Automated Systems
Automated and Emerging Technologies
Every automated system, no matter how simple or complex, is built from the same three kinds of part:
| Component | What it does | Direction |
|---|---|---|
| Sensors | Measure a physical property of the environment (temperature, light, movement, pressure, etc.) and convert it into a digital signal | Input to the system |
| Microprocessor | Receives the sensor readings, compares them against pre-programmed rules or thresholds, and decides what (if anything) to do | Processing |
| Actuators | Receive instructions from the microprocessor and turn them into a physical action (motor turning, valve opening, alarm sounding, heater switching on) | Output from the system |
The pipeline
The three components form a clear input-process-output pipeline:
→ →
- The sensor measures the relevant physical quantity (e.g. temperature) and sends a digital reading to the microprocessor.
- The microprocessor compares the reading against the rules in its program (e.g. "if temperature < 20 °C, switch on heater") and decides what to do.
- If action is needed, the microprocessor sends a control signal to an actuator, which performs the physical change (e.g. turns on the heater motor or opens a valve).
Many sensor types appeared in topic 8 (Input and Output Devices); each one of those sensors can be the input side of an automated system. Common actuators include motors, servos, valves, relays, heaters, pumps, alarms and buzzers.
Common exam question
Explaining the sensor, microprocessor and actuator loop
Question: Explain how the sensor, microprocessor and actuator are used to act only when a condition is met, such as closing a door once the doorway is clear (5–6 marks).
Asked in 2 of the 17 papers, one mark per step, so write the cycle in order. Name a suitable sensor (proximity, infrared or pressure for a doorway), which keeps sending digitised readings to the microprocessor. The microprocessor compares each reading with a stored value. If the reading matches or is in range, the microprocessor sends a signal to the actuator, which closes the door or applies the brakes. If it does not match, the actuator is not activated and no action is taken. The process repeats until the action can happen or the system is turned off.
Keep the roles apart (the sensor measures, the microprocessor compares and decides, the actuator acts), one step per sentence: each is a separate point on the list.