Home ENGINEERING 3-Way Light Switches Working Principle Animation

3-Way Light Switches Working Principle Animation


We use light switches every day, and yet have you ever seen the inside of one? In this video we open up 3 types of light switches: the basic light switch, 3-Way light switches, and 4-Way light switches. We also explore how they can be wired together to turn on one or multiple lights.How do 3-Way Light Switches Work? Also, let’s look at 4-Way Switches, and Basic Light Switches!

source/image(PrtSc): Branch Education

Electrically, a typical “3-way” switch is a single pole, double throw (SPDT) switch. By correctly connecting two of these switches together, toggling either switch changes the state of the load from off to on, or vice versa. The switches may be arranged so that they are in the same orientation for off, and contrasting orientations for on. Video by Branch Education:

3-way switches have three terminals, one common (usually black color) and one pair of travelers (usually brass color).With conventional wiring, the common wire from one switch connects to line, the common wire from the other switch connects to the load (lights). The pair of travelers on one switch connect to the pair of travelers on the other switch.


The switches must create a complete circuit for current to flow and the bulb to light. When both switches are up, the circuit is complete (top right). When both switches are down, the circuit is complete (bottom right). If one switch is up and one is down, the current reaches a dead end, no current flows and the bulb is off (top left and bottom left).These switches appear externally similar to single pole, single throw (SPST) switches, but have extra connections which allow a circuit to be controlled from multiple locations.

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