LED Resistance

Resistor Value XXXX Ω
Wattage Recommendation XXXX W


Supply Voltage:


Forward Voltage:


Forward Current:


Number of LEDs:

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LED Resistance Calculator

LEDs are a part of every celebration in our lives. We use them for decoration of our little toy house to huge stage decorations. As we move ahead in this LED resistance calculator post, we will learn many aspects related to LEDs and the calculations associated with them.

What are the LEDs?

Light Emitting Diodes or as they are popularly known, are the diodes that emit light. They are made up of semiconductor components that are responsible for the emission of colored light from them.

Why are semi-conductors chosen for light emission?

Electrons are the basic particles that are behind the energy emission in the form of light. Based on their conductivity, materials are classified into three major categories:

  • Conductors: They fully conduct electricity through them.
  • Insulators: They never allow the flow of current through them.
  • Semi-conductors: They conduct electricity in certain states and do not conduct in the remaining states.

The advantage with semi-conductors is we can regulate the amount of their electricity flow by controlling their doping concentrations and their working temperature.

One of such devices that work on the principle of semi-conductors is Diode. A main advantage of diodes is that they conduct only in one direction and do not conduct in the other.

Why diodes emit light?

Diodes contain free electrons and holes. When energized through a source of electrical energy, electrons fall into holes, and they lose their energy in the form of packets called photons, which is nothing but the light that we see. The wavelength of the light thus emitted depends on the energy lost by the electrons, which is determined by the type of the semiconductor material.

Thus, in an LED, electrical energy is converted into light energy.

This phenomenon by which an LED emits light under the influence of external electrical energy is known as electroluminescence.

Why different LEDs emit different colors of light?

As mentioned, the energy lost by an electron depends on the type of semiconductor used. For example:

  • Silicon and Germanium diodes emit energy in the form of heat.
  • Gallium arsenide phosphide and Gallium phosphide semi-conductors emit energy in the form of light.

Besides, there exists a relation between the color of the light emitted and the type of semiconductor too:

  • Red light – phosphorous
  • Greenlight – Gallium phosphide
  • Yellow and orange light – Aluminium indium gallium phosphide

LEDs are also made up of other semiconductor materials such as zinc selenide, gallium nitride, silicon carbide, gallium arsenide.

Why do LEDs need resistors?

LED resistors are required for limiting current generated within a LED. This is necessary as:

The relation between the input voltage and current generated in a diode is exponential. Any change in the input voltage can result in a large amount of current being generated in the LED. This can often damage the LED itself. Hence, a resistor is added prior to the LED in a circuit.

A resistor is chosen because:

For a resistor, the relation between the input voltage and the generated current is always linear, as per ohm’s law. Hence, connecting a resistor before a LED ensures that a safe amount of current is allowed to be input into the LED.

Note: On their own, LEDs do not have resistance. Hence when you connect a resistance and LED in a circuit, the overall resistance is the value of the resistors that are present in the circuit.

What is the formula for calculating the value of the LED resistor?

The value of the resistor that has to be connected across a LED depends on the following factors:

  • Supply voltage, Vs
  • Forward Current (If) of LED, which is the maximum current that can safely pass through the LED
  • Forward voltage (Vf) of LED, which is the voltage drop across the LED when it is subjected to the rated forward current (If)

The number (n) of LEDs connected in series or parallel in the entire circuit. Thus:

The value of LED resistor R = ( Vs – Vf ) / If , when there is a single LED in the circuit.

In case LEDs are connected in series, then the value of LED resistor is R = ( Vs – (Vf x n ) ) / If

In case LEDs are connected in parallel, then the value of the LED resistor is R= ( Vs – Vf ) / ( If x n )

What are the types of LEDs?

Based on their electrical properties, broadly three types of LEDs are identified:

  • High power LEDs: They work on currents in the range of hundreds of milli-amperes to an ampere or above.
  • Miniature LEDs: They work at around 2 milli-amperes.
  • AC driven LEDs: They are the latest in the market and can run on AC without the need for DC conversion.

What are the advantages and disadvantages of LEDs?

  • LEDs can run on very low voltage and current. Approximately, 1 to 2 volts and 5 to 20 milliamperes are sufficient for the working of LEDs.
  • They are small, portable and light in weight.
  • They are available in a wide range of colors and shapes.
  • They do not emit ultraviolet light.
  • They are rugged and can withstand vibrations and shock.
  • Their efficiency and reliability are high.
  • They emit less heat compared to other types of bulbs.
  • They need lesser wiring and low maintenance.
  • Their brightness and intensity levels are high.
  • They are easily programmable and controllable.
  • Their lifespan is more than 20 years.
  • They do not need much warm-up time and are provide instant lighting.

However, care should be taken that they are not subjected to excess input voltage or current. Else, they get damaged very easily.

What are the applications of LEDs?

Since their invention, LEDs have grown in their efficiency and output drastically due to the advancement in technology. Besides being used in decoration lamps and traffic signals, LEDs today are practically being used in many applications:

  • Building architecture and facades
  • Interiors for offices, hotels, malls, etc.
  • Industrial purposes
  • Health care
  • Street lighting and outdoor lighting
  • Residential lighting
  • Horticultural lightning

How CalculatorHut’s online free LED resistance calculator helps you?

CalculatorHut is a hub of online free calculators. It contains 100+ online free calculators under many categories: scientific, health, and other calculators. These are designed to make calculations easy for you.

LED resistance calculator is one of the 100+ free online calculators of CalculatorHut. It is specifically designed to make LED resistance calculation simpler for you. All that you need to do is pick the color of LED that you wish, give the values of other parameters in the spaces provided. You can instantly find the value of the resistor that you need to choose for the respective circuit design.

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