1 - System Synthesis

2016-04-18 17:46:00 +0000, 2 years and 4 months ago

1.01 - electronic systems

All electronics systems can be analysed into small, discrete subsystems which will, in general, consist of the following:

Using this concept, large electronic systems can be broken down into smaller, simpler subsystems.
It is important to include arrows, as they denote the direction of data transfer.

          +--------+
  +---<---+feedback+---<---+
  |       +--------+       |
  |                        |
+-+---+   +--------+   +---+--+
+input+->-+process +->-+output+
+-----+   +--------+   +------+

An example is a security light.
lamp = ON when movement detected ‘and’ light level = < x lux
(lux = unit for brightness)

The light system has been broken down into the following subsystems:

+-------------+
+light sensor +-->-+                                 
+-------------+    |   +-----+   +-----+   +------+   +----+
                   +->-+logic+->-+timer+->-+driver+->-+lamp+
+-------------+    |   +-----+   +-----+   +------+   +----+
+motion sensor+-->-+
+-------------+

1.02 - input transducers

sound –> microphone
light –> LDR
temperature –> thermistor
motion –> variable resistor

Therefore,
sound = input (electrical signal)
microphone = input device (transducer)

1.03 - analogue and digital signals

analogue: signals produced by input devices (transducers) vary between MIN and MAX values and can take any value in-between.

| voltage
| 
|   _.--._  <-- LOGIC 1
|  /      \ 
| /        \
|/          \    
+--------------------------- time
|             \          /
|              \        /
|               \      /
|   LOGIC 0 -->  `'--'`
|

Analogue signals can be difficult to process since they carry their information in the value of their voltage.
Most analogue signals are now converted into digital signals, a binary signal - 1 or 0. unlike analogue signals, digital signals are not affected by small levels of electrical noise or interference since their value is absolute.

digital: the voltage of the signal is not critical, so long as value > x, then the signal will be taken as logic 1. and value < x, will be taken as logic 0, where x is the required voltage for a component to switch high, or 1.

| voltage
| 
|                   LOGIC 1
+-----+             +-----+
|     |             |     |
|     |             |     |
+-----+-------------+-----+- time
|     |   LOGIC 0   |
|     :             |
|     |             :
+--=--+             |
| PULSE             |
|                   |
+---------=---------+
|       PERIOD

Digital signals’ values are absolute, meaning that they are either 1 or 0, which is incredibly useful in logic subsystems and computers. The actual information is contained within the binary numbers depicted by the digital signal.

1.04 - processors

The basic types of processing are:

1.05 - output transducers sound => loudspeaker
light => LED, lamp, TV
heat => resistor, heater
motion => motor

output = sound
output device = loudspeaker

Once the electronics system has processed the information, the electrical signals need to be changed so that they can be used to the outside world.

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