Computer control is the use of a computer to monitor and control an external process'

1
Computer control is the use of a computer to
monitor and control an external process. Input
sensors connected to the computer are used to
monitor conditions in the process being
controlled. A control program tells the computer
what to do. Depending upon the value of an input
signal from a sensor and the instructions given
in its control program, the computer makes a
decision about whether an output signal is needed
to switch on or off some part of the processs
hardware.
2
Sensors can send two types of signal to a
computer digital and analogue. Digital signals
can only have two values on (or true) and off
(or false) Analogue signals can have any
value. To be able to process analogue signals
sent to it by a sensor the computer needs an
analogue-to-digital converter (ADC). This device
converts analogue signals, which computers cant
process directly, into equivalent digital signals
which they can process.
3
There are many different types of analogue sensor
which measure physical quantities outside a
computer like temperature pressure light water
and moisture levels relative humidity movement
and wind speed.
4
Feedback control systems use the values of their
output signals to affect the value of their input
signals This is useful when a certain set of
conditions needs to be constantly
maintained Output signals make changes to the
conditions outside which will affect its input
signals
5
Many control systems need to control devices that
can move such as a motor in a greenhouse to open
or close a window. A device called an actuator
is used to generate signals that can make devices
move. Signals are sent from computers to
actuators to control the movement of things like
hydraulic, pneumatic or motorised systems.
6
LOGO is a computer programming language that is
often used in education to teach students about
computer control. LOGO instructions are used to
control the movement of a small shape called a
turtle around the screen. LOGO instructions can
just be typed in one line at a time by the
user. LOGO instructions can also be written as
complete programs using procedures.
7
To draw a square with sides 40 steps long the
following instructions would be needed FORWARD
40 RIGHT 90 FORWARD 40 RIGHT 90 FORWARD
40 RIGHT 90 FORWARD 40 A quicker way to do
this would be to use the REPEAT command, so the
user could type REPEAT 4FORWARD 40 RIGHT 90
8
Microprocessors are used to control automatic
machines. Automatic machines dont need to be
supervised because they are operated by a
microprocessor following a control
program. Microprocessors can be found around the
home inside everyday electrical devices like
video recorders, camcorders, hi-fi systems,
microwave ovens, dishwashers and burglar alarms.