resistor

Basically all the material has a resistive nature, but some materials such as copper, silver, gold and metal materials generally have very little resistance. The material is well deliver an electric current, so called a conductor. The opposite of a conductive material, ie material such as rubber, glass, carbon has a greater resistance to withstand the flow of electrons so it is referred to as an insulator.
Resistors are the basic components of electronics are always used in every electronic circuit that can function as a regulator or to limit the amount of current flowing in a circuit. With a resistor, electrical current can be distributed according to need. As the name implies is resistive resistor and is generally made of carbon materials. Unit resistance of a resistor is called Ohm or represented by the symbol Ω (Omega).
In the electronic circuit, resistors are denoted with the letter "R". Judging from the material, there are several types of resistors in the market include: Carbon Resistor, wirewound, and Metalfilm. There is also a resistor that can be changed resistance value, among others: Potentiometer, Rheostat and Trimmer (trimpot). There was also a resistor that changes its resistance when exposed to light called LDR (Light Dependent Resistor) and resistor resistance value will increase in size when exposed to hot temperatures whose name PTC (Positive Thermal Coefficient) resistor and a small resistance value will increase when exposed to temperatures whose names are hot NTC (Negative Thermal Coefficient).
For the types of carbon resistors and metalfilm typically used color codes to guide the value of resistance (resistance) of the resistor. This resistor has a shape like a tube with two legs on the left and right. In the body there is a circle form a ring color code, the code is great to know without having to measure the magnitude of the resistance with ohmmeter. The color code is the manufacturing standards issued by EIA (Electronic Industries Association) as shown in Table 1.1.

Table 1.1 The color of the ring resistor

Scale resistance of a resistor is read from the most forward position of the ring toward the tolerance ring. Usually the tolerance ring is in position on the resistor body that most corner or even with the width of the more prominent, while the position of the first ring is a bit inward. Thus the user is immediately aware of how much tolerance resistor. If we have been able to determine where the first ring next is to read the resistance value.
Number of rings which are generally circular in accordance with a large resistor tolerance. Usually the resistor with a tolerance of 5%, 10% or 20% have 3 rings (not including the tolerance ring). But the resistor with a tolerance of 1% or 2% (small tolerance) has 4 rings (not including the tolerance ring). The first ring and so on successively demonstrated great value unit, and the last ring is pengalinya factor.
For example a resistor with a ring of yellow, violet, red and gold. Gold-colored ring is the ring of tolerance. Thus the ring resistor color sequence is, the first ring of yellow, violet colored and the second ring to the three red rings. Ring to a four-colored gold is a tolerance ring. From table 1.1 note if golden ring of tolerance, it means that this resistor has a tolerance of 5%. Resistance value calculated in accordance with the order of the color. The first is to determine the unit value of this resistor. Since this resistor resistor 5% (which usually has three rings in addition to tolerance rings), then the value of the units is determined by the first ring and second ring. Still from Table 1.1, note the yellow ring and ring value = 4 value = violet 7. So the first and second rings or yellow and violet respectively, the unit is 47. The third ring is a multiplier, and if the color red ring means pengalinya factor is 100. So with this known resistor value is the value x multiplier units or 47 x 100 = 4700 K Ohm = 4.7 Ohm (in electronic circuits are usually written 4k7 Ohm) and the tolerance is + 5%. The meaning of tolerance itself is a restriction of minimum and maximum resistance value which is owned by the resistor. So the true value of 4.7 k Ohm resistor + 5% is:
4700 x 5% = 235
Thus,
Rmaksimum = 4700 + 235 = 4935 Ohm
Rminimum = 4700 - 235 = 4465 Ohm
If the resistor on the measure using an ohmmeter and its value in the range of maximum and minimum value (4465 s / d 4935), the resistor was still meet the standards. The value of tolerance is provided by the manufacturer of resistors to anticipate the characteristics of a material that is not the same between one resistor with another resistor so that the electronics designers can estimate the tolerance factor in their design. The smaller the tolerance value, the better the quality of the resistor. So that the market value of tolerance resistors have 1% (eg resistors metalfilm) is much more expensive than resistors having tolerances of 5% (carbon resistor)
Other specifications to consider in choosing a resistor on a draft of the resistance is greater than his or watts maximum power that is able to hold the resistor. Because the resistors in aliri working with electric current, there will be a power dissipation of heat for: 

 

The greater the physical size of a resistor, may indicate the greater ability of the resistor power dissipation. Generally available in the market size of 1 / 8, 1 / 4, 1 / 2, 1, 2, 5, 10 and 20 watts. Resistor which has a maximum power dissipation of 5, 10 and 20 watts are generally elongated rectangular-shaped beam of white, but some are cylindrical and are usually for large size of this resistor the resistance value in the direct print dibadannya shaped rings are not color, for example 100Ω5W or 1KΩ10W.

Judging from its function, the resistor can be divided into:

    * Fixed Resistors (Fixed Resistors)
That resistor whose value can not be changed, so it always remains (constant). This resistor usually made from nikelin or carbon. Serves as a voltage divider, regulate or limit the current in a circuit as well as enlarging and reducing stress.

    * Not Fixed Resistor (variable resistor)
That is the resistor whose value can change by shifting or rotating the toggle on the tool, so that the resistor value can be set according to need. Functioning as a volume control (adjust the size of the current), tone control on the sound system, high and low tone control (bass / treble) and serves as a voltage divider current and voltage.

    * NTC and PTC resistors.
NTC (Negative Temperature Coefficient), a resistor whose value will grow smaller when exposed to hot temperatures. While the PTC (Positive Temperature Coefficient), the resistor whose value will be greater when the temperature cools.

    * Resistor LDR
LDR (Light Dependent Resistor) are the type of resistor that changes its resistance due to the influence of light. When exposed to black light the greater the value of his prisoner, when exposed to bright light while the value becomes smaller.

    * The series of resistors
In practice, the designers sometimes need a resistor with a certain value. However, the resistor values ​​are not in the shop, even the factory itself does not produce it. Solution to get a resistor with resistance values ​​that can be done uniquely by assembling several resistors so we get the required resistance value. There are two ways to couple the resistor, namely:
1. Serial Method
2. Parallel Method
The series of resistors in series will result in larger total resistance value. Below is an example of resistors arranged in series.

 Series resistor in the circuit applies the formula: 

While the series of resistors in parallel will result in a replacement value of the smaller resistance. Below are examples of resistors arranged in parallel

In a parallel resistor circuit applies the formula: 

3. Standard resistor values
Not all resistance values ​​are available on the market. Table 1.2 is an example table standard resistor value in the market. Data on the resistors on the market can be obtained from the Data Sheet issued by the manufacturer of resistors.

Below are some formulas (Ohm's Law) which is often used in the calculation of electronics: 

Where:
V = voltage measured in Volts
I = current measured in amperes
R = resistance measured in Ohms
P = power measured in Watts
Conversion unit:
1 Ohm = 1 Ω
1 K Ohm = 1 K Ω
1 M Ohm = 1 M Ω
1 K Ω = 1.000 Ω
1 M Ω Ω = 1,000 K
1 M Ω = 1,000,000 Ω
(M = Mega (106); K = Kilo (103)

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