Systems Approach To Designing

A hotel corridor light that comes on when you walk into it is doing three things, in order. Something notices you. Something decides whether to switch on, which depends on whether it is dark and on how long ago it last saw anybody. And something puts the light on and then, after a while, off again. Those three things are the whole of this topic, and they have names: input, process and output.

A systems approach lets you design a product without knowing how every part works inside. You specify what goes into a block and what must come out, and you can then buy that block, or design it later, or swap it for a better one without redesigning anything else. In this lesson you will learn the use of light sensors, temperature sensors, pressure sensors and switches as inputs; the use of programmable devices, meaning microcontrollers, as counters, timers and for decision making; and the use of buzzers, speakers and lamps as outputs. You will size a resistor for a lamp using Ohm's law, work out a sensor threshold, and decide when a system is the right answer and when it is an expensive way to avoid a spring. This is core technical principles content, examined in Section A of Paper 1, and it supplied question 2 of the specimen paper.