Rocker Switch

Overview of the rocker switch

The rocker switch is an electrical component which opens or closes electrical circuits by means of a rocking action on a broad, flat lever. This differentiates it from other switches which actuate by means of a tripping action instead. In other words, when one side of the rocker switch is pressed, the other side rises, very much like a rocking horse or a seesaw. Frequently, these switches are marked with a small circle on one end to designate that the device it actuates is “on” and a horizontal line or dash at the other to designate that the device is “off”.

Pervasively used throughout Europe, many Asian countries, the USA and Australia, rocker switches are now being designed with an almost wafer thin wall-plate, although they are generally built to be mounted with the minimum of protrusion from the wall.  The trend in Australia is for especially small rocker switches with a 16 mm rocker mechanism. The chief advantage of these miniature versions is that they occupy considerably less space than the larger versions typically used in the UK and USA: in the “footprint” of a single standard UK rocker switch, for example, up to six Australian rocker switch mechanisms can be mounted.

Even when rocker switches come with a metallic faceplate, none of their external parts need to be earthed (the decorative metal faceplate simply slips on top of a plastic casing).

Engineers should note that wall-plates, cover-plates and the switches themselves are generally not interchangeable when they’ve been made by different manufacturers.

Broadly, there are four main types of rocker switch:

  • Single pole, double throw (SPDT)
  • Single pole, single throw (SPST)
  • Double pole, double throw (DPDT)
  • Double pole, single throw (DPST)

 

The SPST switch simply breaks or makes a circuit by closing or opening it via the rocking movement of the actuator.  The SPDT version permits the connection one of two available terminals to the main circuit, such as upstairs and downstairs switches operating the same light circuit. DPST rocker switches have four terminals connecting or disconnecting two pairs of terminals, such two lighting circuits (e.g., ground and first floor circuits) each with on/off switches. DPDT rocker switches have six terminals, permitting connection of one pair of terminals to two other terminal pairs.

The variety of electronic rocker switches available today is huge. They include:

  • Illuminated Power Rocker Switches
  • Miniature Single Pole (SPST) Rocker Switches
  • Miniature Snap-in Power Rocker Switches
  • Miniature Double Pole (DPST) Power Rocker Switches
  • Miniature Rocker & Lever Handle Switches
  • Miniature Illuminated Power Rocker Switches
  • Miniature Power Rocker Switches
  • Subminiature Rocker Switches
  • Micro Power Rocker Switches
  • Power Rocker Switches
  • Power Rocker and Lever Handle Switches
  • Single Pole Power Rocker Switches
  • Waterproof Rocker Switches

 

History of Rocker Switches

Science was aware of the potential of electrical current some time before the advent of light switches. Faraday's experiments and other important ideas advanced by physicists of the calibre of William Hyde Wollaston had seen a growth in the general understanding of technologies designed to exploit electromagnetism. However it would be 1884 before the light switch appeared as a consequence of the work of Newcastle-based pioneer John Henry Holmes. This new device used "quick break technology" – a technology still in use in light switches today.

Holmes innovation provided a technical workaround for the 'arcing problem' that had obstructed the development of the switch. In the past, electrical contacts in switches were subject to rapid deterioration, because they were repeatedly damaged by electrical arcs. These pitted one of the contacts and coated the other in a non-conductive residue. As its name implies, quick break technology caused the contacts to join or part at lightning speed, irrespective of the amount of pressure applied by the switch’s user. This meant a concomitant decrease in the damage caused by arcing as the amount of time between the components flying together or coming apart was simply to short for arcs to form.

22 years later in 1916, still using Holmes’ technology, New Yorkers William J. Newton and Morris Goldberg invented a new design for the light switch: the toggle switch, actuated by the “toggling” movement of a protruding bar or lever.

 

Technical aspects

Typically, in a simple Single Pole Double Throw (STDP) rocker switch, the rocker level or actuator pivots in two holes located inside the casing of the switch (the “body”). On the interior surface of the actuator are two grooves, inside which an electrically conductive metal “actuator bar” is slipped. This is then pressed downwards by means of a “compression spring” onto a flat, conductive metal plate, the “common contact bar”, which is made of copper and is free to pivot on a small metal rod fixed onto the common terminal. Due to the pressure exerted by the compression spring, however, the common contact bar will always be pressed against one of the two contacts, opening or closing the circuit (it can slide lengthways but is prevented from moving sideways by the construction of the switch body).

When the actuator is pressed, kinetic energy is transferred to the compression spring as potential energy until the actuator passes through the mid-position (the “over-centre” or tipping point), whereupon the spring releases its stored energy and forces the common contact bar in the opposite direction via the sliding actuator bar until it presses against the other contact.

Manufacturers take into consideration two key variables when calculating the life expectancy of rocker switches: the component’s electrical life and its mechanical life. Although there are tens of thousands of rocker switches on the market which express these values, it will rapidly become clear that the values are rarely, if ever, equal. The switch’s electrical life is nearly always shorter than its mechanical life, largely because it is weakened by the pressure of current that passes through it whenever it is closed.

 

Where the rocker switch is used in manufacturing

These components are ideal for compact, economical switching where current ratings do not exceed 20 amps.

Their applications in industry are legion; they are used in marine environments, automotive applications, computer power supplies, display monitors, coffee machines and much else besides. Just about anything that needs an on-off switch can utilise a rocker switch. They are also used in calculators, kitchen appliances, magnetic locks, telephone push-buttons and a plethora of other domestic and commercial electrical devices.

 

How the rocker switch differs from other switches

While the rocker switch shares with the toggle switch the same principles of quick break technology, the internal actuating mechanisms of the two switches are quite distinct. The two levers joined at a pivoting elbow in the toggle are replaced by the actuator bar, compression spring and common contact bar in the rocker. The switching process is also much easier on the rocker switch, as comparatively small pressures need be exerted by the user to flip the switch to open or close the circuit due to the movement of the actuator bar and the rapid transfer of potential energy into kinetic energy from the compression spring.

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