How a Touch Dimmer Switch Works

Under normal, non-dimmed operation, light bulbs illuminate when electricity passes from the home or office electrical wiring though an attached power cord and into a light bulb. As the electricity passes over the light bulb's filament, the high-resistance filament impedes the flow of electrons across the circuit. As more and more electricity attempts to flow, but cannot pass because of the resistance, the filament begins to produce large amounts of both heat and light. While this operation is the same in both alternating current (like the ones found in home or office wiring) and direct current circuits (like the ones found in common flashlights), touch dimmers generally act on the alternating properties of household wiring to reduce the flow of electricity to the attached light bulb.

Under normal operation, as described above, electricity flows from a wall outlet through a light bulb's filament to produce light and heat. In an alternating current circuit, the electrical flow varies, or alternates, from positive to negative voltages. Electricians refer to this back and forth flow, which follows a standard cycle, as the current's "duty cycle." When a user activates a dimmer switch, thyristors, electronic versions of electrical resistors, interrupt one portion of the electrical duty cycle. This interruption prevents a portion of the voltage from reaching the light bulb, and the reduced amount of voltage flowing across the filament causes it to glow dimmer than it would if it received the full voltage. Most touch dimmers offer varying degrees of dimming ability, and higher dimmer settings interrupt a broader range of the current's duty cycle. Although a user activates the thyristors in a mechanical dimmer switch by physically moving a switch, the absence of this switch in touch dimmer equipment requires some special considerations.

Because touch dimmers rely on a series of human touches rather than a physical switch position to dim lighting, the devices must employ special components that replace all functions of the physical switch. According to ePanorama, an electrical appliance organization, touch dimmers use a special touch-sensitive metal plate to pick up the electricity present in human touches at either 50 or 60 hertz, depending on the dimmer's application. In addition to the special touch plate, touch dimmers also employ a timing mechanism that measures the time between touches; this mechanism prevents the device from interpreting two very quick touches as two individual commands, and enables special "long touch" functionality. Touch dimmer switches also include special memory circuitry that stores the light's current dimmer level, as the absence of a physical switch removes the device's ability to mechanically adjust the light intensity. Finally, touch dimmers must include special circuitry that translates the human touch input into the electrical impulses necessary for triggering the dimmer's thyristors.