The main technical documents for an electrician and electrician are drawings and electrical diagrams. The drawing includes the dimensions, shape, material and composition of the electrical installation. It is not always possible to understand the functional connection between elements. It helps you understand the electrical diagram, which you need to have when using electrical installation drawings.

To read, you need to know and remember well: the most common symbols of windings, contacts, transformers, motors, rectifiers, lamps, etc., symbols used in the area with which you mainly encounter due to profession, diagrams of the most common components electrical installations, for example motors, rectifiers, lighting with incandescent and gas-discharge lamps, etc., properties of series and parallel connections of contacts, windings, resistances, inductances and capacitances.

Dividing schemes into simple chains

Any electrical installation meets certain operating conditions. Therefore, when reading the diagrams, firstly, it is necessary to identify these conditions, secondly, to determine whether the obtained conditions correspond to the tasks that must be solved by the electrical installation, and thirdly, it is necessary to check whether “extra” conditions have arisen along the way, and evaluate them consequences.

To solve these issues, several techniques are used.

The first one is that The electrical installation diagram is mentally divided into simple circuits, which are first considered separately and then in combination.

A simple circuit includes a current source (battery, transformer secondary, charged capacitor, etc.), a current receiver (motor, resistor, lamp, relay winding, discharged capacitor, etc.), a direct wire (from the current source to the receiver ), return wire (from the current receiver to the source) and one contact of the device (switch, relay, etc.). It is clear that in circuits that do not allow opening, for example in circuits of current transformers, there are no contacts.

When reading a diagram, you must first mentally break it down into simple circuits to check the capabilities of each element, and then consider their joint action.

The reality of circuit solutions

Engineers know well that circuit solutions cannot always be implemented in practice, although they do not contain obvious errors. In other words, Design electrical diagrams are not always realistic.

Therefore, one of the tasks of reading electrical diagrams is to check whether given conditions can be met.

The unreality of circuit solutions usually has mainly the following reasons:

there is not enough energy to operate the device,

“Extra” energy penetrates into the circuit, causing unexpected operation or preventing timely release,

there is not enough time to complete the specified actions,

the device has set a setpoint that cannot be achieved,

devices that differ sharply in properties are used together,

switching capacity, insulation level of devices and wiring are not taken into account, switching overvoltages are not suppressed,

the conditions in which the electrical installation will be operated are not taken into account,

when designing an electrical installation, its working condition, but the question of how to bring it into this state and in what state it will end up, for example, as a result of a short-term power interruption, is not resolved.

How to Read Electrical Diagrams and Drawings

First of all, you need to familiarize yourself with the available drawings (or create a table of contents if there is none) and systematize the drawings (if this is not done in the project) according to their intended purpose.

The drawings are alternated in such an order that reading each subsequent one is a natural continuation of reading the previous one. Then understand the accepted system of notation and labeling.

If it is not reflected in the drawings, then it is found out and written down.

On the selected drawing, read all the inscriptions, starting with the stamp, then notes, explications, explanations, specifications, etc. When reading the explication, be sure to find the devices listed in it on the drawings. When reading the specifications, compare them with the explanations.

If the drawing contains links to other drawings, then you need to find these drawings and understand the contents of the links. For example, one circuit includes a contact that belongs to a device shown in another circuit. This means that you need to understand what kind of device it is, what it is used for, under what conditions it works, etc.

When reading drawings covering power supply, electrical protection, control, alarm, etc.:

1) determine the power sources, type of current, voltage, etc. If there are several sources or several voltages are applied, then understand what caused this,

2) break down the scheme into simple prices and, considering their combination, establish the conditions of action. We always begin to consider the device that interests us in this case. For example, if the engine does not work, then you need to find its circuit in the diagram and see which devices contacts are included in it. Then they find the circuits of the devices that control these contacts, etc.,

3) build interaction diagrams, using them to find out: the sequence of work in time, the consistency of the operation time of devices within of this device, consistency of operation time of jointly operating devices (for example, automation, protection, telemechanics, controlled drives, etc.), consequences of a power outage. To do this, one by one, assuming that the switches and power supply circuit breakers are turned off (the fuses are blown), they evaluate the possible consequences, the possibility of the device returning to the operating position from any state in which it could find itself, for example, after an inspection,

4) assess the consequences of probable faults: non-closure of contacts one at a time, violations of insulation relative to the ground one by one for each section,

5) violation of insulation between the wires of overhead lines extending outside the premises, etc.,

5) check the circuit for the absence of false circuits,

6) evaluate the reliability of the power supply and the operating mode of the equipment,

7) check the implementation of measures to ensure safety, subject to the organization of work stipulated by the current rules (, SNiP, etc.).

An electrical diagram is a specialized graphic representation that displays pictograms various elements, located in a certain order in the circuit, as well as interconnected in parallel or in series. It is worth noting the fact that any such drawing does not demonstrate the real location of certain elements, but is used only to indicate their connection with each other. Thus, a person who knows how to read electrical diagrams can understand the operating principle of a particular device at a glance.

The diagram contains three groups of elements:

• power supplies that take on the function of generating current;
• various devices that are responsible for further energy conversion;
• nodes that transmit current (conductors).

The source can be a wide variety of galvanic elements characterized by low resistance. In this case, energy conversion is carried out by various electronic motors. In this case, it is quite important to know the symbols of each individual object that makes up this circuit, since it is difficult to read electrical circuits without this knowledge.

What are they needed for?

Many people often wonder why they are required at all. However, in fact, understanding them is important for every motorist, because if you know how to read electrical diagrams, you can subsequently save significantly on the services of professionals. Of course, it will not be easy for you to implement do-it-yourself repair any particularly complex malfunctions without involving qualified specialists in this work, and in principle, this is fraught with further complications. But if you need to correct some minor malfunction or connect the headlights, ECU, battery and other elements, you can even do it yourself if you know how to read electronic circuits.

Why do motorists need them?

Often people want to connect a wide variety of electronic devices to the circuit, including a radio, alarm, air conditioning and many other devices that significantly simplify the driving process and make our lives more comfortable. In this case, it is also important to understand how to learn to read electrical diagrams, because in the vast majority of cases they are necessarily attached to almost every device.

This is especially true for owners of cars with a trailer, because the most different problems with its connection. In such cases, you will need to use the wiring diagram of a passenger car trailer, and at the same time be able to understand it, since it will not be possible to learn how to read electrical diagrams in a short time.

Basic Concepts

To understand on what principle this or that device works, a knowledgeable person can simply look at its electrical diagram. At the same time, it is quite important to take into account several basic nuances that will help even a beginner read such drawings in detail.

Of course, no device can function properly without current flowing through its internal conductors. These paths are indicated by thin lines, the color of which is chosen to match the actual color of the wires.

If the electrical circuit includes a sufficiently large number of elements, the route on it is displayed in the form of breaks and segments, and the places of their connection or connection must be indicated.

In addition, the numbers that are indicated on the nodes must also fully correspond to the real numbers, since reading electrical diagrams (designations) otherwise will be pointless. The numbers indicated in the circles determine the locations of the negative connections with the wires, while the designation of the current-carrying paths makes it more simple search elements located on different diagrams. The combinations of letters and numbers fully correspond to detachable connections, and there are quite a large number of specialized tables with the help of which you can quite simply identify the elements of any electrical circuit. Such tables are quite easy to find not only on the Internet, but also in various manuals for specialists. In general, figuring out how to read electrical circuit diagrams correctly is not that difficult. The main thing in this is to understand the functionality of the various elements, as well as to be able to correctly follow the numbers.

To understand how to correctly read automotive electrical circuits, you need not only to have a detailed understanding of the symbols of various components, but also to have a good understanding of how they are formed into blocks. In order for you to understand the peculiarities of the interaction between several elements of an electronic device, it is worth learning how to determine how the signal passes and is converted. Next, we'll look at how to read electrical diagrams. For beginners, the instructions are as follows:

1. Initially, you need to familiarize yourself with the power circuit allocation diagram. In the vast majority of cases, the places where the supply voltage is supplied to the device cascades are located closer to the top of the circuit. Power is directly supplied to the load and then transferred to the anode vacuum tube or directly into the collector circuit of the transistor. You should determine where the electrode joins the load terminal, since in this place amplified signal completely removed from the cascade.
2. Install input circuits on each stage. You should select the main control element, and then study in detail the auxiliary ones that are adjacent to it.
3. Look for capacitors located near the input of the cascade, as well as at its output. These elements are extremely important in the process of amplifying alternating voltage. Capacitors are not designed for the passage of direct current through them, as a result of which the value of the input resistance of the next block will not be able to bring the cascade out of a stable state according to DC.
4. Start studying those stages that are used to amplify a specific DC signal. All kinds of voltage-forming elements are combined with each other without capacitors. In the vast majority of cases, such cascades operate in analog mode.
5. The exact sequence of stages is determined in order to establish the direction of the signal. In this case, special attention will need to be paid to detectors, as well as all kinds of frequency converters. You should also determine which stages are connected in parallel and which in series. When using parallel cascade combining, several signals will be processed completely independently of each other.
6. In addition to understanding how to read electrical circuit diagrams, you should also understand the wiring diagrams that come with them, which are commonly called wiring diagrams. The layout features of the various components of an electronic device will help you understand which blocks are the main ones in a given system. Besides everything else, wiring diagram makes it easier to identify the central component of the system, as well as understand how it interacts with auxiliary systems, since it is difficult to read automotive electrical diagrams without these values.

How to learn?

Even if a person has a thorough understanding of the various symbols used in electronic circuits, this does not mean that he will immediately be able to understand how signals are transmitted between components. That is why, in order to learn not only to name specific components on a diagram, but also to determine their interaction with each other, you need to master a certain number of techniques on how to read electrical circuit diagrams.

Circuit types

First of all, you need to learn to distinguish standard power circuits from signal circuits. You should pay attention to the fact that the place where power is supplied to the cascade is almost always displayed at the top of the corresponding circuit element. In almost all cases, the constant supply voltage initially passes through the load, and only over time is transmitted to the anode of the lamp or to the transistor collector. The point of connection of a certain electrode with the lower terminal of the load will be the place where the amplified signal is removed from the cascade.

Input circuits

Often, for those people who roughly understand how to read the electrical circuits of a car, the cascade input circuits do not require any explanation. However, you should note that the additional elements located around the control electrode of the active component are much more important than it might seem at first glance. It is with the help of these elements that the so-called bias voltage is formed, with the help of which the component will be introduced into a much more optimal DC mode. We should also not forget that different active components have individual characteristics in the way they apply bias.

Capacitors

You definitely need to pay attention to the capacitors located both at the input and output of the cascade, which amplifies the alternating voltage. These capacitors do not conduct direct current, and therefore neither the input resistance nor the input signal has the ability to remove the cascade from the direct current mode.

Gain stages

Next, be sure to pay attention to the fact that certain stages are used for DC amplification. The design of such cascades completely lacks specialized voltage conditioners, while they are connected to each other without the use of capacitors. Certain instances are capable of operating in analog mode, while some others operate only in key mode. In the latter case, the minimum possible heating of the active component is ensured.

Subsequence

If the system uses several stages simultaneously, you will need to learn to understand exactly how the signal passes through them, since you will not be able to correctly read the electrical circuits of the car without this knowledge. It is imperative to develop skills in identifying cascades that deal with certain transformations in relation to a signal, for example. It should be taken into account that one circuit may simultaneously contain several parallel cascade chains that process several signals absolutely independently of each other.

It is impossible to immediately outline all the subtleties, without knowledge of which it would be possible to understand how to correctly read electrical circuits without any errors. It is for this reason that many people who do this professionally study specialized textbooks on circuit design.

How to draw?

Accordingly, before installing any electrical circuit, its image must be drawn, but it is worth noting that manufacturers do not always prefer to attach an electrical circuit to certain devices. If you assemble electronic equipment yourself, you can complete this circuit completely yourself. With the help of modern computer programs This procedure has become extremely simple and can be easily performed even by beginners.

What is needed for this?

To carry out this procedure, you will only need a few available things:

• Paper.
• Standard pencil.
• A utility from Microsoft called Office Visio Professional.

Instructions

1. Initially, you need to draw a schematic image of a certain device design on paper. A diagram made in this way will provide the opportunity to arrange the different elements of the system as correctly as possible and arrange them in the correct sequence, as well as unite them with each other with conditional lines that display the order of connection of certain electronic elements.
2. For a more accurate numerical representation of your electronic diagram, you need to use the Visio program mentioned above. After software will be fully installed, run it.
3. Next, you should go to the “File” menu and select “Create Document” there. On the presented toolbar, select items such as “Snap” and “Snap to Grid”.
4. Configure all page parameters in detail. To do this, you need to use a special command from the “File” menu. In the window that appears, you will need to select the diagram image format and, depending on the format, determine the orientation of the drawing being compiled. It is best to use a landscape layout in this case.
5. Determine the unit of measurement in which the electrical circuit will be drawn, as well as the required image scale. At the end, click the “Ok” button.
6. Go to the "Open" menu and then to the stencil library. You should transfer the required form of the main inscription, frame and a host of other additional elements to the drawing sheet. In the latter you will need to include inscriptions that will explain the features of your scheme.
7. To draw the components of the circuit, you can use both already prepared stencils located in the program library, and any of your own blanks.
8. All kinds of blocks of the same type or components of the circuit will need to be depicted by copying the presented elements, making the necessary additions and edits later.

After work on the diagram is completed, you should check how correctly it was drawn up. Also try to correct the explanatory notes in detail, and then save the file under the desired name. The finished drawing can be printed.

Beginners who are trying to independently assemble some electronic circuits and devices are faced with the very first question in their new activity: how to read electrical circuits? This is actually a serious question, because before assembling a circuit, it must be somehow marked on paper. Or find a ready-made option for implementation. That is, reading electrical circuits is the main task of any radio amateur or electrician.

What is an electrical circuit

This is a graphic image that shows all the electronic elements connected to each other by conductors. Therefore, knowledge of electrical circuits is the key to a properly assembled electronic device. This means that the main task of the assembler is to know how electronic components are indicated on the diagram, what graphic icons and additional alphabetic or numerical values.

All basic electrical circuits consist of electronic elements that have a conventional graphic designation, in short RCD. As an example, we will give a few of the simplest elements, which in graphic design are very similar to the original. This is how a resistor is designated:

As you can see, it is very similar to the original. And this is how the speaker is designated:

Same great similarity. That is, there are some positions that can be immediately recognized. And it's very convenient. But there are also completely different positions that either need to be remembered, or you need to know their designs in order to easily identify them on a circuit diagram. For example, the capacitor in the figure below.

Anyone who has long been versed in electrical engineering knows that a capacitor is two plates with a dielectric placed between them. Therefore, this icon was chosen in the graphic image; it exactly repeats the design of the element itself.

The most complex icons are for semiconductor elements. Let's look at a transistor. It should be noted that this device has three outputs: emitter, base and collector. But that's not all. U bipolar transistors There are two structures: “n – p – n” and “p – n – p”. Therefore, in the diagram they are designated differently:

As you can see, the transistor in its image does not look like it. Although, if you know the structure of the element itself, you can figure out that this is exactly what it is.

Simple diagrams for beginners, knowing a few icons, can be read without problems. But practice shows that simple electrical circuits in modern electronic devices are almost impossible to do. So you have to learn everything that concerns circuit diagrams. This means that you need to understand not only the icons, but also the alphabetic and numerical designations.

What do letters and numbers mean?

All numbers and letters on the diagrams are additional information, this again comes to the question of how to read electrical circuits correctly? Let's start with letters. A Latin letter is always written next to each RCD. Essentially, this is the letter designation of the element.

This was done specifically so that when describing the circuit or device of an electronic device, its parts could be identified. That is, do not write that it is a resistor or capacitor, but put a symbol. It's both simpler and more convenient.

Now the digital designation. It is clear that in any electronic circuit There will always be elements of the same meaning, that is, of the same type. Therefore, each such detail is numbered. And all this digital numbering goes from the upper left corner of the diagram, then down, then up and down again.

Attention! Experts call this numbering the “AND” rule. If you pay attention, this is how the movement according to the pattern occurs.

And one last thing. All electronic elements have certain parameters. They are usually also written next to the icon or placed in a separate table. For example, next to the capacitor, its rated capacity in micro- or picofarads, as well as its rated voltage (if such a need arises), may be indicated.

In general, everything related to semiconductor parts must be supplemented with information. This not only makes the diagram easier to read, but also allows you to avoid making mistakes when choosing the element itself during the assembly process.

Sometimes there are no digital symbols on electrical circuits. What does it mean? For example, take a resistor. This suggests that in this electrical circuit, its power indicator does not matter. That is, you can install even the most low-power option that will withstand the load of the circuit, because a low current flows in it.

And a few more notations. Conductors are graphically indicated by a straight continuous line, soldering points by a dot. But keep in mind that the dot is placed only in the place where three or more conductors are connected.

Conclusion on the topic

So, the question of how to learn to read electrical diagrams is not the easiest. You will need not only knowledge of RCDs, but also knowledge regarding the parameters of each element, its structure and design, as well as the principle of operation and why it is needed. That is, you will have to learn all the basics of radio and electrical engineering. Difficult? Not without it. But if you understand how everything works, then horizons that you never dreamed of will open up for you.

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 the closed position, electric current begins to flow through it unhindered.

Diode.

It allows electric current to pass in only one direction and blocks the passage in the other direction. electric current. 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 order to understand the contents of the circuit, you need to know the correspondence between the circuit symbols and the real elements of the device. What functions do these devices perform and how do they interact with each other?

Let's define the terms:

• Schematic element- an integral part of a circuit that performs a specific function in a product and cannot be divided into parts that have an independent purpose.
• Device- a set of elements representing a single structure (block, board, etc.).
• Schematic diagram (complete)- a diagram that defines the complete composition of elements and connections between them, and, as a rule, gives a detailed idea of ​​the principles of operation of the product. Schematic diagrams are used to study the principles of operation of products, as well as for their adjustment, control and repair. They serve as the basis for the development of other design documents, for example, connection diagrams (installation diagrams) and drawings.
• Connection diagram (installation)- a diagram showing the connections of the component parts of the product and identifying the wires, harnesses, cables that make these connections, as well as the places of their connections and input (connectors, boards, etc.).
• Layout diagram- a diagram defining the relative location components products, and, if necessary, also harnesses, wires, cables, etc.
• Tourniquet- a set of wires packaged in a certain way into a single whole.

In the electrical equipment diagrams of automobiles, the schematic, installation, and layout diagrams are combined into one in a simplified form; the simplification concerns the wiring and layout diagrams. In the diagrams, the devices have a drawing that to some extent corresponds to their appearance, and they are located according to the diagram (top view) as in reality physically, with a certain simplification. This combination applies mainly to the circuits of cars of early releases. The circuits of modern cars are designed differently, due to the significant complexity of electrical equipment, the layout is carried out separately.

When reading diagrams, you need to know the fundamental principles:

1. All connection wires are color coded, which can consist of one color or two (main and additional). Additional color transverse or longitudinal strokes are applied.
2. Within one harness, wires of the same marking have a galvanic connection (physically connected to each other).
3. In the diagrams, the wire at the entrance to the harness is inclined in the direction where it is laid.
4. Black color, as a rule, indicates a wire that is connected to the car body (ground).
5. The positions of the relay contacts are indicated in the state when no current flows through their winding. According to the initial state, the relay contacts differ - normally closed and normally open.
6. Some wires have a digital designation at the point of connection to the device, which allows you to determine where it comes from without tracing the circuit. See table.

According to DIN 72552 (commonly used values):

Contact	Meaning
15	Battery positive after the ignition key contacts.
30	Plus the battery directly.
31	Minus the battery directly or the housing.
50	Starter control.
53	Wiper.
56	Headlight.
56a
56b	Low beam.
58	Parking lights.
85	Relay winding (-).
86	Relay coil (+).
87	Common relay contact).
87a	Normally closed relay contact.
87b	Normally open relay contact.
88	Common contact 2 relays.
88a	Normally closed relay contact 2.
88b	Normally open relay contact 2.

List of the most used symbolic drawings:

Also often with a circuit element there is a symbolic drawing explaining which device this element belongs to.

Designations of circuit elements.

" /> Three-lever switch. This switch consists of several types of contacts. Non-fixed ones are contacts for turning on the washer, sound signal and a short-term high beam signal (contacts 2 and 6 are closed), fixed ones are low beam (contacts 4 and 5 are closed), high beam (contacts 2 and 5 are closed), turning on the turn signal and turning on the windshield wiper, which has 3 modes:

• 1.Off (contacts 1 and 6 are closed);
• 2. Switched on “slowly” (contacts 2 and 4, as well as 5 and 6 are closed);
• 3. Switched on "fast" (contacts 3 and 4 are closed).

How to read electrical circuit diagrams of foreign cars?

Let's look at an example of reading Nissan car diagrams. To do this, we need to familiarize ourselves with the designation system for elements of electrical equipment on the diagrams. Let's start with the designation of connector contacts. As shown in Fig.1.

Next to the picture of the connector there is a designation on which side of the connector it is to be viewed, from the contact side (Terminal Side) (T.S.) or from the harness side (Harness Side) (H.S.). Please note that the outline of the connector, where the contacts are viewed from the wire side, is outlined with a line.

Figure 2 and Figure 3 show the designations of the circuit elements, the meaning of which is explained in Table 1.

Number	Name	Description
1	Battery	Battery
2	Fusible link	Fuse installed in the wire
3	Number fusible link or fuse	Serial number of fused line or fuse
4	Fuse	Fuse
5	Current rating	Fuse rating in amperes
6	Optional splice	The circle indicates that the connection depends on the vehicle version
7	Connector number	Connector number
8	Splice	The black circle indicates the connection of conductors
9	Page crossing	This chain continues on the next page
10	Option abbreviation	The chain between these marks is present only for all-wheel drive
11	Relay	Shows internal relay connections
12	Option description	Shows a variant of the circuit depending on the vehicle
13	Switch	State of contacts depending on switch position (closed or open)
14	Circuit	Chain
15	System branch	Indicates that the connection is going to another system (head lighting)
16	Shielded line	The line is shielded
17	Component name	Schematic element name
18	Ground(GND)	Grounding
19	Connector	The numbering order of the contacts when viewed from the harness side is indicated.
20	Connectors	Indicates that the wire has 2 connectors
21	Wire color	Abbreviation for wire color
22	Terminal number	Describes the pin number, wire color and signal name

Table 1.

Color abbreviations

B=Black	LA = Lavender
W=White	OR or O = Orange
R = Red	P=Pink
G = Green	PU or V (Violet) = Purple
L = Blue	GY or GR = Gray
Y=Yellow	SB = Sky Blue
LG = Light Green	CH = Dark Brown
BG = Beige	DG = Dark Green
BR = Brown

In Fig. Figure 4 shows a diagram of normally open and normally closed contacts, this is the state when no current flows through the relay coil.

In Fig.5. shows the windshield wiper switch in the form of a graphical drawing and two tables. The figure shows a schematic diagram of the internal connections of the switch. The tables describe to us the operation of the switch as a “black box”; it is unknown how the circuit is implemented inside, but at the output the state of the contacts corresponds to those indicated in the table, for the modes:

1. OFF - disabled;
2. INT - interval;
3. LO- low speed;
4. HI- high speed;
5. WASH - plus turning on the washer.