Input & Output devices

1. Input & Output devices

2. Input Device :keyboard • a keyboard is an input device, partially modeled after the typewriter keyboard, which uses an arrangement of buttons or keys, to act as mechanical levers or electronic switches. • A keyboard is also used to give commands to the operating system of a computer. • Connectors to keyboard AT(DIN-5) PS2 andUSB. • XT with 83 keys,At with 84 keys, 104 keys by adding window keys. • Keys includes: Typing keys numeric keypad,function keys,control keys • Virtual Laser Keyboard(sensor,Signalsto computer)

3. Input Device :keyboard • Components of Keyboard • Keyboard switches • Keyboard processor or circuitry • Key matrix • Types of keySwitches • Capacitive switch • Hall effect switch • Opto electronic switch • Membrane switch • Mechnical switch

4. Input Device :keyboard • Key matrix: keyboard matrix is the arrangement of circuit connections between the keyboard controller and all the keys. • Key switch: The main component of any keyboard is the key switch. These switches generate typical codes of signal when they are depressed and it is used for interfacing with computer system

5. Input Device :keyboard

6. Input Device :keyboard

7. Input Device :keyboard • Key matrix: keyboard matrix is the arrangement of circuit connections between the keyboard controller and all the keys. • each key is placed at the intersection of a matrix row and a matrix column. The keyboard repeatedly applies current to each column in turn, and checks to see which rows output current. From this, the keyboard can deduce which keys in that column have been depressed.

8. Input Device :keyboard • Capcitive switch:two plates of the capacitor are brought closer when the key is pressed. • Change in capacitance of switch changes and change in capacitance is detected in terms of voltage. • Basedon the switch open/close voltage is recived thisvoltage is converted into proper signals to inform CPU. • Lifespan 20 millonkey strokes. • Hall effect switch: magnetic field is applied to any device the resistance of device will be increases or decresed(current starts flowing) • This allow current flow • Lifespan 100 million keystrokes

9. Input Device :keyboard

10. Input Device :keyboard • opto-electronic switch: have LED light generate light when electric power is applied.uses photo- transistor which allow current to flow in the circuit. • When key is pressed not pressed the light from LED falls onto photo-transistor • When key is pressed the value will be produced at the ouput Vout • membrane switch:it is multi layered plastic or rubberuses the row and colum conductor sheets. • Mechanical switch: it uses two metal pieces or contacts . • Rubber dome:madeup of polyester domes • Refered as direct switches.

11. Input Device :keyboard opto-electronic switch membrane switch

12. Input Device :keyboard Mechanical switch

13. Keyboard Interfaces • Connects to PC • KEYBOARD • KEYBOARD CONNECTOR • Inside keyboard a processor and circuit which carry information to or from that processor. • Keyboard controller is single chip contains memory RAM, processor ROM(control operations of keyboard) • Key matrix: row and columns made up wires and each key act like switch • Key matrix is grid of circuits when key is pressed the row wire makes contact with colmn wire and completes the circuit . KM passes current to keyboard controller . • Keyboard controller will detects the closed circuit and registers the key press and controller read the key pressed.

14. Keyboard Interfaces • KEYBOARD CONNECTOR • Interface between keyboard and pc • AT keyboard connector(DIN5) • PS2 keyboard connector or(MIN-DIN6) • USB connector • AT keyboard connector(DIN5) • Uses 5 pins: KBDCLK(provide clock pulse), KBDAT(send/recive data),KBRST (reset keyboardinternal buffer),GND(ground),VCC(+5v provides power to keyboard) PS2 keyboard connector or(MIN-DIN6): With 6 pins

16. USB keyboard connector: • USB keyboard connector: uses 4 pins VDC(+5V),DATA- carries -ve data signal,DATA+it carries +ve data Signal, • Keyboard working:key is pressed it pushes down the rubber dome • Dome tuches a pair of conductive lines on circuit • Allow current flow

17. Mouse: • Mechanical Mouse : Mechanical Mouse uses ball for the movement of cursor on thecomputer screen. When the ball is rolled in any direction, a sensor of the mouse detects it and also moves the mouse pointer in the same direction. • Optical Mouse : Optical Mouse uses Laser rays for the movement of cursor on the computer screen. It is an advanced pointing device. Movement is detected by sensing changes in the reflected light rather than the motion of a rolling sphere. • Cord-Less Mouse : Cord-Less Mouse is battery driven and does not need any wire for the physical connection with the motherboard. It transmits data through infrared or radio signal.

18. Mechanical mouse

19. Mouse types 1.Mechanical mouse: a rubber ball rolls as the mouse is moved across table top or mouse pad. The wheels are referred as encoders have tiny metal contact points on rims Location of mouse is identified by how many times the contact points have touched the bars. mouse moved across flat surface. As balls rotate it touches and turns two rollers inside the mouse Two rollers are used for vertical and horizontal movements of cursor 19

20. Mouse types • Each roller attached to encoder. • Each time a contact bar touches a point an electrical signal. • Signals generated are sent to PC over the mouse cables • And number of mouse time mouse button is clicked. 2. Optical-mechanical mouse: • When mouse moves the ball of mouse moves and two separate rollers fixed at 90 degree to each other one roller is for vertical and horizontal movement of cursor. • Each roller connected to wheel these rollers are rotated by movement of rollers. • Wheel rotate pair of LED and photo detectors • Signals sent to PC through mouse connectors 20

21. Mouse types • Optical mouse: • LED produces a red light that is emitted onto surface the light reflected back to CMOS sensor then to DSP(digital signal processor) for analysis • DSP analysis the signal and and patterns and determines mouse movements. • Along with coordinates are received by computer and will show mouse movement on screen.

22. Installing Mouse • Locate the mouse port(USB,PS/2 COM1/COM2) on computer system back. • Plug the mouse carefully on the mouse port of computer. • Turn on system. • Installing of mouse driver software • window have built in drivers • Insert driver CD • Run the dialog box displayed on screen. • Fallow installation instruction • Restart computer.

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