Mechanical Switching explained

Mechanical Switching explained

Beloved by gamers, the mechanical keyboard is making a comeback for users of all types – John Gillooly looks at the different varieties available.

Once upon a time keyboards were made with mechanical switches. Each key had an individual switch below it that would register a keypress when pushed past a certain threshold. The most famous of these was the buckling spring mechanism used in IBM’s Model 15, a design still beloved by many who keep these aging keyboards alive.

Most mass market keyboards are now made with rubber membranes rather than individual switches. This cheap-to-produce design basically consists of a rubber sheet with domes pointing upwards. Each of these domes corresponds with a key, and the inside is lined with a conductive material.

When you press down on a key this dome gives way and touches a conductive material underneath the rubber sheet. This then registers the keypress electronically and sends it to the keyboard controller, which relays it to the PC.

Laptops use a similar design, but in order to ensure that the keyboard can sit in a small space the domes are smaller. To counteract this most laptop keyboards use a ‘scissor switch’ design, where plastic arms hold the keycaps in place over the domes. This ensures that the keys stay centred over the domes and that keypresses register correctly. The side effect of this low profile design is that the amount of key travel is even lower than that on a dome keyboard.

These rubber dome designs work consistently well but are commonly accused of feeling ‘mushy’. This is a side effect of relatively short key travel and rubber membranes diminishing in springy-ness with age. This complaint is largely brought by gamers, but anyone who spends a decent amount of time typing will know all too well how unsatisfying rubber dome keyboards can be over prolonged periods.

A rubber membrane keyboard uses a series of domes over a grid to register key presses. 

Mechanical Switching 

Despite the sheer prevalence of membrane based keyboards, the old style mechanical design hasn’t gone anywhere. Products from small companies like Das Keyboard and Cherry have been keeping the design alive, and over the past year more mainstream manufacturers like Razer, Coolermaster and Thermaltake have jumped into the mechanical keyboard market.

Modern mechanical keyboards don’t use the buckling spring mechanism of days gone by, rather they all use switches from German manufacturer Cherry. So important is the role of Cherry’s switches that keyboards are marketed around the type of switch used, which directly correlates to what it feels like to push a key.

To understand modern mechanical keyboards, one first needs to understand these switches and how they are differentiated. Switches are specifically drawn from the Cherry MX range of products, and models are commonly referred to by the colour of the stem.

Each of these models has a slightly different design, which in turn affects the feel of the switch and the noise that it makes. This is down to the way in which these switches register keypresses as well as other factors like the type of spring used in the switch. The anatomy of these switches is surprisingly well documented online for those who want to go further, but at a base level the ‘feel’ of a mechanical switch is down to a few key features.

Most Cherry MX switches use a similar internal design. The Key sits on top of a stem, the colour of which is commonly used to differentiate between models. This stem has a spring at its base and a plastic tab on one side. This tab holds two metal contacts apart when the key is in its normal position. However when you depress the key, the tab moves downward and allows the metal contacts to join, which registers as a keypress.

The complexity of a mechanical keyboard is pretty astonishing, with hundreds of individual parts going into each one.

Unlike a rubber dome keyboard, where the point at which the keypress is registered is at the base of the key’s travel, the Cherry switches allow the keypress to register before the key bottoms out. The point at which this happens is known as the actuation point.

The actuation point is important when looking at one of the major means of differentiating between mechanical switches. Generally speaking switches are referred to as linear or tactile in design, with some also being given the moniker ‘clicky’.

A tactile switch is one designed so that there is a noticeable feel when the key passes the actuation point. This is achieved by adding a physical bump to the tab that holds the contacts apart. In practice this means that the amount of force needed to actuate the key will change, depending on where in the travel the key is. This is of particular benefit to typists as it provides feedback that the key has registered without having to consistently bottom out the key. Tactile switches include the Cherry MX Brown and Blue models

Linear switches have no such bump, and the amount of force required to depress the key increases the further the key travels. The Cherry MX Black and Red switches use Linear designs, and are rapidly becoming the go-to switches for gaming.

Clicky refers to switches designed to make a noise when they hit the actuation point, there is only one such model of Cherry MX switch, the Blue, which uses a two part stem design to achieve a distinctive noise when it actuates. The inherent nature of this design means that only tactile switches can be clicky.

While this information is just scratching the surface of mechanical keyboards, it is likely more than a mere mortal will ever want to know. However it is important to keep this information in mind when looking at the new crop of mechanical keyboards. Unlike rubber dome models, which largely feel the same to type on, each type of switch imparts a different feel when hitting keys.

Take for example Razer’s keyboard, the BlackWidow. It comes with the tactile and clicky Cherry MX Blue switches, however as a very distinct nod to how annoying some people find the noise, there is now a Stealth Edition, which uses the tactile but non-clicky Cherry MX Brown models.

As a corollary Thermaltake has decided to go with the linear Cherry MX Black switches for its Meka line of keyboards. Similarly Corsair is using the linear Cherry MX Red switches for its upcoming Vengeance keyboards. The major difference between these two models is that the Black takes slightly more actuation force than the red one.

Coolermaster has taken a different approach to most of the other players and has three different models of its Quickfire keyboard, which are differentiated solely by the type of Cherry MX switch used.

With so much choice out there, purchasing a mechanical keyboard involves so much more than just choosing the right looks and the largest number of extraneous macro buttons. Unlike the nearly ubiquitous feel of Rubber Dome keyboards, each type of Cherry MX switch has its own unique quirks, and choosing the right one becomes quite a personal choice.

Even around the PC & Tech Authority labs there is debate as to which switch is ‘best’. After a few months of use this writer has taken a real aversion to the noise made by Cherry MX Blues, whilst others engage heavily in the tactile vs linear switch debate. The take home lesson is that if you can get a feel of how the different switches work before you buy then jump at the opportunity. Work out which one you like, and then use that information to decide which keyboard to get. Remember that because the switches all come from the same company, the feel of the keys won’t vary too much between manufacturers.

Source: Copyright © PC & Tech Authority. All rights reserved.

See more about:  pcbuilding  |  keyboards  |  mechanical  |  switching
 
 

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