An electrical schematic tells an expert how the components of an electrical device are connected---but only if all the electrical symbols are understood. The actual components that go into electrical devices look remarkably similar---canisters with wires coming out. The symbols in schematic diagrams are often based on what the components do, so reading a schematic diagram can also tell you how and why the device works---if you know how to understand the electrical symbols.
- Skill level:
Things you need
- Schematic diagrams
- Lists of symbols
Look at a schematic diagram. The lines represent wires---the simplest electrical component---but in a logical and not a physical sense. The lines are arranged to create a diagram that explains the circuit. Two components that are far apart on the diagram may be close in the physical device and vice versa. Lines that are parallel in the schematic may not represent wires that are parallel, but if there is a line between component A and component B in the diagram, there is a wire between component A and component B in the electrical device.
Learn the basics. Some symbols show up in almost every diagram. One of these is the ground symbol: a series of parallel lines---usually about 5---that get shorter until the last line is a dot. Another basic symbol is the battery---a series of alternating short and long lines. The wire that connects to a short line goes to the negative terminal of the battery, and the wire that connects to a long line goes to the positive terminal of the battery. The other three basic symbols are resistors (a zig zag), capacitors (two short parallel lines) and coils (a series of loops).
Learn the symbols for semiconductor devices. Diodes are represented by an arrowhead that intersects a short line. Simple transistors are represented by the intersection of three wires. One wire ends in a short perpendicular line. The other two wires go to the other side of the short line---one of them having an arrowhead. If the arrow points inward it is a PNP transistor, and if the arrow points outward it is an NPN transistor. Output amps are represented as an isosceles triangle, where the output is the apex.
Tips and warnings
- Learn the symbols for the particular type of electronics you will be working with. Power electronics, audio electronics and computer electronics have special symbols. There is no use learning the symbols you will not be using.
- The values given for electrical components---and stated on a schematic diagram---are notoriously inaccurate. They are cheaper to manufacture if they are in the range of 15% to 20% off the stated value. This is usually close enough.
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