Input Devices

Input Devices

1. Keyboard

   • uses an arrangement of buttons or keys to act as mechanical levers or electronic switches.
   • They use switches and circuits to translate a person's keystrokes into a signal a computer can understand.
   • 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

2. Scanner

   • Flat bed
     • a moving belt slides a light source across the entire surface of the document.
   • Sheet - fed
   • Drum
   • Handheld

3. optical mouse

   • The CMOS sensor sends each image to a digital signal processor (DSP) for analysis.
     • The DSP, operating at 18 MIPS (million instructions per second), is able to detect patterns in the images and see how those patterns have moved since the previous image.
       • Based on the change in patterns over a sequence of images, the DSP determines how far the mouse has moved and sends the corresponding coordinates to the computer.
         • The computer moves the cursor on the screen based on the coordinates received from the mouse.
   • The original optical-mouse technology bounced a focused beam of light off a highly-reflective mouse pad onto a sensor. The mouse pad had a grid of dark lines. Each time the mouse was moved, the beam of light was interrupted by the grid. Whenever the light was interrupted, the sensor sent a signal to the computer and the cursor moved a corresponding amount.

4. Sensors

5. Trackerball

6. Joystick

   • Translates the movement of a plastic stick into electronic information a computer can process.
   • The base houses a circuit board that sits directly underneath the stick. The circuit board is made up of several "printed wires," which connect to several contact terminals.
     • Ordinary wires extend from these contact points to the computer.
       • When the joystick is in the neutral position -- when you're not pushing one way or another -- all but one of the individual circuits are broken.
     • The printed wires form a simple electrical circuit made up of several smaller circuits. The circuits just carry electricity from one contact point to another.
   • Each broken section is covered with a simple plastic button containing a tiny metal disc. When you move the stick in any direction, it pushes down on one of these buttons, pressing the conductive metal disc against the circuit board. This closes the circuit -- it completes the connection between the two wire sections. When the circuit is closed, electricity can flow down a wire from the computer (or game console), through the printed wire, and to another wire leading back to the computer.

7. Microphone

   • a device which converts energy from one form to another. Microphones convert acoustical energy (sound waves) into electrical energy (the audio signal).
   • They all share one thing in common: The diaphragm.
     • This is a thin piece of material (such as paper, plastic or aluminium) which vibrates when it is struck by sound waves.
     • When the diaphragm vibrates, it causes other components in the microphone to vibrate. These vibrations are converted into an electrical current which becomes the audio signal.