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What Are Schematic Symbols?

Whether you’re a student working towards a degree in Electronics, or a hobbyist trying to dive in, one of the first subjects you need to learn is how to read a schematic. What is a schematic? It’s a simplified wiring diagram that shows all of the components and electrical connections within a circuit. But before reading a schematic, you’ll need to learn different component symbols. This guide will review the most common components that beginners should learn first.

Schematic symbols have been standardized by two different guidelines: American National Standards Institute (ANSI) and the International Electrotechnical Commission (IEC). Each standard is going to have their own versions of a component’s schematic symbol. It is important to follow one of these two standards so that if anyone else comes across a schematic you’ve created, they are able to read it properly. Without these standards, anyone required to read a schematic and fix electronic devices would have an almost impossible task.

Examples:

Resistors

Left is ANSI, Right is IEC

Potentiometers

Just add arrows to the ANSI and IEC Resistor symbols. The arrow indicates the wiper terminal.

Left is ANSI, Right is IEC

Capacitors

Polarized will not always appear with the + symbol

Left is ANSI Polarized, Center is IEC Polarized, Right is ANSI/IEC Non-Polarized

LED: Light Emitting Diode

These have the same appearance as diodes, except for the small arrows that indicate emitting light.

These are interchangeable from ANSI to IEC

Power Sources

Main

The two on the far left are DC battery cell power sources, with the far left being for multiple cells, and the other for a single cell. These won’t always have the + and - symbols. The third one in from the left with the + and - circled is a non-battery cell DC source. The Far right is an AC power source.

Secondary

These are primarily used in large schematics that encompass multiple pages, or just to clean the schematic up when there are too many connections back to the main power source.

Switches

These are a few variations of switches showing a couple different combinations of poles and throws.

IC: Integrated Circuits

Also known as chips

The physical IC may either have a notch on one end or a dot near one corner. The pin to the left of the notch and to the left of the dot on the examples above are pin 1. Going down (counter-clockwise) the left side of each is 1-4, then up the right side is 5-8, with pin 8 being the top right in the left and center examples. The symbol on the right is how ICs are more commonly displayed in a schematic. Here the pins are placed haphazardly based on where they fit best in the schematic. It is important to pay attention to this when making connections.

These are the most common symbols found within a schematic. There are far more to learn, but sometimes it’s easiest to learn those as needed. If you’d like to learn more about this topic, go to https://www.digikey.com/schemeit/project/, select the box next to “Show only catalog parts with symbols” and play around by pulling different parts into the schematic to see what the symbols look like.

About this author

Image of Ashley Awalt

Ashley Awalt is a Technical Content Developer that has been with Digi-Key Electronics since 2011. She earned her Associate of Applied Science degree in Electronics Technology & Automated Systems from Northland Community & Technical College through the Digi-Key scholarship program. Her current role is to assist in creating unique technical projects, documenting the process and ultimately participating in the production of video media coverage for the projects. In her spare time, Ashley likes to – oh, wait, is there such a thing as spare time when you’re a mom?

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