← IGCSE Computer Science Paper 1

Actuator

An output device that turns a control signal from a processor into physical action, such as a motor turning, a valve opening or a heater switching on, in control systems and robots.

Part of: IGCSE Computer Science 0478 — 3.2 Input and Output Devices — Module 30, IGCSE Computer Science 0478 — 6.1 Automated Systems — Module 6, IGCSE Computer Science 0478 — 6.2 Robotics — Module 6, QCE Digital Solutions Unit 3 — Interactions Between Users, Data and Digital Systems — Module 80

Understanding Actuator in IGCSE Computer Science Paper 1

What it does: The valve is the actuator. The processor checks the sensor data and sends a signal that makes the valve physically open. An actuator is an output device. Sensors are the input devices that measure physical quantities. The motor receives the control signal and turns it into movement, so it is an actuator. A relay is a switch used as an actuator. Measuring temperature is the job of a temperature sensor.

Common mistakes: The control signal must go to the actuator. The heater is the actuator. A temperature sensor is an input device and cannot be switched on. It should be SEND ON TO heater. An actuator receives signals from the processor, so the command is sent TO the motor. It should be SEND STOP TO motor.

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This module's key terms are also in a printable crossword (Modules 273–282) and word search (Modules 262–282).

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Learning

Duo

Which statement describes an actuator?

An output device that turns a control signal into physical actionAn input device that measures a physical quantity

Matches

A temperature sensor is an actuator because it makes the heater switch on

↓

A sensor is an input device that captures data. The actuator is the heater, which carries out the action.

Applying

Meanings

Term

actuator

Meaning

An output device that turns a control signal from a processor into physical action, such as a motor turning, a valve opening or a heater switching on, in control systems and robots.

Practice

WHILE TRUE

Testing

Gaps

IF temperature 20 THEN

Check Answer

Spots

2IF temp < 18 THEN

3 SEND ON TO TempSensor

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Quick Questions

1. Which statement describes an actuator?

A. An input device that measures a physical quantity

B. An output device that turns a control signal into physical action ✓

An actuator is an output device. Sensors are the input devices that measure physical quantities.

2. A microprocessor sends a signal to a motor to make a robot arm move. What is the motor acting as?

A. A sensor

B. An actuator ✓

The motor receives the control signal and turns it into movement, so it is an actuator.

3. Which of these is an example of an actuator?

A. A valve that opens to let water flow ✓

B. A pH probe in a fish tank

A valve produces physical action (opening). A pH probe is a sensor that captures data.

4. What does an actuator receive from the processor?

A. A control signal ✓

B. Raw measurements of the environment

The processor decides what to do and sends a control signal. Sensors are what send measurements to the processor.

5. The processor works in digital. An actuator often needs an analogue signal. What must happen?

A. The digital signal is converted (DAC) so the actuator can use it ✓

B. The actuator converts the sensor data back into readings

A digital-to-analogue converter changes the processor's digital output into a signal the actuator can use.

Match the Pairs

actuator → An output device that turns a control signal from a processor into physical movement or action

motor.turn(ON) → The processor sends a signal that makes a motor actuator start turning

A processor decides a valve must open, so it sends a signal to the valve actuator → IF level > 90 THEN valve.open()

The processor's digital signal is converted so the actuator can use it, such as switching a heater on → IF temp < 18 THEN heater.on()

A temperature sensor is an actuator because it makes the heater switch on → A sensor is an input device that captures data. The actuator is the heater, which carries out the action.

An actuator sends data to the processor so it can decide what to do next → The direction is wrong. An actuator receives a control signal from the processor, it does not send data to it.

Key Term

actuator

An output device that turns a control signal from a processor into physical action, such as a motor turning, a valve opening or a heater switching on, in control systems and robots.

Fill in the Blanks

1. IF temperature < 20 THEN heater ← ON ENDIF

Hint: Type the comparison operator that means 'lower than', so the heater actuator switches on when the room is cold.

2. IF level < 30 THEN valve ← OPEN ENDIF

Hint: Type the name of the actuator that opens to let liquid flow into the tank.

3. value ← 180 signal ← DAC(value) motor ← signal

Hint: Type the abbreviation for the converter that changes the processor's digital signal into an analogue signal for the motor.

4. WHILE distance > 10 motor ← FORWARD ENDWHILE

Hint: Type the keyword that starts a loop which keeps the robot's motor running while a condition is true.

5. IF temp > 30 THEN relay ← ON ENDIF

Hint: Type the name of the actuator that is a switch worked by a small control signal to turn on a bigger circuit, such as a fan.

Spot the Error

Question 1

A temp ← READ(TempSensor)

B IF temp < 18 THEN

C SEND ON TO TempSensor

D ENDIF

Line C — The control signal must go to the actuator. The heater is the actuator. A temperature sensor is an input device and cannot be switched on. It should be SEND ON TO heater.

Question 2

A WHILE running = TRUE

B dist ← READ(ProxSensor)

C IF dist < 10 THEN

D SEND STOP FROM motor

E ENDIF

F ENDWHILE

Line D — An actuator receives signals from the processor, so the command is sent TO the motor. It should be SEND STOP TO motor.

Question 3

A level ← READ(LevelSensor)

B WHILE level < 90

C SEND OPEN TO valve

D level ← level + 1

E ENDWHILE

Line D — The level must be read from the sensor each time round the loop. The valve actuator opens or closes based on real data. It should be level ← READ(LevelSensor).

Question 4

A speed ← 128

B signal ← DAC(speed)

C SEND signal TO keyboard

D OUTPUT "Motor on"

Line C — The converted signal must be sent to an actuator, such as the motor. A keyboard is an input device. It should be SEND signal TO motor.

Question 5

A SEND STOP TO motor

B WAIT 10

C SEND STOP TO motor

Line A — The motor must be told to START before it turns. Sending STOP first means the actuator never moves. It should be SEND START TO motor.

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