The symbols you'll meet most in Arduino/ESP32 projects. Print me.
Remember the two rules from Lesson 2:
lines are wires (joined points are one node), and each symbol is a part
with a letter label (R, C, D, Q, U, SW…).
Resistor (R)Limits current / sets voltage. Zig-zag (US).
Capacitor (C)Stores charge; smooths/decouples. Two plates.
Diode (D)One-way valve for current. Bar = cathode (−).
LEDDiode that emits light. Arrows point out.
Battery / DC sourceLong line = +, short line = −.
Ground (GND)The 0V reference / return path.
Switch (SW)Opens/closes the loop. Button is a momentary version.
Transistor (Q)Electrically-controlled switch. Base = control.
IC / chip (U)A box with named pins. e.g. your ESP32.
Relay coil + contactCoil (left) magnetically moves the switch (right).
Note on style variation
European schematics often draw a resistor as a plain rectangle instead of a zig-zag. Same part —
don't let the shape throw you. Full reference:
SparkFun — How to Read a Schematic.