What is LED?
LED is an abbreviation for a light-emitting diode. An LED is an electronic light source. A diode is not a light bulb. Traditional incandescent light bulbs heat tungsten filaments until they glow, like a toaster heating element. These filaments gradually evaporate until they break and burn out.
LEDs work on a totally different premise, similar to transistors or other electronics along those lines. There is no filament to burn out. They’re also a much more efficient light source, producing considerably more light per watt than a traditional bulb. Most LEDs are about 2/10 of an inch in diameter and about 1/3 of an inch in length. Whereas typical household lamps require 120 volts, an LED uses just two or three volts. What’s more, typical household lamps are rated for 1,500 to 2,000 hours while LEDs can last 100,000 hours or more.
How Light Emitting Diodes Work?
Light emitting diodes, commonly called LEDs, are real unsung heroes in the electronics world. They do dozens of different jobs and are found in all kinds of devices. Among other things, they form the numbers on digital clocks, transmit information from remote controls, light up watches and tell you when your appliances are turned on. Collected together, they can form images on a jumbo television screen or illuminate a traffic light.
Basically, LEDs are just tiny light bulbs that fit easily into an electrical circuit. But unlike ordinary incandescent bulbs, they don’t have a filament that will burn out, and they don’t get especially hot. They are illuminated solely by the movement of electrons in a semiconductor material, and they last just as long as a standard transistor.
In this article, we’ll examine the simple principles behind these ubiquitous blinkers, illuminating some cool principles of electricity and light in the process.
Why use LED drivers?
Traditionally LED bulbs have been driven using series resistance, this usually works okay if there are no external loads applied to the circuit which may affect it. If an external heavy load is applied when an LED bulb is running, for example, as the compressor or pump switch is turned on the current and the voltage immediately decrease. These dips in voltage and current seriously affect the lifetime of the LED bulb. Examples of heavy inductive loads include swimming pool pumps and large refrigerators and these can cause traditional incandescent and halogen bulbs to fail at times.
However, constant current LED drivers have a small integrated circuit incorporated which sense any voltage variations within the lighting circuit and will automatically compensate for any losses.
LED bulbs are infinitely more susceptible to current and voltage spikes due to their low start-up demand.
Low battery voltages can cause heat build-up due to increased resistance and high voltages can cause the LED to overdrive risking premature failure or dimming.
Also in the manufacturing process, there are sometimes minute variations in the chemical substrate, this can cause fluctuations in current demand.
Temperature is also a serious consideration in that it is hard to control without proper current regulation.
As current increases, the temperature correspondingly rises.This can cause the voltage to rise across the junction leading once again to early failure if not properly regulated.
How long do LEDs generally last?
The industry standard for LED is around 50,000hrs. As all things do, they will degrade initially up to 10% over the first 1,000hrs of operation followed by a slower rate of decline to 30% loss after 50,000 hrs. Commercially available LEDs are generally blue LEDs with a fluorescence applied to them and it’s the fluorescence that degrades not the chip/diode itself. It also depends if the LEDs are being “driven” hard or voltage is variable. The types of commercial dome-type LEDs available these days are called “static sensitive” and can be badly affected by variations in voltage and current – that’s why they’re okay on batteries (if not run too low) but sensitive to other forms of power like 240vAC/12vAC transformers.
How long is 100,000 hours?
Based on how long a fixture is illuminated per day, here’s what 100,000 hours works out to:
24 hours a day – 11.4 years
18 hours per day – 14.8 years
12 hours per day – 22.8 years
8 hours per day – 34.2 years
Why is the life span of an LED measured as lumen depreciation?
The life span of an LED is vastly longer than that of incandescent, fluorescent or HID lamp sources, generally lasting 50,000 hours or longer. Although the LED never really burns out, product life span is measured by lumen depreciation.
The Illuminating Engineering Society’s (IES) current standard for calculating the life of an LED is the point at which the LED reaches 30 percent lumen depreciation.
Remember, a 100,000-hour rating is not equivalent to lamp life rating. LED life is rated where it has reached 30 percent lumen depreciation. At 100,000 hours an LED would still be operating, but at a decreased lumen output.
How does ambient temperature affect LED efficiency?
LED fixtures must be designed with junction temperature thermal management as a key component and use the correct LEDs. These products will then be robust enough to operate in most ambient temperature applications. Unlike fluorescent sources, cold temperatures do not impact the performance of LEDs.
What is lighting efficiency?
Lighting efficiency measures the efficiency of a lighting fixture. It is the ratio of the the total amount of light given off by a lighting fixture to the power that is consumed. We use the power of the lighting fixture when we measure the lighting efficiency. Some manufacturers use the power of lighting source when they measure the lighting efficiency, which is inaccurate. They exaggerate the efficiency and deceive the consumer.
What is junction temperature?
Junction temperature is the temperature at the point where an individual diode connects to its base. Maintaining a low junction temperature increases output and slows LED lumen depreciation. Junction temperature is a key metric for evaluating an LED product’s quality and ability to deliver long life.
The three things affecting junction temperature are: drive current, thermal path, and ambient temperature. In general, the higher the drive current, the greater the heat generated at the die. Heat must be moved away from the die in order to maintain expected light output, life, and colour. The amount of heat that can be removed depends upon the ambient temperature and the design of the thermal path from the die to the surroundings. [Source: DOE]
The Department of Energy advises: “Heat management and an awareness of the operating environment are critical considerations to the design and application of LED luminaires for general illumination. Successful products will use superior heat sink designs to dissipate heat, and minimise junction temperature. Keeping the junction temperature as low as possible and within manufacturer specifications is necessary in order to maximise the performance potential of LEDs”.
While all diodes release light, most don’t do it very effectively. In an ordinary diode, the semiconductor material itself ends up absorbing a lot of the light energy. LEDs are specially constructed to release a large number of photons outward. Additionally, they are housed in a plastic bulb that concentrates the light in a particular direction. As you can see in the diagram, most of the light from the diode bounces off the sides of the bulb, travelling on through the rounded end.
Is there a difference between an E14 and an E27 type lamp base?
The E14 is slightly smaller than the E27.
Why LED Bulbs?
This is a question that millions of people will be asking for the foreseeable future. The answer is simple. LED bulbs can save you thousands of dollars on your electricity bill. LED bulbs will help make the planet we live on a cleaner one. LED light bulbs last so long, you won’t need to change them for years. Finally, The incandescent & fluorescent bulb will be obsolete in 10 years.
Do LED bulbs contain Mercury like CFLs?
Benefits of LED Bulbs
– Save money and energy by using LED light bulbs. Generally, an LED consumes less than 0.1 watt to operate. This incredibly low consumption means you will save on your energy costs right from the start.
– The typical LED bulb will last for 50,000 hours. This is over 10 years of light from one bulb used half the time. Compared to an incandescent bulb, which lasts 1,000 hours, a halogen bulb lasts 2,000 hours, and a compact fluorescent bulb may last up to 10,000 hours.
– The extremely long life of an LED bulb will virtually eliminate your maintenance costs. There will be no need to change light bulbs throughout the year.
– The solid state technology of an LED is very durable and can withstand high levels of shock and vibration. It’s able to operate in extreme temperatures, both cold and hot (-35C to 80C).
– LEDs convert almost all the energy used into the light output, making them a highly efficient light source. LEDs generate less than 30% of the heat of traditional lighting technologies. With minimal heat generated, LEDs are safe to the touch and do not produce any harmful UV rays.
– LEDs are environmentally friendly, they are made from non-toxic materials unlike fluorescents which contain Mercury.