LED - The LED the light source of the future

LED - The LED the light source of the future: LEDs

10 questions about LEDs
  1. What is an LED and how does an LED work?
  2. Important terms around the LED
  3. Which LED lamps are good?
  4. When will LED lamps pay off?
  5. Are LED lamps getting hot?
  6. Why do you need an LED transformer?
  7. How long do LEDs last?
  8. Where can LED lighting be used?
  9. What do I save with LED lighting?
  10. Where can not LED lamps be used?

LEDs are an interesting but also much discussed topic, which is mostly based on misinformation, prejudices and unnecessary bad experiences. We want to bring a little light into the darkness here and remove prejudices from the way.

LED lighting is the future and that's a good thing. It is extremely economical, small, cheap and almost unlimited use. It can decorate discreetly and in color, make the living room appear in daylight and also imitate the old proven "light bulb" deceptively real. Already here we contradict the very common opinion that LED light is cold and unnatural.

In ten points we will clarify frequently asked questions, inform and hopefully eliminate one or the other erroneous beliefs. Find out where LEDs can be used and what advantages they have in home improvement and DIY.

1. What is an LED and how does an LED work?

LED stands for"Light Emitting Diode" or in German"Light emitting (emitting) diode", This is already a lot said - It is a diode that emits light. In this case, however, the term diode is also important, since it specifies a peculiarity.

Diodes are semiconductorsthat only let the current through in one direction. This means in practical use that light-emitting diodes on the one hand can only be used properly polarized and need direct current for a flicker-free light.

Why LEDs are lit and what material they must pass to emit light, UV light or infrared radiation is of little importance to the end user. Light-emitting diodes are offered according to their purpose and if you deal a little with the technical data, you can easily find the right LEDs for your own application. For this purpose, a few frequently mentioned statements and technical terms are briefly presented in the next paragraph.

2. Important terms around the LED

Anyone who wants to tinker and decorate with LEDs can not avoid having to deal with a few technical data. You do not have to become an electronics engineer. However, anyone who knows what information stands for, can compare at least offered light-emitting diodes and get the best out of it.

Anode and cathodeThey indicate the two connections of a diode and at the same time the polarity in which the LED is connected. Anode stands for the shorter connection (leg) and the positive pole. The cathode is characterized by a longer leg and forms the negative pole. At the same time, many LEDs have a flattening to make it easier to detect the negative pole.
BeamUnlike incandescent bulbs LEDs emit their light rarely around. Due to the lens shape, the light emerges bundled as a cone, which enhances the luminosity to a point. The larger the beam angle, the wider the cone of light. The beam angle is crucial for individual LEDs, but is also indicated for other lamps (halogen spot or reflector lamps).
diffuseIf an LED is marked as diffuse, it has no emission angle. Their surface is usually frosted and / or has a depression above. Both ensure that the light emitted is scattered and the LED emits its light all around.
SMD LED"Surface mounted device": SMD LEDs do not have the typical cylindrical shape with two legs, but are usually flat and intended for direct mounting of printed circuit boards. Due to their slightly different construction, they are brighter and more durable than typical LEDs. For their own craft and decoration work, they are due to their shape but rather unsuitable.
RGB LEDRGB stands for the primary colors red, green and blue. In an RGB LED, these three colors are combined in one LED and can be individually addressed and mixed with four connections.
reverse voltageSemiconductors let the applied current through in only one direction. If you reverse the polarity of a semiconductor, the current flow is blocked. The blocking voltage is higher than the voltage required for lighting, but also limited (usually about 5V). If the blocking voltage is exceeded, this will destroy the LED in most cases. But since the blocking voltage is higher than the operating voltage, a LED can also be connected to the wrong way without danger. In this it simply does not shine.
luminanceThe luminosity of many bulbs is given in lumens and refers to the light emitted around. Since LEDs do not light up on all sides, the information here can be used poorly. Instead, the term Candela is used, which describes the light emitted in one direction on a surface. If two LEDs emit the same light, but have a different beam angle, the generated luminous dot appears much brighter with a smaller beam angle than with a large beam angle. The indication of the luminance of LEDs therefore gives only in combination with the Abstahlwinkel a real value to the total emitted light. For comparison, many "Candela Lumen Calculator" can be found online.
warm white / cool whiteWhile yellowish light is perceived as "warm", pure white to bluish light is rather cool. The terms hot and cold white refer to this. Although there are defined for this purpose (2700-3300 Kelvin = warm white, 3300-5300 Kelvin = neutral white, over 5300 daylight white or cold white), but often take it the lamp vendors not so accurate and your own senses plays a big roll.

3. Which LED lamps are good?

LED - The LED the light source of the future: LEDs

Cheap import with dangerous output

Should I buy an Opel or a Ford?

Of course, such questions can not be answered in a lump sum. A Dacia can be on the road for 20 years, while a Mercedes in the dealership already fails the windows. There are certainly so-called "Monday articles" everywhere, although they are probably less likely to be found under branded products. Likewise, you can also be lucky with import bargains on Ebay or, as in the picture on the right, with a loud bang the items fly out of the lamp. An explosion hazard can not be ruled out.

Note d. Red: Despite the CE sign actually happened and the photo shows the personal experience of the editor.

If you're willing to invest a lot of time to get special bargains, you can test yourselves through cheap offers and claim defective, unusable or quickly broken models. Most providers are accommodating and exchange very generously or refund the purchase price.

However, those who prefer quality can use Amazon ratings or buy their LED lamps from specialist retailers. Here, the risk is significantly lower that the light is already off after a few days. If in doubt, you have a contact person who speaks the same language and you have the applicable German warranty. For many import purchases on Ebay, this is unfortunately not.

4. When are LED lights worthwhile?

LED - The LED the light source of the future: lighting

An LED refrigerator lighting hardly causes heat.

In short: LED lamps are always worthwhile!Often the bill starts with it: how often do I use the light? How long do I use the light? What do I save on electricity costs and when does the investment pay off?

The approach is certainly not wrong with devices that are subject to high wear or are very expensive. However, LEDs are so far superior to conventional light bulbs in terms of their lifetime that they definitely pay off. For frequently used and large-scale lighting, of course, rather than in under-used storage room, but at some point here also starts saving.

The idea "Oh the light I use so seldom, since the conversion to LED does not pay off." is therefore wrong.

LED lamps have their advantage but not only in the electricity costs. The heat development can also be of great importance. As an example, the refrigerator lighting is mentioned here. Conventional bulbs are deliberately small in size, but still emit more heat than light. LEDs, on the other hand, stay cool and can illuminate the fridge better without adding heat to it. This also saves energy.

5. Are LED lamps getting hot?

Compared to conventional incandescent or halogen bulbs, this question could clearly be answered with no. While incandescent lamps use only 5% of the energy used to generate light and convert the remaining 95% to heat, LED lamps are much more effective. Around 40% is used for light generation and 60% escape through heat generation.

Due to the high luminous efficacy, LEDs thus have a significantly lower power, which in turn reduces the heat output. In direct comparison, a conventional incandescent lamp gives about 15 times as much heat with the same light output as a comparable LED lamp.

luminosityinputlight outputheat
light bulb930 lm75 watts3.75 watts71.25 watts
LED1050 lm8 watts3.2 watts4.8 watts

Where light is, of course, is also shadow and so it can happen that LEDs are relatively hot. Although an incandescent lamp emits 15 times as much heat, it is also much larger and can emit the resulting temperature due to its radiation.

LEDs, on the other hand, are very small and require an extra heat sink for greater power. In addition, an LED is never connected directly to the power source. An LED requires electronics that lowers and stabilizes the voltage. These components also dissipate heat that must be dissipated. In a small housing, such as LED spots, it can therefore already get hot, what the life of a LED lamp is not exactly useful.

6. Why do you need an LED transformer?

If you like to tinker and decorate with LEDs, you should pay close attention to the voltage supply. Power supply is not the same power supply and you can in the Vorwiderstandsberechnung (calculation of the series resistor) still give so much trouble, with the wrong power supply burn the LEDs through.

LED - The LED the light source of the future: lighting

LED power supplies always deliver a constant voltage.

The explanation is quite simple:

A simple power supply with the characteristics 12 volt and 3 watts guarantees a voltage of 12 V with a power output of 3 watts.However, such a power supply will deliver 14 volts or more without loss of power.Lamps or smaller engines are not bothered because they have on the one hand with a little more voltage no problem and on the other hand, the voltage by the higher power consumption quickly on the specified 12 V "collapse".

Unlike the LED - it requires very little power, the power supply continues to deliver the higher voltage and the LED lighting must instead of 12 volts 14 volts or more process. This results in a higher load of the LED, it is warmer, aging faster or is destroyed immediately.Therefore, LED lamps require special power supplies - stabilized power supplies. Such stabilized power supplies are electronically controlled and deliver the same specified voltage without load as under load.

7. How long do LEDs last?

The pure life of the light-emitting diode is undisputed and lies with 20 to 50,000 operating hours far above all other light sources. And even if the theoretical life is reached, the LED does not have to fail. Rather, instead, their luminosity decreases and can still find their place in an LED underfloor luminaire, which depends on the decorative application.

LED - The LED the light source of the future: future

With a small size LEDs can be used individually.

The problem with the LED technology is less the LED itself. In most cases, it is the ballast electronics that fails and thus the LED lamp lights up the light.

The same applies to the switching stability. While the LED itself is not really impressed by many switching cycles, it is again the ballast electronics that matter. Here, the switching resistance varies greatly with the quality and can well fall to 5000 cycles. If such an LED lamp is connected to a short-switching motion detector, which causes 20 switching operations a day, the end of life of the lamp can already be reached in less than a year. If one goes from daily 5 shifts and a good ballast electronics, attacks the average life and it can be quite reach 20 years.

But no matter if many switching cycles, or if the LED is working 24 hours a day, an incandescent lamp with 1000 cycles or a life of about 1000 hours will not even approach these values.

8. Where can LED lighting be used?

LEDs have many advantages and are not only suitable for reducing electricity costs. Special fields of application result from the low heat emission, their size and the low power requirement.

  • LED - The LED the light source of the future: LEDs

    With the low voltage of 12 V everyone can tinker.
    Low heat emission: If no high-power LEDs are required, the heat output of LED lamps is negligible. Therefore, they are suitable where no high heat may arise. Be it the fridge, flammable rooms or even the decorative ceiling lamp made of paper.
  • Small size: Incandescent lamps emit their light in all directions and can therefore illuminate rooms well. However, due to the glass bulb and the heat given off, they require a lot of space and can only be used to a limited extent for decoration. Here light-emitting diodes can trump. They are small, do not get hot and can be placed anywhere. They are available in different colors, so that you can easily use colorful and very decorative.
  • Low power consumption: LEDs are economical and require very little power, which makes them very easy to use mobile. Even the smallest batteries are enough to provide a small flashlight with sufficient energy. But even with a fixed installation much thinner lines are needed because of the low read access, which can be easily hide.
  • Low voltage: A single LED requires between 1.5 and 3.4 V, but is operated with a series resistor for safety. A power supply of 12 V with a series connection of 3 or more LEDs with a corresponding series resistor has been pronounced. 12 V belongs to the so-called low voltage and is harmless for humans and animals. This means that even a layman can try and implement his own projects here. If you like to make decorative things, you will find a light source in the LED, which can be used very flexibly. However, be careful with the voltage source. Not too big here - even a car battery belongs to the low voltage, but delivers so much power that a short circuit can easily trigger a fire.

9. What do I save with LED lighting?

The extent to which electricity costs can be reduced by converting to LED lamps depends on many factors and can not be quantified directly.

According to online data, an average household with four people needs about 5000 kWh per year, of which about 9% (450 kWh) are to be included in the lighting (source: heizsparer.de). Let's start with the above example of a 75 watt incandescent lamp versus an 8 watt led, which could save about 90% of the 450 kWh. At 30 Ct / kWh that would be about 120 € per year.

However, one must take into account that the information about the light output of an LED lamp like to shoot a little beyond the target and thus lags such an invoice. The blogger Wolfgang Messer came in a self-experiment but at least on a total power savings of about 6%, which was effectively about 50 € a year. Meanwhile, the electricity prices have risen regularly, which of course also increases the savings.

10. Where can not LED lamps be used?

LEDs will burn out the bulbs in the long term, but there are also places where LED bulbs reach their limits and can not or may not be used.

  • LED - The LED the light source of the future: source

    Only 3-wire motion detectors are suitable for LED lamps.
    LEDs like it cool. A warm environment can not only shorten the life, but even lead to immediate destruction due to the plastic housing. As lighting in the stove they are therefore unsuitable.
  • Many motion detectors of the two-wire technology require a switching load of about 40 watts (incandescent). If LED spots are used here, it often happens that they light up permanently despite inactivity. The background is the motion detector, which draws its own power consumption through the line of the lamp and thus generates a current flow, which lights the LED lamp.
  • With the right 3-wire motion detector but can also switch LED lamps.But it does not always make sense, depending on the power consumption of the motion detector. The motion detector also consumes power 24 hours a day. If it is just a small staircase lighting, it may even be more effective to turn on the lights manually in the evening and off again in the morning.
Contribution: Riccardo Düring
Photo Credits:
  • Cover picture: Pixabay / Klaus Hausmann
  • Cheap import: © Riccardo Düring
  • LED fridge lighting © NCC-Design GmbH - gluehbirne.de
  • LED power supply: © NCC-Design GmbH - gluehbirne.de
  • Kitchen lighting: © Riccardo Düring
  • Cordless screwdriver racer: © Riccardo Düring
  • 3-wire motion detector: © NCC-Design GmbH - gluehbirne.de

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