Reading Schematics

Posted on Feb 7, 2014

This page was created in response to all the email I receive, on how to read a schematic. Learning to read a schematic diagram, is similar to map reading. You need to know which wires connect to which component and where each wire starts and finishes. With a map book this would be equivalent to knowing your origin and destination points and which

Reading Schematics
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roads connect to the motorway network, etc. However schematics are a little more complicated as components need to be identified and some are polarity conscious (must be wired up in the circuit the correct way round) in order to work. You do not need to understand what the circuit does, or how it works, in order to read it, but you do need to correctly interpret the schematic. Here are some basic rules that will help with reading a diagram. Look at the circuit diagram shown below: The blue lines represent wires and for simplicity i have labeled them as A, B, C. There are just three components here and it is easy to see where each wire starts and ends, and which components a wire is connected to. As long as the wire labelled A connects to the switch and negative terminal of the battery, wire B connects to the switch and lamp, and C connects to the lamp and the battery positive terminal then this circuit should work. Before moving on, it is important to realise that any schematic may be drawn in a number of different ways. In Fig 1 and Fig 2 i have drawn two electrically equivalent lamp dimmer circuits, they may look very different, but in fact, if you mentally label the wires and trace them, you will see that in both diagrams each wire starts and finishes at the same components on both diagrams. The components have been labelled and so have the three terminals of the transistor. In Fig1 there are two wire junctions as...

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