Basic Electronic
Components
A SIMPLE INTRODUCTION TO THE MOST COMMON COMPONENTS
USED IN ELECTRONICS
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Basic Electronic Components Used in Circuits
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Basic Electronic Components Used in Circuits
Table Of Contents
1. Light-Emitting Diode (LED) ..........................................................................4
2. The Resistor ........................................................................................................7
3. The Switch ........................................................................................................11
4. The Capacitor ..................................................................................................13
5. The Transistor ..................................................................................................15
6. The Inductor ....................................................................................................18
7. The Integrated Circuit ..................................................................................21
8. Learn Electronics Online .............................................................................24
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Basic Electronic Components Used in Circuits
Light-Emitting Diode (LED)
Figure 1: A Light-Emitting Diode (LED)
A Light Emitting Diode – or LED for short – is a small component that lights up
when current flows through it.
Sometimes you use it for simple tasks like indicating that your circuit has power,
that the circuit is working or that the circuit has failed.
But you can also combine several LEDs to create simple 7-segment displays that
can display numbers or use them to make cool light decorations. If you combine
enough LEDs in a square, you can even use them to show images.
The LED exist in many different colors; Red, green, blue and many more.
There is also a special type of LED called RGB. This is an LED where a red, green and
blue LED has been combined into one package. The colors mix, so by controlling
the intensity of each of the three colors you can create a wide spectrum of different colors.
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Basic Electronic Components Used in Circuits
Figure 2: The symbol used in circuit diagrams for a Light-Emitting Diode (LED)
Example
To use an LED, you need to connect it in a circuit with a resistor, as shown in Figure
3.
Figure 3: A simple LED circuit
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Basic Electronic Components Used in Circuits
The reason you need the resistor is to make sure the LED does not burn up. A common LED can only handle a very low current. If you don’t use a resistor to control
the current, your LED will quickly die and become unusable.
But what is a resistor?
That’s next. Jump on over to the next page to learn what a resistor is.
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Basic Electronic Components Used in Circuits
The Resistor
Figure 4: The resistor in a circuit
I didn’t understand the resistor in the beginning. It seemed like it didn’t do
anything! It was just there, consuming power.
But eventually, I learned that the resistor is actually extremely useful.
You’ll see resistors everywhere. And as the name suggests, they resist the current.
But you are probably wondering:
“What do I use it for?”
You use the resistor to control the voltages and the currents in your circuit.
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Basic Electronic Components Used in Circuits
Figure 5: You always need a resistor with the LED
Let’s say you have a 9V battery and you want to turn on an LED. If you connect the
battery directly to the LED, LOTS of current will flow through the LED! Much more
than the LED can handle. So the LED will become very hot and burn out after a
short amount of time.
But – if you put a resistor in series with the LED, you can control how much current
is going through the LED.
Figure 6: A rectangle or a zigzag line is used as a symbol for the resistor
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Basic Electronic Components Used in Circuits
Example
In Figure 7 you can see a common example of how a resistor is used to control the
current for protecting the LED.
Figure 7: A common way to use resistors is to control the current for an LED
A standard LED can only handle up to around 20-30 mA. If the current it much bigger than that, the LED will quickly die.
Let’s say the LED in the circuit above needs 15 mA to give a good light, and it has a
voltage drop of 2 volts. (These values should be specified by the supplier when you
buy an LED.)
If you have a 9 V battery that you would like to power it with, which resistor value
do you need?
The voltage specified for the LED is the voltage drop the LED will have under normal conditions. That means you know you will have 2V over the LED.
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Basic Electronic Components Used in Circuits
To find the resistor value, we start by finding the voltage drop over the resistor.
Since there is a 2-volt drop over the LED, there will be a 7V drop over the resistor
(9V - 2V equals 7V).
You have 7V over the resistor, and whatever amount of current flows through it will
also flow through the LED. So by setting the resistor value to a value that gives you
15 mA, you’ll also get 15 mA through the LED.
To find the necessary resistor value we use Ohm’s law.
By placing your hand over the R in the Ohm’s law triangle, you get that Resistance
(R) equals voltage (V) divided by current (I). This means you get:
R = 7V / 0.015 A = 467Ω
470Ω is a standard value close enough, so by choosing this resistor value you decide that the current flowing in your circuit is 15 mA.
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Basic Electronic Components Used in Circuits
The Switch
Figure 8: The push-button is a popular switch
The switch is a component that connects one pin to another. For current to flow
through a circuit, there needs to be a path from the plus of the battery to the minus of the battery.
If you build a simple circuit with an LED and a resistor and connect this to a battery,
your LED will light up. If you disconnect the plus of the battery from the circuit, the
LED turns off.
The switch is nothing more than a way to connect and disconnect two or more
things. For example to make a light-switch. Or a keyboard.
Figure 9: The switch symbol comes in many forms. This is the pushbutton switch.
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Basic Electronic Components Used in Circuits
Example
In Figure 10, you can see how you can use a switch to turn on and off an LED.
Figure 10: In this circuit, the switch turns on the LED when pushed down
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Basic Electronic Components Used in Circuits
The Capacitor
Figure 11: Two capacitors (Non-polarized on left and polarized on right)
You can think of a capacitor as a battery with very low capacity. You can charge and
discharge it, just like a battery.
The capacitor is often used to introduce a time-delay in a circuit. For example to
blink a light (check out the example in the Integrated Circuit section). But it’s also
useful for removing noise in an audio signal, or make the power supply of a circuit
more stable.
Capacitors come as polarized and non-polarized capacitors. The biggest difference
is that with the polarized capacitor, you have a positive and a negative pin and you
need to make sure to connect them correctly. You can connect non-polarized capacitors any way you want.
So which one to choose?
You never need your capacitor to be polarized. But for larger values, the capacitors
are made with a material that makes them polarized. So, sometimes you don't
have any choice but to use a polarized one.
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Basic Electronic Components Used in Circuits
Figure 12: Three different variations of the capacitor symbol. If a plus is
shown, it means it’s a polarized capacitor.
Example
By connecting a capacitor in parallel with a resistor and an LED, the capacitor can
store energy and use the energy after the battery is disconnected. This creates a
“fading out”-effect of the LED.
In Figure 13 you can see such a circuit. To build this circuit, you'll need a capacitor
of at least 1000µF to see the effect.
Figure 13: A circuit where the LED fades out because of the energy stored in the capacitor
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Basic Electronic Components Used in Circuits
The Transistor
Figure 14: A transistor placed onto a breadboard
This is the component that seems to be the hardest to understand when starting
out. At least it was for me.
But don’t worry, it’s not that hard.
A transistor is like a switch that is controlled by an electrical signal.
Figure 15: A little bit of current flowing through the base of the transistor turns it ON
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Basic Electronic Components Used in Circuits
In Figure 15, you can see an illustration of how the transistor works:
It has three pins named base, collector, and emitter. If you have a small current
flowing from base to emitter, you turn it on. With no current, it is off. To get current
flowing you need about 0.7V from base to emitter (for this type of transistor).
Unlike a normal switch that only has two states (ON or OFF), the transistor can also
be “partly on” by controlling the current that goes through its base. A bit of current
on the base produces a current of maybe 100 times more (depending on the transistor) through the Collector and Emitter. You can use this effect to build an amplifier.
Figure 16: The transistor symbol for a NPN transistor
Example
A simple example of using a transistor is for building a touch-sensor, like in Figure
17.
In this example, the transistor does not let any current flow through the LED and
resistor if there is no current flowing through the base. That means there is no light
in the LED.
When you touch your finger to the touch-pad (for example two metal pins), your
finger acts as a resistor, and lets a little bit of current flow down through the
base of the transistor. The transistor “opens its gate” and lets about 100 times the
amount of current flow through the LED and resistor, which makes the LED light
up.
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Basic Electronic Components Used in Circuits
Figure 17: A touch-sensor that turns on a light when you touch it.
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Basic Electronic Components Used in Circuits
The Inductor
Figure 18: An inductor on a small circuit board
An inductor is just a coil of wire. If you take a wire and wind it up into a coil, you
have created an inductor. When you apply a current through the coil, a magnetic
field is created around it, and this field stores energy.
When the current through the inductor stays the same, the inductor does nothing.
It just lets the current pass through, just like it was a normal wire.
But when the current through the inductor changes, the built-up energy in the
magnetic field will resist this change by changing the resistance of the inductor.
Resistance to change is a good thing for example to create a filter to reduce noise.
Figure 19: The symbol used in circuit diagrams for an inductor
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Basic Electronic Components Used in Circuits
If the wire is wound around a magnetic core (for example iron), the magnetic field
becomes much stronger. A transformer is a component made up of two inductors
wound around the same magnetic core.
The transformer is a classical component used to reduce the voltage in power supplies. If you constantly change the current through one inductor (the input), the
change in magnetic field is picked up by the other inductor (the output).
If the input inductor has 1000 windings, and the other inductor has only 100, then
the resulting voltage on the output inductor is ten times less than the input voltage.
Example
Inductors are often used in filters and oscillators, for example in radio equipment.
But it’s hard to find a practical circuit example that is both simple and really demonstrates how an inductor works, without going into mathematical explanations.
Instead, a fun example to demonstrate the magnetism that is created in an inductor is to create an electromagnet!
Figure 20: A homemade electromagnet
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Basic Electronic Components Used in Circuits
Here's how to do it:
1. Take some insulated wire.
2. Wind it around an iron screw, maybe about 50 times.
3. Connect a big 1.5 V flashlight battery (You can try a higher voltage, but then
be very careful as it gets hot really fast.)'
4. Place it over some small metallic objects to test it.
Note: Not all metals are magnetic. For example, copper coins won’t be attracted to the
magnet.
Figure 21: The electromagnet pulling some metallic objects
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Basic Electronic Components Used in Circuits
The Integrated Circuit
Figure 22: An Integrated Circuit (IC) connected on a breadboard
An integrated circuit is any kind of circuit that is integrated onto a chip. It can be a
radio transmitter, a microcontroller, an audio amplifier or any other circuit you can
think of.
By making a circuit on a small chip, it’s much easier to make advanced projects.
Let’s say you want to make a tracking device for your car. You can find a GPS chip
for positioning, a GSM chip to send text messages, and a microcontroller chip to
control everything.
To figure out exactly what a specific IC does, you need to check its datasheet. The
datasheet is a document that comes with every IC. You can find the datasheet for
almost any IC by just searching for the chip name + “datasheet” in Google.
The datasheet explains what each of the pins does, how much voltage it needs,
and often contains an example circuit to show you how to connect it.
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Basic Electronic Components Used in Circuits
Figure 23: The symbol for an IC is often a box with pins. But it can also be the symbol of the function of the IC (like a logic gate or an operational amplifier).
Example
The 555 timer is a very useful and popular Integrated Circuit. You can use it to blink
a light, to create sound, to create a clock signal, add a countdown timer and a lot of
other things.
A simple example is to blink an LED. By carefully selecting the values of the capacitor and resistors on the input side, you can control how fast the light should blink.
Figure 24: This circuit will make the LED blink
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Basic Electronic Components Used in Circuits
The circuit shown in Figure 24 will blink an LED about once per second.
The resistors R1 and R2, together with the capacitor C1, set the output frequency
of the output pin. The frequency is the number of times the output goes high per
second. So an output frequency of 5 Hz would mean the output goes high 5 times
per second.
You can find the output frequency of your circuit by using the following formula:
To find the frequency, just replace R1, R2, and C1 with the values you use, and put
it all into a calculator.
Let's say you have a circuit with the following component values:
R1 = 100 kΩ
R2 = 10 kΩ
C1 = 10 µF
The resistor values are in ohms, and the capacitance is in farads. That means R1 =
100 000Ω, R2 = 10 000Ω, and C1 = 0.00001 F.
Frequency = 1.44 / ((100 000Ω + 10 000Ω + 10 000Ω) * 0.00001 F)
Frequency = 1.44 / ((120 000Ω) * 0.00001 F)
Frequency = 1.2 Hz
According to this calculation, the output should turn on and off 1.2 times per second with those values.
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Basic Electronic Components Used in Circuits
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Transformer
Transformer with symbol
A transformer is an electrical device, wherein two coils of wire are linked by an iron core.
Transformers provide much needed capability of changing the voltage and current levels easily.
They are used to step-up (increase) or step-down (decrease) AC voltages. The working principle of
a transformer is Faraday’s law of electromagnetic induction, that is, mutual inductance between two
circuits, which is linked by a common magnetic flux. Transformer transforms electrical energy from
one circuit to another circuit with the help of mutual induction between the two windings without
electrical connection between them, and also transforms power from one circuit to another circuit
without changing the frequency but with a different voltage level.
A transformer that has more turns on the secondary coil than the primary coil is called as a step-up
transformer and a step-down transformer has more turns in the primary coil than the secondary coil
(step-down transformer). Transformers are one of the main reasons we use AC current in our homes
and not DC: DC voltages cannot be changed using transformers. Transformers come in sizes
ranging from small ones equivalent to an inch across, to large ones that weigh hundreds of pounds
or more, depending on the voltage and current they must handle.
Battery
Battery with symbol
A battery is used to convert chemical energy into electrical energy through electrochemical
discharge reactions. Batteries are composed of one or more cells each containing an anode (), cathode (+) and the electrolyte. The anode and the cathode are kept up to an electrical circuit.
Cells are classified into two types’ primary cells and secondary cells, wherein the primary cells are
not rechargeable while the secondary cells are rechargeable.
Fuse
Fuse with symbol
A fuse is a piece of wire of a material, which is used to protect the components from damage due to
extreme current flowing through them. When an excessive current flows through the circuit, the wires
get heated up and melt. As a result, the current stops flowing. When the fuse melts, the fuse element
absorbs some energy. This energy is given by I2t, where ‘I’ is the peak value of the current
interrupted, and‘t’ is the time taken to clear the fault. When the fuse blows, it gives an indication that
there is some kind of malfunctioning in the circuit.
Each type of fuse is designed for a precise amount of current. A standard fuse consists of main
components such as metal-fuse element, a set of contacts, support body and connection. A fuse
element is made of copper, zinc, silver, alloys or aluminum to provide predictable characteristics.
This may be surrounded by material or air, which is proposed to speed the quenching of the arc
non-conducting liquids or silica mat used.
Relays:
Relays
Relays are electromechanical switches, which are used to control the circuits by using one signal or
low power signal. The first relays were used as amplifiers in long distance telegraph circuits.
Basically, a relay consists of an armature, an electromagnet, a spring and a series of electrical
contacts. There is no electrical connection between inside the relay between the two circuits and
these circuits are connected each other through magnetic connection. Relays are used to perform
logical operations in computers and telephone exchanges.
Switches:
Switches
A switch is an electrical component which is used to break an electrical circuit, interrupting the
current and to deliver the current from one conductor to another conductor. It is works with ON and
OFF mechanism. Switches are classified into four types such as single pole single throw (SPST),
single pole double throw (DPST), double pole single throw (DPST) and double pole double throw
(DPDT).
Motors:
Motors
A motor is a device, which converts electrical energy into mechanical energy. It includes stator,
rotor, bearings, conduit box, eyebolt, and enclosure. Electric motors are all around us, from common
appliances to our most complicated computers. These motors are clean and relatively competent
for the tasks they perform when compared to hydraulic alternatives or pneumatic. These are
classified into different types such as, stepper motor, brushed DC motor, brushless DC motor,
permanent magnet synchronous motor, Ac inductance motor and switched reluctance motor.
Circuit Breakers:
Circuit Breakers
A circuit breaker is a mechanical switching device which is operated automatically. A
circuit breaker is used to protect an electrical circuit from damage caused by short circuit overload.
The basic function of the circuit breaker is to interrupt the current flow and detect a fault condition.
It consists of two contacts such as moving and fixed contact. Moving contact is used to make and
break the circuit using stored energies in the form of spring or compressed air.
Fixed contact includes a spring which holds the moving contact after closing. Circuit breakers
consist of two coils, closing and tripping coil. Where closing coil is used to close the circuit and
tripping coil is used to trip the circuit.