Introduction

A basic understanding of electronic circuits is important even if the

designer does not intend to become a proficient electrical engineer. In many

real-life engineering projects, it is often necessary to communicate, and also

negotiate, specifications between engineering teams having different areas of

expertise. Therefore, a basic understanding of electronic circuits will allow evaluating

whether or not a given electrical specification is reasonable and feasible

Electronics is a know how of how to manage electrical energy. It deals

with electrical circuits and components like transistors, diode, resistors,

capacitors, amplifiers and integrated circuits.

In an MFC project it is of prime importance to consider the study of

electronics as it has a major role to play. A study to understand the basic

electronics components, it implementation and circuit designs is deemed to be

able to make optimal and reap maximum benefits.

In the following discussion,the basic components of electronics and its

implementation will be discussed.

Resistors

An electrical component to create resistance in electric current is

called is Resistor.

The resistance value and tolerance are indicated with several colored

bands around the component body.

Fixed resistor symbolANSI standard

Fixed resistor symbol

Resistor color code

To determine the amount or magnitude

of the electrical current flowing around an electrical or electronic circuit,

we need to use certain laws or rules that allow us to write down these currents

in the form of an equation. The network equations used are those according to

Kirchhoff’s laws, and as we are dealing with circuit currents, we will be

looking at Kirchhoff’s current law, (KCL).

Resistor

with a resistance of 5600 ohm with 2 % tolerance, according to the marking code

IEC 60062.

Effect of

Temperature on Resistance

Change in temperature causes the resistance to change. This may happen

because temperature changes the dimension of a conductor. Also wires with high

thickness have less resistance and vice versa.

Resistors in Parallel

Let’s

look how we could apply Kirchhoff’s current law to resistors in parallel,

whether the resistances in those branches are equal or unequal. Consider the

following circuit diagram:

In this simple parallel resistor

example there are two distinct junctions for current.

Kirchhoff’s First Law

As

per Kirchhoff’s law the charge entering a node is equal to the charge leaving

the node and the total current is zero. There is no loss of current.

Kirchhoff’s Current Law

A junction or a connection of two or more current

carrying routes like cables and other components is called as Node. Parallel

circuits can also be analyzed by Kirchhoff’s current law.

In the above figure, the currents I1, I2 and

I3 are entering the node are positive and two currents I4 and

I5 are negative. This can be expressed as:

I1 + I2 + I3 – I4 – I5 = 0

Kirchhoff’s Second Law

In any closed network the sum of voltage is equal to

zero if we do an algebraic summation of all the voltage across each loop.

Kirchhoff’s Voltage Law

We

can begin from one point of the loop and continue in the same direction,

clockwise or anti clock wise.

The

final voltage value will not be zero if the direction is not maintained. It has

to either clockwise or counter clock wise.

We

need to be clear with all the terms like

nodes, loops etc so that we can understand it for the AC and DC circuit

analyses base on Kirchhoff’s Current Law.

Superposition Theorem:

The total current in any part of linear bilateral

circuit can be calculated by evaluating the separate current by open circuiting

the current source and short circuiting the voltage source and summing them to

calculate the total current.

Thevenin’s Theorem

A two terminal combination of battery

and resistance can be replaced by a single current source and voltage source

across the terminals.

Norton’s Theorem

A two

terminal collection of resistance and battery can be considered to be equivalent

to an ideal current source in parallel arrangement with a resistor. The value

of current can be derived by diving the voltage by r, where r’s value is same

as Thevenin’s equivalent.

Capacitor

Capacitor

components

A capacitor is designed by sandwiching an insulating

material between two metal plates. The insulation material in between is called

dielectric.The dielectric ensure there is not physical contact between the

metal plates.

Any material which is impede the flow

of current can be used as a dielectric. For ex; glass, plastic, rubber, paper

etc

A capacitors capacitance depends on

how it has be constructed. More the surface are overlap, more is the

capacitance value, but lesser distance results into higher capacitance. Large

capacitors have higher capacitance value.

Below is the equation for total

capacitance

In the above equation ?r is the

dielectric’s permittivity, d is the distance between the capacitor plates and A

is the area of the plates which overlap.

Charging and Discharging

A

capacitor is said to be charged when the positive and negative charged

accumulate on each plate, but could not meet as they are separated by an

insulator.

At some point the plates become fully charged and hence cannot accept any

more charge. This is the maximum amount of charge a capacitor can hold.

If a path is created in the circuit

through which it could dissipate it discharges the capacitor and is called as discharging

of capacitor.

Calculating Charge, Voltage,

and Current

The potential difference between the

plates determines how much charge can be stored in a capacitor. The equation to

depict the same is

V is the voltage applied, Q is the Charge store and C is

the capacitance.

One Farad can be defined as the capacity to store one

unit of energy per one volt

Features of Capacitors

Different types of capacitors have

different utility

When deciding on capacitor types there

are a handful of factors to consider:

Size –Physical and

Capacitance.

Maximum voltage –Each

capacitor has a voltage rating for ex 1.5 V. Exceeding it could be a destroy

it.

Leakage current -. Every

capacitor leaks small amount of current through the dielectric. It is called leakage.

Equivalent series resistance (ESR) –The

resistance provided by the terminals of capacitor is called Equivalent

resistance. It is usually very small.

Tolerance –All capacitors

might vary from the ideal defined capacitance which could be from 1% to 20 %

Ceramic

Capacitors

This is one of the most commonly used

and produced capacitor. The name has been derived from the material from which

their dielectric is made.

Ceramic capacitors are usually small both

physically and capacitance-wise. Ceramic capacitor much larger than 10µF is

hard to find.

Two caps in a

through-hole, radial package; a 22pF cap on the left, and a 0.1µF on the right.

In the middle, a tiny 0.1µF 0603 surface-mount cap.

Compared to the popular electrolytic

capacitors, ceramics are a more near-ideal capacitor (much lower ESR and

leakage currents), but their small capacitance is a limitation.

Aluminum and Tantalum Electrolytic

These type of capacitors are good for high voltage

applications and they have a high capacitance and are relatively small. It

ranges from 1µF-1mF.It looks like a tin can with two leads at the bottom.

An assortment of

through-hole and surface-mount electrolytic capacitors. Notice each has some

method for marking the cathode (negative lead).

Supercapacitors

These are uniquely made to store very

high capacitance.

A 1Fsupercapacitor.

High capacitance, but only rated for 2.5V. Notice these are also polarized.

These capacitors have very high

capacitance, but have relatively low voltage. A high voltage rating is achieved

arranging them in series.

Capacitors in Series/Parallel

Multiple capacitors can be combined

in series

or parallel to create a combined equivalent capacitance. Capacitors,

add together in a way that’s completely the opposite of

resistors.

Capacitors in Parallel

The total capacitance of capacitors in

paralleled is the sum of all capacitances. This is analogous to the way resistors add when they are in

series.

For example, if you had three

capacitors of values 10µF, 1µF, and 0.1µF in parallel, the total capacitance

would be 11.1µF (10+1+0.1).

Capacitors in Series

Similar to resistors in parallel, the

total capacitance of Ncapacitors in series is the inverse of the

sum of all inverse capacitances.

If you only have two capacitors

in series, you can use the “product-over-sum” method to calculate the total

capacitance:

Capacitor Colour Code Table

Band Colour

Digit A

Digit B

Multiplier D

Tolerance (T) > 10pf

Tolerance (T)