Switches and Relays
Mechanical switches and electromagnetically operated relays make or break circuits.
Switch types are described by poles (separate circuits) and throws (positions): SPST, SPDT, DPDT. Push buttons are momentary; toggles are latching.
A relay uses a coil to move contacts, letting a small current (e.g. 5 V, 70 mA from a transistor) switch a large isolated load (230 V lamp). Always add a flyback diode across the coil and drive it through a transistor, never directly from a microcontroller pin.
Solid-state relays (SSRs) switch with semiconductors: silent and fast, but with leakage current and heat.
Sub-topics (1)
Switch Debouncing
Mechanical contacts bounce for a few milliseconds; debounce in hardware or software to count one press.
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