← IGCSE Computer Science Paper 1

Automated systems in agriculture

Sensors, a microprocessor and actuators keep crop conditions right, such as watering or heating a greenhouse, without a farmer checking all the time.

Part of: IGCSE Computer Science 0478 — 6.1 Automated Systems — Module 30

Understanding Automated systems in agriculture in IGCSE Computer Science Paper 1

What it does: The light sensor reading is compared with a stored value. If it is too low, the microprocessor switches the grow lamp (actuator) on. Actuators produce the physical action, such as opening a valve. Sensors only measure and send data. Too hot means the system must cool the greenhouse. A fan or window motor does this, while the heater would make it worse. A humidity sensor measures moisture in the air. A moisture sensor measures the water content of soil. The sensors, microprocessor and actuators work continuously, so the farmer does not need to keep checking. Microprocessors only process digital data, so an analogue-to-digital converter (ADC) changes the sensor readings first.

Common mistakes: The valve would open when the soil is already wet. It should open when moisture is LESS than the limit: IF moisture < limit THEN. When the greenhouse is too hot, the window motor should open the window to let heat out. It should be OpenWindow().

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Learning
Duo
A moisture sensor in a field reads below the stored value. What should the microprocessor make happen?
It signals the actuator to open the irrigation valveIt signals the sensor to open the irrigation valve
Matches
IF moisture < 30 THEN sensor OPEN
↓
A sensor only inputs data, so it cannot be opened. The irrigation valve is the actuator that should open.
Applying
Meanings
Term
agricultural automation
Meaning
Sensors, a microprocessor and actuators keep crop conditions right, such as watering or heating a greenhouse, without a farmer checking all the time.
Practice
WHILE TRUE
Testing
Gaps
IF moisture 30 THEN
Check Answer
Spots
2limit ← 30
3IF moisture > limit THEN

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Quick Questions

1. A moisture sensor in a field reads below the stored value. What should the microprocessor make happen?
A. It signals the sensor to open the irrigation valve
B. It signals the actuator to open the irrigation valve ✓
The microprocessor compares the reading with the stored value, then sends a signal to an actuator. The valve is the actuator, not the sensor.
2. Which part of an automated irrigation system is the actuator?
A. The motor that opens the water valve ✓
B. The moisture sensor in the soil
Actuators produce the physical action, such as opening a valve. Sensors only measure and send data.
3. In a greenhouse, the temperature sensor reads higher than the stored maximum. What happens next?
A. The microprocessor switches on the heater
B. The microprocessor switches on the fan or opens the window motor ✓
Too hot means the system must cool the greenhouse. A fan or window motor does this, while the heater would make it worse.
4. In a greenhouse, the temperature drops below the stored minimum. Which actuator does the microprocessor switch on?
A. The heater ✓
B. The window motor to open the window
Too cold means the system must warm the greenhouse. Opening the window would let more cold air in.
5. Which statement about a greenhouse humidity sensor is correct?
A. It measures the amount of water vapour in the air ✓
B. It measures the amount of water in the soil
A humidity sensor measures moisture in the air. A moisture sensor measures the water content of soil.

Match the Pairs

IF moisture < 30 THEN valve OPEN → When the soil is too dry, the microprocessor makes the irrigation valve open to water the crops.
IF temp > 28 THEN window OPEN → When the greenhouse is too hot, the window motor opens the window to cool the air.
A light sensor lets the system turn on grow lights automatically when it is too dark for the plants → IF light < 40 THEN lamp ON
The microprocessor compares the temperature with a stored value and switches the heater on or off to keep the greenhouse warm enough → IF temp < 15 THEN heater ON ELSE heater OFF
IF moisture < 30 THEN sensor OPEN → A sensor only inputs data, so it cannot be opened. The irrigation valve is the actuator that should open.
IF humidity > 80 THEN heater ON → A heater does not remove damp air. The actuator for high humidity should be a fan or a window motor.

Key Term

agricultural automation
Sensors, a microprocessor and actuators keep crop conditions right, such as watering or heating a greenhouse, without a farmer checking all the time.

Fill in the Blanks

1. IF moisture < 30 THEN OPEN valve ENDIF
Hint: Type the comparison operator that detects soil that is drier than the stored value.
2. IF temperature > 28 THEN OPEN window ENDIF
Hint: Type the command the window motor actuator follows to let hot air out of the greenhouse.
3. IF temperature < 15 THEN TURN_ON heater ENDIF
Hint: Type the command that switches the heater actuator on when the greenhouse is too cold.
4. IF light < 40 THEN TURN_ON growLights ENDIF
Hint: Type the name of the sensor reading that is compared with the stored value to decide on grow lights.
5. reading ← READ(humiditySensor) IF reading > 80 THEN START fan
Hint: Type the assignment symbol that stores the humidity sensor value in a variable.

Spot the Error

Question 1
A moisture ← ReadMoisture()
B limit ← 30
C IF moisture > limit THEN
D OpenValve()
E ENDIF
Line C — The valve would open when the soil is already wet. It should open when moisture is LESS than the limit: IF moisture < limit THEN.
Question 2
A temp ← ReadTemp()
B IF temp > 28 THEN
C fan ← ON
D CloseWindow()
E ENDIF
Line D — When the greenhouse is too hot, the window motor should open the window to let heat out. It should be OpenWindow().
Question 3
A WHILE TRUE
B light ← ReadLight()
C IF light < 40 THEN
D growLight ← OFF
E ENDIF
F ENDWHILE
Line D — When the light level is low, the grow light must be switched ON to help the plants. It should be growLight ← ON.
Question 4
A humidity ← ReadHumidity()
B target ← 60
C IF humidity > target
D SwitchOn(fan)
E ENDIF
Line C — An IF statement needs the keyword THEN after the condition. It should be IF humidity > target THEN.
Question 5
A WHILE FALSE
B moisture ← ReadMoisture()
C IF moisture < 30 THEN
D OpenValve()
E ENDIF
F ENDWHILE
Line A — The system must keep checking the sensor all the time without a farmer. WHILE FALSE means the loop never runs. It should be WHILE TRUE.

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