Electronic Systems: Process (Microcontrollers & Timers)

This lesson covers the process stage of electronic systems — the components that receive input signals, make decisions and control outputs. This is part of AQA GCSE Design and Technology (8552), Section 3.1.4.

---

Recap: The Systems Approach

Stage	Function	Examples
Input	Detects environmental changes	LDR, thermistor, switch, microphone
Process	Makes decisions based on input	Microcontrollers, timers, comparators
Output	Produces a response	LED, motor, buzzer, speaker

The process stage is the "brain" of the system — it determines what happens in response to the input signal.

---

Microcontrollers

A microcontroller is a small, programmable computer on a single integrated circuit (IC). It contains a processor, memory and input/output pins, and can be programmed to perform a wide range of tasks.

Popular Microcontrollers for D&T

Microcontroller	Description	Programming Language
Arduino Uno	Widely used in education; many shields and sensors available	C/C++ (Arduino IDE)
BBC micro:bit	Designed for education; built-in sensors, LEDs, Bluetooth	MakeCode (block-based), Python
Raspberry Pi Pico	Affordable, powerful microcontroller board	MicroPython, C/C++
PIC microcontroller	Industry-standard; used in commercial products	C, Assembly
Arduino LilyPad	Designed for wearable e-textiles; can be sewn onto fabric	C/C++ (Arduino IDE)

How a Microcontroller Works

1. Input signals (from sensors, switches) are read through input pins.
2. The program (stored in memory) processes the input data using logic and calculations.
3. Output signals are sent through output pins to control LEDs, motors, buzzers, etc.

Example: Automatic Night Light

INPUT:  LDR connected to analog input pin
PROCESS: Microcontroller reads LDR value
         IF light level < threshold THEN
           Turn LED ON
         ELSE
           Turn LED OFF
         END IF
LOOP

Advantages of Microcontrollers

Advantage	Explanation
Programmable	The same hardware can perform completely different tasks by changing the software
Compact	A single chip replaces dozens of discrete components
Cheap	An Arduino Nano costs ~£3; a PIC chip costs ~£1
Accurate timing	Can generate precise delays and pulse-width modulation (PWM) signals
Multiple I/O	Can handle many inputs and outputs simultaneously
Reprogrammable	Code can be updated and improved without changing hardware

Disadvantages of Microcontrollers

Disadvantage	Explanation
Programming skill required	Users must learn to write or modify code
Processing limitations	Simple microcontrollers cannot run complex software (e.g. video processing)
Power consumption	Continuously running a microcontroller drains battery power
Debugging difficulty	Errors in code can be hard to find and fix

AQA Exam Tip: In D&T exams, microcontroller questions often ask you to describe how a microcontroller could be used to control a simple product (e.g. a greenhouse heater, a security alarm). Structure your answer as: input → process (what the program decides) → output. Use the terms "input pin", "output pin" and "program" in your answer.

---

Programmable Components

Microcontrollers can control many types of output based on programmed conditions: