Cambridge IGCSE Computer Science · Syllabus 0478 · Hardware
Actuator
What is Actuator?
An output device that converts an electrical control signal from a computer or microprocessor into a physical action such as movement, opening or closing a valve, or switching something on or off; it is an output device, never a sensor.
This definition is part of the Hardware chapter in Cambridge IGCSE Computer Science.
Actuator in context
Topic 3 is one machine seen from four distances. Up close, the CPU repeats a single loop — fetch an instruction, decode it, execute it — using named registers and three buses. Step back and the CPU is only useful because input devices and sensors turn physical things into data and output devices and actuators turn data back into physical things. Step back again and nothing survives a power cut unless storage holds it: RAM while the machine runs, secondary or cloud storage afterwards. Step back once more and the machine needs network hardware — a NIC with a MAC address, an IP address and a router — before it can be found and reached by anything else.
Common mistakes with Actuator
- 16. “A sensor makes the final control decision.” Why wrong A sensor has no stored target value and nothing to compare against. It cannot know whether a reading is acceptable. Correct model A sensor measures a physical property and produces data. A microprocessor compares that data with a stored value and decides. If a condition is met, a signal is sent to an actuator or another output device. Exam-safe “The sensor sends readings to the microprocessor, which compares them with a stored value and, if necessary, sends a signal to an actuator.” Check: fill the gaps — sensor → ______ → ______.sensor → microprocessor (compares with a stored value) → actuator (or another output device).
- 17. “An actuator is an input device.” Why wrong It has the direction backwards. An actuator receives a signal; it does not produce data for the computer. Correct model An actuator is an output device that converts a control signal from the computer into a physical action — movement, opening or closing, switching on or off. Exam-safe “An actuator is an output device that converts a signal from the microprocessor into a physical action.” Check: in a greenhouse system, which is the sensor and which is the actuator — the device that measures the temperature, or the motor that opens the vent?The device that measures the temperature is the sensor (input); the motor that opens the vent is the actuator (output).