Introduction: Electronics for Absolute Beginners, Chapter 2
Welcome to Chapter 2.
In Chapter 2, we will go through:
1. Resistor Color Code
2. Determine Needed Wattage for A Resistor
3. Electronic Test Equipments
4. Basics of Wires
5. The Metric System
6. Electronic Components and Their Schematic Symbols
Chapter 3 https://www.instructables.com/id/Electronics-for-Absolute-Beginners-Chapter-3/
It is important that you understand Chapter 1 to move forward. Below is the link:
https://www.instructables.com/id/Electronics-for-Absolute-Beginners-Study-Guide/
Step 1: Resistor Color Codes
Resistors provide resistance to current flow. The amount of resistance of a resistor is based on its value. To determine the value of a resistor without any test equipment, we must know the resistor color code. Each color stands for a number and place holder. A Resistor can contain from 3 up to 6 color bands.
Please click this link for a visual presentation of what numbers designated for each color:
http://fellowshipcreative.com/wp-content/uploads/2010/06/res-color-code4.gif
Notice that the color starts from darkest to lightest as it goes up.
Black - 0
Brown - 1
Red - 2
Orange - 3
Yellow - 4
Green - 5
Blue - 6
Violet - 7
Gray - 8
White - 9
Tolerance Rating Color Codes
Brown = +1%, -1%
Red = +2%, -2%
Green = +.5%, -.5%
Blue = +.25%, -.25%
Violet = +.1%, -.1%
Gold = +5%, -5%
Silver = +10%, -10%
Temperature Coefficient Color Codes
Brown = 100ppm
Red = 50ppm
Orange = 15ppm
Yellow = 25ppm
Step 2: 3 Band Resistor
For a 3 band resistor,
The 1st band = first significant digit
The 2nd band = second significant digit
The 3rd band = the number of zeros to be added to the significant digits
Let's figure out the value of this 3 band resistor http://www.create-california-online.net/Tutorials/Resistor_color_code_2/1k-20percent.png
1st band = Brown
2nd band = Black
3rd band = Red
Now we must remember the equivalents of those colors.
Brown = 1
Black = 0
Red = 2, so add 2 zeros
Okay, the value of this resistor is 1000Ω, which can also be written as 1k Ω.
Remember that the 3rd band means the number of zeros to be added to the significant digits. So since the 3rd band is red which has an equivalent of two, it means two zeros must be added to the significant digits 10, which makes it 1000.
When a resistor, does not have a 4th band, which determines the tolerance rating, the resistor automatically assumes a +20% or -20% tolerance. That means that whatever the value is of the resistor, it can go above that value +20% more or -20% less, and the resistor can still be considered in good operational condition. However, once it goes beyond the +20% or -20% tolerance, the resistor is considered bad and must be replaced.
Step 3: 4 Band Resistor
For a 4 band Resistor:
1st band = 1st digit
2nd band = 2nd digit
3rd band = number of zeros to be added to the digits
4th band = tolerance rating
Let's figure out the value of this 4 band resistor
https://www.dlsweb.rmit.edu.au/toolbox/electrotech/toolbox1204/resources/01principles/04properties/images/100_ohm_resistor2.jpg
1st band = Brown
2nd band = Black
3rd band = Brown
4th band = Gold
So based on the color codes this resistor is 100Ω and has a tolerance rating of +5% or -5%. This is because of the following.
Brown = 1
Black = 0
Brown = 1, so add 1 zero
Gold = +5% or -5%
The colors used for the tolerance lever are usually gold and silver. Gold is +5% or -5% tolerance and Silver is +10% or -10% tolerance. For example, if a resistor has a gold tolerance band, it means that it can go +5% or -5% of the value of the resistor, in order to be considered in good operational condition. For example, if the resistor's value is 100Ω and its tolerance band is gold (which is +5% or -5%), it can be as high as 105Ω and and as low as 95Ω to be considered in good operational condition. If the resistor is tested with an ohm meter and it reads 106Ω or more, it is considered a bad resistor. Similarly, if it reads 94Ω or less, it is also considered a bad resistor.
Tolerance Rating Color Codes
Brown = +1%, -1%
Red = +2%, -2%
Green = +.5%, -.5%
Blue = +.25%, -.25%
Violet = +.1%, -.1%
Gold = +5%, -5%
Silver = +10%, -10%
Step 4: 5 Band Resistor
For a 5 band resistor
1st band = first digit
2nd band = second digit
3rd band = third digit
4th band = number of zeros to be added to the significant digits.
5th band = tolerance rating.
Let us determine the value of this 5 band resistor
http://www.cdxetextbook.com/images/resistorratings_03.jpg
1st band = Orange
2nd band = Orange
3rd band = White
4th band = Black
5th band = Brown
Based on the color codes this resistors value is 339Ω with a tolerance rating of +1% and -1%. This is because of the following;
Orange = 3
Orange = 3
White = 9
Black = 0, so add NO zeros
Brown = +1% or -1%
For more detailed tolerance values
Brown = +1%, -1%
Red = +2%, -2%
Green = +.5%, -.5%
Blue = +.25%, -.25%
Violet = +.1%, -.1%
Gold = +5%, -5%
Silver = +10%, -10%
Step 5: 6 Band Resistor
For a 6 band resistor:
1st band = first digit
2nd band = second digit
3rd band = third digit
4th band = the number of zeros to be added to the significant digits.
5th band = tolerance rating.
6th band = temperature coefficient.
Let us determine the value of this resistor
http://static.electro-tech-online.com/imgcache/1150-013az.jpg
1st band = Orange
2nd band = Yellow
3rd band = Gray
4th band = Red
5th band = Brown
6th band = Red
This resistor has a value of 34800 Ω, which can also be written as 34.8K Ω, and has a tolerance rating of +1%, -1%, and has a temperature coefficient of 50ppm. A resistor with a temperature coefficient of 50ppm means that , for every 1 degrees celcius change in it temperature, it can increase or decrease it total resistance by 50Ω. This is because of the following:
Orange = 3
Yellow = 4
Gray = 8
Red = 2, so add two zeros
Brown = +1%, -1%
Red = 50ppm
Temperature Coefficient Color Values
Brown = 100ppm
Red = 50ppm
Orange = 15ppm
Yellow = 25ppm
The term "ppm" is an abbreviation for "part per million."
For more information on what the term "temperature coefficient" means, click the link below and scroll down to "WHAT DOES THE TERM "PPM/°C" MEAN ?"
http://people.usd.edu/~schieber/psyc770/resistors/r4beginner.html
Step 6: Resistors Under 10 Ohms
For Resistors Under 10 Ohms,
1st band = 1st digit
2nd band = 2nd digit
3rd band = multiplier
4th band = tolerance rating
The colors for the 3rd multiplier band for resistors under 10 Ohms are Gold and Silver.
Gold = multiply by .01
Silver multiply by .1
Exercise 1: Let us determine the value of this resistor
1st band = blue
2nd band = gray
3rd band = gold
4th band = gold
The value of this resistor is .68Ω or 680mΩ. This is because of the following:
1st band = 6
2nd band = 8
3rd band = multiply by .01
4th band = +5%, -5% tolerance rating.
When we multiply 68 by .01, we obtained .68, which when converted in the metric system is 680mΩ.
Step 7: Determine Needed Wattage for Resistor
The physical size of the resistor is directly related to how much wattage it can accomodate. The larger the resistor the more wattage, or the more power it can dissipate. The amount of heat dissipated per unit time is measured in watts.
In order to determine a resistor's wattage we must know the power formula: P = I x E
P = Power
I = Current
E = Voltage
Exercise 1: You have 15Vdc and a 100 Ohm resistor. Determine the wattage needed for the resistor.
First we must determine how much current is in the circuit.
I = V / R
I = 15 / 100
I = .15A
I = 150mA
To get the power let's use the PIE formula.
P = I x E
P = .15 x 15
P = 2.25 watts
So for this circuit you will need at least 2 1/4 watts to 3 watts to prevent the circuit from burning out.
Step 8: Electronics Test Equipments
Basic Electronics Test Equipments
Voltmeter - measures voltage
Ohmmeter - measures resistance
Ammeter - measures current
Multi-meter - measure voltage, current and resistance
Oscilloscope - used to view exact wave shape of an electrical signal
Function Generator - used to generate electrical waveforms or frequency
Power Supply - supplies voltage and current to the circuit
DC Power Supply - supplies DC voltage and current to circuit
AC Power Supply - supplies AC voltage and current to circuit
Step 9: Basics of Wires
Wires have a natural but minimal resistance to current and they can increase or decrease based on their classifications and based on temperature.
Conductors/wires increase in resistance as temperature increases, and it decreases in resistance as temperature decreases. The ideal conductor has zero resistance, however, ideal does not exist.
Superconductivity
The closest to zero resistance can be achieved when a conductor is cooled or exposed to 0 degrees Kelvin or -273 degrees Celcius. Under this condition the resistance in a conductor is virtually close to zero.
Physical Factors Influencing Conductor Resistance
1. The type of material making up the conductor (i.e. copper, bronze, silver, gold)
2. The length of the conductor. When length is longer, resistance is higher.
3. The cross-sectional area of the conductor. When the diameter of a wire is bigger, resistance is lower.
4. The temperature of the conductor. When temperature increases, resistance increases.
To figure out how much resistivity is in a wire, we must know the following formulas:
A = Area in mils, d = diameter in mils
Formula: A = d^2
Exercise 1: The diameter of a wire is 6 mils, find its area in circular mils (CM).
A = 6^2
A = 36 CM
R = resistance in ohms p = resistivity of material per length and cross sectional area in circular mils (CM) l = length in feet
Formula: R = (pl) / A
Exercise 2: What is the resistance of a copper wire that is 100 feet in length and has an area of 20 CM?
Note: p for copper is 10.4 CM-Ω/ft
R = (10.4Ω x 100) / 20 CM
R = 52Ω
Take a look at the wire gauge image provided in this lecture. Notice the holes in the wire gauge where the wire would fit? Above those holes are numbers designated to them. Each hole has a different size. As the number goes higher, the size of the wire gets smaller. Correspondingly as the number goes smaller, the size of the wire gets bigger.
Another important analogy of wire and current flow is a water hose. When the water hose is bigger in diameter, more water can flow through it. Additionally when the water hose is smaller in diameter, less water can flow through it. The same applies to current and wires.
Step 10: The Metric System
The knowledge of the metric system is very important in electronics. When values electrical values are represented in circuits, books, schematics, and tests, the use of the metric system is required. For example, when we know that the total resistance of a circuit is 1000 ohms, we must write it as 1kΩ, writing it otherwise would be unacceptable.
Here are the important metric terms you must remember:
pico - the symbol for pico is p
nano - the symbol for nano is n
micro - the symbol for micro is u
milli - the symbol for milli is m
kilo - the symbol for kilo is k
mega -the symbol for mega is M
giga - the symbol for giga is G
tera - the symbol for tera is T
The number equivalent of the metric terms above
pico = 10^-12 (12 zeros after the decimal) or .000000000001
nano = 10^-9 (9 zeros after the decimal) or .000000001
micro = 10^-6 (6 zeros after the decimal) or .000001
milli = 10^-3 (3 zeros after the decimal) or .001
kilo = 10^3 (multiply by 1 thousand) or 1000
mega = 10^6 (multiply by 1 million) or 1, 000, 000
giga = 10^9 (multiply by 1 billion) or 1, 000, 000, 000
tera = 10^12 (multiply by 1 thrillion) or 1, 000, 000, 000, 000
Exercise 1: Convert 256 thousand ohms to the metric system.
Answer: 256kΩ
This is because kilo is 1,000. So if we multiply 256 x 1000, we get 256, 000.
Exercise 2: Convert .5 ohms to the metric system
Answer: 500mΩ
This is because milli is 3 places after the decimal. So if we move the decimal from .5 three places to the right we get 500.
Exercise 3: Convert .0075 ohms to the metric system.
Answer: 7.5mΩ
This is because milli is 3 places after the decimal. So if we move the decimal from .0075 to the right we get 7.5.
Exercise 4: Convert 10 million ohms to the metric system.
Answer: 10MΩ
This is because mega is 1 million. So if we multiply 10 million by 1 million, we get 10.
Step 11: Electronic Components and Their Schematic Symbols
Electronic Components and Their Function
Battery - provides voltage.
Switch - a device used to break or complete the current path.
Relay - a switch that is designed to trigger another switch.
Circuit breaker - a switch designed to protect an electrical circuit from overload. When the circuit breaker senses an overload in voltage or current it switches off to discontinue electrical flow to the rest of the circuit.
Resistor - produces opposition to current flow. The amount of resistance (resistor value) determines how much current can flow through a resistor.
Potentiometer/Variable Resistor - a resistor whose resistance value is not fixed and can be adjusted.
Capacitor - stores charge and used to filter signal. A capacitors storage capacity can be fixed or adjustable.
Variable Capacitor - a capacitor whose charging capacity is not fixed and can be adjusted.
Inductor - stores energy in a magnetic field and opposes change in current.
Transformer - amplifies or reduces energy.
Transistor - amplifies signal.
Comparator - a device that compares two voltages or currents and switches its output to indicate which is larger.
Operational Amplifier - amplifies output voltage.
NE555 - can be used as a timer, produce pulse or oscillation.
Diode - allows current to pass in one direction while blocking it from passing the opposite direction.
LED (light emitting diode) - a device that produces light.
Varactor Diode - variable capacitor which stores energy and controlled by voltage.
Zener Diode - allows current to pass in the opposite direction after the circuit reaches a certain threshold (for example, it can conduct after voltage reaches -5v).
Photoresistor - light sensing resistor whose resistance decreases as light intensity increases.
Thermistor - a temperature sensing resistor whose resistance increases or decreases based on changes in temperature.
Thryistor - acts as a switch, conducting when it receives current trigger and continues to conduct while it is forward biased.
Darlington Pair Transistors - two transistors connected at the base, which amplifies current twice as much.
Voltage Divider - a strategically placed resistor to decrease the voltage at a certain point of the circuit.
Bridge Rectifier - an arrangement of four or more diodes that can convert AC to DC.
Devices for constructing a circuit:
Breadboard - a board that can be used to construct a circuit which does not require soldering. It has holes where components can be pushed in.
Printed Circuit Board (PCB) - a board that can be used to construct a circuit which requires solodering.
Here is the link for Chapter 3 https://www.instructables.com/id/Electronics-for-Absolute-Beginners-Chapter-3/
