Electromechanical Devices#

Components where electrical signals cause physical motion — or physical motion creates electrical signals. Relays, reed switches, and contactors use magnetic fields to mechanically open and close contacts. Speakers and buzzers convert electrical signals into sound. They predate semiconductors by decades, and many persist because they do things solid-state devices can’t: true galvanic isolation, near-zero on-resistance, or direct conversion between electrical and mechanical domains.

The tradeoff is speed, size, and lifetime. Mechanical contacts bounce, wear, arc, and eventually fail. Understanding when an electromechanical device is the right choice — and how to drive it without destroying the controller — is a practical skill that comes up constantly.

What This Section Covers#

• Relays — Electromagnetic relays: coil drive, contact ratings, bounce, flyback protection, and when to choose them over solid-state switches.
• Reed Switches — Magnetically actuated contacts in a sealed glass envelope: sensing, low-level switching, and their unique failure modes.
• Contactors — Heavy-duty relays for high-power loads: motor control, mains switching, and arc suppression at scale.
• Speakers & Buzzers — Dynamic speakers, piezoelectric elements, and electromagnetic buzzers: drive requirements, impedance, and acoustic behavior.