Feedback cycle

The diagram below shows a control programprogram: a list of instructions written in a programming language for maintaining the water level in a fish tank.

Feedback cycle for a fish tank

The control program stores the highest and lowest acceptable water levels and what action to take if they're exceeded.

The process is continuous and is called a feedback cycle.

Stages of the feedback cycle

1. water level falls too low
2. sensor detects water level is too low
3. valve opened to let water in
4. sensor detects water level is too high
5. valve opened to let water out