A central heating system in a house is controlled automatically. The diagram shows the feedback loop used by the system. (a) Describe the process by which t...

(a) The automated central heating system maintains a set temperature through a continuous feedback cycle involving three components:

1. A temperature sensor continuously measures the current temperature of the room and sends this reading as a signal to the microprocessor. [1]
2. The sensor sends the temperature reading as a digital signal (after analogue-to-digital conversion if the sensor is analogue) to the microprocessor. [1]
3. The microprocessor compares the current temperature reading with the set point (the desired temperature chosen by the user). [1]
4. If the current temperature is below the set point, the microprocessor sends a control signal to the actuator to switch on the boiler/heater, producing heat to raise the room temperature. [1]
5. If the current temperature is at or above the set point, the microprocessor sends a signal to the actuator to switch off the boiler/heater, stopping unnecessary heating. [1]
6. This process repeats continuously, with the sensor providing updated readings to the microprocessor so the system can react to changing conditions (e.g. a window being opened). [1]

(b) This is described as a feedback loop because the output of the system (the heater turning on or off) directly affects the condition being measured (the room temperature). [1] The sensor then feeds this changed condition back to the microprocessor, which adjusts its output accordingly. This creates a continuous cycle of monitoring and adjustment - the system's own actions change its input, which in turn changes its next action. [1]

(c) Two advantages of an automated system over manual control:

• The system maintains a constant, comfortable temperature without the user needing to intervene - it reacts faster than a person could and works even when no one is home. [1]
• It saves energy by automatically turning off the heating the moment the desired temperature is reached, rather than overshooting because a person forgot to turn it off. [1]

(d) If the temperature sensor failed, the microprocessor would stop receiving accurate temperature readings and could not compare the room temperature with the set point. [1] The feedback loop would be broken: the heater might remain permanently on (causing the room to overheat, wasting energy and potentially creating a fire hazard) or permanently off (leaving the room cold), because the system has no way to know when to switch states. [1]