At present, the common keyboards on the market are generally distinguished according to the trigger mode of the keys. The so-called trigger mode refers to how the electronic components inside the keyboard detect the way the user presses the keys. Mainly divided into two types: mechanical keyboard, membrane keyboard, and the uncommon capacitive keyboard.
- Mechanical keyboard
Mechanical keyboards use the principle of metal contact switches to make the contacts turn on or off. Each key of the mechanical keyboard has a separate switch to control the closing. This switch is also called “axis”. There are many types of shafts, and the pressing force and stroke are also different. They are mainly distinguished by the color of the shaft.
- Membrane keyboard
There are four layers in the plastic film keyboard, one layer of plastic film has raised conductive rubber, one layer is an isolation layer, and the upper and lower layers have contacts. Press down the rubber bump by pressing the button, so that the upper and lower layers of contacts are in contact, and the code is output. This keyboard has no mechanical wear and high reliability.
- Capacitive keyboard
Capacitive keyboard It is similar to the principle of capacitive switch. By changing the distance between electrodes by pressing the button, the change of capacitance is generated, and the conditions for allowing the passage of the oscillating pulse are temporarily formed. We know that the capacity of the capacitor is determined by the medium, the distance between the two poles and the area of the two poles. Therefore, when the key cap is pressed, the distance between the two poles changes, which causes the capacitance to change. When the parameter design is appropriate, there is output when the key is pressed, but no output when the key is not pressed. The output is then shaped and amplified to drive Encoder.
Since the capacitor has no contact, the bond does not have problems such as wear and poor contact during the working process, and the durability, sensitivity and stability are relatively good. In order to avoid dust entering between the electrodes, the capacitive key switch adopts a sealed assembly.
Structurally, the structure of the electrostatic capacitive keyboard can be said to be the fusion of membrane keyboard and mechanical keyboard. After the keyboard is disassembled, the main body is a PCB board, and the PCB board is covered with a layer of rubber film with a bowl shape, much like a membrane keyboard; the bottom of the PCB board is generally reinforced with steel plates, which are sandwiched between the rubber bowl and the PCB board. with a conical spring.
In principle, the electrostatic capacitance keyboard is triggered by the principle of electrostatic capacitance, so its PCB board is very different from that of a mechanical keyboard. Because it has a huge PCB board, it can weld a large number of anti-collision diodes, and it can also achieve full-key no-collision.
Among the three major types of mechanical keyboards, electrostatic capacitive mechanical keyboards are the most expensive. Although they have a unique feel, they are expensive and have not become popular.
In general, although keyboards have various formats, there are basically three types of them, and our daily office or home use is basically a membrane keyboard. At present, this kind of keyboard can be seen almost everywhere, and the price is very cheap.
Mechanical keyboards are suitable for those who want a higher input experience, such as programmers, editors, e-sports gamers, and enthusiasts;
For more questions about mechanical keyboards, see an article I wrote earlier：
The capacitive keyboard is a pure high-end keyboard, and the demand for use in special environments will be greater, such as in medical care.