Electronics Badge
S. Robinson
Requirements
current and resistance in a simple circuit.
Continued….
digital and at least one having been
soldered.
These slides aim to cover all the
required areas of
the badge.
i
‘Passive’ Components
The action of a passive component does not depend
on any sort of control input.
They are components with no brains!
They include:
Resistors
Resistors are used
to control current and voltage
They are commonly used to protect other components
and to act as “pull-up’s” in digital
circuits.
The value of a resistor is given by the
coloured bands.
1
2
3
4
5
6
7
8
9
1
2
3
4
5
6
7
8
9
Gold ÷ 10
x1
x10
x100
x1,000
x10,000
x100,000
0
0
Black
Brown
Red
Orange
Yellow
Green
Blue
Violet
Grey
White
x1,000,000
Silver ÷ 100
Continued….
This gives the colours as BBROYGBVGW
Can YOU think of a mnemonic?
The last band shows the Tolerance.
[How accurate it is (usually 5%)]
All resistors have a power rating!
In the case of carbon resistors the most
common are 1/4, 1/2, 1, and 2 watts.
!
Continued….
Standard Resistor
Variable Resistor
(Potentiometer)
Preset/ Cermet
Capacitors
Capacitors are used for charge storage
They are commonly used as “smoothers” and timers
and are most often found in AC
circuits.
Capacitors fall into two main categories:
Electrolytic
These have Polarity
(must be connected right
way around)
The negative leg is indicated by a series of
black arrows or similar.
The value of an electrolytic capacitor can be
easily read off from
the side, (e.g 1F).
They also have voltage ratings (e.g. 63V)
Continued….
Symbol for a
capacitor
Variable capacitor:
Commonly used in radio
tuning circuits.
Slightly different symbols can be used
Most electrolytic
capacitors
are aluminium
Non-Electrolytic
These come in many different
varieties such as:
Ceramic, MICA, Polyester,
Tantalum, Polypropylene,
Polythene, PET.
Again, they ALL have voltage ratings
The value of a ceramic capacitor is
given by a code.
First two numbers of
code gives value in pF.
Last number gives
number of zero’s
(e.g. 101 = 10(+0))
= 100
?
Continued….
Symbol for non-electrolytic
capacitor
Non-electrolytic capacitors tend to be used in
preference to electrolytic types.
Applications include oscillators and filters
Active components are "Devices with
smarts!"
They include:
Active Components
Diodes
These are the simplest type of active
device
They act as a miniature valve by allowing current
flow in one
direction only
Diodes are identified by the code written
across their sides (e.g. 1N4148, 1N4001)
Continued….
A diode has two connections:
The cathode on a real diode
is identified by a white or black
band.
LED’s
LED’s (Light Emitting Diodes) are basically
diodes which give off light!
The CATHODE is identified by a flat on the
LED body and the ANODE has a longer leg.
Many colours are now available including white.
LED’s have current ratings (typically 20mA) and need
to be protected by a resistor.
The resistor is chosen using:
Resistance = Voltage
Current
Example,
using a 9V battery the resistor needs to be
9 ÷ 20mA = 450
Continued….
Transistors are very
important devices which perform two major roles in electronic circuits:
Transistors (Bipolar)
They are identified by the code
written on one of their faces
(e.g. BC109, BC557)
Continued….
They are essentially two diodes “clagged”
together
Transistors fall into two main categories:
They are basically the same but one
switches on whilst the other switches
off.
E = Emitter
B = Base
C = Collector
If you apply a base current you get a
larger current (typically 50-500x) at the collector.
Continued….
Bipolar transistors
are current controlled devices
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Read the pins
clockwise
from the tag.
Integrated Circuits
Integrated circuits are miniature circuits housed in a
plastic package.
A huge range of chips are available of different sizes
and complexity as more and more things are being
squeezed in.
Chips are identified by the part
number written on top, e.g.
CA3140, SN7401.
Continued….
Pin numbers read anti-clockwise from
notch/ white dot
Precautions should be taken when
handling IC’s since they can be
damaged by static.
Common pin counts are 8, 14, 16 and 18
Other Symbols
Battery
Cell
Continued….
Fuse
Bulb
Continued….
Push-to-make
Push-to-break
Single Pole
Double Pole
Relay
Switches:
Analog ‘v’ Digital
(e.g. 0.5, 1.225, 5.647, 10 etc).
capacitors, diodes, op-amps etc.
Analog signals looks like this:
Continued….
0’s and 1’s (e.g. 011000101110)
Digital signals look like this:
There are two main families of logic:
These are commonly known as 4000 series
and 74 series.
Digital logic is basically numerous gates
which perform different
Logical functions.
Digital Logic
NOT Gate (Inverter)
This type of gate simply inverts the input.
(i.e. a 1 becomes a 0 and visa-versa).
Truth Table:
Y = (NOT) A or
Y = A
AND Gate (2-Input)
This gate controls an output based on
the inputs
Y = A (AND) B or
Y = A . B
OR Gate
The output of an OR gate depends upon the state
of
either input.
Y = A (OR) B or
Y = A + B
XOR Gate
The Exclusive OR gate is very similar to the OR gate.
Note the last line of the truth table!
Y = A (XOR) B or
Y = A + B
Inverted Gates
As well as these standard gates we can also have
NAND, NOR and XNOR.
These are equivalent to “clagging” a NOT gate
to the output of each one.
Project Pages
1. Melody Generator
This uses the readily available M66T chip, obtainable
from Maplin, RS, and Rapid Electronics
etc.
Circuit Diagram:
Continued….
to the melody generator which only requires
1.5V.
drive an 8 speaker directly.
Can be soldered using
this PCB.
Scale 2:1
Continued….
Finished PCB Layout
2. Automatic Light
This simple circuit uses an LDR to turn on a light
when it goes dark.
A relevant application
is switching on a buoys
light signal at night time.
As the light level falls, the resistance
of the LDR increases.
As the LDR resistance becomes larger, the voltage
prefers to flow through the 1K resistor.
Think of the analogy of a walker encountering
a cross roads where one path is tarmac and
one is thick mud.
This constitutes a base current sufficient to
drive the transistor into saturation.
Continued….
Continued….
“Breadboard” Layout
3. Traffic Light Controller
This circuit uses an important digital
component called a “flip-flop”.
Flip-Flop
Truth Table:
JK Flip-Flop
The flip-flop is so called since, when properly set,
the output will flip to one state and flop back to the other.
The flip-flop will toggle on each
clock pulse
Continued….
A commonly available flip-flop is the
74LS109 (dual flip-flop)
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Traffic Light Controller
The first flip-flop is set to constantly toggle
with the YELLOW LED connected to its
output. The YELLOW therefore lights on
every other clock pulse.
The RED LED is connected to the output
of the second which is driven by the first.
The RED repeats after 4 clock cycles and
stays lit for 2 of them.
The GREEN LED is driven by a NOR gate connected
to both flip-flops. It only lights when
both outputs are low. The GREEN repeats every 4 clock cycles but only stays
lit for 1 of them.
Continued….
Continued….
“Breadboard” Layout
Other Projects
Other projects you could try are:
Or how about your
OWN design!
You can always ask your instructor for any help
Congratulations
If you have followed all this then you should be in
possession of your electronics badge.
Hope you found the world of electronics
an interesting one!