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An Introduction to Electronicsby

William O’Shaughnessy

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An Introduction to Electronics

Electronics is the study of the flow of electrons in an electronic circuit made of electronic components connected in a closed path.

An electronic component is something that affects the flow electrons, by resisting their flow, creating potentials, or storing them.

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An Introduction to Electronics

The flow of electrons is called a current Its mathematical symbol is “I”. The unit of current flow is the Ampere,

very commonly abbreviated as Amp. An Amp is the flow of 6.24 * 10^18

electrons past a point in one second.

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An Introduction to Electronics Two Things are needed to create a

current flow a source of electrical potential and a path for the electrons to flow through

Consider filling this room with water with the doors sealed. (The water is the electrons) It can not leave the room without a hole in the floor. That hole is the path for the water to flow.

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An Introduction to Electronics Consider filling this room with water

with the doors sealed. (The water is the electrons) It can not leave the room without a hole in the floor. That hole is the path for the water to flow.

How fast the water hits the next floors is determined by the height between floors. This is called potential or voltage in electricity.

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An Introduction to ElectronicsTwo Kinds of Current

Direct Current: Flows only one way Alternating Current: First flows one way and

then the opposite direction How often current changes its direction in

one second is called its frequency. The unit of frequency is the Hertz Abbreviated Hz = cycles per sec Wall Current 60 Hz at 120 volts

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An Introduction to Electronics So we have the two most important

characteristics of electronics and the movement of electrons:

1.) Current: how many are flowing 2.) Voltage: how fast they are

moving or how fast they could move.

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Electronic ComponentsThe Battery

A battery produces electronic potential by chemical reactions for example:

Lead Acid or Lithium Ion A battery's greatest potential is called

its voltage It produces Direct Current How many electrons it can put out is

called its Amp*hour rating

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Electronic ComponentsThe Resistor

The resistor is a conductor of electrons A wire is a resistor with a very low

resistance The unit of resistance is Ohms, Its units symbol is Its math symbol is R

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Electronic ComponentsThe Resistor

A conductor can be thought of as a pipe

The resistance of a wire could be about .1 ohms; this could be thought of as a 10 inch diameter pipe

A resistor of 100 ohms would be like a pipe of .01 inches diameter

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Electronic ComponentsThe Resistor

The voltage across a resistor is proportional the amount of current that is passing through it.

V = IR This is Ohm's Law. It is the most important Law of Electronics

Resistors do not generate potential Resistors give off heat when they

pass current Pwr = V*I = I^2 R

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Electronic ComponentsThe Capacitor

A Capacitor is a circuit element that stores charge, that is electrons.

A capacitor can generate potential. That potential is proportional to the charge in the capacitor.

Will accept charge until its potential equals the potential of the source

A capacitor will not pass DC current It will pass Alternating Current

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Electronic ComponentsThe Capacitor

A Capacitor can pass AC current Small capacitors act as resistors

with high values to AC current. Its resistance to AC is 1/(2 F C)

Where F is the Frequency of the AC The unit of capacitance is the Farad A capacitor of 1 Farad is almost a

battery. Micro nano pico More common 1uf, 1nf, 1pf

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Electronic ComponentsThe Inductor

Is coil of wire around an iron core or air The inductance, symbol L, is

proportional to the square of the number of turns of wire

Its resistance to AC is 2 F L Where F is the Frequency of the AC The unit of inductance is the Henry Common sizes are milli Henries(mH),

microHenries(uH), and nanoHenries(nH)

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Electronic ComponentsL C Summary

Capacitors in parallel with a voltage source oppose any change in its potential.

In series capacitors pass AC but not DC.

Inductors in series with a current source oppose any change in its current.

They pass DC and AC but they delay and oppose any change in current.

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Electronic ComponentsThe Transformer

Is two inductors wound around the same core Is used to multiply an AC voltage by the ratio of the

turns in the two inductors. If 120 VAC is applied to 4 turns, 60 VAC comes out of

the two turns If 120 VAC is applied to 2 turns, 240 VAC comes out of

the 4 turns The coil that gets the voltage is called the “primary” The other coil is called the “secondary” Is the primary component in a Wall Wart

(formal name Power Adapter) And the biggest thing on an electrical pole.

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Electronic ComponentsThe Diode

Is a semiconductor circuit element that will pass current only in one direction.

Electrical current flows in the direction of the arrow, electrons flow in the direction opposite the arrow.

Is the second major component of a Wall Wart; the third is a capacitor.

The wire with the bar is the Cathode The wire with the arrow is the Anode

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Electronic ComponentsThe Diode

Is a semiconductor circuit element that will pass current only in one direction.

Electrical current flow in the direction of the arrow, electrons flow in the direction opposite the arrow.

Is the second major component of a Wall Wart; the third is a capacitor.

The wire with the bar is the Cathode The wire with the arrow is the Anode

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Electronic Components Bipolar Transistor

Is a semiconductor circuit element that amplifies the base to emitter current.

The bar is the base, the arrow is the emitter, the line is collector

The amplified current flows from the collector to the emitter in an NPN and from the emitter to the collector in a PNP transistor.

The amplification factor is called the Beta or h npn pnp

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Electronic Components Field Effect Transistor

Is a semiconductor circuit element that switches a current with a voltage

The current goes from a Drain to a Source (electrons from the Source to the Drain)

Take very, very little current to turn on They are said to have a high impedance input n-channel p-channel

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Rules of Using a Multimeter

Never measure current without the instructors permission (A or ma)

Never measure resistance in a powered on circuit

Don't touch the metal part of the probe when measuring in a circuit.

Always measure voltages starting with the highest scale and work down to smaller scales

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Soldering Always assume all metal parts of

a soldering iron are hot. First rule of soldering: get the connection hot

before applying solder. (Now obsolete) New rule: nothing conducts heat like

liquid metal. Have a little liquid solder on the tip of you soldering iron and use it and contact pressure to transfer heat from your iron to the connection before applying solder.

Besure you see solder flow onto the components. Keep the iron over the bench.