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).
- Input devices, usually sensors, send data readings to the microprocessor (computer) at set intervals
- To be understood, this data may have to be converted using an ADC (analogue to digital converter)
- The microprocessor compares the data readings against pre-set values that it has stored (using a control program)
- 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?)
- 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)
- This may involve an actuator (e.g. a motor to open the gates or shop doors)
- This process repeats in a continuous loop
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