A greenhouse uses an embedded system to control the growing conditions for plants.
Describe how the embedded system controls the growing conditions in the greenhouse.
Mark scheme
Award up to two marks for a linked description such as:
- It reads/monitors the temperature/humidity/light level using sensors (1) to switch the heaters/vents/lamps/watering system on or off when the reading is outside the set range (1)
- It compares the readings from the sensors with the set values/thresholds stored in its memory (1) to decide whether the conditions need to be changed (1)
- It monitors the light level using a light sensor (1) and turns the lamps on when the light falls below the level the plants need (1)
- It monitors the soil moisture using a soil moisture sensor (1) and turns the water pump/irrigation on when the soil is too dry (1)
For the second mark, the action/response must be linked to the sensor reading given in the first point.
Allow named sensors (temperature/humidity/light/soil moisture) and named outputs (heater, fan, vent/window, lamp, irrigation/water pump).
Do not accept answers that only name a sensor or only name an output, e.g. 'it has a temperature sensor and a heater', as there is no link between the reading and the control action.
Do not accept answers where a person switches the equipment on or off, as the embedded system controls the conditions automatically.
Example answers and how they were marked
The embedded system reads the temperature using a sensor and switches the heater on when the temperature is below the set value.
Why: Sensor reading point (1) and linked control action (1).
The embedded system compares the readings from the sensors with the set values stored in its memory.
Why: First point only (1) - the comparison with stored values - with no linked action.
The greenhouse has a temperature sensor and a heater.
Why: Only names a sensor and an output, which the mark scheme says is not accepted.