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1. Learning Objectives:
• be able to define the term sensor
• understand how a range of sensors input data into a
computer system
• describe how a range of sensors are used in many areas
of our lives

2.  Sensor
a device that detects and responds to some type of input from the physical
environment.
input could be light, heat, motion, moisture, pressure, or any one of a
great number of other environmental phenomena
Ear: Sense sound in the environment, Nose: sense Smell, Tounge: sense taste of
food,
Skin: sense Hotness and coldness of body, Eye: sense different color seen in
environmnet.

3. Light sensors
Detect How bright and dark it is (ambient) Light level. Like: our Eyes.
Uses:
street lights,.
A security system
Household, garage door that opens and closes at the push of the button.
In Mobiles phones, for brightnesss of our screen.
Input device( barcode and QR code scanners.)
Robot ability to see by light sensor

4. Temperature sensor ()
• Device measure the heat generated by an object or system.
2 Types:
1. Contact sensor (Physical contact with object (Solid, Liquid, gas) ) and
2. Non contact (measure energy transmitted or radiated from an object.).
Household items Like Refrigerator and oven. Temperature sensor.
(i) Thermostat:
• Heating System in Household uses Temperature sensor called Thermostat.
(device that keeps temperature at a consistent level.)
Thermostat: 2 piece of metal that will close together or open up depends on the
current temperature.
pieces of metal close together a circuit is created and current flow to heat up
and cool down the atmosphere.

5. (ii) Infrared sensor measure temperature .
• Detect infrared radiation (cant be seen by human eye) that emits from a person or object.
• Uses: Control TV from remote control.
 Special kind of camera.
 helicopter. Detect person criminal by heat .
 formula 1 Racing to show hot tyres on car.
 astronomy to view objects in the universe Like star, radiate infrared waves.
 Aerospace engineers: to monitor the heat of aeroplane in the flight to see risk of damage.

6. Motion Sensors
Detect movement. Sensor detect motion lights on .
Save money and save energy light from wasting.
Use:
• Automatic doors.
• Gaming. Introduced Nintendo will 2006
Benefit: disable people.
Sony (device Move) and Microsoft (device KInect) have their own version.
Control motion use: Accelerometer.(Motion sensor).
Detect:any rotation , tilting and direction .
Used in Mobile phones.

8. IR Infrared Obstacle Avoidance Sensor Module
About: Rain Sensor senses the droplets of water on its detector plate.
Motion / Infra-red (sensor)
e.g. to detect any persons in an unauthorised area of the factory
2. Ultrasonic Sensor
About: An Ultrasonic Sensor sends and receives the Sound Waves.

9. Magnetic Field Sensors:
• Detect: Change in magnetic field.
• Measure strength and direction of magnetic field..
• Earth itself has magnetic field .
Magnetometers :Sensor
• Used in mobile phone
• They allow application to act as a compass.
• Wakeup: turning the screen on. (Mangnet is placed inside the cover of
mobile phone case.)
 Sensor detect the magnet close by mobile screen turn off.

10. Gas Sensors:
Detect the pressure of gas (too high or too low).
• At home, or large area it detect the pressure of carbon monoxide
• At nuclear energy plant to detect gases cause fire or any harm
• At waste water treatment plant.

12. Pressure Sensors:
Measure pressure of liquid and gas.
to measure the pressure of chemicals flowing through pipes to check that level are
not too high / low
A pressure sensor usually acts as a transducer:
Transducer:
device that converts energy from one form to another. Usually a
transducer converts a signal in one form of energy to a signal in another)

13. Moisture and humidity Sensors:
Measure amount of moisture in certain material.
Detecting the level in soil.
Former use automated system: for watering the crop. When soil moisture level get too low
or too high..

14. Humidity Sensors:
Measure amount of moisture in the air along with its temperature.

15. Humidity Sensors:(Hygrometer)
Amount of water vapour present in the air and temperature of the air.
• Use:
• At House,
• At museums, and art galleries.

16. pH Sensor.
• Detect how acidic or basic (alkaline) it is.
• values of the hydrogen ion concentration, ranges between about numbers between 0
and 14.
7 value indicate the pH neutral.
Less than 7 indicate material is Acidic
Greater than 7 called Basic..
Pure water pH is 7.
pH of fish aquarium.

17. Q:#01 A cold store is kept at a constant low temperature
using a sensor, a microprocessor and a cooling unit.
Explain how the sensor and microprocessor will maintain
a constant low temperature?

18. Answer:
 temperature sensor
 analogue data / temperature is converted to digital data (with an ADC)
 sensor sends signal to the microprocessor
 microprocessor compares input values with stored values/pre-set values
 if the temperature value input is too high/low
 a signal is sent from the microprocessor to turn on / off / up / down the cooling
unit «
 if temperature matches the stored values
 no action is taken
 an actuator is used to turn the cooling unit on / off / up / down
 the process is a continuous loop

19. Q:#01 Describe how the sensors and a
microprocessor are used to monitor a process?

20. Answer:
o Sensors send signals to microprocessor
o Analogue signals are converted to digital (using ADC)
o Microprocessor compares value to stored value
o If out of range / matches stored values
o signal sent to alert workers (e.g. sound alarm)
o microprocessor send signal to cause an action to occur e.g. cool a process
down, heat a process up, add a chemical
o no action taken
o Output/record readings
o Monitoring is continuous