Computer Control Software

This is the use of a computer to monitor and control an external process. Input sensors are used by the computer to monitor the various parts of a process that it is controlling. Before any process can be controlled by a computer a control program must be written by a human to tell the computer what to do.

Analogue and digital signals

• A sensor 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 process analogue signals the computer needs an analogue-to- digital converter.

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Feedback

• 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.

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Sensors

Many different types which can each measure some physical quantity outside the computer such as:

• Temperature;
• Pressure;
• Light;
• Water and moisture levels;
• Relative humidity;
• Movement and wind speed.

Sensors detect analogue data which is converted into digital data before it is sent to the computer

Actuators

• 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.

Microprocessors

These are used to control automatic machines by following pre-programmed sets of instructions called control programs.

Found around the home in for example:

• Video recorders;
• Camcorders;
• Hi-fi systems;
• Microwave ovens;
• Dishwashers;
• Burglar alarms

Robots

Used in hundreds of applications e.g.

• Assembling and spray-painting cars
• Maintaining overhead power cables
• Testing blood samples

They all have the same basic hardware components:

• sensors which are used to monitor changes in physical conditions such as speed and position;
• a microprocessor to process the information received from sensors;
• actuators to produce movement or turn external devices like switches on or off

Advantages of robots

• They can work in environments that are hazardous to humans, such as in outer space, underwater or in radioactive environments
• They can perform repetitive and boring tasks without needing to stop for a break
• The quality of their work is always the same because they never get bored or have an off-day
• They can work to a greater level of accuracy than humans
• They can work 24 hours a day, seven days a week, resulting in increased productivity

The main disadvantage of robots is that they are expensive to buy and install