Introduction to Relays and Relay Logic

Build relays by energizing a coil to move a metal plate and close contacts, using normally open, normally closed, and common terminals for isolated high-voltage switching.

Draw a relay with a common, normally open, and normally closed contact driven by a 24-volt coil, illustrating a three-way switch and isolation across voltages.

Learn how to identify relay terminals, distinguish common, normally open, and normally closed contacts, and wire a ladder diagram with a PLC using 24V AC coils and 240V AC contacts.

Contactors are large relays that handle higher current to power motors, using a coil to switch three‑phase or single‑phase lines through normally open contacts and overloads.

Label ladder logic diagrams by identifying rails as power supplies and rungs as wires, read left-to-right and top-to-bottom, showing 24V feeds, normally open/closed contacts, switches, relays, and lights.

Explore the constructor, an industry-standard ladder logic software for designing and simulating relay circuits. It features a symbol library, wires, rails, coils, three-phase and single-phase options, and testing capabilities.

Wire a 24-volt supply through a single-pole switch to energize the relay coil (terminals 7 and 8) and return to the source, demonstrating the relay’s contacts closing and opening.

This lecture shows wiring a 120-volt load with a 24-volt relay on a separate line diagram, using common 5 and normally open 3 contacts to light the load.

Learn to add an indicator light to a motor circuit using relay contacts, illustrating coil versus switching voltages and how to steal contacts safely.