Automated systems

Computer Science · Automated and emerging technologies. The idea in plain words, the rules to remember, the mistake to avoid and a worked example, written and checked by Mega Lecture.

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The idea

An automated system does a task with little or no human action. It is built from three parts that work together: sensors, a microprocessor and actuators.

A sensor measures a physical quantity, such as temperature, light or moisture, and sends the reading to the microprocessor. The microprocessor compares the reading with a stored (preset) value and decides what to do. If action is needed, it sends a signal to an actuator, which carries out a physical action such as opening a valve or starting a motor.

This happens again and again in a continuous loop. Exam questions give a scenario and ask for the sequence, or for advantages and disadvantages that fit that scenario.

Rules to remember

Sensor = input device that measures a physical quantity. It does not make decisions and does not control anything.
The signal from a sensor is often analogue, so it is converted to digital (by an ADC) for the microprocessor.
Sequence: sensor sends reading → microprocessor compares it with the preset value → signal sent to actuator if needed → process repeats.
Actuator = device that turns a signal into movement, for example to open a window, turn on a pump or raise a barrier.
Advantages: works continuously without breaks, consistent results, faster response, safer in dangerous places, less waste of materials and energy.
Disadvantages: high set-up cost, needs maintenance, a faulty sensor gives wrong results, can be hacked, cannot deal with unexpected situations, may replace jobs.

Common mistake

Students often write that the sensor decides or the sensor switches the device on. The sensor only sends readings; the microprocessor makes the decision and the actuator acts.

Worked example

An automatic door at a shop opens when a person walks up to it. Describe how the sensor, microprocessor and actuator work together.

An infrared (or pressure) sensor sends readings to the microprocessor all the time.
The microprocessor compares each reading with its stored value to decide whether a person is there.
If a person is detected, the microprocessor sends a signal to the actuator, which drives the motor that opens the door.
The readings continue, and when no person is detected the actuator closes the door.

Answer: Sensor detects → microprocessor compares and decides → actuator opens the door, in a continuous loop.

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