What is a microcontroller, and how does a capacitor set the timing in a circuit?
Microcontrollers (PICs) and timing: programmable control with a microcontroller, and resistor-capacitor timing where the capacitor charges to create a delay.
A CCEA GCSE Technology and Design answer on microcontrollers (PICs) and timing circuits: how a programmable microcontroller controls inputs and outputs, the advantages of programmable control, and how a resistor-capacitor circuit charges to create a time delay.
Reviewed by: AI editorial process; not yet individually human-reviewed
Have a quick question? Jump to the Q&A page
Jump to a section
What this dot point is asking
CCEA wants you to know what a microcontroller (PIC) is and the advantages of programmable control, and to understand a resistor-capacitor (RC) timing circuit - how a capacitor charges to create a time delay. This is the more advanced control content, central to the electronic and microelectronic option.
The answer
What a microcontroller is
A microcontroller is the "process" block of a system made programmable: instead of fixed wiring, its behaviour is decided by the program stored in it.
Advantages of programmable control
This is why microcontrollers are used in almost all modern products - washing machines, toys, alarms - where flexible, complex control is needed.
Programming with flowcharts
A microcontroller program is often planned as a flowchart (sequence and decision symbols) and then written in a simple language or flowchart-based software. The flowchart decides the order of actions and the decisions the controller makes, linking directly to the digital-control topic.
The resistor-capacitor timing circuit
The length of the delay depends on the resistor and capacitor values:
Worked example: designing a time delay
Examples in context
- Example 1. A washing machine
- A microcontroller runs the whole wash program, reading sensors and switching the motor, valves and heater in sequence - flexible control from one chip.
- Example 2. A timed porch light
- An RC timing circuit keeps the light on for a set time after the button is pressed; a bigger capacitor extends the on-time.
- Example 3. A reprogrammable toy
- The same microcontroller hardware can be given different behaviours by changing its program, showing the flexibility of programmable control.
Being able to explain the microcontroller's advantages and how an RC circuit times a delay lets you answer both the "advantages of a microcontroller" and the timing-circuit questions.
Try this
Q1. What three main parts does a microcontroller contain? [3 marks]
- Cue. A processor, memory, and input/output pins.
Q2. Give one advantage of a microcontroller over fixed logic gates. [1 mark]
- Cue. Its behaviour can be changed by reprogramming without rewiring (or one chip replaces many components).
Q3. In an RC timing circuit, what creates the time delay? [2 marks]
- Cue. The capacitor charges gradually through the resistor, and the next stage switches when its voltage reaches a set level.
Q4. How can the delay in an RC timing circuit be made longer? [1 mark]
- Cue. Increase the capacitance (or the resistance), as both slow the charging.
Q5. What is often used to plan a microcontroller program? [1 mark]
- Cue. A flowchart (sequence and decision symbols).
Exam-style practice questions
Practice questions written in the style of CCEA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
CCEA style4 marksGive two advantages of using a microcontroller instead of fixed logic gates to control a system.Show worked answer →
The behaviour is set by a program, so it can be changed by reprogramming without rewiring the circuit (1), making it flexible (1).
One small chip can replace many logic gates and components (1), so the circuit is smaller, cheaper for complex tasks and easier to build (1). Markers also accept that it can handle complex sequences and timing easily.
CCEA style4 marksIn a resistor-capacitor timing circuit, explain how the time delay is produced and how it could be made longer.Show worked answer →
When the circuit is switched on, the capacitor charges up through the resistor, and its voltage rises gradually rather than instantly (1). When the voltage reaches a set level, the next stage switches, which gives the time delay (1).
The delay can be made longer by increasing the capacitance of the capacitor (1) or by increasing the value of the resistor, because both slow down the rate of charging (1).
Related dot points
- The systems approach: representing electronic and control systems as input, process and output blocks, with feedback, using block (systems) diagrams.
A CCEA GCSE Technology and Design answer on the systems approach: describing an electronic or control system as input, process and output blocks, the idea of feedback, and using block (systems) diagrams to design and analyse a system.
- Electronic components and quantities: conductors and insulators, resistors, capacitors, diodes and LEDs, and using Ohm's law V = I R.
A CCEA GCSE Technology and Design answer on basic electronics: conductors and insulators, resistors, capacitors, diodes and LEDs, current, voltage and resistance, and using Ohm's law V = I R including a current-limiting resistor calculation.
- Input subsystems: switches, the light-dependent resistor, the thermistor, and the voltage divider that turns a sensor's resistance change into a voltage signal.
A CCEA GCSE Technology and Design answer on input subsystems: switches, the light-dependent resistor (LDR) and the thermistor, and how a voltage divider (potential divider) turns a change in a sensor's resistance into a changing voltage signal for the process stage.
- Output devices: lamps, buzzers, motors and relays, and the transistor used as an electronic switch to control a larger current from a small input.
A CCEA GCSE Technology and Design answer on output devices: lamps, buzzers, motors and relays, and how a transistor acts as an electronic switch, turning a small input current into the switching of a much larger output current, with a protection diode for inductive loads.
- Logic gates and digital control: the AND, OR, NOT, NAND and NOR gates with truth tables, combining gates, and flowcharts for program control.
A CCEA GCSE Technology and Design answer on digital control: the AND, OR, NOT, NAND and NOR logic gates with their truth tables, combining gates to make a decision, and using flowcharts (sequence and decision) for program control.
Sources & how we know this
- CCEA GCSE Technology and Design specification — CCEA (2017)
- CCEA Factfile 2.18: Microcontrollers (PICs) — CCEA (2019)