Any electrical circuit can be visually represented in the form of a circuit or wiring diagram, in other words, in the drawings. Each image of an element must comply with the unified system of design documentation (ESKD). For a correct reading of the drawings, it is necessary to understand these conventional graphic symbols in electrical circuits.
Normative documents
The UGO system was specially designed to eliminate confusion and discrepancy when working with documents. In addition to UGO, alphanumeric designations are widely used, for example, when marking radio and electrical components.
Requirements for dimensions, displays, diagrams and plans of electrical equipment are contained in the following GOST regulatory documents:
- 21.404-85;
- 21.614-88;
- 2.755-87;
- 2.756-76;
- 2.747-68;
- 2.709-89;
- 2.710-81.
The element base is constantly subject to change, therefore, appropriate adjustments are made to the design documentation. Specialists in the field of electrical and electronics regularly monitor all innovations in GOSTs, while the rest do not have to do this. In domestic conditions, it is enough to know how the designation of the main elements is deciphered.
Types of electrical circuits
First of all, it is worth considering that a diagram is a graphical display of structural elements, nodes and their connections on paper, or in electronic form using generally accepted symbols. In total, about a dozen types of schemes differ, but the following are most common:
- functional;
- Fundamental;
- Mounting.
They can be found in the documentation for complex electronic devices, in DIY repair manuals, or in wiring plans. In view of their prevalence, each species should be considered separately.
Functional diagram
It does not display the design in detail, but contains an image of the main blocks of the device with signatures and functional units. Focusing on this drawing, you can only learn about how the entire system of the device works, how the various elements are interconnected. It is expedient to use the functional diagram to describe, for example, a complex electronic device, but not always for power supply devices.
circuit diagram
Contains a certain set of element designations, in accordance with the composition of the device.For the correct interpretation of the drawing, it is necessary to know the basic conventionally graphical representations of electrical elements. In this form of diagrams, the connections between devices and their constituent elements are indicated. To display power lines, it is advisable to draw a linear diagram, and to indicate the types of electrical circuits and partings for control, management - a complete circuit diagram.
It should be noted that the single-line drawings show only the power part of the structure, while the full principal drawings show all the elements of the circuit.
Wiring diagram
It is used when installing elements on printed circuit boards, when assembling devices and electrical circuits. With its help, the wizard determines which component should be placed where, at what distance from each other and in what sequence, according to the alphanumeric abbreviation next to the element, the decoding of which is given either in a separate document, or is located in a table in the lower right corner above the main inscription. In addition, the arrangement of denominations is allowed.
Detailed information on each type of scheme can be found in GOST 2.702-2011.
Basic conventionally graphic symbols
We turn to the consideration of the designations of the elements themselves, made according to interstate standards. By remembering the most basic and most frequently encountered, the understanding of many schemes will become much easier.
Basic images
No electronic device is complete without the presence in its device resistors, coils, capacitors, transistors, diodes, contacts and switches.Moreover, some models of elements, such as coils and capacitors, are very small in size, depending on their face value, so beginners should not be surprised at their widespread use, but learn and remember how they are depicted in the drawings.
So, for example, according to GOSTs:
- the resistor is indicated by a rectangle, dimensions 4X10mm;
- Capacitor - two parallel segments, the distance between which is 1.5 mm;
- Coils - arc lines, from 2 to 4, depending on the destination;
- Diodes - triangles, to the top of which a line parallel to the base is drawn. The “arrow” formed by the graphics indicates in which direction the diode is open and which is closed;
- transistors - a circle with a diameter of 12 mm, from which three lines or, in other words, contacts emanate. The arrow inside indicates that this transistor output is an emitter and what type the element belongs to (n-p-n or p-n-p);
- Instruments such as an ammeter, wattmeter or voltmeter are also indicated by a circle, but with a diameter of 10 mm and the generally accepted letter abbreviation PA, PW and PV, respectively;
- Contacts - an open line, at one end of which a segment 6 mm long is drawn at an angle of 30 °.
Lines of wiring and conductors
The conductors in all diagrams are depicted mainly by straight lines connecting the elements in the desired sequence. It is allowed to apply data above the line to clarify the parameters of the supplied voltage and current to the device as a whole or to a separate part of it. In such cases, it is allowed to indicate:
- Type of current (constant, alternating, pulsed);
- Voltage value;
- Material;
- Wiring methods.
- Marks, etc.
Also on the line of conductors it is permissible to indicate the total number of wires with notches, for example, in cable. Points at the intersection of two or more conductors indicate their connection to each other, if absent, then wires do not interact with each other and just intersect.
Grounding on the diagrams
The ESKD and GOST 2.721-74 standards also stipulate the symbolism of the ground sign on the diagrams. The system allows the use of three different options and the connection of leads to the body of the device:
- The most common designation looks like a line, with three perpendiculars drawn to it, located at a small distance from each other and having different sizes depending on the distance of the conductor (the farther, the smaller). On old drawings, only such a sign of "earth" is found.
- In the second option, noiseless grounding is given. The sign itself completely repeats the first one, with one exception: an incomplete circle is drawn around it. This means that the device as a whole or the element requires a separate grounding, isolated from the common "land" highway. Such an image is rare, but may well be found in the drawings.
- Protective ground is similar to a hybrid of the previous two signs, only the circle is not shown partially, as on silent, but completely covers the image. Most common in power electrical drawings. In accordance with safety requirements, the meaning of the image is such that it reflects the connections of current-carrying parts of the electrical circuit that are without voltage to ground.
- The fourth option displays not quite the "ground", but the connection of the current-carrying parts of the device with its case.However, even if the case is grounded, this type of connection cannot be called "ground", but can often occur.
How different currents are designated
Among other things, of particular importance in the drawings is the correct indication of the currents, for which the following signs are introduced (indicated next to the power source, or inside it):
- Permanent - straight short line
- Variable - wavy line
- Pulse - dotted line
A current value can be assigned next to the symbol.
Sockets, switches and switches
Among all the accepted designations, the graphic representation of switches is divided into a number of groups according to:
- degree of protection;
- installation method (open, hidden);
- the number of keys.
Important! UGO does not exist for dimmers and push-button light control devices.
Switches for two or three directions have become common. They save energy and can also control two or three points respectively.
Sockets are also divided according to the degree of protection and the number of poles. In accordance with this, additional alphanumeric signatures indicating the number and purpose of devices have been adopted.
Designation of light sources
A graphic representation of lighting devices is necessary when drawing up plans and wiring diagrams for the energy supply of private houses, apartments, as well as special complex lighting installations and various types of light bulbs. Therefore, their own symbols have been introduced for them, which significantly speeds up the time for compiling documentation.
Knowing these signs will be useful in everyday life for those who are going to independently study or make plans for the energy supply of their homes.
Power supplies and fuses
The most widely used sources are galvanic cells and batteries (letter G on the diagrams). Outwardly, it resembles the designation of a capacitor, with one difference - the segments are used in different lengths (short - “minus”, long - “plus”). In cases where the supplied current or voltage from one source is not enough, they are combined into a battery. This changes:
- letter code from G to GB;
- only the extreme elements are indicated, and the rest are replaced by a dotted line;
- The outline of the battery is encircled by a circle or an oval, depending on its size.
The devices also use fuses (FU), the designations of which are similar to resistors, but have an internal line, indicating a burning metal thread inside. In addition, ordinary arresters (F2) or vacuum arresters (F3) are used in devices with high-voltage power supply.
Knowing the symbols will be useful to anyone who plans to repair an electrical appliance or start installation work to equip their home, because thanks to a single system, there is no need to come up with their own graphic images. Just remember the common ones.
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