LAPTOP ,DESKTOP ,LED/LCD,TABLET PC CHIP LEVEL SERVICING TUTORIALS: Basics: Resistors

1. The concept of resistance.

Resistance is What I understand simple - resistance is the resistance of a power line conductor, if a good conductor of electricity, the resistive small, poor electrical conductor, the greater the resistance, electrical insulators, the resistance is extremely large.

Resistance of wires:
wire resistance of rice on the material side, and the length of the wire cross section. is calculated as follows:

R = ρ.L / S

In which ρ is the resistivity of the material depends on

L is the length of the wire

S is the cross-wires

R is the resistance unit is Ohm

2. Resistance in electronics.

a) Form and sign: In the electronics resistor is an important component , they are made from carbon and metal compounds, depending on the mixing ratio that we create the type of resistor value different.

The shape of the resistor in electronics.

The symbol of the resistance on the principle diagram.

b) The unit of resistance

Resistance unit is Ω (Ohm), KΩ, MΩ

1KΩ = 1000 Ω

1MΩ = 1000 K = 1,000,000 Ω Ω

b) The stated value of the resistor

The smaller resistance values are recorded in the stripe by a general convention of the world. (See above)

The resistance is larger than from 2W or more often written directly on the relative values. For example, the capacity of resistance, resistance porcelain.

Back export porcelain of great value are recorded directly.

3. How to read resistor values.

International conventions on color

Colour	Value	Colour	Value
Black	0	Green	5
Brown	1	Blue	6
Red	2	Purple	7
Oranges	3	Gray	8
Gold	4	White	9
		Golden Maiden	-1
		Silver Maiden	-2

Resistance is often denoted by four round color, precision resistors are denoted by the five colored rings.

* How to read resistor values 4 ring color:

4 How to read resistor color ring

Round 4 of the ring at the end there is always color as gold or silver, this is only within the error of resistance, when we ignore the value read loop.

Faced with the last round is round 1, next to the second round, No. 3

Round No. 1 and No. 2 is within tens and units

Round 3 is a multiple of the number 10.

Value = (first round) (round 2) x 10 ^{(3 caps)}

Can be calculated within the three is the number zero "0" added

Sample as the only error in the first round or the third round if the round number 3 as the exponent of the number 10 is negative.

* How to read resistor values within five colors: ( precision resistor )

Round No. 5 is the last round, the ring recording errors, or 5 round color is the color error of many colors, thus making it difficult for us to determine what is diinh final round, but the last round is always a gap a little further.

For the last round is a round number

Similar to reading more of four rings of color, but here the fourth round of a multiple of 10, round 1, No. 2, No. 3, respectively hundreds, tens and units.

Value = (first round) (round 2) (3) x 10 ^{(caps round 4)}

Maybe the ring number 4 is the number zero "0" added

4 - Practice reading resistor values.

The resistance of different colors in the 3rd round

When the resistance of different colors in the 3rd round, then we see multiple colors within this color often changes from silver to green, the equivalent resistance <1 MΩ Ω to the row.

The resistors have colored rings 1 and 2 change.

In the figure above is the resistance value of our common practice, when the third round color change, the resistance value in increments of 10.

Exercise - You guessed quickly before the answer values appear, when all the values that you guess correctly before the results appear to be in your knowledge that this was okay!

Exercise - Guess the results of the resistance value.

5 - The common resistor values.

I can not get a resistor of any value, the manufacturer only offers about 150 kinds of common resistor values, the table below are the colors and values of common resistance.

The common resistance value.

6 -. Classification of resistance.

Resistance often: Resistance usually has a small resistance from 0.125 W to 0.5 W

Resistance of production : The resistors have a larger capacity of 1W, 2W, 5W, 10W.

Resistor, heat : The calling of the capacity of resistance, this resistance ceramic casing, heat when operating them.

The resistance: 2W - 1W - 0.5 W - 0.25 W

Resistor or heating

7 - Power of the resistor.
When you have a resistor in the circuit, the resistor itself consumes a capacity of P calculated by the formula

P = U. I = U ² / R = I ² . R

According to the formula above we can see, the consumption of the resistor depends on the electric current through the resistor or voltage dependent resistors on both ends.

Power consumption of the resistor is completely calculated before you put the resistor in the circuit.

If you bring a resistor has a nominal production capacity of less than it would consume the resistance to fire.

Usually a resistor mounted on the circuit have nominal capacity of> = 2 times the production that it will consume.

Fire Resistance due to the production

The diagram above shows: source Vcc is 12V, the resistor has a value of 120Ω, but have different origins, when the switches K1 and K2 closed, the resistors have a capacity of consumption is

P = U ² / R = (12 x 12) / 120 = 1.2 W

When K1 is closed, the resistor has a production capacity of greater than consumption, so the resistor does not burn.

When K2 is closed, the resistor has a smaller production capacity of consumption, resistance to fire.

8 - Turn back, philosophical pressure
or variable resistor is adjustable to change the value, is denoted by VR are shaped as follows:

Shape variable resistor on the schematic symbol

Rheostat generally assembled in the factory for repair and calibration of the technician, or a structure variable as shown below.

The construction of a rheostat

Pressure Philosophy: Philosophy pressure similar but more variable resistor to adjust and often arranged in front of the machine for the user to adjust. For example - Philosophy Pressure Volume, Bass applied philosophy, etc. Treec. , Philosophy applied philosophy that is a part of the input voltage depending on the severity adjustment.

Symbols philosophical principles applied on the diagram.

Shape Design philosophy in philosophy applied pressure

9 - resistors connected in series.

Resistor connected in series.

The resistor in series with the equivalent value of the resistor elements combined. RTD = R1 + R2 + R3

Current flowing through the resistor connected in series have equal value and equal to I I = (U1 / R1) = (U2 / R2) = (U3 / R3)

From the above formula shows that the pressure drop over the resistor connected in series proportional to the value dient back.

10 - resistors in parallel.

Resistors in parallel

The resistor in parallel with RTD equivalent value is calculated by formula (1 / RTD) = (1 / R1) + (1 / R2) + (1 / R3)

If only two resistor circuit parallel to the
RTD = R1.R2 / (R1 + R2)

Current flowing through the parallel resistance is inversely proportional to the resistor value. I1 = (U / R1), I2 = (U / R2), I3 = (U / R3)

The voltage on the resistors in parallel are equal

11 - Crazy or mixed questions

Resistors get mixed.

Higher resistance of resistors to create a more optimal.

For example, if you need a resistor 9k we can get two 15K resistors in parallel then in series with a 1.5 K resistor.

12 - Application of the resistor
resistance is ubiquitous in the electronics and such resistance is an important component indispensable, in the circuit, the resistor has the following effects:

To control the current through load accordingly, for example a 9V bulb, but have only 12V, it can be connected to the lamp with the resistor to reduce voltage drop on resistor 3V.

Connect with a light resistance.

- As shown above we can calculate the value of the resistor and accordingly as follows: lamp voltage is 9V and the current consumption of 2W so that I = P / U = (2 / 9) = amperes which is also the current through the resistor.
- As power is 12V, 9V bulbs should drop on R is 3V so we infer that the resistance to find R = U / I = 3 / (2 / 9 ) = 27 / 2 = 13.5 Ω
- Power consumption of the resistor is: P = UI = 3. (2 / 9) = 6 / 9 W, so we have to use resistors with a capacity of P> 6 / 9 W

Getting power to become a distribution pressure to obtain a desired voltage from a voltage to the front.

Demand for the pressure distribution voltage U1 discretion.

From 12V on demand distributed application through R1 and R2 we get the voltage U1, U1 pressure depends on the value of two resistors R1 and R2.theo formula.

U1 / U = R1 / (R1 + R2) => U1 = U.R1 / (R1 + R2)

Change the value of R1 or R2 will get the desired voltage U1.