacts of multi-position devices;

5) a list of devices and equipment used in this scheme;

6) a list of drawings related to this scheme, general explanations and notes. To read circuit diagrams, you need to know the algorithm for the functioning of the circuit, understand the principle of operation of devices, devices on the basis of which the circuit diagram is built.

Schematic diagrams of monitoring and control systems according to their intended purpose can be divided into control circuits, process control and signaling, automatic regulation and power supply. Schematic diagrams by type can be electrical, pneumatic, hydraulic and combined. Currently, electrical and pneumatic circuits are most widely used.

The electrical circuit diagram is the first working document, on the basis of which:

1) carry out drawings for the manufacture of products ( common types And wiring diagrams and tables of switchboards, consoles, cabinets, etc.) and their connections with devices, actuators and among themselves;

2) check the correctness of the connections made;

3) set settings for protection devices, means of monitoring and regulating the process;

4) set up travel and limit switches;

5) analyze the circuit both during the design process and during commissioning and operation in case of deviation from the specified operating mode of the installation, premature failure of any element, etc.

Thus, depending on the work being done, reading a circuit diagram has different purposes.

In addition, if reading wiring diagrams comes down to determining what, where and how to install, route and connect, then reading a circuit diagram is much more difficult. In many cases, it requires deep knowledge, mastery of reading techniques and the ability to analyze the information received. And finally, an error made in a schematic diagram will inevitably be repeated in all subsequent documents. As a result, you will again have to return to reading the circuit diagram in order to identify what error was made in it or what in a particular case does not correspond to the correct circuit diagram (for example, a multi-contact software relay is connected correctly, but the duration or sequence of contact switching set during setup does not correspond to the task) .

The listed tasks are quite complex, and consideration of many of them is beyond the scope of this article. Nevertheless, it is useful to explain what their essence is and list the main technical solutions.

1. Reading a schematic diagram always begins with a general familiarization with it and the list of elements, finding each of them on the diagram, reading all the notes and explanations.

2. They determine the power supply system for electric motors, windings of magnetic starters, relays, electromagnets, complete instruments, regulators, etc. To do this, find all power sources on the diagram, identify for each of them the type of current, rated voltage, phasing in the circuits alternating current and polarity in circuits direct current and compare the obtained data with the nominal data of the equipment used.

Using the diagram, general switching devices are identified, as well as protection devices: circuit breakers, fuses, maximum current and minimum voltage relays, etc. The settings of the devices are determined from the inscriptions on the diagram, tables or notes and, finally, the protection zone of each of them is assessed.

Familiarization with the power supply system may be necessary to: identify the causes of power failure; determining the order in which power should be supplied to the circuit (this is not always indifferent); checking the correct phasing and polarity (incorrect phasing can, for example, in redundancy schemes lead to short circuit, change in the direction of rotation of electric motors, breakdown of capacitors, disruption of circuit separation using diodes, failure of polarized relays, etc.); assessing the consequences of blowing each fuse.

3. They study all possible circuits of each electrical receiver: electric motor, magnetic starter windings, relays, devices, etc. But there are many electrical receivers in the circuit and it is far from indifferent from which one to start reading the circuit - this is determined by the task at hand. If you need to determine its operating conditions from the diagram (or check whether they correspond to the specified ones), then start with the main electrical receiver, for example, with a valve motor. Subsequent electrical receivers will reveal themselves.

For example, to start an electric motor you need to turn on. Therefore, the next electrical receiver should be the winding of the magnetic starter. If its circuit includes the contact of an intermediate relay, it is necessary to consider the circuit of its winding, etc. But there may be another problem: some element of the circuit has failed, for example, a certain signal lamp does not light up. Then it will be the first power receiver.

It is very important to emphasize that if you do not adhere to a certain focus when reading the scheme, you can waste a lot of time without solving anything.

So, when studying the selected electrical receiver, you need to trace all its possible circuits from pole to pole (from phase to phase, from phase to zero, depending on the power system). In this case, it is necessary, firstly, to identify all contacts, diodes, resistors, etc., included in the circuit.

We especially emphasize that you cannot consider several circuits at once. You must first study, for example, the circuit for turning on the winding of the “Forward” magnetic starter with local control, establishing in what position the elements included in this circuit should be (the mode switch is in the “Local control” position, the “Backward” magnetic starter is disabled), which needs to be done to turn on the winding of the magnetic starter (press the “Forward” push-button switch), etc. Then you should mentally turn off the magnetic starter. Having examined the local control circuit, mentally move the mode switch to the “ Automatic control” and study the next chain.

Familiarization with each circuit of the electrical circuit has the purpose of:

A) determine the action conditions that the circuit satisfies;

b) identify errors; for example, a circuit may have contacts connected in series that should never be closed at the same time;

V) define possible reasons refusal. A faulty circuit, for example, includes contacts of three devices. By examining each of them, it is easy to identify the faulty one. Such tasks arise during setup and troubleshooting during operation;

G) identify elements in which timing relationships may be violated, either as a result of incorrect adjustment or due to an incorrect assessment by the designer of actual operating conditions.

Typical shortcomings are too short pulses (the controlled mechanism does not have time to complete the started cycle), too long pulses (the controlled mechanism, having completed the cycle, begins to repeat it), violation of the required switching order (for example, valves and the pump are turned on in the wrong order , or sufficient intervals are not maintained between operations);

d) identify devices that may have incorrect settings; a typical example is an incorrect setting of the current relay in the valve control circuit;

e) identify devices whose switching capacity is insufficient for the switched circuits, or the rated voltage is lower than required, or the operating currents of the circuits are greater than the rated currents of the device, etc.. P.

Typical examples: the contacts of an electric contact thermometer are directly inserted into the magnetic starter circuit, which is completely unacceptable; in the 220 V voltage circuit a diode is used reverse voltage 250 V, which is not enough, since it may be under a voltage of 310 V (K2-220 V); the rated current of the diode is 0.3 A, but it is connected to a circuit through which a current of 0.4 A passes, which will cause unacceptable overheating; the signal switch lamp 24 V, 0.1 A is connected to a voltage of 220 V through an additional resistor of the PE-10 type with a resistance of 220 Ohms. The lamp will glow normally, but the resistor will burn out, since the power released in it is approximately twice the rated one;

and) identify devices susceptible to switching overvoltages and evaluate protective measures against them(for example, damping circuits);

h) identify devices whose operation may be unacceptably influenced by adjacent circuits, and evaluate means of protection against influences;

And) identify possible false circuits both in normal modes and during transient processes, for example, recharging of capacitors, the entry into a sensitive electrical receiver of energy released when the inductance is turned off, etc.

False circuits are sometimes formed not only when there is an unexpected connection, but also when a contact is not closed or one fuse is blown, while the rest remain intact. For example, the intermediate relay of a process control sensor is connected through one power circuit, and its opening contact is connected through another. If the fuse blows, the intermediate relay will release, which will be perceived by the circuit as a violation of the mode. In this case, it is impossible to separate the power circuits or you need to design the circuit differently, etc.

False circuits can be formed if the supply voltage supply order is not observed, which indicates poor design quality. In correctly designed circuits, the sequence of supply of supply voltages, as well as their restoration after disturbances, should not lead to any operational switching;

To) evaluate the consequences of insulation failure one by one at each point of the circuit. For example, if the buttons are connected to the neutral working conductor, and the starter winding is connected to the phase winding (it is necessary to turn it on the other way around), then when the “Stop” push-button switch is connected to the grounding conductor, the starter cannot be turned off. If the wire after the “Start” push-button switch is shorted to ground, the starter will turn on automatically;

k) evaluate the purpose of each contact, diode, resistor, capacitor, for which we proceed from the assumption that the element or contact in question is missing, and evaluate what consequences this will lead to.

4. Set the behavior of the circuit during a partial power outage, as well as when it is restored. This most important issue, unfortunately, is often underestimated, so one of the main tasks of reading a circuit is to check whether the device can come from any intermediate state to a working state and whether unexpected operational switching will occur. That is why the standard requires that circuits be depicted under the assumption that the power is turned off and the devices and their parts (for example, relay armatures) are not subject to forced influences. From this starting point we need to analyze the schemes. Interaction time diagrams, which reflect the dynamics of the circuit’s operation, and not just some steady state, are of great help in analyzing circuits.

Content:

Each electrical circuit consists of many elements, which, in turn, also include various parts in their design. The most striking example is Appliances. Even a regular iron consists of a heating element, temperature regulator, pilot light, fuse, wire and plug. Other electrical appliances have an even more complex design, complemented by various relays, circuit breakers, electric motors, transformers and many other parts. An electrical connection is created between them, ensuring full interaction of all elements and each device fulfilling its purpose.

In this regard, the question very often arises of how to learn to read electrical diagrams, where all components are displayed in the form of conventional graphic symbols. This problem It has great importance for those who regularly deal with electrical installations. Correct reading of diagrams makes it possible to understand how the elements interact with each other and how all work processes proceed.

Types of electrical circuits

In order to correctly use electrical circuits, you need to familiarize yourself in advance with the basic concepts and definitions affecting this area.

Any diagram is made in the form of a graphic image or drawing, on which, together with the equipment, all the connecting links of the electrical circuit are displayed. There are different types of electrical circuits that differ in their intended purpose. Their list includes primary and secondary circuits, alarm systems, protection, control and others. In addition, there are and are widely used principled and fully linear and expanded. Each of them has its own specific features.

Primary circuits include circuits through which the main process voltages are supplied directly from sources to consumers or receivers of electricity. Primary circuits generate, convert, transmit and distribute electrical energy. They consist of a main circuit and circuits that provide their own needs. The main circuit circuits generate, convert and distribute the main flow of electricity. Circuits for their own needs ensure the operation of the main electrical equipment. Through them, voltage is supplied to the electric motors of the installations, to the lighting system and to other areas.

Secondary circuits are considered to be those in which the applied voltage does not exceed 1 kilowatt. They provide automation, control, protection, and dispatch functions. Through secondary circuits, control, measurement and metering of electricity are carried out. Knowing these properties will help you learn to read electrical circuits.

Full-linear circuits are used in three-phase circuits. They display electrical equipment connected to all three phases. Single-line diagrams show equipment located on only one middle phase. This difference must be indicated on the diagram.

Schematic diagrams do not indicate minor elements that do not perform primary functions. Due to this, the image becomes simpler, allowing you to better understand the principle of operation of all equipment. Installation diagrams, on the contrary, are carried out in more detail, since they are used for the practical installation of all elements electrical network. These include single-line diagrams displayed directly on the construction plan of the facility, as well as diagrams of cable routes along with transformer substations and distribution points, plotted on a simplified general plan.

During the installation and commissioning process, extensive circuits with secondary circuits have become widespread. They highlight additional functional subgroups of circuits related to switching on and off, individual protection of any section, and others.

Symbols in electrical diagrams

Every electrical circuit contains devices, elements, and parts that together form a path for electrical current. They are distinguished by the presence of electromagnetic processes associated with electromotive force, current and voltage, and described in physical laws.

In electrical circuits, all components can be divided into several groups:

1. The first group includes devices that generate electricity or power sources.
2. The second group of elements converts electricity into other types of energy. They perform the function of receivers or consumers.
3. The components of the third group ensure the transfer of electricity from one element to another, that is, from the power source to electrical receivers. This also includes transformers, stabilizers and other devices that provide the required quality and voltage level.

Each device, element or part corresponds to a symbol used in graphic images electrical circuits, called electrical circuits. In addition to the main symbols, they display the power lines connecting all these elements. The sections of the circuit along which the same currents flow are called branches. The places of their connections are nodes, indicated on electrical diagrams in the form of dots. There are closed current paths that cover several branches at once and are called electrical circuit circuits. The simplest electrical circuit diagram is single-circuit, while complex circuits consist of several circuits.

Most circuits consist of various electrical devices that differ in different operating modes, depending on the value of current and voltage. In idle mode, there is no current in the circuit at all. Sometimes such situations arise when connections are broken. In nominal mode, all elements operate with the current, voltage and power specified in the device passport.

All components and symbols of the elements of the electrical circuit are displayed graphically. The figures show that each element or device has its own symbol. For example, electrical machines may be depicted in a simplified or expanded manner. Depending on this, conditional graphic diagrams. Single-line and multi-line images are used to show winding terminals. The number of lines depends on the number of pins, which will be different for various types cars In some cases, for ease of reading diagrams, mixed images can be used, when the stator winding is shown in expanded form, and the rotor winding is shown in a simplified form. Others are performed in the same way.

They are also carried out in simplified and expanded, single-line and multi-line methods. The way of displaying the devices themselves, their terminals, winding connections and other components depends on this. For example, in current transformers for image primary winding a thick line highlighted with dots is used. For the secondary winding, a circle can be used in the simplified method or two semicircles in the expanded image method.

Graphic representations of other elements:

• Contacts. They are used in switching devices and contact connections, mainly in switches, contactors and relays. They are divided into closing, breaking and switching, each of which has its own graphic design. If necessary, it is allowed to depict the contacts in a mirror-inverted form. The base of the moving part is marked with a special unshaded dot.
• . They can be single-pole or multi-pole. The base of the moving contact is marked with a dot. U circuit breakers The image indicates the type of release. Switches differ in the type of action; they can be push-button or track, with normally open and closed contacts.
• Fuses, resistors, capacitors. Each of them corresponds to certain icons. Fuses are depicted as a rectangle with taps. For permanent resistors, the icon may have taps or no taps. The moving contact of a variable resistor is indicated by an arrow. The pictures of capacitors show constant and variable capacitance. There are separate images for polar and non-polar electrolytic capacitors.
• Semiconductor devices. The simplest of them are pn junction diodes with one-way conduction. Therefore, they are depicted in the form of a triangle and an electrical connection line crossing it. The triangle is the anode, and the dash is the cathode. For other types of semiconductors, there are their own designations defined by the standard. Knowing these graphical drawings makes reading electrical circuits for dummies much easier.
• Sources of light. Available on almost all electrical circuits. Depending on their purpose, they are displayed as lighting and warning lamps with corresponding icons. When depicting signal lamps, it is possible to shade a certain sector, corresponding to low power and low luminous flux. In alarm systems, along with light bulbs, acoustic devices are used - electric sirens, electric bells, electric horns and other similar devices.

How to read electrical diagrams correctly

A schematic diagram is a graphical representation of all the elements, parts and components between which an electronic connection is made using live conductors. It is the basis for the development of any electronic devices and electrical circuits. Therefore, every novice electrician must first master the ability to read a variety of circuit diagrams.

It is the correct reading of electrical diagrams for beginners that allows you to understand well how to connect all the parts to get the expected end result. That is, the device or circuit must fully perform its intended functions. To correctly read the circuit diagram, it is necessary, first of all, to familiarize yourself with the symbols of all its components. Each part is marked with its own graphic designation - UGO. Typically, such symbols reflect the general design, characteristic features and purpose of a particular element. The most striking examples are capacitors, resistors, speakers and other simple parts.

It is much more difficult to work with components represented by transistors, triacs, microcircuits, etc. The complex design of such elements also implies a more complex display of them on electrical circuits.

For example, each bipolar transistor has at least three terminals - base, collector and emitter. Therefore, their conventional representation requires special graphic symbols. This helps distinguish between parts with individual basic properties and characteristics. Each symbol carries certain encrypted information. For example, bipolar transistors may have completely different structures - p-p-p or p-p-p, so the images on the circuits will also be noticeably different. It is recommended that you carefully read all the elements before reading the electrical circuit diagrams.

Conditional images are often supplemented with clarifying information. Upon closer examination, you can see Latin alphabetic symbols next to each icon. This way, this or that detail is designated. This is important to know, especially when we are just learning to read electrical diagrams. There are also numbers next to the letter designations. They indicate the corresponding numbering or specifications elements.

Let's look at the operating principle of a simple circuit

So let's move on. We sort of figured out the load, work and power in the last article. Well, now, my dear crooked friends, in this article we will read the diagrams and analyze them using previous articles.

Out of the blue, I drew a diagram. Its function is to control a 40 Watt lamp using 5 Volts. Let's take a closer look at it.

This circuit is unlikely to be suitable for microcontrollers, since the MK leg will not carry the current that consumes the relay.

Looking for power sources

The first question we need to ask ourselves is: “What is the circuit powered by and where does it get its power from?” How many power supplies does it have? As you can see here, the circuit has two different sources supply voltages of +5 Volts and +24 Volts.

We understand each radio element in the circuit

Let us remember the purpose of each radio element that is found in the circuit. We are trying to understand why the developer drew it here.

Terminal block

Here we drive or hook either or another piece of the circuit. In our case, we drive +5 Volts to the upper terminal block, and therefore zero to the lower one. The same goes for +24 Volts. We drive +24 Volts to the upper terminal block, and zero to the lower one.

Grounding to the chassis.

In principle, it seems possible to call this icon earth, but it is not advisable. In diagrams this is how a potential of zero volts is indicated. All voltages in the circuit are read and measured from it.

How does it act on electric current? When it is in the open position, no current flows through it. When it is in a closed position, then electricity begins to flow through it unhindered.

Diode.

It allows electric current to pass in only one direction and blocks the passage of electric current in the other direction. I will explain below why it is needed in the circuit.

Electromagnetic relay coil.

If an electric current is applied to it, it will create a magnetic field. And since it smells like a magnet, all sorts of pieces of iron will rush towards the coil. There are key contacts 1-2 on the piece of iron, and they are closed to each other. You can read more about the operating principle of an electromagnetic relay in this article.

Bulb

We apply voltage to it and the light comes on. Everything is elementary and simple.

Basically, diagrams are read from left to right, if, of course, the developer knows at least a little about the rules for designing diagrams. The circuits also operate from left to right. That is, on the left we drive a signal, and on the right we remove it.

Predicting the direction of electric current

While the S key is turned off, the circuit is inoperative:

But what happens if we close the key S? Let us remember the main rule of electric current: current flows from higher potential to lower potential, or popularly, from plus to minus. Therefore, after closing the key, our circuit will look like this:

An electric current will run through the coil, it will attract contacts 1-2, which in turn will close and cause an electric current in the +24 Volt circuit. As a result, the light will light up. If you know what a diode is, then you will probably understand that electric current will not flow through it, since it only passes in one direction, and now the direction of the current for it is the opposite.

So, what is the diode for in this circuit?

Don't forget the property of inductance, which states: When the switch is opened, a self-induction emf is generated in the coil, which maintains original current and can reach very large values. What does inductance even have to do with it? In the diagram, the inductor coil icon is nowhere to be found... but there is a relay coil, which is precisely an inductance. What happens if we sharply throw the key S back to its original position? The magnetic field of the coil is immediately converted into an EMF of self-induction, which will tend to maintain the electric current in the circuit. And in order to put this resulting electric current somewhere, we have a diode in the circuit ;-). That is, when you turn it off, the picture will be like this:

It turns out a closed loop relay coil --> diode, in which the self-induction EMF decays and is converted into heat on the diode.

Now let's assume that we don't have a diode in the circuit. When the key was opened, the picture would be like this:

A small spark would jump between the contacts of the key (highlighted with a blue circle), since the self-induction EMF is trying with all its might support current in the circuit. This spark has a negative effect on the key contacts, as deposits remain on them, which wears them out over time. But this is not the worst thing yet. Since the self-induction EMF can be very large in amplitude, this also negatively affects radio elements that can go BEFORE the relay coil.

This impulse can easily penetrate semiconductors and damage them to the point of complete failure. Currently, diodes are already built into the relay itself, but not yet in all copies. So don't forget to check the relay coil for the built-in diode.

I think now everyone understands how the scheme should work. In this circuit we looked at how voltage behaves. But electric current is not only voltage. If you haven't forgotten, electric current is characterized by such parameters as directionality, voltage and current strength. Also, do not forget about such concepts as power released by the load and load resistance. Yes, yes, all this must be taken into account.

Calculate current and power

When considering circuits, we do not need to calculate current, power, etc. to the penny. It is enough to roughly understand what current strength will be in this circuit, what power will be released on this radio element, etc.

So, let's go over the current strength in each branch of the circuit when the S key is turned on.

First, let's look at the diode. Since the cathode of the diode in this case is positive, it will therefore be locked. That is, in this moment The current through it will be some microamperes. Almost nothing, one might say. That is, it does not affect the enabled circuit in any way. But as I already wrote above, it is needed in order to dampen the jump in the self-induction EMF when the circuit is turned off.

Relay coil. Already more interesting. The relay coil is a solenoid. What is a solenoid? This is a wire wound around a cylindrical frame. But our wire has some kind of resistance, therefore, we can say in this case that the relay coil is a resistor. Therefore, the current strength in the coil circuit will depend on how thick the wire is wound and what the wire is made of. In order not to measure every time, there is a sign that I stole from my fellow competitor from the article electromagnetic relay:

Since our relay coil is 5 Volt, it turns out that the current through the coil will be about 72 milliamps, and the power consumption will be 360 ​​milliwatts. What do these numbers even tell us? Yes, that a 5 Volt power source must at least deliver more than 360 milliwatts to the load. Well, we figured out the relay coil, and at the same time the 5-volt power supply.

Next, relay contacts 1-2. How much current will pass through them? Our lamp is 40 Watt. Therefore: P=IU, I=P/U=40/24=1.67 Ampere. In principle, the current strength is normal. If you received any abnormal current strength, for example, more than 100 Amperes, then you should be wary. We also don’t forget about the 24 Volt power supply, so that this power source can easily deliver more than 40 Watts of power.

Summary

The diagrams are read from left to right (there are rare exceptions).

We determine where the circuit has power.

Let's remember the meaning of each radio element.

We look at the direction of the electric current in the diagram.

Let's look at what should happen in the circuit if power is applied to it.

We approximately calculate the current in the circuits and the power released by the radioelements in order to make sure that the circuit will actually work and there are no anomalous parameters in it.

If you really want, you can run the circuit through a simulator, for example through the modern Every Circuit, and look at the various parameters that interest us.

In this article we will look at the designation of radio elements on diagrams.

Where to start reading diagrams?

In order to learn how to read circuits, first of all, we must study what a particular radio element looks like in a circuit. In principle, there is nothing complicated about this. The whole point is that if the Russian alphabet has 33 letters, then in order to learn the symbols of radio elements, you will have to try hard.

Until now, the whole world cannot agree on how to designate this or that radio element or device. Therefore, keep this in mind when you collect bourgeois schemes. In our article we will consider our Russian GOST version of the designation of radioelements

Studying a simple circuit

Okay, let's get to the point. Let's look at a simple electrical circuit of a power supply, which used to appear in any Soviet paper publication:

If this is not the first day you have held a soldering iron in your hands, then everything will immediately become clear to you at first glance. But among my readers there are also those who are encountering such drawings for the first time. Therefore, this article is mainly for them.

Well, let's analyze it.

Basically, all diagrams are read from left to right, just like you read a book. Any different circuit can be represented as a separate block to which we supply something and from which we remove something. Here we have a circuit of a power supply to which we supply 220 Volts from the outlet of your house, and a constant voltage comes out of our unit. That is, you must understand what is the main function of your circuit?. You can read this in the description for it.

How are radioelements connected in a circuit?

So, it seems that we have decided on the task of this scheme. Straight lines are wires or printed conductors through which electric current will flow. Their task is to connect radioelements.

The point where three or more conductors connect is called knot. We can say that this is where the wiring is soldered:

If you look closely at the diagram, you can see the intersection of two conductors

Such intersection will often appear in diagrams. Remember once and for all: at this point the wires are not connected and they must be insulated from each other. IN modern schemes Most often you can see this option, which already visually shows that there is no connection between them:

Here, it is as if one wire goes around the other from above, and they do not contact each other in any way.

If there was a connection between them, then we would see this picture:

Letter designation of radioelements in the circuit

Let's look at our diagram again.

As you can see, the diagram consists of some strange icons. Let's look at one of them. Let this be the R2 icon.

So, let's first deal with the inscriptions. R means . Since we have him not the only one in the scheme, the developer of this scheme gave him the serial number “2”. There are as many as 7 of them in the diagram. Radio elements are generally numbered from left to right and top to bottom. A rectangle with a line inside already clearly shows what it is constant resistor with a dissipation power of 0.25 Watt. It also says 10K next to it, which means its denomination is 10 Kilohms. Well, something like this...

How are the remaining radioelements designated?

Single-letter and multi-letter codes are used to designate radioelements. Single letter codes are group, to which this or that element belongs. Here are the main ones groups of radioelements:

A - This various devices(eg amplifiers)

IN – converters of non-electrical quantities into electrical ones and vice versa. This may include various microphones, piezoelectric elements, speakers, etc. Generators and power supplies here do not apply.

WITH – capacitors

D – integrated circuits and various modules

E – miscellaneous elements that do not fall into any group

F – arresters, fuses, protective devices

H – indicating and signaling devices, for example, sound and light indicating devices

K – relays and starters

L – inductors and chokes

M – engines

R – instruments and measuring equipment

Q – switches and disconnectors in power circuits. That is, in circuits where high voltage and high current “walk”

R – resistors

S – switching devices in control, signaling and measurement circuits

T – transformers and autotransformers

U – converters of electrical quantities into electrical ones, communication devices

V – semiconductor devices

W – microwave lines and elements, antennas

X – contact connections

Y – mechanical devices with electromagnetic drive

Z – terminal devices, filters, limiters

To clarify the element, after the one-letter code there is a second letter, which already indicates element type. Below are the main types of elements along with the letter group:

BD – ionizing radiation detector

BE – selsyn receiver

B.L. – photocell

BQ – piezoelectric element

BR – speed sensor

B.S. – pickup

B.V. - speed sensor

B.A. – loudspeaker

BB – magnetostrictive element

B.K. – thermal sensor

B.M. – microphone

B.P. - pressure meter

B.C. – selsyn sensor

D.A. – integrated analog circuit

DD – digital integrated circuit, logic element

D.S. – information storage device

D.T. – delay device

EL - lighting lamp

E.K. - a heating element

F.A. – instantaneous current protection element

FP – inertial current protection element

F.U. - fuse

F.V. – voltage protection element

G.B. - battery

HG – symbolic indicator

H.L. – light signaling device

H.A. – sound alarm device

KV – voltage relay

K.A. – current relay

KK – electrothermal relay

K.M. - magnetic switch

KT – time relay

PC – pulse counter

PF – frequency meter

P.I. – active energy meter

PR – ohmmeter

PS – recording device

PV – voltmeter

PW – wattmeter

PA – ammeter

PK – reactive energy meter

P.T. - watch

QF

QS – disconnector

RK – thermistor

R.P. – potentiometer

R.S. – measuring shunt

RU – varistor

S.A. – switch or switch

S.B. – push-button switch

SF - Automatic switch

S.K. – temperature-triggered switches

SL – switches activated by level

SP – pressure switches

S.Q. – switches activated by position

S.R. – speed-triggered switches

TV – voltage transformer

T.A. - current transformer

UB – modulator

UI – discriminator

UR – demodulator

UZ – frequency converter, inverter, frequency generator, rectifier

VD – diode, zener diode

VL – electrovacuum device

VS – thyristor

VT –

W.A. – antenna

W.T. – phase shifter

W.U. – attenuator

XA – current collector, sliding contact

XP – pin

XS - nest

XT – collapsible connection

XW – high frequency connector

YA – electromagnet

YB – brake with electromagnetic drive

YC – clutch with electromagnetic drive

YH – electromagnetic plate

ZQ – quartz filter

Graphic designation of radioelements in the circuit

I will try to give the most common designations of elements used in the diagrams:

Resistors and their types

A) general designation

b) dissipation power 0.125 W

V) dissipation power 0.25 W

G) dissipation power 0.5 W

d) dissipation power 1 W

e) dissipation power 2 W

and) dissipation power 5 W

h) dissipation power 10 W

And) dissipation power 50 W

Variable resistors

Thermistors

Strain gauges

Varistors

Shunt

Capacitors

a) general designation of a capacitor

b) variconde

V) polar capacitor

G) trimmer capacitor

d) variable capacitor

Acoustics

a) headphone

b) loudspeaker (speaker)

V) general designation of a microphone

G) electret microphone

Diodes

A) diode bridge

b) general designation of a diode

V) zener diode

G) double-sided zener diode

d) bidirectional diode

e) Schottky diode

and) tunnel diode

h) reversed diode

And) varicap

To) Light-emitting diode

l) photodiode

m) emitting diode in the optocoupler

n) radiation receiving diode in the optocoupler

Electrical quantity meters

A) ammeter

b) voltmeter

V) voltammeter

G) ohmmeter

d) frequency meter

e) wattmeter

and) faradometer

h) oscilloscope

Inductors

A) coreless inductor

b) inductor with core

V) tuning inductor

Transformers

A) general designation of a transformer

b) transformer with winding output

V) current transformer

G) transformer with two secondary windings (maybe more)

d) three-phase transformer

Switching devices

A) closing

b) opening

V) opening with return (button)

G) closing with return (button)

d) switching

e) reed switch

Electromagnetic relay with different groups of contacts

Circuit breakers

A) general designation

b) the side that remains energized when the fuse blows is highlighted

V) inertial

G) fast acting

d) thermal coil

e) switch-disconnector with fuse

Thyristors

Bipolar transistor

Unijunction transistor

Any radio or electrical device consists of a certain number of different electrical and radio elements (radio components). Take, for example, a very ordinary iron: it has a temperature regulator, a light bulb, a heating element, a fuse, wires and a plug.

An iron is an electrical device assembled from a special set of radio elements that have certain electrical properties, where the operation of the iron is based on the interaction of these elements with each other.

To carry out interaction, radioelements (radio components) are connected to each other electrically, and in some cases they are placed on a short distance from each other and interaction occurs through an inductive or capacitive connection formed between them.

The easiest way to understand the structure of the iron is to take an accurate photograph or drawing of it. To make the presentation more complete, you can take several photographs. appearance close-ups from different angles, and several photographs of the internal structure.

However, as you noticed, this way of understanding the structure of the iron does not give us anything at all, since only general picture about the details of the iron. And what radioelements it consists of, what their purpose is, what they represent, what function they perform in the operation of the iron and how they are connected to each other electrically is not clear to us.

That’s why, in order to have an idea of ​​what radioelements such electrical devices consist of, we developed graphic symbols radio components. And in order to understand what parts the device is made of, how these parts interact with each other and what processes take place, special electrical circuits were developed.

Electrical diagram is a drawing containing in the form of conventional images or symbols the components (radio elements) electrical device and connections (connections) between them. That is, the electrical diagram shows how the radio elements are connected to each other.

Radio elements of electrical devices can be resistors, lamps, capacitors, microcircuits, transistors, diodes, switches, buttons, starters, etc., and connections and connections between them can be made by wiring, cable, detachable connection, tracks printed circuit boards etc.

Electrical circuits must be understandable to everyone who has to work with them, and therefore they are carried out in standard symbols and used according to a certain system established by state standards: GOST 2.701-2008; GOST 2.710-81; GOST 2.721-74; GOST 2.728-74; GOST 2.730-73.

There are three main types of schemes: structural, fundamental electrical, electrical connection diagrams (assembly).

Structural scheme(functional) is developed in the first stages of design and is intended for general familiarization with the operating principle of the device. On the diagram, rectangles, triangles or symbols depict the main nodes or blocks of the device, which are connected to each other by lines with arrows indicating the direction and sequence of connections to each other.

Electrical circuit diagram determines what radioelements (radio components) an electrical or radio device consists of, how these radio components are electrically connected to each other, and how they interact with each other. In the diagram, the parts of the device and the order of their connection are depicted with symbols symbolizing these parts. And although the circuit diagram does not give an idea of ​​​​the dimensions of the device and the placement of its parts on circuit boards, boards, panels, etc., it does allow you to understand in detail its operating principle.

Electrical connection diagram or it is also called wiring diagram, is a simplified design drawing depicting an electrical device in one or more projections, which shows the electrical connections of parts to each other. The diagram shows all the radioelements included in the device, their exact location, connection methods (wires, cables, harnesses), connection points, as well as input and output circuits (connectors, clamps, boards, connectors, etc.). Images of parts on diagrams are given in the form of rectangles, conventional graphic symbols, or in the form of simplified drawings of real parts.

The difference between a structural, circuit and wiring diagram will be shown further with specific examples, but we will place the main emphasis on circuit diagrams.

If you carefully examine the circuit diagram of any electrical device, you will notice that the symbols of some radio components are often repeated. Just as a word, phrase or sentence consists of letters assembled into words alternating in a certain order, so an electrical circuit consists of separate conventional graphic symbols of radio elements and their groups alternating in a certain order.

Conventional graphic symbols of radioelements are formed from the simplest geometric shapes: squares, rectangles, triangles, circles, as well as from solid and dashed lines and dots. Their combination according to the system provided for by the ESKD standard ( one system design documentation), makes it possible to easily depict radio components, instruments, electrical machines, electrical communication lines, types of connections, type of current, methods of measuring parameters, etc.

As a graphic designation of radioelements, their extremely simplified image is taken, in which either their most general and characteristic features are preserved, or their basic principle of operation is emphasized.

For example. A conventional resistor is a ceramic tube, on the surface of which is applied conductive layer, having a certain electrical resistance. Therefore, on electrical diagrams, a resistor is designated as rectangle, symbolizing the shape of a tube.

Thanks to this construction principle, memorizing conventional graphic symbols is not particularly difficult, and the compiled diagram is easy to read. And in order to learn how to read electrical circuits, first of all, you need to study the symbols, so to speak, the “alphabet” of electrical circuits.

We'll leave it at that. We will analyze three main types of electrical circuits that you will often encounter when developing or reproducing electronic or electrical equipment.
Good luck!