LESSON 13 · Components
Switches & Relays
Manual and electrical ways to open or close a circuit.
A switch is the simplest control component: it physically connects or breaks a path. A "SPST" (single-pole, single-throw) switch is a basic on/off; a "SPDT" switch routes power to one of two paths.
SWITCH SYMBOLTwo dots (the contacts) with a lever that connects or lifts away from them.
A relay is an electrically controlled switch: a small coil, energized by a low-power signal, pulls a mechanical contact closed to switch a completely separate, often much higher-power circuit — letting a microcontroller safely control mains-voltage appliances.