dimmer

A dimmer is an electrical device that adjusts the brightness of a light source by controlling the amount of power delivered. In residential and commercial lighting, dimmers enable lowered light levels for ambience or energy savings, while preserving color quality and lamp life. Most dimmers are designed to be installed in place of a standard light switch.

Most modern dimmers are solid-state and operate on AC power. The common method is phase-cut control, which reduces the portion of each AC cycle that reaches the lamp. Leading-edge dimmers use a triac to cut the beginning of each half-cycle, while trailing-edge dimmers use a semiconductor switch to trim the end of the half-cycle. For some lighting technologies, particularly electronic LEDs, trailing-edge or electronic dimmers are preferred to minimize flicker and provide smoother regulation. There are also DC dimmers that use pulse-width modulation for DC lighting systems.

Performance depends on lamp compatibility. Only dimmable bulbs should be used; non-dimmable lamps can flicker, shimmer, or be damaged. LED and CFL lamps require compatible dimmers and may have minimum load requirements. Incorrect pairing can cause buzz, flicker, or reduced lifespan. Safety considerations include heat at the dimmer, proper enclosure, and adherence to electrical codes.

Dimming is widely used in homes, offices, theaters, and stage lighting. The technology evolved from rheostats and electromechanical dimmers to solid-state devices in the late 20th century, improving efficiency and reliability. Standards and certifications for dimmers typically cover electrical safety, electromagnetic compatibility, and compatibility with lighting loads, in addition to local electrical codes.