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Simple Electrical Circuit
pictorial
Simple Electrical Circuit
schematic
A voltage divider used for volume control.
Block Diagram Drawing
Standard symbol for a dc voltage source.
electrical schematic of flashlight
Resistance symbol and notation.
Film resistors:
FIG. 3.25
Color coding for fixed resistors.
Color-code bands on a resistor
• 1st band is the first digit of the resistance value
• 2nd band is the second digit of the resistance
value
• 3rd band is the multiplier (number of zeros)
• 4th band indicates the tolerance
Color coding.
Standard Values of Resistors
Potentiometer control of voltage levels.
Potentiometer and rheostat symbols and basic construction of
one type of potentiometer.
Typical potentiometers and two construction views.
Typical fuses and circuit breakers and their symbols.
Common Ground Symbol
Circuit Ground
• Voltage is relative
• The voltage at one point in a circuit is
always measured relative to another point
• This reference point in a circuit is usually
the ground point
Notation
Voltage sources and grounds
Ground
symbol
Voltage source
symbol
Symbols for ground
.
A simple circuit with ground connections.
Using an ohmmeter to measure the total resistance of a
series circuit.
Schematic representation for a dc series circuit.
Parallel combination of resistors.
Same resistance value
Connections or NODES
The voltage divider as a bias circuit for a transistor amplifier.
Symbol for the inductor.
Typical Inductors
Relative sizes of different types of inductors: (a) toroid, highcurrent; (b) phenolic (resin or plastic core); (c) ferrite core.
Symbols for the capacitor: (a) fixed; (b) variable.
(a) Film/foil polyester radial lead; (b) metalized polyester-film
axial lead; (c) surface-mount polyester-film; (d)
polypropylene-film, radial lead.
Capacitors
Variable Capacitors
 Most common are shown in the figure below.
The dielectric for each is air. The capacitance is
changed by turning the shaft at one end to vary the
common area of the movable and fixed plates. The
greater the common area the larger the
capacitance.
Symbol for a sinusoidal voltage source.
Volts A.C.
Some common types of transformers
(step AC voltage up or down)
Schematic symbols specify the type of core
.
Utility-pole transformer in a typical
power distribution system.
Operational Amplifier
Op-amp symbols and packages.
European schematic design
European schematic design
Transistors
Amplifier Output stage
D.C. 5volt Power Supply
Connections
• Wire To pass current very
easily from one part of a
circuit to another
• A ‘DOT' should be drawn
where wires are
connected (joined), but it
is sometimes omitted.
Connections
• In complex diagrams it is often necessary to
draw wires crossing even though they are not
connected, the 'bridge' symbol shown on the
right is preferred because the simple crossing
on the left may be misread as a join where
you have forgotten to add a ‘DOT'!
Test Instruments
A voltmeter is used to
measure voltage. The proper
name for voltage is 'potential
difference', but most people
prefer to say voltage!
An ammeter is used to
measure current.
Test Instruments
An ohmmeter is used to
measure resistance. Most
multimeters have an
ohmmeter setting.
A galvanometer is a very
sensitive meter which is used
to measure tiny currents,
usually 1mA or less.
Solid Core hook-up wire
This is one solid wire with a plastic coating
available in a wide variety of colors. It can
be bent to shape but will break if repeatedly
flexed. Use it for connections which will not
be disturbed, for example links between
points of a circuit board.
Stranded wire
This consists of many fine strands of wire covered
by an outer plastic coating. It is flexible and can
withstand repeated bending without breaking. Use
it for connections which may be disturbed, for
example wires outside cases to sensors and
switches. A very flexible version ('extra-flex') is
used for test leads
Signal cable
Signal cable consists of several color-coded cores
of stranded or solid core wire housed within an
outer plastic sheath. it is suitable for low voltage,
low current signals where screening from electrical
interference is not required.
Shielded Cable
The central wire
carries the signal and
the shield (screen) is
connected to 0V
(common). to shield
the signal from
electrical interference.
Shielded cable is used
for audio signals and
dual versions are
available for stereo.
Co-axial cable
This type of shielded cable is
designed to carry high frequency
signals such as those found in cable
TV connections and oscilloscope
leads.
Fender Musical Instruments
Frontman 15G
Amplifier
Schematic and Parts Layout
READING