Syllabus & Goals 3 min
Cambridge 3.2 · Input and output devices Paper 1 · Computer Systems
By the end of this lesson you can:
- Identify common input and output devices and their uses.
- Explain what sensors and actuators are.
- Describe how sensors are used in monitoring and control systems.
Recap / Warm-Up 5 min
Embedded systems take inputs and produce outputs. This lesson names the devices that do that — and the sensors that feed real-world data into a computer.
Quick starter
Sort these into input or output: microphone, speaker, keyboard, printer.
Reveal the answer
Input: microphone, keyboard. Output: speaker, printer. Input into the computer; output out to the user.
Key Concept 14 min
1 · Input devices
| Device | Typical use |
|---|---|
| Barcode / QR scanner | Reading product codes at a till; quick links from posters |
| Keyboard / mouse | Entering text and pointing/selecting |
| Touch screen | Phones, tablets, info kiosks |
| Digital camera | Capturing photos and video |
| Microphone | Recording sound; voice input |
| 2D / 3D scanner | Digitising documents (2D) or objects for 3D printing (3D) |
2 · Output devices
| Device | Typical use |
|---|---|
| LED / LCD / OLED screen | Monitors, TVs and phone displays |
| Inkjet printer | Small runs of high-quality colour photos |
| Laser printer | Fast, high-volume office printing |
| 3D printer | Building solid objects layer by layer |
| Speakers | Producing sound (via a DAC) |
| Light projector | Projecting an image onto a large screen |
| Actuator | Producing movement — motors, valves, pumps |
3 · Sensors and actuators
Worked Example 12 min
(a) Monitoring vs control
| System | Monitoring or control? |
|---|---|
| A weather station that records temperature and rainfall | Monitoring (reports only) |
| A greenhouse that turns on heaters when it gets cold | Control (sensors + actuators act) |
| A patient monitor that beeps if a reading is abnormal | Monitoring (it alerts but doesn't act) |
(b) Pick the right device
| Need | Best device |
|---|---|
| Print 500 invoices quickly | Laser printer |
| Print a few glossy photos | Inkjet printer |
| Make a prototype part | 3D printer (with a 3D scanner to capture the shape) |
Try It Yourself 12 min
Goal: Name two sensors and state what each one measures.
Goal: A car park sign shows how many spaces are free. State whether this is a monitoring or a control system, and why.
Goal: Describe how a sensor, a microprocessor and an actuator work together to keep a room at 22 °C.
📝 Exam Practice 10 min
Define the term actuator.
Mark scheme
- An output device that converts an electrical signal into movement (1).
Give a suitable output device for (a) printing 1000 pages a day, and (b) displaying a presentation to a large audience.
Mark scheme
- (a) Laser printer (1).
- (b) Light projector (1).
Describe the difference between a monitoring system and a control system.
Mark scheme
- Both read data from sensors (1).
- A monitoring system only records / reports / alerts (1).
- A control system also acts on the readings, using actuators to change something (1).
Recap & Key Terms 3 min
Input devices bring data in (scanners, keyboard, camera, microphone, sensors); output devices present results (screens, printers, speakers, actuators). Sensors feed a processor, which may drive actuators — that's a control system; a system that only reports is a monitoring system.
- Sensor
- An input device measuring a physical quantity (temperature, light, pressure…).
- Actuator
- An output device that produces movement from an electrical signal.
- Monitoring system
- Reads sensors and reports/alerts, but does not act.
- Control system
- Reads sensors and acts via actuators to change the situation.
Homework 1 min
Task (≤ 15 min): For an automatic greenhouse, list two sensors it would use, the decision the processor makes, and two actuators it would control.
Model answer (example)
- Sensors: temperature sensor, moisture (soil) sensor.
- Decision: if too cold, heat; if soil too dry, water.
- Actuators: a motor/valve for the heater, a pump for the watering system.