Toggle Switch

Overview of the Toggle Switch

A variant of the electrical switch, this component opens or closes circuits (or diverts the flow of current to another conductor) by means of the manual movement of a protruding handle, rocking mechanism or lever. The word “toggle” refers to the mechanical parts which between them distinguish this type of switch from others: most, though not all, toggle switches actually have two arms (only one of which may be visible from the outside of the component) which meet together at a pivoting elbow joint.

The key distinguishing feature, however, is that the component is actuated by means of the snap action of a short handle, even if there is no second arm inside the device. Switches in this category which produce a sound when toggled are called “positive on-off switches”.

Broadly, there are four main types of toggle switch:

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

The simplest of these is the SPST switch, which simply interrupts or completes a circuit by closing or opening it via snap movement of the toggle handle. The SPDT version is used to connect one of two available terminals to the main circuit, such as a hallway and an upstairs switch operating the same light circuit. DPST toggle switches have four terminals simultaneously connecting or disconnecting two pairs of terminals such as two lighting circuits (e.g., first storey and ground floor circuits) each with on/off switches, while DPDT toggle switches have six terminals, connecting one pair of terminals to two other terminal pairs.

Toggle switches can be further subdivided into smaller categories depending on whether they are used to actuate temporary or permanent functions, what kind of contact and insulation they have, their torque, operating temperature and their dielectric strength.

They are manufactured in a broad range of dimensions, depending largely on what purposes they are destined for, accommodating the widely different needs of engineers and DIY enthusiasts. Technological advances have now enabled manufacturers to make miniature toggle switches as well.

Depending on their position in relation to the circuit board, toggle switches can be mounted vertically or horizontally. While the direction of the mounting does not affect their functionality, it can affect the practicality and usefulness of the final product they are fitted on.


History of the Toggle Switch

While electricity had been known about for centuries, the humble electrical light switch didn’t make an appearance until 1884, when the Shieldfield inventor John Holmes created one based on his newly discovered “quick-break” technology (which is still in use today). The toggle switch was not to emerge, however, for another 22 years, when New York inventors William J. Newton and Morris Goldberg created one for lighting circuits in 1916. These switches are now used in countless products and buildings across the globe.


Technical aspects

Many of the products which incorporate toggle switches have an industrial use, which typically means that these components have to be securely protected against liquids and damage from moving solid particles like dust if their safe and effective functioning is to be ensured. Manufacturers will usually include an IP rating (sometimes known as an Ingress Protection Code or International Protection Code) which indicates to the prospective user whether or not the switch will continue to function after being immersed in liquids, industrial dusts or other solid objects.

Manufacturers factor in two parameters when working out the life expectancy of the toggle switches they produce: their electrical and mechanical lifespans. Literally tens of thousands of toggle switches express these values but almost invariably they are not equal to one another: in the vast majority of cases, the mechanical life of the switch far outweighs its electrical life. The latter is always shortened because of the level of current which passes through it during times when the circuit it controls is closed.


Where the Toggle switch is used in manufacturing

Any building will contain numerous light switches – an almost innumerable quantity, in fact, for large complexes such as factories, warehouses or hospitals - and any which simply flip lighting circuits on or off (as opposed to dimming lights) will almost certainly be a category of toggle switch. Similarly a large number of appliances and other kinds of machinery, including industrial machinery, will usually have a Power On/Power Off switch which will typically be a toggle switch design.

Sophisticated and intricate machines such as lift trucks and, at the upper end of the spectrum, aircraft, will often have several arrays of toggle switches, and some styles of circuit breaker are effectively based on the toggle switch design. The electrical mixing boards used by musicians utilize toggle switches to actuate their numerous input- and output-channels. There are countless applications of the toggle switch in industry, from industrial controls to agriculture, marine panels to marine and agricultural transportation.

In addition to their mechanical varieties, toggle switches are used in software, usually to actuate a number of functions from the same switch on, say, a computer keyboard. The software toggle enables switching between numerous choices, such as the windows on a PC or laptop display, for instance. Typically they work according to the number of taps they receive from the user: for example, pressing a software toggle key once will progress the user from Choice 1 to Choice 2, while another press will progress to Choice 3. Once all the choices available have been navigated, another press will return the user to Choice 1.

Mechanical throwing by pressing a keyboard key is just a part of the functioning of the software toggle; it is effectively, a sequence of code that yields a menu of choices, only one of which may be needed at any one time. On websites, the same basic idea is used on virtual checklists. For example, customers ordering a restaurant or take-home meal via online registration can often be invited to click the checkbox for “vegetarian” as their superordinate option for making their food choices. If a user were to click “salmon” as a meal following making the vegetarian choice, the software toggle would automatically disconnect the “vegetarian” option as the “salmon” tick is placed.