In these keyboards, each key sits over a small, flexible rubber dome with a hard carbon center. When the key is pressed, a plunger on the bottom of the key pushes down against the dome. This causes the carbon center to push down also, until it presses against a hard flat surface beneath the key matrix.
As long as the key is held, the carbon center completes the circuit for that portion of the matrix. When the key is released, the rubber dome springs back to its original shape, forcing the key back up to its at-rest position.
Rubber dome switch keyboards are inexpensive, have pretty good tactile response and are fairly resistant to spills and corrosion because of the rubber layer covering the key matrix. Membrane switches are very similar in operation to rubber dome keyboards. A membrane keyboard does not have separate keys though. Instead, it has a single rubber sheet with bulges for each key. You have seen membrane switches on many devices designed for heavy industrial use or extreme conditions.
Because they offer almost no tactile response and can be somewhat difficult to manipulate, these keyboards are seldom found on normal computer systems. Capacitive switches are considered to be non-mechanical because they do not simply complete a circuit like the other keyboard technologies.
Instead, current is constantly flowing through all parts of the key matrix. Each key is spring-loaded, and has a tiny plate attached to the bottom of the plunger. When a key is pressed, this plate is brought very close to another plate just below it. As the two plates are brought closer together, it affects the amount of current flowing through the matrix at that point.
The processor detects the change and interprets it as a keypress for that location. Capacitive switch keyboards are expensive, but do not suffer from corrosion and have a longer life than any other keyboard.
Also, they do not have problems with bounce since the two surfaces never come into actual contact. Metal contact and foam element keyboards are not as common as they used to be. Metal contact switches simply have a spring-loaded key with a strip of metal on the bottom of the plunger.
When the key is pressed, the metal strip connects the two parts of the circuit. The foam element switch is basically the same design but with a small piece of spongy foam between the bottom of the plunger and the metal strip, providing for a better tactile response. Both technologies have good tactile response, make satisfyingly audible "clicks" and are inexpensive to produce.
The problem is that the contacts tend to wear out or corrode faster than on keyboards that use other technologies. Also, there is no barrier that prevents dust or liquids from coming in direct contact with the circuitry of the key matrix.
From the Keyboard to the Computer As you type, the processor in the keyboard is analyzing the key matrix and determining what characters to send to the computer. It maintains these characters in a buffer of memory that is usually about 16 bytes large. Visit the course. Clear structure 09 Sep, There is a good range of questions to challenge your understanding of the content discussed A good course 26 Oct, The course was very good 05 Nov, Intellectual skills 23 Aug, Understanding Computer Systems 26 May, The ideas are presented in a way that is easy to understand Excellent course 15 Jun, A good guide for teachers 24 May, Last week, we talked about what happens when you press the power button: what components and systems work together to start up your computer, what slows it down, what speeds it up, and what else is inside your computer.
Want to keep learning? This content is taken from Raspberry Pi Foundation online course,. This content is taken from Raspberry Pi Foundation online course.
See other articles from this course. This article is from the online course:. News categories. Other top stories on FutureLearn. We explore the current business landscape in India, identity the 5 best startup opportunities and ….
Find out about some of the best startup ideas for the Philippines, as well as …. We explore the challenges and opportunities of the healthcare system in India, looking at how …. Some modern keyboards come with "hot keys" or buttons that give you quick, one-press access to programs, files, or commands.
Other models have volume controls, scroll wheels, zoom wheels, and other gadgets. For details about these features, check the information that came with your keyboard or computer, or go to the manufacturer's website. Using your keyboard properly can help avoid soreness or injury to your wrists, hands, and arms, particularly if you use your computer for long periods. Here are a few tips to help improve keyboard use:.
Center your keyboard in front of you. If your keyboard has a numeric keypad, you can use the spacebar as the centering point. Type with your hands and wrists floating above the keyboard, so that you can use your whole arm to reach for distant keys instead of stretching your fingers. Avoid resting your palms or wrists on any type of surface while typing. If your keyboard has a palm rest, use it only during breaks from typing. Windows 8. Using the numeric keypad, type the first number in the calculation.
Type the next number in the calculation. Press Enter to complete the calculation. Need more help? Join the discussion. Was this information helpful? Yes No. Thank you! Any more feedback? The more you tell us the more we can help. Can you help us improve? Resolved my issue. Clear instructions. Easy to follow. No jargon. Pictures helped. A keyboard is a lot like a miniature computer. It has its own processor and circuitry that carries information to and from that processor.
A large part of this circuitry makes up the key matrix. The key matrix is a grid of circuits underneath the keys. In all keyboards except for capacitive models, which we'll discuss in the next section , each circuit is broken at a point below each key.
When you press a key, it presses a switch , completing the circuit and allowing a tiny amount of current to flow through. The mechanical action of the switch causes some vibration, called bounce , which the processor filters out.
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