Light Switch Overview

Light switches can be configured to operate several different lighting spaces from a single location, and be integrally linked to motion sensors to provide automatic lighting - useful in security/intruder detection - and in large spaces such as manufacturing complexes, hospitals, large hotels/apartment complexes and corporate buildings.

They have several designs, amongst them the toggle switch, the rocker switch, the dimmer switch and the push-button switch.

Technical aspects

When the contacts of a light switch are in the open position, the switch offers virtually infinite resistance to the conductance of electrons, effectively breaking the lighting circuit. When in the closed, position however, resistance plunges to virtually zero. No matter how instantaneous it might appear to the human eye, the transition between open and closed states always involves a short period of partial contact, during which resistance reaches an intermediate level between two absolutes, zero and infinity. Brief though it may be, it is sufficiently long for heat to be generated, and if the period of contact exceeds an upper limit, this heat can be fierce enough to weld the contacts together.

For this reason, still employing the quick-break technology developed by Holmes in 1884, mechanically-actuated light switches are designed to ensure that their contacts are in touch with one another for the tiniest period possible. Typically a spring made of hardened beryllium copper alloy is used in smaller switches; when maintained under stress by the switch design, it stores potential energy. At a certain point (when, say, the switch’s toggle is moved beyond a particular position) the potential energy ‘snaps’ into kinetic energy and very rapidly effects the transition between open and closed states. In this way, excessive heating is prevented and the working life of the switch is prolonged.

The light circuit’s electrical inductance energy will escape in the form of an electrical arc just as contacts begin to separate, a phenomenon which has the potential to damage the switch by extending the period of transition and intensifying the amount of heat generated. Inevitably, even with quick-break design enabling exceptionally rapid opening and closing, light switches have a finite working life and will eventually need to be replaced. However, their functioning can be prolonged by ensuring they are fitted to circuits for which they have been intended: they are manufactured in different durabilities depending on the magnitude of the current they permit or break, as well as the voltage and wattage of the system. Placing a switch designed for one specific combination of current, voltage and power into a higher-rated one for which it was not intended will ruin it especially quickly.

For durability, reliability and safety, light switches are manufactured in such a way that contacts are held forcibly together upon closure and break apart rapidly upon opening, irrespective of user manipulation. These switches can, however, be deliberately misused to hold them in extended transition states, which ultimately corrupts the beryllium copper spring and destroys the quick-break action.

Where the light switch is used in manufacturing

Thanks to the advent of the light switch, easily controlled electrical lighting circuits became available for large manufacturing spaces, displacing potentially dangerous and ineffective gaslight and candle-light predecessors. Vast lighting areas can be differentially controlled from different switches, and light switches can be linked to motion sensors to provide automated lighting in environments as diverse as public lavatories, warehouses, hospitals, schools/educational institutions and factories.

How the light switch differs from other switches

Light switches are rated during design and manufacture for specific deployment in lighting circuitry. They may not be used in power mains circuits, or in circuits carrying greater voltages, current and power than for which they have been specifically rated, without risk of severe degradation and malfunction.

Current product advantages and limitations

Quick-break technology has remained a tried and tested means of conserving the working life of light switches since its invention in 1884. However, mechanical operation and arcing will inevitably cause a degree of wear and tear, limiting the working life of any mechanically operated light switch.

Where necessary, suitable alternatives

The new generation of touch sensitive switches, which do not depend on mechanical action to actuate them, may provide more durable alternatives to quick-break technology.