Welcome to Lesson 110! You wouldn’t try to build a house by just looking at a photo of the finished building. You need blueprints. In electronics, those blueprints are called Schematics.
A schematic is a map. It doesn’t show you what the physical components look like; instead, it uses universal symbols to show exactly how electricity is supposed to flow between them.
The Core Symbols
Every component we’ve learned so far has a specific symbol:
- Battery/Power Source: Shown as a series of alternating long and short parallel lines. The longest line is always the positive (+) side.
- Ground (GND): Shown as a series of decreasing horizontal lines, or sometimes a downward-pointing triangle. It represents the negative return path.
- Resistor: Shown as a jagged, zig-zag line. (In some European schematics, it is drawn as an empty rectangle).
- Capacitor: Shown as two parallel lines with a gap between them (like two plates holding a charge). If it’s an electrolytic (polarized) capacitor, one line will be curved, or it will have a small
+sign. - Diode & LED: Shown as a triangle pointing to a straight line (the one-way valve). An LED will have two small arrows pointing outward, representing light escaping.
- Switch: Shown as a break in a line, with a line hovering above the gap, ready to close it.
Following the Wires (Nets)
The solid lines connecting the symbols are wires. But what happens when two lines cross each other on the drawing?
- Crossing without connecting: If two lines cross in a simple ’+’, they are not connected electrically. They are just overlapping on the drawing. (Sometimes, schematics will draw a little semi-circle “jump” over the wire to make this obvious).
- Junctions (Nodes): If two lines cross and there is a solid black dot (a node) right at the intersection, that means those wires are physically tied together at that point.
Reading the Flow
Schematics are generally drawn to be read from Left to Right, and Top to Bottom.
- Power inputs (like batteries or 5V rails) are usually placed at the top or left.
- Ground (GND) is almost always placed at the bottom.
- The “flow” of logic moves from inputs on the left, to processing in the middle, to outputs on the right.
Don’t let massive schematics intimidate you. They are just collections of small, simple circuits tied together. Start at the power source and trace the path!
Recommended Gear:
- Breadboard Starter Kit - Now that you can read schematics, it’s time to build them!