Programmable control: microcontrollers, sensors and actuators

A smart bin that opens when you wave, a plant pot that waters itself: products become 'intelligent' when a microcontroller is programmed to respond to sensors.

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Microcontrollers

A microcontroller is a small computer on a single chip. It has a processor, memory and input and output pins.
It is the process part of a system: it reads inputs, follows a program and switches outputs.
Microcontrollers can be reprogrammed, so one circuit can do many different jobs. They are found in washing machines, toys, microwaves and many school project boards.

Sensors and actuators

Sensors are inputs. Digital sensors give only on or off (1 or 0), such as a switch. Analogue sensors give a range of values, such as a light sensor or temperature sensor.
Actuators are outputs that make something move, such as a motor, a servo (turns to a set angle) or a solenoid.
Other outputs include LEDs, buzzers and screens.

Flowcharts

Programs can be planned with flowcharts:
A loop sends the program back to an earlier step so it repeats.
SymbolMeaning
Rounded rectangleStart or end
RectangleProcess (an action, such as 'turn LED on' or 'wait 1 second')
DiamondDecision (a yes or no question, such as 'Is it dark?')
ParallelogramInput or output
Worked example

A program turns an LED on for 0.5 s and off for 0.5 s, and repeats this 10 times. How long does the program take?

  1. One flash takes 0.5 + 0.5 = 1 s.
  2. It repeats 10 times.
  3. 1 × 10 = 10 s.

Answer: 10 seconds.

Key idea

A microcontroller is a programmable computer on a chip: it reads sensors (inputs) and controls actuators and other outputs. Digital signals are on or off; analogue signals vary. Flowcharts use a diamond for a decision and a rectangle for a process.

Key words
Microcontroller
A small programmable computer on a single chip, used to control products.
Sensor
An input component that responds to a change, such as light, temperature or pressure.

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Quick check

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Extra practice

2 more questions

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  1. Which of these is a microcontroller board used in schools?

    1. A coping saw
    2. A try square
    3. A vacuum former
    4. BBC micro:bit
    Show the answer

    Answer: BBC micro:bit

    The micro:bit is a programmable board.

  2. Which of these is NOT an actuator?

    1. A servo motor
    2. A solenoid
    3. A DC motor
    4. A light sensor
    Show the answer

    Answer: A light sensor

    A light sensor is an input.

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Sources and references

Last updated 2 October 2026. Spotted a mistake? Tell us and we will fix it.

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