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.



  • 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.



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


  • 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.


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


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


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