Topics / Hardware and Software / Control Systems

Control Systems

A control system is a set of devices that work together to regulate an environment or achieve some set objectives.  This is achieved through a control loop.

Examples of control systems:

  • Maintaining healthy conditions in a fish tank
  • Automatic shop doors
  • Automatic street or security lighting
  • Burglar alarms
  • Automated greenhouses
  • Heating and cooling systems

How does a control system work?

To understand how a control system works, it helps to remember how a computer system is structured (see diagram below).

Computer System Diagram

  1. Input devices, usually sensors, send data readings to the microprocessor (computer) at set intervals
  2. To be understood, this data may have to be converted using an ADC (analogue to digital converter)
  3. The microprocessor compares the data readings against pre-set values that it has stored (using a control program)
  4. The microprocessor then makes a decision as to whether any action is needed (e.g. is more heat needed to maintain the pre-set value?)
  5. If needed, the microprocessor will send a signal to instruct an output device to do something (e.g. turn on heater, turn off oxygen pump etc)
  6. This may involve an actuator (e.g. a motor to open the gates or shop doors)
  7. This process repeats in a continuous loop

Important:

At no point does an input device directly communicate with an output device, or make any judgement calls.  Because of this, a statement such as the following is completely wrong:

“When it gets dark, the light sensor turns on the light bulb”

The computer system diagram above confirms this cannot happen.

Benefits of control systems

  • Computers are quick to respond to change and can process data very quickly
  • Can run all day every day, without wages or needing a break
  • Can operate in places dangerous to humans
  • Consistent and error free
Topics / Hardware and Software / Control Systems