LEDs today have found application in almost all areas of human activity. But despite this, for most ordinary consumers it is completely unclear, thanks to what and what laws apply when LEDs work. If such a person wants to arrange lighting through such devices, then a multitude of questions and finding solutions to problems cannot be avoided. And the main question will be  "What kind of thing is this  resistors, and why do they need LEDs?"
Content

1 What is a resistor and its purpose?
 1.1 Video: Why do we need resistors

2 Connection Diagrams
 2.1 Video: Parallel LED connection

3 Calculation of resistors for LEDs
 3.1 Video: Resistor Selection for LED
 4 Calculation of resistors using a special calculator
What is a resistor and its purpose?
Resistor is one of the components of the electrical network, characterized by its passivity and, at best, different indicator of resistance to electric current. That is, at any time, Ohm’s law must be valid for such a device.
The main purpose of the devices is the ability to vigorously resist electric current. Thanks to this quality,
What is the use of resistors in the case of a LED lighting device?
Most consumers know that an ordinary incandescent bulb gives light when it is directly connected to any power source. The lamp can work for a long time and burns out only when, because of the application of too high voltage, the incandescent thread is excessively heated. In this case, the bulb, in some way, realizes the function of a resistor, because the passage of electric current it is difficult through it, but the higher the applied voltage, the easier it is for the current to overcome the resistance light bulbs. Of course, it is impossible to put such a complex semiconductor part as a LED and an ordinary incandescent bulb in one row.
It is important to know that the LED  it is such an electrical device, for the operation of which it is preferable not the current itself, but the voltage available in the network. For example, if the voltage of 1.8 V is chosen by such a device, and 2 V comes to it, then, most likely, it will burn out  if the voltage is not reduced in time to the level required by the device. It is for this purpose that a resistor is required, by means of which stabilization of the used power source is carried out so that the voltage supplied by it does not destroy the device.
In this regard, it is extremely important:
 decide what type of resistor is required;
 determine the need to use an individual resistor for a particular device, which requires calculation;
 take into account the type of connection of light sources;
 The planned number of LEDs in the lighting system.
Video: Why do we need resistors
Connection Diagrams
With a consistent arrangement of LEDs, when they are placed one by one, usually one resistor is enough, if it is possible to correctly calculate its resistance. This is explained by the electric circuit has the same current, in each installation site of electrical appliances.
But in the case of a parallel connection, each LED requires its own resistor. If we neglect this requirement, then all the voltage will have to pull one, the socalled "limiting" LED, that is, the one that needs the lowest voltage. is he too fast will failIn this case, the voltage will be supplied to the next device in the circuit, which similarly suddenly fails. Such a turn of events is unacceptable, therefore, in the case of parallel connection of any number LEDs require the use of the same number of resistors whose characteristics are matched by calculation.
Video: Parallel LED connection
Calculation of resistors for LEDs
With proper understanding of the physics of the process, the calculation of the resistance and power of these devices cannot be called an impossible task that an ordinary person cannot cope with. To calculate the required resistance of resistors, it is necessary to take into account the following points:
 special markings present on the devices usually show not the required supply voltage, but the voltage chosen by the LED for its operation, that is, the drop voltage. This numerical value is used to calculate the determination of the minimum required voltage or for the selection of power resistors;
 the numerical value of the voltage across the resistor is defined as the difference between the supply voltage of the LED and the voltage of the unit;
 the value flowing through the current resistor is obtained by dividing the residual voltage on the device by the value of its resistance;
 To calculate the required resistance, the residual voltage should be divided by the current required for the smooth operation of the system.
Video: Resistor Selection for LED
Calculation of resistors using a special calculator
Usually, the calculation of the resistance of such devices, required for any LED, is made by means of specially designed for these purposes calculators. Such calculators, convenient and highly efficient, do not need to be downloaded and installed from somewhere  it is quite possible to calculate the resistor online.
Resistor Calculator allows with high accuracy determine the required power and resistance value of the resistor installed in the LED circuit.
To calculate the required resistance, you need to add the following lines to the corresponding lines of the online calculator:
 LED supply voltage;
 LED rated voltage;
 rated current.
Next, you need to select the used connection scheme, as well as the required number of LEDs.
After pressing the corresponding button, the calculation is performed and The resulting calculated data is displayed on the monitor.With which you can in the future without much difficulty to organize an artificial LED lighting.
Also in online calculators there is some database containing data on LEDs and their parameters. Presented the possibility of calculation:
 the value of the device;
 color marking;
 consumed by the current circuit;
 power dissipation.
A person who is not well versed in electrics and physics, in most cases will not be able to independently calculate devices for LEDs. For this reason, the calculations using a functional and convenient online calculator  invaluable help for ordinary peoplewho do not own the methodology of calculations using physical formulas.
Most wellknown manufacturers of LEDs and ribbons based on them are on their official websites. Spread and own online calculator, with which you can not only pick up the required resistors and LEDs, but also calculate the parameters used current devices in different operation modes with variable values of current, temperature supplied voltage, etc.