AQA GCSE 7 Electronic systems processing Design and Technology 8552 Unit 2 Energy, materials, systems and devices 7

Objectives Understand the difference between analogue and digital signals Understand how microcontrollers are programmed as counters, timers and for decision making to provide functionality to products and processes Understand the use of buzzers, speakers and lamps to provide functionality to products and processes

Do products make decisions? How does an electronic dice know which number to display? What is a process? Timing Counting Amplifying Comparing Name any other electronic processes you have come across

Digital vs analogue There are two types of signal in electronic systems: Analogue signals have an infinite range of values between the minimum and maximum points Digital signals are either on or off, and are usually represented by a 0 for off and a 1 for on Which type of signal is a switch likely to produce?

Integrated Circuit (IC) Also known as microchips, ICs are capable of performing specific tasks There are many different types of IC A programmable IC is called a microcontroller ICs come in all different shapes and sizes Most come in a dual in line (DIL) package

Microcontroller IC A microcontroller IC is known as a peripheral interface controller (PIC) These programmable ICs are very adaptable They can be programmed to perform multiple processes This reduces the amount of components needed to perform a task (component redundancy) What are the benefits of having a smaller circuit board?

Programming a PIC A PIC’s functions are controlled by a program or code that is received via a download cable Specialist software enables the program to be drawn graphically as a flowchart It can also be written in a coding language, such as BASIC Most PICs can be reprogrammed multiple times, allowing for corrections and updates What might be the drawback of using a PIC for a simple one-off task?

Digital or analogue inputs? When programming PICs, the type of input required will need to be considered, for example: Switches are input components that give a digital signal Components such as thermistors, LDRs and microphones require an analogue input

Using analogue sensors PICs cannot process the infinite range of values that analogue inputs provide so it is divided into smaller parts Analogue inputs divide a signal in to 256 equal sections The range is labelled 0 to 255 When the input signal reaches a particular value or intensity, the PIC will function as the program dictates

Input components Complete Task 1 of Worksheet 7

Output components Buzzers and speakers produce sound Buzzers normally give out a set frequency meaning they are good for system alerts Speakers have a broader frequency range and are used for speech and audio Suggest one instance where a buzzer would be more appropriate than a speaker

Two timers Timing is a critical process in a circuit Many microcontrollers have an accurate internal clock Time delays can be programmed Monostable devices are single-shot timers, going on once, then staying off Astable devices constantly alternate between on and off Which device does a flashing road beacon use?

Monostable device The single pulse produced is usually triggered by a switch or sensor The length of the pulse can be varied by changing the delay time Monostable devices are used for timing how long events occur such as an automatic door opening and shutting Where else might one be used?

Astable device The stream of pulses produced are oscillating and constant One cycle is the time (t) a single pulse takes to go from 0 (off) to 1 (on) and back to 0 The speed of the pulses is known as the frequency and is measured in hertz (Hz) Flashing lights are used on tall buildings and aircraft – where else are they used?

Counting PICs can be programmed to count up and down, and can take over the roles of many traditional ICs Popular counters include the decade counter (4017) which has 10 outputs and counts up or down one on each pulse 7-segment display decoder (4026) converts pulses into numbers and outputs to a 7-segment display Both of these ICs can ‘cascade’ – what does this mean?

Worksheet 7 Complete Task 2 of the worksheet

Plenary When you download a track from a music site, how does the file get onto your computer or device? What happens to the track when you play it through speakers or headphones?