Optical Key Switches Explained
More and more keyboards are coming with “optical” switches, they seem to be the new trend especially among the higher end boards, but what are they? What makes them different and why are so many new boards coming with them? Are they all the same? There’s lots of questions, but I’ve got some answers so lets get started. Of course, if you haven’t already, consider subscribing for more videos every Monday, Wednesday and Friday!
Lets first start with explaining what normal switches do. Inside a Cherry MX style switch, you have a springy piece of metal that the moving part of the switch, when not pressed, gets in the way of it springing outwards and making contact. When you press the switch, the moving piece slides out the way so the springy metal can make contact with the other, fixed piece and complete the circuit. This works really reliably, and can be tweaked to provide a lot of different feelings, including linear, tactile and clicky.
There are some downsides though, because this relies on a springy piece of metal bending over and over, it can wear out and become less springy and therefore not make as good and reliable contact. Also, because it’s a spring hitting another piece of metal, it very slightly bounces, enough to break the contact a few times before actually resting and making a solid connection. The keyboard controller has to do something called “debouncing”, basically adding delay to make sure you have actually pressed a switch rather than just firing every time it actually makes contact, since you don’t want to press a key once but have it type the same letter 20 times per key press. This means the keyboard can take multiple milliseconds just to actually send the signal to your PC, on top of the tens of milliseconds it takes for your system to register those changes and display anything new on screen.
So, in comes optical switches. There are a lot of styles of these so I’m going to start with the one that is becoming the most common, the style that Corsair use in their new K100. This type of optical switch still uses the same Cherry MX style housing, spring and movable piece, but replaces the metal contactors with an infrared beam and receiver, that when the switch is pressed, the beam is broken and registers a key press. This doesn’t need debouncing, which means the keyboard, even with a “standard” 1000Hz polling rate, can send the signal to your system much faster and help reduce input lag.
This style of switch is also found in Razer’s mice, like the Viper and their 8000Hz test mouse they sent me, video on this and the K100 in the cards above by the way. They do it slightly differently, having a gap in the moving part of the switch instead so the beam is made rather than broken, but the concept is the same.
This style of switch resolves both drawbacks of standard mechanical switches. It’s much more reliable as there are no moving parts other than the part you press, and can actuate much faster thanks to a lack of debouncing. But that’s not the only style of optical switch available. Wooting use Flaretech Prism switches, which instead of shining the beam horizontally, having the switch make or break the beam, they instead use a set of mirrors and have the beam shine into the switch through one hole, and out another to the receiver. The benefit of this is you don’t need to connect the switch to the PCB at all, everything can be surface mounted and the actual switches can be hot swapped.
The other benefit is this design accurately measures how much you’ve pressed the switch in, instead of just if you’ve actuated it or not. That means, with the help of some clever software, you can do some really, really cool stuff. You can change the actuation point of the switch, so if you like to hammer type, really bottoming out the keys, you can set it really low, but then you want a light touch while gaming, just set it nice and high. You can also use them as analogue inputs just like an xbox controller – it’s not very intuitive, but really cool to have. And they also offer a truly standout feature, having multiple key presses per stroke. For example, if you half press the W key, you’d slow walk, something normally bound to control and W, then when you bottom the key out, it’ll sprint instead, pressing shift and W for you. All from one key, just depends how far you press it. It’s really, really cool.
But that isn’t the only fancy new switch type, Steelseries also have a switch with an adjustable actuation point, but instead of using beams of light, they use a magnet in the movable part of the switch, and what’s called a “hall effect sensor” on the PCB. A hall effect sensor measures the strength of a magnetic field. They are really interesting, and can be used to measure current through a cable, but can also tell you how far away a magnet is from one, hence why Steelseries use it here. In theory, they could offer all the same functionality as Wooting do, although as far as I’m aware they only allow for adjustable actuation point at the moment.
So to recap, the benefits of an optical, or magnetic, switch are improved response time, better longevity and durability, but remember not all optical switches are the same, some use a pretty basic style where the optical part just replaces the contactors, whereas some are much more advanced and can offer really unique and innovative features.
