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LEDs Test, LEDs design and How do LEDs work[FAQ&Video]

Author: Apogeeweb
Date: 17 Oct 2022
LED materials

What is a LED?

Video related to LED

LED Colours and materials

How do LEDs work?

Types of Leds

Calculating LEDs resistor value

How to Test LED Lights

The warning of LEDs use


What is a LED?

LED = Light Emitting Diode. An LED must be prevented against transferring too much current because its electrical behavior differs significantly from that of a light. Typically, this is done by connecting a resistor in series with the LED. Never attach an LED directly to a power source or battery.

LEDs must be wired in the proper direction; the diagram may be labeled with the letters an or + for the anode and k or - for the cathode (yes, it really is k, not c, for cathode). In the case of spherical LEDs, the cathode is the short lead and there may be a slight flat on the body. Although the cathode is the larger electrode within the LED if you can see it, this is not a recognized method of identification.



Video Description: This video is mainly talk about how to design LED circuits, how to calculate resistor size, how to protect LED, how long will a battery power a circuit, how to calculate resistor power rating, how to connect LED and much more.


LED Colours and materials

The semiconductor material, not the coloring of the "package," determines the color of an LED (the plastic body). All colors of LEDs are available in uncolored, diffused (milky), or clear (commonly referred to as "water clear") packaging. The colored packaging is also offered in diffused (the typical type) and clear forms. White and blue LEDs could cost more than the other colors.

Color Wavelength (nm) Voltage Drop (V) Semiconductor Material
Infrared > 760 < 1.9 Gallium Arsenide
Infrared > 760 < 1.9 Aluminium Gallium Arsenide
Red 610 - 760 1.6 -2.0 Aluminium Gallium Arsenide
Red 610 - 760 1.6 -2.0 Gallium Arsenide Phosphide
Red 610 - 760 1.6 -2.0 Aluminium Gallium Indium Phosphide
Red 610 - 760 1.6 -2.0 Gallium Phosphide
Orange 590 - 610 2.0 -2.1 Gallium Arsenide Phosphide
Orange 590 - 610 2.0 -2.1 Aluminium Gallium Indium Phosphide
Orange 590 - 610 2.0 -2.1 Gallium Phosphide
Yellow 570 - 590 2.1 -2.2 Gallium Arsenide Phosphide
Yellow 570 - 590 2.1 -2.2 Aluminium Gallium Indium Phosphide
Yellow 570 - 590 2.1 -2.2 Gallium Phosphide
Green 500 - 570 1.9 -4.0 Gallium Indium Phosphide
Green 500 - 570 1.9 -4.0 Aluminium Gallium Indium Phosphide
Green 500 - 570 1.9 -4.0 Aluminium Gallium Phosphide
Green 500 - 570 1.9 -4.0 Indium Gallium Nitride
Blue 450 - 500 2.5 -3.7 Zinc Selenide
Blue 450 - 500 2.5 -3.7 Indium Gallium Nitride
Blue 450 - 500 2.5 -3.7 Silicon Carbide
Blue 450 - 500 2.5 -3.7 Silicon
Violet 400 - 450 2.8 -4.0 Indium gallium Nitride
Purple multiple types 2.4 -3.7 Dual Blue/Red LEDs
Purple multiple types 2.4 -3.7 Blue with Red Phosphor
Purple multiple types 2.4 -3.7 White with Purple Plastic
ultraviolet < 400 3.1 -4.4 Diamond
ultraviolet < 400 3.1 -4.4 Boron Nitride
ultraviolet < 400 3.1 -4.4 Aluminium Nitride
ultraviolet < 400 3.1 -4.4 Aluminium Gallium Nitride
ultraviolet < 400 3.1 -4.4 Aluminium gallium Indium Nitride
Pink multiple types 3.3 Blue with phosphor
Pink multiple types 3.3 Yellow with Red, Orange or Pink phospor
Pink multiple types 3.3 White with Pink pigment
White Broad spectrum 3.5 Blue/UV diode with Yellow Phosphor


How do LEDs work?

A P-type semiconductor (which has a higher hole concentration) and an N-type semiconductor are combined to create LEDs, which are semiconductor light sources (larger electron concentration). The P-N junction's electrons and holes will join once more when a strong enough forward voltage is applied, releasing energy in the form of light.

LEDs (Light Emitting Diodes) transform electrical energy directly into light as opposed to conventional light sources, which first convert electrical energy into heat before turning it into light. This results in efficient light creation with minimal electricity waste.

LEDs Emit Light


Types of Leds

Dual In-Line Package (DIP) LEDs:

The first LED chips were DIP ones, which are what most people think of when considering LED lights. Despite being more established than its more recent counterparts, DIP LED chips are still in use and are more frequently seen integrated into electronics because of their small size. However, they are not very strong and can only provide a small amount of brightness.



Surface Mounted Diode (SMD) LEDs:

These are likely the most popular sort of LED chip available; they are installed and soldered onto the circuit board. They are more adaptable when it comes to encasing them within smaller electronics or across other forms of lighting, such as strip lighting, because they are brighter than their DIP counterparts and are also smaller. Three diodes can fit on a single SMD chip, allowing you to produce a variety of colors and provide customers more options. The LED market has undergone this significant progress. SMD 3528 and SMD 5050, both of which measure 5mm in width, are the two most used SMD chip sizes.



Chip on Board (COB) LEDs:

The most recent advancement in LED technology is represented by these chips. Out of the three, COB LED chips are the brightest since they can frequently fit nine or more diodes onto a single chip. In what ways does this affect LED lighting? First off, it increases lighting efficiency by improving brightness-to-energy output. They can therefore be utilized with a variety of various lighting types. However, it's important to keep in mind that a COB LED chip's circuitry prevents it from emitting a wide variety of colors.



Calculating LEDs resistor value

To limit the current flowing through an LED, a resistor must be connected in series with the LED; otherwise, the LED will burn out fairly immediately. R, the resistor's value, is determined by:

R = (VS - VL) / I

R = resistor value in ohms (ohm).

VS = supply voltage.

VL = LED voltage (2V, or 4V for blue and white LEDs).

I = LED current in amps (A)


The LED current needs to be lower than what your LED is capable of handling. Since the The maximum current for typical 5mm diameter LEDs is frequently 20mA; however, many circuits can work with 10mA or 15mA. Divide the mA current by 1000 to convert it to amps (A) for the calculation.

If the projected value is unavailable, pick the nearest larger standard resistor value so that the current will be a little less than what you chose. If you choose a higher resistor value to reduce the current, the LED will be less bright (for example, to extend the battery life).

The color of the LED affects the voltage VL of the LED. The voltage of red LEDs is the lowest; yellow and green have a somewhat higher value. The highest voltages are used in blue and white LEDs. You can use 2V for red, yellow, and green LEDs and 4V for blue and white LEDs for the majority of applications where the precise value is not crucial. According to Ohm's law, the resistor's resistance, R = V/I, is determined by:

V = voltage across the resistor (= VS - VL in this case) I = the current through the resistor

So R = (VS - VL) / I

Resistor Value


How to Test LED Lights

Step One: Use a Multimeter

Get a digital multimeter with a diode reading capability. Simple multimeters only measure voltages, amps, and ohms. A multimeter with a diode setting is required to test LED lighting. Mid-range to high-range multimeters, which are more likely to offer this capability than affordable versions, can be found online or at your neighborhood hardware store.



Step Two: Connect the black and red test leads

To the outlets on the front of the multimeter, attach the red and black test leads. The positive charge is in the red lead. The input marked "COM" should be connected in with the black lead, which is the negative.

Multimeter Connect


Step Three: Select the diode setting on the multimeter's dial

To move your multimeter's front dial from the "off" position, turn it clockwise. Up till you reach the diode setting, keep twisting it. The diode setting may be represented by the diode circuit symbol if it is not labeled explicitly. The cathode and the anode of a diode are both visually represented by the diode symbol. In this digital multimeter dial picture, we need to set the multimeter’s dial on 14 to test diode.

Multimeter dial


Step Four: The red probe should be connected to the anode and the black probe to the cathode

The cathode end of the LED, which is typically the shorter prong, should be touched with the black probe. The red probe should then be pressed against the anode, which is the longer prong. Ensure that the black probe is connected before the red probe because doing so can result in inaccurate readings. During this test, be sure the cathode and anode are not in contact with one another since this could prevent electricity from flowing through the LED light and affect your results. Throughout the test, the red and black probes must not come into contact. After making the connections, the LED ought should turn on.

Diode test


Step Five: Verify the reading on the digital multimeter display

A healthy LED light should show a voltage of about 1600 mV when the probes are in contact with the cathode and anode. If during the test there is no reading displayed on your screen, repeat the procedure to ensure that the connections were completed correctly. This can indicate that the LED light isn't functioning if the test was done correctly. The transformer needs to be changed if your supply does not provide any output voltage. LED lights need to be replaced if there is voltage present at the output.


The warning of LEDs use

In general, it is not a good idea to connect multiple LEDs in parallel with just one resistor shared between them. Only the lowest voltage LED will light if the other LEDs require slightly different voltages, and the higher current running through it could damage the other LEDs. One resistor can be used to successfully link identical LEDs in parallel, but since resistors are so inexpensive and the current utilized is the same as connecting the LEDs separately, this rarely provides any significant benefit.

LEDs in parallel

Instead, we should do as follows: Connecting LEDs in series

Connecting LEDs in series



What can the LEDs be applied to?

LEDs (Light Emitting Diodes) are mostly used to illuminate items and even spaces. Due to its small size, low energy consumption, long lifespan, and versatility in terms of use in many applications, it is applied everywhere. LED usage and applications include TV backlighting.


How many types that LEDs own?

Fundamentally, LED lighting uses three major forms of LED technology: DIP, SMD, and COB.


What is LED and how it works?

When an electric current passes through a semiconductor device called a light-emitting diode (LED), the LED emits light. When current flows through an LED, the electrons and holes recombine and produce light.


How long do LED lights last?

The longer lifespan of LED lighting fixtures is one of its main benefits. The most durable LED light fixtures have been evaluated to survive as long as 100,000 hours, whereas incandescent light bulbs were designed to last roughly 1,000 hours. On average, LED light bulbs last at least 20 years before needing to be replaced.


Which is not a benefit of LED?

On a capital cost basis, LEDs are now more expensive (price per lumen) than the majority of conventional lighting solutions.

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