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Circuit diagram facts for kids

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Circuit diagram – pictorial and schematic
Comparison of pictorial and schematic styles of circuit diagrams

A circuit diagram (electrical diagram, elementary diagram, electronic schematic) is a graphical representation of an electrical circuit. A pictorial circuit diagram uses simple images of components, while a schematic diagram shows the components and interconnections of the circuit using standardized symbolic representations.

Circuit diagrams are used for the design (circuit design), construction (such as PCB layout), and maintenance of electrical and electronic equipment.

In computer science, circuit diagrams are useful when visualizing expressions using Boolean algebra.


Circuit elements
Common schematic diagram symbols (US symbols)

Circuit diagrams are pictures with symbols that have differed from country to country and have changed over time, but are now to a large extent internationally standardized.

Simple components often had symbols intended to represent some feature of the physical construction of the device. The internationally standardized symbol for a resistor is a simplified oblong, sometimes with the value in ohms written inside.


Wire Crossover Symbols for Circuit Diagrams
Wire Crossover Symbols for Circuit Diagrams.

It is a usual although not universal convention that schematic drawings are organized on the page from left to right and top to bottom in the same sequence as the flow of the main signal or power path. For example, a schematic for a radio receiver might start with the antenna input at the left of the page and end with the loudspeaker at the right.

Detailed rules for the preparation of circuit diagrams, and other document types used in electrotechnology, are provided in the international standard IEC 61082-1.


Rats nest diagram
A rat's nest

Once the schematic has been made, it is converted into a layout that can be fabricated onto a printed circuit board (PCB). Schematic-driven layout starts with the process of schematic capture. The result is what is known as a rat's nest. The rat's nest is a jumble of wires (lines) criss-crossing each other to their destination nodes.

These wires are routed either manually or automatically by the use of electronics design automation (EDA) tools. The EDA tools arrange and rearrange the placement of components and find paths for tracks to connect various nodes. This results in the final layout artwork for the integrated circuit or printed circuit board.

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