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Computer Components: Input Devices (Sensors Some data can be obtained…
Computer Components: Input Devices
Manual input devices
All input devices transfer data from the source in the outside world to the computer.
Some input devices require greater human intervention than scanners or cameras to generate the data. These include:
-
Keyboards and keypads
-
Pointing devices
-
Microphones
-
Touch screens
-
Interactive Whiteboards
Pointing Devices
Examples: Mouse and the trackerball
-
Trackerballs have a ball on the top of the device which is moved by the user.
-
The actual device itself remains stationary, thus requiring less desk place.
Touchscreens
Touchscreen technologies are used with tablets, watches and mobile phones.
Interactive whiteboards
Interactive whiteboards are used to show audiences at meetings or classroom students (computer output)
-
They allow the user to use the board as a touchscreen or write over the screen to create annotations.
-
At the end of the meeting, hand annotations can be saved along with the screen image for future reference.
Barcode readers
Two common types barcode systems:
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Universal Product Code version 'A' (UPC-A)
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Used in retail and warehousing
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Code 128
-
Used in transport and shipment tracking
Code 128 can represent letters and numbers
whilst UPC-A can only represent numeric digits.
QR (Quick Response) codes
QR codes are 2D barcodes and can be read by smartphones or tablets.
They can contain:
-
Links to websites or
-
Information
2D scanners
These are used to convert a hard/paper copy document or photograph into a computer-readable format.
Useful for emailing hand-drawn images or text to someone else.
3D face recognition
Security cameras may use face recognition.
-
Specialist software measures and compares the proportions of a person’s face with those stored.
3D scanners
3D scanners are used in both industrial and medical fields.
Many 3D scanners rely on a technology called
Tomography
which basically means to image something in very thin slices (less than 0.1 mm thick).
-
Here a solid cone has been sliced up into several thin slices which when put back together again from the original cone.
Sensors
Some data can be obtained directly through the use of sensors.
Sensors often collect data in an analogue form and require conversion to digital data to be processed.
-
Sensors are used in both
monitoring
and
control
applications.
A sensor is
a hardware device that can take measurement of physical properties, such as temperature or pressure, from real world surroundings. These measurements are usually a representation of the actual property being measured
.
Data taken by sensors is usually in analogue form.
Analogue Measurements
Analogue means that data has no discrete value and the data changes smoothly rather than in exact jumps.
Examples include:
-
A thermometer where temperature is represented by the height of the mercury.
-
A speedometer showing speed represented by a needle on a gauge.
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A seismometer recording the force and duration of ground movements by visualisation the motion of a weight on a string using a pen.
Types of sensor
https://docs.google.com/document/d/1pVdvYhsCb4PnCX_TwTyx_eLPQGXFW4mNLVVPEFBJ9G0/edit
Monitoring and control
Monitoring:
With these application, the computer or microprocessor will make
no changes
to the actual process; it will simply
report
the values
.
Control:
A control system manages, commands, directs or regulates the behaviour of other devices or systems using control loops
.
Detection Systems
The
pressure sensors
monitors an intruder stepping on the floor next to the windows, doors or on the floor next to valuable paintings.
The
acoustic sensors
pick up the sound of breaking glass or footsteps on the floor.
The
infrared sensors
pick up movement in the rooms but also any changes in heat (e.g. heat radiation from an intruder)
Monitoring Systems
This example of monitoring involves an intruder detection and alarm system in a house:
How does it work?
The system is first activated by the user keying in a PIN code or by placing an alarm fob near a receiver.
Sensors constantly monitor the rooms for intruders.
Data is converted into digital form using an ADC and is sent to a microprocessor.
Pollution levels in a river
Monitoring processes:
Sensors constantly send data to computer via an interface box.
Data is converted into digital form at the control room before being analysed by computer using an ADC.
The computer checks oxygen levels against pre-set values.
If oxygen levels
<15%
then the computer warns operators in control room.
Computer checks pH levels against set values and if
pH <6
or
pH >8
,then computer warns operators in control room.
Monitoring continues until systems switched off.
Sensor Feedback
Sensors constantly take readings for monitoring:
If any of the sensor readings exceed the pre-set values, then the microprocessor sends a signal to warn the user (this could be a screen output, a siren or flashing light or all three).
Each sensor will feed into an interface box so that the microprocessor can pinpoint exactly which sensor sent the high value.
Monitoring continues until the user keys in a PIN/passcode to deactivate the system.
