There are many different schemes, and each of them has its own purpose. Scheme is a graphical representation of conventional symbols and the connection between them. Letters and numbers can be used to explain a particular sign. Every year there are more and more new and more complex electronic devices and systems. It is simply impossible to understand them without a schematic diagram.
Content
- Modern drawing editors
- Requirements for circuits
- Labeling standards
- Application of Ley Lines
Modern drawing editors
As a rule, work begins on the conceptual diagram after the creation of a functional project. At this moment, there is already a complete picture of the expected operation of the upcoming device and the task is to make this device work with the help of radio elements. When creating a schematic diagram (it is designated E3), it is important to indicate each element of an electronic device and its relationship with other elements.
It should be noted that the location of the parts in the drawing and on the board do not match
, since the purpose of this diagram is to show the principle of operation, and the exact location of the parts is displayed on the wiring diagram.
Previously, electrical circuits were drawn by hand. With the advent of computers, this task became easier, until the P-CAD program appeared, which completely automated this work. In fact, this is a whole system, it has many editors, allowing you to create the following schemes:
- principled;
- assembly (for printed circuit boards).
Currently, P-CAD has been replaced by another system - Altium Designer. The manufacturer is the Australian company Altium.
Requirements for circuits
The main requirement is clarity and readability. What does this mean? The diagram shows a huge number of elements and the connections between them. It is necessary to make such a drawing so that one graphic image did not overlap or obscure another. Much easier to read when the symbols are in order. So, in disconnected circuits, where many relays are indicated, and therefore contacts, the details of one circuit are put on one line, and the lines are placed one under the other. Each chain is assigned its own serial number.
An important role is played by the saturation of the signs and their size, the uniformity of the arrangement of parts. To show the electrical connection, lines are used, but they must also be located strictly vertically or horizontally. Since these lines are constantly crossing, it is necessary to clearly define when there is a simple crossing of wires, and when there is a connection.
In Soviet times, there were diagrams in which an arc was used to show the intersection of wires, and the electrical connection was denoted by a dot. In subsequent drawings, the intersection of conductors began to be shown with lines intersecting at right angles (no arc), and the electrical connection was shown as a point. Interestingly, the old system is still in effect in America.
If power circuits are present in the drawing, then they are indicated by thicker lines. On some plans, for example, for electrical installations, the circuits are combined into one common line. Then, at the input and output of this line, each chain of the same name is assigned the same serial number. Some drawings are placed on several sheets, in this case, the same marking passes on all these sheets.
When drawing up an electrical circuit diagram, they try to follow one more rule: the signal must follow from left to right. If this condition is difficult to meet, then an arrow is drawn on the line, showing in which direction the signal is going.
Labeling standards
The drawing is depicted without observing the scale, however, individual elements of the same type have the same size. Each radio component is assigned its own conventional image. In addition, next to such an element there may be a code indicating:
- title;
- type of;
- face value;
- power;
- other data.
If necessary, images of the same type of elements connected in parallel, one first conventional symbol can be shown. Sequential numbers of other elements are indicated above it. Because all radio components are of the same type, their data is recorded near the first image, thereby avoiding cluttering the drawing.
If the same elements are sequentially included, then the first and the last are displayed, between them there is a dashed line, above which the number indicates how many elements are missing. For example, the first element is numbered 17, the last is numbered 26, and the number 8 is above the dashed line.
Each element of the circuit has its own serial number, and the counting goes from top to bottom and from left to right. If some information cannot be shown schematically or it is difficult, it is allowed to make brief entries, tables, and the like. You cannot use abbreviations other than those permitted by GOST.
Application of Ley Lines
When power lines of alternating voltage are displayed, each phase is assigned its own letter - A, B, C or the letter and number L1, L2, L3. To avoid confusion, all subsequent chains extending from these lines will have the same index, for example, A1.1, B1.1, L1.1, L2.1, etc. There are two types of such schemes:
- single-line;
- multi-line.
The difference is that in a single line, all three phases are enclosed in one line. This greatly simplifies the drawing, allowing you to immediately grasp the whole or most of the structure, and is widely used where AC electrical appliances are often used, such as motors. When it is necessary to show only one phase, mark this phase next to the conventional sign.
Suppose two thermal relays KK1 and KK2 are used to protect the motor. Then a conventional sign of the thermal relay is drawn in the drawing and the marking KK1, KK2 is placed next to it, in brackets L13, L33. This means that the thermal relay KK1 is in phase L1 and belongs to the third group. Accordingly, KK2 is in the L3 phase and belongs to the same group.
When using branching blocks (terminal blocks), in the drawing for each contact, if a circuit fits to it, an explanation is given of what kind of circuit it is and where it should go. The pads themselves are also marked.
