Electronic Systems: Sensing, Processing and Output

The systems approach

Electronics becomes much easier once you see that almost every electronic product is built from three subsystems joined in a line: input, process and output. The input subsystem senses a change in the surroundings, using a sensor such as a light-dependent resistor for light or a thermistor for temperature. The process subsystem takes that signal and works out the response, using building blocks such as logic gates, a latch, a time delay or a comparator. The output subsystem then produces a result you can see, hear or feel, using a device such as a lamp, an LED, a buzzer, a loudspeaker or a motor. Because output devices often need more current than the process can supply, a transducer driver sits between them. This module covers the systems approach, the sensors and output devices, and how a signal flows from sensing to result.

Electronics words

Learn what each of these means before you use it.

Input against output

The two ends of a system do opposite jobs.

How to read any electronic product

Whenever you meet an electronic product, split it into three parts and it becomes easy to explain. Ask three questions: what does it read from the world, what does it work out, and what does it make happen. The reading is the input, the working-out is the process, and the making-happen is the output. An automatic light shows all three at once: it reads the level of light, works out that it has grown dark enough, and makes the lamp come on. If you can split any system into input, process and output in this way, you can describe how almost any electronic product does its job.

Match the component to its subsystem

Which subsystem?

A microphone in a sound-activated toy turns a sound into an electrical signal. Which subsystem does the microphone belong to?

• the input subsystem, because it senses a change and creates a signal
• the process subsystem, because it decides what to do
• the output subsystem, because it produces a result
• none, because a microphone is not electronic

Output devices

Select the TWO components that are output devices.

• An LED, which gives out light
• A buzzer, which gives out sound
• An LDR, which senses light
• A comparator, which compares voltages

Counting the subsystems

An electronic system is built from 3 subsystems: input, process and output. A lesson has covered the input and the output. Subtract to find how many subsystems are left.

Order the signal flow

Put these stages of how a signal flows through an electronic system in order.

• A sensor detects a change in the surroundings
• The signal passes to the process subsystem
• The process decides on the response
• The output device produces a result

Complete the electronics facts

An electronic system is built from three subsystems: input, _____ and output. The input subsystem uses a _____ to sense a change such as light or heat. The subsystem that produces a result you can see or hear is the _____. A small circuit that lets a weak signal switch a larger device is a transducer _____.

Match the subsystem to its job

Spot the true electronics facts

Tap the TWO statements that are true.

• An LDR is an input device that senses light
• An electronic system has input, process and output subsystems
• A motor is an input device
• The process subsystem produces the final visible result

Design the system

Read each case and choose the best response, with a reason.

• A security light comes on when the light level drops at dusk. Which subsystem senses the low light?
• A weak signal from the process is not strong enough to run a motor directly. What is needed?
• You must describe how an automatic system works. What is the clearest structure to use?

Explain electronic systems

A friend is starting GCSE Electronics and asks how an electronic system is organised. Explain electronic systems and their subsystems.

• Explain the three subsystems of an electronic system
• Explain what the input subsystem does, with an example sensor
• Explain what the output subsystem does, with an example device
• Explain what a transducer driver is for
• Finish by explaining how input, process and output work together in one example