# 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:

• inputs
• processing
• outputs
• possibly some feedback

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:

• Amplifying
• Analogue to Digital conversion
• Digital to Analogue conversion
• Equalisation
• Logical operations
• Memorising signals
• Signal limiting<
• Timing

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.

Return?