How can I understand electrical circuit diagrams

How do you read an electrical schematic?

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In order to understand a circuit, one has to interpret it and follow the current flow in the circuit. How do you go about this?

The crossing of two conductors - on the right with electrical connection

Various switching symbols (light, button, bell, motor, coil, switch, battery)

Simple series connection with two lights

Simple parallel connection with two lights

Parallel connection with two lights and one switch each

A circuit diagram (previously called a "circuit diagram", "circuit diagram", today also "circuit" or "circuit diagram") represents a circuit. It uses graphic symbols to show the flow of electrical current. There are symbols for electrical components, the circuit symbols. A closed line from one component to the next symbolizes an electrical connection (also known as "line"). It does not matter whether this connection is made with a jumper wire, a copper braid or a piece of sheet metal. Like the components, the line is a symbol.

If two electrical conductors cross each other without being electrically connected at the crossing point, then the lines in the circuit diagram are drawn smoothly throughout. You can think of it as two insulated jumper wires that are simply lying on top of each other and have no electrical contact due to the insulation. However, if the conductors have an electrical connection at the crossing point, a point is drawn on the crossing in the circuit diagram. You can think of it as two bare, stripped jumper wires lying on top of each other and firmly connected by a drop of solder - the point symbolizes the drop.
 
When following a circuit, one usually starts with the positive pole of the voltage source. It has been defined by definition that the current flows from the positive pole of the voltage source through the circuit to the negative pole (technical current direction). This approach is not physically correct, because the charge carriers (electrons) actually migrate from the negative to the positive pole (physical current direction).

Current flow is only possible in a circuit when the circuit is closed. So an important point when reading and understanding a circuit diagram is to check whether it is a closed circuit. Circuits can usually be identified as a series or parallel connection or a combination of the two.

Understand a schematic
To understand the circuit diagram, one must
- identify the voltage source (e.g. by means of the battery symbol),
-follow the path of the current (series or parallel connection?),
-recognize the individual circuit symbols and know about their effect.

According to the principle of cause and effect, one can now try to find out what will happen to the respective circuit when current flows. You either have to know what the meaning of the circuit diagrams is or you can look up the relevant overviews.

Examples:
-in a circuit with battery and lamp: the cause is current flow, the effect: a lamp lights up.
-in a series connection of battery, switch and motor: when the switch is closed, current flows. When current flows, the motor turns.
-in a parallel connection of battery and 3 lights: all 3 lights will light up, but probably weaker, as if only one light was connected in series with the same battery.

From the circuit diagram to the established circuit
If you want to recreate a circuit according to a circuit diagram, you can start by placing the components in front of you analogous to the circuit diagram and "wiring" them starting at one pole of the voltage source. The arrangement of the components as on the plan makes the transition from the circuit diagram on paper to the real circuit easier for many. In the further learning process, you will understand that the real arrangement of the components does not always have to follow the circuit diagram exactly, but can take place as desired, as long as the electrical connections follow the diagram. You can also use a board or very sturdy, thick cardboard and fix individual components with thumbtacks.

Electrical connections are made using jumper wire or stranded wire, using existing screw contacts or soldering the wire to the components. In the course of time, you will gain experience that will facilitate the construction of circuits. Many circuits are only set up for experiments, so it's not a question of beauty, just function. There are electrical components that are not connected directly, but aids are used. There are sockets for lamps that allow the connection of a jumper wire via screw contacts. Such provisional circuits are mostly used for experiments, which is why one also says "test or experimental circuit".

From the circuit to the board (layout)
In the case of complex electronic circuits, one would like to produce a finished circuit on a printed circuit board (circuit board, printed circuit card) after the test phase has been completed. To do this, one draws a "layout" of the circuit or one designs it with the help of a computer program. Here, too, many begin by first arranging the electronic components on the board and, in the second step, thinking about how to connect the components on the conductor side of the board with copper tracks. Crossings must be prevented, because they would be electrically conductive. After completing the layout, a chemical etching process is used to remove all copper coatings that are not required; only the conductor tracks remain. The components are inserted through drill holes and soldered to the soldering eyes on the conductor side.

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