How Do Lamp Dimmers Work?
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Lamps Work on Alternating Current
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Lamps draw their electrical power from standard household electricity known as alternating current. In an alternating current configuration, electricity flows first in one direction, and then in the other (thus the "alternating" name). This cycle is reversed 50 to 60 times per second, and the reversal process is referred to as 50 or 60 hertz (the scientific term for cycles per second). As the cycle reverses, the electricity reaches a neutral balance known to electricians as a "zero point"; this zero point is the basis of electrical dimming.
Dimmer Switches Analyze Electrical Flow
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As electricity flows and alternates direction, dimmers use a form of semiconductor known as a thyristor; when the alternating current switches directions, the thyristor self-activates to provide conductivity to the electrical circuit. When the alternating current switches direction again, the thyristor deactivates and a second, separate thyristor completes the electrical circuit in the opposite direction. This action is performed using either an analog circuit, as is common in older dimmer switches, or an electronic, digitally controlled microprocessor that analyzes the flow of electricity and automatically switches the electrical circuits. This function differs somewhat, though, from standard on/off toggle switches that work by simply completing or breaking an electrical circuit.
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Dimmers Cut Electrical Flow
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When a dimmer switch is activated, the switch uses its analog or digital circuitry to delay the flow of electricity in one of the two directions; this function is performed by reducing the function of the thyristor, preventing electricity flowing in one direction from reaching the connected lamp. The reduction of thyristor function is increased as the lamp is made dimmer until the light no longer illuminates (the lamp is turned "off" by completely breaking the electrical circuit). Because the electrical flow is partially interrupted when the lamp is dimmed, some lamps may emit a buzzing sound as power is very quickly switched from full flow to the reduced flow. This function also disallows use of most dimmers with fluorescent lights, which rely on a constant flow of electricity to function.
Dimmer Switches Have Limitations
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As mentioned above, incandescent lamps attached to dimmer switches may emit a buzzing sound as electrical flow rapidly alternates between full and reduced power. Older dimmer switches also cause some lamps to slightly fluctuate in their light production, since these early dimmer switches lack the built-in regulators that provide a smooth, even flow of electricity even at reduced rates. Newer dimmers with microprocessor controls handle this function electronically, providing a smooth, even adjustment to light levels. As with all electrical switches, the internal components of dimmer switches eventually wear out and become nonfunctional, requiring complete replacement of the switch; because dimmer switches require the added thyristor components, users may notice that they wear out slightly faster than standard on/off switches.
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