Section 1 - Overview
Electronic Systems
Electronic systems consist of three main parts: input, process and output. This can be represented in a
block diagram:
input process output
Digital and Analogue Outputs
The output of an electronic system can either be analogue or digital.
Digital outputs can only have certain values (usually this is either ON or OFF).
Analogue outputs have a continuously varying value.
Analogue and digital signals can be identified from the waveforms produced on an oscilloscope.
digital analogue
, Section 2 - Output Devices
Digital Output Devices Analogue Output Devices
Solenoid electrical to kinetic (in a line) Motor electrical to kinetic (rotation)
Buzzer electrical to sound Loudspeaker electrical to sound
LED electrical to light Bulb electrical to light
Relay electrical to kinetic
7-Segment electrical to light
Display Choosing Output Devices
Output devices should be chosen for a
particular situation according to what form on
The LED energy is required and whether the output
needs to be digital or analogue.
An LED (Light Emitting Diode) converts
electrical energy into light, but it will only do so
when is connected the correct way round.
7- Segment Display
A 7-segment display consists of seven LED
bars. Different numbers can be produced by
lighting the appropriate segments:
electron flow a Digit Segments lit
b 0 abcdef
A resistor is always placed in series with an f g
1 bc
LED to prevent it being damaged by too large a 2 abged
e c
current passing through it. d
etc. etc.
Calculating the Series resistance for an LED
The following circuit would allow an LED to light: The value of the series resistance that must be
used can be calculated as follows:
Firstly VR = V s - VLED
= 6 - 1.8
R LED Data
= 4.2 V
6V ILED = 10 mA Then IR = ILED = 10 mA = 0.01 A
VLED = 1.8 V So R = V LED / I LED
= 4..01
= 420 Ω
Electronic Systems
Electronic systems consist of three main parts: input, process and output. This can be represented in a
block diagram:
input process output
Digital and Analogue Outputs
The output of an electronic system can either be analogue or digital.
Digital outputs can only have certain values (usually this is either ON or OFF).
Analogue outputs have a continuously varying value.
Analogue and digital signals can be identified from the waveforms produced on an oscilloscope.
digital analogue
, Section 2 - Output Devices
Digital Output Devices Analogue Output Devices
Solenoid electrical to kinetic (in a line) Motor electrical to kinetic (rotation)
Buzzer electrical to sound Loudspeaker electrical to sound
LED electrical to light Bulb electrical to light
Relay electrical to kinetic
7-Segment electrical to light
Display Choosing Output Devices
Output devices should be chosen for a
particular situation according to what form on
The LED energy is required and whether the output
needs to be digital or analogue.
An LED (Light Emitting Diode) converts
electrical energy into light, but it will only do so
when is connected the correct way round.
7- Segment Display
A 7-segment display consists of seven LED
bars. Different numbers can be produced by
lighting the appropriate segments:
electron flow a Digit Segments lit
b 0 abcdef
A resistor is always placed in series with an f g
1 bc
LED to prevent it being damaged by too large a 2 abged
e c
current passing through it. d
etc. etc.
Calculating the Series resistance for an LED
The following circuit would allow an LED to light: The value of the series resistance that must be
used can be calculated as follows:
Firstly VR = V s - VLED
= 6 - 1.8
R LED Data
= 4.2 V
6V ILED = 10 mA Then IR = ILED = 10 mA = 0.01 A
VLED = 1.8 V So R = V LED / I LED
= 4..01
= 420 Ω
