Electronic and Microelectronic Control Systems (Option A)

Systems that sense and respond

An electronic control system does a simple thing very reliably: it senses a change, decides what to do, and then makes something happen. Think of a light that comes on by itself at dusk, or a fan that starts when a room gets too warm. Every such system has three parts. The input is a sensor that detects a change, such as light, heat or a push of a switch. The process is where the decision is made, by logic gates, a transistor acting as a switch, or a small programmable chip. The output is the device that acts, such as a light emitting diode, a buzzer or a motor. This module covers each of those three parts, a simple circuit calculation, and why one programmable chip can do the work of many parts.

Electronics words

Learn these five terms before you follow a signal through a system.

Match each part to its job in the system

The three parts of a control system

Every electronic control system splits into the same three parts. Learn what belongs in each.

Which sensor fits?

A security light must switch on only when it gets dark outside. Which input sensor should the system use?

• A light dependent resistor
• A buzzer
• A motor
• A lamp

Why one chip can replace many parts

In older circuits every decision needed its own logic gates and wiring, so a complicated job meant a large, fixed board that could not be changed. A programmable chip changed all of that. It holds a set of instructions that you write, so the same small chip can behave in many different ways, and if the design needs to change you rewrite the instructions instead of rebuilding the circuit. It is smaller, it is cheaper once many are made, and it can be reprogrammed again and again. This is why so many everyday gadgets now hide one tiny programmable part where a crowd of separate components used to sit.

Pick the true electronics facts

Select every statement about electronic control systems that is true.

• A light emitting diode is an output device
• A logic gate makes a decision based on its inputs
• A microcontroller can be programmed to control a system
• A thermistor gives out light
• A buzzer is an input sensor

Order the signal through the system

Put the stages a signal passes through in the correct order.

• A sensor detects a change
• The input signal reaches the process stage
• A logic gate or chip decides what to do
• A signal is sent to the output
• The output device switches on

Complete the electronics facts

A part that detects a change such as light or heat is a _____. A part that makes a decision from the signals fed into it is a _____. A light emitting diode is an _____ device. A single programmable chip that can run a whole system is a _____.

A house that looks after itself

Think of a modern house that seems to look after itself. When dusk falls the porch light comes on by itself, when a room grows too warm a fan starts up, and when someone steps onto the drive a chime sounds indoors. Nobody is flicking any switches. The house is quietly watching for changes, working out what each change means, and then making something happen in response. Every electronic control system runs on that same three-part idea: notice a change, decide, then act. Once you can spot those three parts in any gadget, from a kettle to a games console, the electronics inside stops being a mystery and starts to make plain sense.

Tap the output devices

Tap every part below that is an output device, not an input.

• a light emitting diode
• a buzzer
• a motor
• a light dependent resistor

Work out the voltage

A current of 2 amps flows through a resistance of 3 ohms. Voltage is current times resistance. What is the voltage?

Design the control system

Read each situation and choose the best part for the job.

• You want a lamp to come on automatically when it gets dark. Which input do you choose?
• You need to control a whole system with one small part that you can reprogram later. What do you use?
• A greenhouse fan must turn on when it gets too hot. Which input senses this?

Build an electronics point

Choose the word for each gap to complete one accurate point about a control system.

Explain electronic control systems

A friend wants to build a gadget that senses something and then responds, but does not know where to start. Explain clearly how an electronic control system works.

• Explain the three parts input, process and output
• Give an example of an input sensor and what it detects
• Explain what the process stage does, using logic gates or a microcontroller
• Give an example of an output device
• Explain one advantage of using a microcontroller