How does it works ???
GLOBAL POSITIONING SYSTEM
( GPS )
BICYCLE AIR PUMP
HOW DOES THE
A touch screen is computer display screen that is
sensitive to human touch.
The display screen has a sensitive glass overlay
placed on it and we could give the desired input by
A touch screen kit includes a touch screen panel, a
controller and a software driver.
Internal touch screen kits are available but require
professional installation because the must be
installed inside the monitors.
MODEL OF TOUCHSCREEN
WORKING OF TOUCHSCREEN
Main components are :Touch
A touch screen sensor is a clear glass panel with a
touch responsive surface.
The sensor generally has an electrical current or
signal going through it and touching the screen
causes a voltage or signal change.
The controller is a small PC card that connects
between the touch sensor and the PC.
The controller determines what type of
interface/connection you will need on the PC.
The driver is a software that allows the touch
screen and computer to work together.
Most touch screen drivers today are a mouseemulation type driver.
Public Information Displays:::
Tourism displays, Trade show display
Stores, Restaurants, ATMs, Airline ticket terminals
and Transportation hubs.
Digital jukeboxes, Computerized gaming, Student
Registration systems, Multimedia software , Scientific
Direct pointing to the
Finger or pen is usable (No
No keyboard necessary
Suited to: novices,
application for information
Low precision by using
User has to sit or stand
closer to the screen
The screen may be covered
more by using hand
No direct activation to the
Review of GPS
Theory of Positioning
Accuracy of time and location of
A method for determining the intersections
of three sphere surfaces given the centers and
radii of the three spheres.
Simplifying the problem
Let’s assume several factors for easy understanding.
GPS Satellites are on the ground (3D 2D)
We know the exact location of satellites
We can calculate the distance from each of the
Start with first satellite
Your location is somewhere on the circumference of the circle.
Second satellite gives two points
Real trilateration in 3D space
Real trilateration in 3D space
Measuring the Distance
GPS receiver uses speed equation to calculate the
distance to satellites.
GPS satellites use radio signal
Instead of throwing balls, the GPS satellites send
radio wave and GPS receivers catch them.
Radio wave fly at the same speed of light.
(about 300,000 km/s)
Signal from GPS satellites
Each satellites continuously transmits messages including :
time the message was transmitted
orbital information (location of itself, ephemeris)
orbits of all GPS satellites (the almanac)
How a Microwave Oven
What are Microwaves?
Microwaves are a form of electromagnetic energy, like light
waves or radio waves
Microwaves are used extensively in communications
such as to relay long-distance telephone signals, television programs and computer
information across the earth or to a satellite in space.
Good for transmitting information because it can penetrate haze,
light rain and snow, clouds, and smoke.
Also used in radars and in detecting speeding cars.
Microwave has become most familiar as the energy source for
How the Oven Works ?
Electricity from the wall outlet travels through the power
cord and enters the microwave oven through a series of
fuse and safety protection circuits.
These circuits include various fuses and thermal
protectors that are designed to deactivate the oven in the
event of an electrical short or if an overheating condition
When the oven door is closed, an electrical path is also
established through a series of safety interlock switches.
• Sensing that all systems are set to go, the signal activates triac,
producing a voltage path to the high-voltage transformer.
• The high-voltage transformer along with a special diode and
capacitor arrangement increases the typical household voltage from
~115 volts to ~3000 volts
•The magnetron converts the high voltage in to the microwave frequency for
•The microwave energy is transmitted into a waveguide
•The waveguide feeds the energy to the stirrer blade and into the cooking
•When the door is opened, or the timer reaches zero, the microwave energy
Electrons from a hot filament would travel radially to
the outside ring if it were not for the magnetic field.
The magnetic force deflects them as shown and they
tend to sweep around the circle. In doing so, they
“pump” the natural frequency of the cavities. The
currents around the resonant cavities cause them to
radiate electromagnetic energy at that resonant
How Foods Get Cooked
The microwaves that penetrate the food have an electric
field that oscillates 2.45 billion times a second, a
frequency that is well absorbed by polar liquid molecules
such as water, sugars, fats and other food molecules.
Water interacts with the microwave:
flipping its orientation back and forth very rapidly
bumping into one another and producing heat, cooking the food.
Glass, paper, ceramic, or plastic containers are used in
microwave cooking because the microwaves pass
Metal reflects microwaves
Unsafe to have metal pans/aluminum foil in oven, may damage
HOW DOES THE BIKE AIR
PUMP WORKS ???
What does a Pump Do?
• A pump moves a
– A fluid is either a
gas (like air or
steam) or a liquid
(water, oil, coolant,
How does a Bike Pump Work?
compresses the air and
drives it down into the tire
To insure that the fluid
does not come back out of
the tire, there is a one way
valve that stops the fluid
from returning into the
HOW DO THE SPEAKERS
Speakers vibrate and push on the air
pushing out creates compression
pulling back creates rarefaction
Speaker must execute complex motion according to
Speaker is driven via “solenoid” idea:
electrical signal (AC) is sent into coil that surrounds a
permanent magnet attached to speaker cone
depending on direction of current, the induced magnetic
field either lines up with magnet or is opposite.
results in pushing or pulling (attracting/repelling) magnet
in coil, and thus pushing/pulling on center of cone.
I NSI DE THE SPEAKER
Electromagnet ( coil )
PUSH ME, PULL ME
When the center of the speaker cone is kicked, the whole cone
can’t respond instantaneously
the fastest any mechanical signal can travel through a material is at
the speed of sound in the material
The whole cone must move into place well before the wave period
otherwise, different parts of the cone might be moving in while others
are moving out (thus canceling the sound)
if we require the signal to travel from the center to the edge of the
cone in 1/N of a wave cycle (N is some large-ish number):
available time is t = 1/Nf = /Ncair
ripple in cone travels ccone t, so radius of cone must be < ccone/Ncair
basic point is that speaker size is related to wavelength of sound
low frequency speakers are big, high frequency are small.