Infra-red sensor

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Quick Questions

Shade in the A or B circle for each question.

1. What does an infra-red sensor detect?

A The amount of acidity in a liquid

B Infra-red radiation, such as heat given off by people and objects

2. Which data does an infra-red sensor in a burglar alarm capture?

A Heat or movement of an intruder

B The humidity of the room

3. How can an automatic door use an infra-red sensor?

A It detects a person's heat or a broken infra-red beam and opens the door

B It measures the air pressure and slides the door open

4. A beam of infra-red light is aimed across a doorway. What does the sensor detect when someone walks through?

A The beam gets louder

B The beam is broken

5. Which of these uses an infra-red sensor?

A A TV remote control receiver

B A pH probe in a swimming pool

Match the Pairs

Draw a line connecting each item on the left to its match on the right.

Left column		Right column
1infra-red sensor		Aif infraRedSensor = HIGH then open_door()
2if infraRedSensor = HIGH then sound_alarm()		BA burglar alarm that sounds when the sensor detects heat or movement from an intruder
3An automatic door uses an infra-red sensor to detect a person's body heat or a broken beam, then opens		CThe alarm should sound when the sensor detects heat or movement (HIGH), not when nothing is detected (LOW).
4The data an infra-red sensor captures is heat or movement		DAn infra-red sensor detects infra-red radiation (heat), not visible light. It works in the dark because it senses heat, as in night vision.
5An infra-red sensor detects visible light so it works in the dark		Edata ← infraRedSensor.read()
6if infraRedSensor = LOW then sound_alarm()		FA sensor that detects infra-red radiation, such as the heat given off by people and objects

Definitions

infra-red sensor

Fill in the Blanks

Complete each line of code by filling in the missing parts.

__ beamBroken = TRUE THEN OUTPUT "Alarm" ENDIF

heat ← _____ FROM infraredSensor OUTPUT heat

IF heat _ 30 THEN OUTPUT "Person detected" ENDIF

IF beamBroken = ____ THEN OUTPUT "Open door" ENDIF

IF motion = TRUE THEN ______ "Alarm on" ENDIF

Spot the Error

Shade in the letter of the line that contains an error.

Question 1

A WHILE alarm_set = TRUE

B data ← read_ir_sensor()

C IF data = heat_detected THEN

D open_door()

E ENDIF

F ENDWHILE

Question 2

A data ← read_ir_sensor()

B IF data = beam_broken THEN

C close_door()

D ENDIF

Question 3

A IF light_level < 10 THEN

B turn_on_uv_camera()

C display_heat_image()

D ENDIF

Question 4

A WHILE camera_on = TRUE

B heat ← read_sound_sensor()

C display_image(heat)

D ENDWHILE

Question 5

A intruders ← 0

B IF ir_beam_broken = FALSE THEN

C intruders ← intruders + 1

D ENDIF

Answer Key

Infra-red sensor

Section A: Quick Questions

B — Infra-red radiation, such as heat given off by people and objects

A — Heat or movement of an intruder

A — It detects a person's heat or a broken infra-red beam and opens the door

B — The beam is broken

A — A TV remote control receiver

Section B: Match the Pairs

infra-red sensor → A sensor that detects infra-red radiation, such as the heat given off by people and objects

if infraRedSensor = HIGH then sound_alarm() → A burglar alarm that sounds when the sensor detects heat or movement from an intruder

An automatic door uses an infra-red sensor to detect a person's body heat or a broken beam, then opens → if infraRedSensor = HIGH then open_door()

The data an infra-red sensor captures is heat or movement → data ← infraRedSensor.read()

An infra-red sensor detects visible light so it works in the dark → An infra-red sensor detects infra-red radiation (heat), not visible light. It works in the dark because it senses heat, as in night vision.

if infraRedSensor = LOW then sound_alarm() → The alarm should sound when the sensor detects heat or movement (HIGH), not when nothing is detected (LOW).

Section C: Definitions

infra-red sensor — A sensor that detects infra-red radiation, such as heat given off by people and objects, or a broken infra-red beam. Used in burglar alarms and automatic doors.

Section D: Fill in the Blanks

IF beamBroken = TRUE THEN
    OUTPUT "Alarm"
ENDIF

heat ← INPUT FROM infraredSensor
OUTPUT heat

IF heat > 30 THEN
    OUTPUT "Person detected"
ENDIF

IF beamBroken = TRUE THEN
    OUTPUT "Open door"
ENDIF

IF motion = TRUE THEN
    OUTPUT "Alarm on"
ENDIF

Section E: Spot the Error

D — A burglar alarm that detects body heat with an infra-red sensor should sound the alarm, not open a door. Line 4 should be sound_alarm().

C — In an automatic door, a person breaking the infra-red beam means someone wants to go through, so the door should open. Line 3 should be open_door().

B — Night vision cameras use infra-red radiation to see heat in the dark, not ultraviolet. Line 2 should be turn_on_ir_camera().

B — Night vision needs the heat data captured by an infra-red sensor, not sound data from an acoustic sensor. Line 2 should use read_ir_sensor().

B — An intruder is detected when the infra-red beam IS broken. The condition should test for TRUE, not FALSE.