Transcript Document

GCSE Electronic Products
Revision Flashcards
555 timer
•8 pin Integrated Circuit (I.C.)
•Analog
•can be used as an astable or monostable
•Low cost
Monostable
(the egg timer)
•Has a single (mono) stable state
• when it is timing
•The output is normally off
Pin 2 = Trigger
• The trigger sets the
timer going
• Timer starts when
trigger is < 2V
• Connects to a 10K
pull-up resistor
Pull-up resistor
• Pulls the voltage up on a
wire to supply voltage
• Makes a “nice” logic
high
Pull Down Resistor
• Pulls the voltage on a
wire down to 0V
• Gives a “nice” logic 0
Pin 6 = Threshold
• Detects when the bucket
(capacitor) is 2/3rds full
• The capacitor fills up
through a resistor
• Time to fill to 2/3rds full =
Resistor Value x Capacitor
Value (T = RC)
Pin 7 = discharge
• Empties the bucket
(capacitor)
Astable
(The “flasher” circuit)
• Has no stable states
• Keeps on flashing
forever
• Number of flashes per
second = frequency
• Automatically triggers
The Op-Amp
• - input = inverting
• + input = non-inverting
• used as an inverting
amplifier or a comparator
• An analog device
• A 741 I.C. is an example of
an op-amp
Inverting
• Means it turns the
signal upside down
Gain
• The ability of a device
to make a signal
bigger
• Op-amps have huge
“open loop” gain
• Transistors also have
gain
Feedback
• Gain can be reduced by
using feedback
• Some of the output is
taken away and added to
the input
• We use resistors to do
this
+
Comparator
(Which input is bigger)
-
• If “+” is bigger than “” we get a logic 1
• If “+” is smaller than
“-” then we get a
logic 0
• A simple analog to
digital converter
Ohms Law
• As resistance
increases, current
decreases
• As resistance
increases, voltage
increases
Sources of power
P.I.C.
(Peripheral Interface Controller)
• Digital
• A mini-computer in a
single Integrated Circuit
• Programmable using
flowcharts
• Can be programmed many
times
• Remembers program even
when the power is off
Diode
(A one way valve)
• Current flows from
anode to cathode
• Prevents current flowing
the wrong way
• Protects circuits if the
power supply is
connected up wrong
Transducer
(A device for converting energy
from one form to another
• Motor – converts electrical
energy to kinetic energy
• LED – converts electrical
energy to light
• Microphone - converts
sound energy to electrical
energy
Transducer Drivers
(Things that provide power to output transducers)
• Bipolar Transistors
• FET’s
• Darlington Pairs
Tolerance
• The amount of “spread”
in a components value
• 100Ω and 10% tolerance
gives a spread between
90Ω and 110Ω
E12 Series
• The values that 10%
tolerance resistors are
made in to avoid value
overlap
• 10, 12, 15, 18, 22 etc
• 100, 120, 150, 180 etc
Polymorph – Smart Material
• Used to rapidly
model complex
shapes
+
• Granules put in hot
water turn solid and
can be immediately
shaped
clock
• A digital signal that
has a regular
repeating on/off
pattern
• Often generated by an
astable
• Used by PICs &
counters
HIPS
• Plastic material used for
vacuum forming
• Available in different
colours
• Used to make complex
3d shapes
• Boxes must have angled
sides to get the mold
out
Breadboard
• Used to model circuit
using real component
• No soldering
• Easy to change
connections
• Components can be reused
CAD
(Computer Aided Design)
• Testing by simulation
• Links to CAM (Computer Aided
Manufacture)
• Easy to share designs with
others and keep track of
changes
• Making changes is a quick &
easy process
Latch Circuit
• Can be made using a
thyristor
• Can be made with NOR
or NAND gates
• When activated, stays
activated until reset
– Remembers that it
has been activated
Thyristor
• Used in latch circuits
• A pulse on the gate
causes current to flow
from Anode to Cathode
until reset
• Reset by making the
Anode voltage the
same as the Cathode
Potential Divider
• A circuit for dividing
voltages
• Voltage splits based upon
the ratio of two resistors
Schmitt Trigger
• A type of circuit used
to remove switch
bounce
Thermistor
• Device for measuring
temperature
• As temperature
increases, resistance
decreases
• Often used as part of a
potential divider
LDR
(Light Dependent Resistor)
• As light increases,
resistance decreases
• Often used as part of a
potential divider
Multimeter
• Device for measuring:
– Current
– Voltage
– Resistance
• Has red & black probes
The 3 R’s
(Helping The Environment)
• Reduce
cut the materials you
use
• Reuse
make use of existing
products
• Recycle
stop the product going to
landfill when obsolete
Resistors
• Measured in Ohms
(Ω)
• Used to reduce
current
• Colour bands
indicate the value
Integrated Circuits
• Pin 1 is to the left of the notch
• Lots of components on a
single piece of silicon
• Examples are:
– PICS
– 555’s
– 741’s
Switch Bounce
• A problem with
mechanical PTM &
PTB switches
• One press of the
switch generates
more than one pulse
AND Gate
• Both inputs must
be at logic 1 to get
a logic 1 out
• A = 1 AND B= 1
OR GATE
• Either one of the two
inputs can be at logic 1
to create a 1 on the
output
• A=1 OR B=1
Relay
• A device that allows one
circuit to turn on
another circuit that
works at a different
voltage
• Uses electro-magnets
Variable Resistor
• Used for
– volume controls
– Changing astable
frequencies
– Changing mono-stable
time periods
4017
• Output 0 is on
• When a clock pulse is
received:
– Output0 turns off
– Output1 turns on
• On next clock pulse
– Output1 turns off
– Output2 turns on
SPDT SWITCH
(Single Pole Double Throw)
•
•
•
•
One circuit
Two positions
Three pins
Two different sets of
components can be
switched into one
circuit
Life Cycle Analysis
• What happens to a
product when it is
disposed of:
– Reused in a new
product
– Recycled
– Goes to landfill
Multipliers
1,000,000,000
1,000,000
1,000
= 1G = 1 x 109
= 1M = 1 x 106
= 1K = 1 x 103
1
= 1
= 1 x 101
0.001
= 1m = 1 x 10-3
0.000,001
= 1µ = 1 x 10-6
0.000,000,001
= 1n = 1 x 10-9
0.000,000,000,001
= 1p = 1 x 10-12
Units of Measure
Measurement
Unit
Symbol
Resistance
Ohms
Ω
Capacitance
Farads
F
Voltage
Volts
V
Current
Amps
I
Power
Watts
W
Time
Seconds
S