Some of the strategies for reducing the cost of LEDs in the future are:
Here are some of the aspects that need to be taken into consideration: when
Lights built into wardrobes can be of the following types:
LEDs have the following advantages over neon:
Using LEDs in mining areas has the following benefits:
LEDs are driven by constant current (350mA, 700mA or 1A) drivers or constant voltage (10V, 12V or 24V) drivers.
Constant current drivers fix the current of the system and vary the voltage depending on the load of the LED.
Constant voltage drivers require a fixed voltage, and the LED loads are added in parallel across the output of the driver until maximum output currents are reached.
Following are the advantages of PWM dimming:
Smooth dimming capability
More precise output levels
Better consistency in color over various levels
Following are the disadvantages of PWM dimming:
Relatively more expensive
Flicker perceived in peripheral vision if the driver is run below 100Hz frequency
Stroboscopic effect evident in fast moving environments when the driver frequency is low.
Electromagnetic Interference (EMI) issues due to rise and fall of the current in PWM dimming.
Performance issues arise when the driver is mounted remotely from the light source.
CCR dimming is good in:
Outdoor applications and damp locations.
Places that have strict EMI requirements like medical suites.
Places where there is a lot of motion and rotary machinery.
Applications where the drivers are to be placed at long distances from the light source.
Although LED products are marked as compatible with traditional dimmers, there are various degrees to which LED products are compatible with incandescent dimmers. Compatibility needs to be checked and tested on a product by product basis for the following most common undesirable behaviors:
Reduced dimming range
Flickering of the lamp
Inconsistent performance based on the number and different types of LEDs connected to a single incandescent dimmer
Dimming LEDs offer the following advantages:
Saves energy, because less energy is used for reduced output levels.
Extends life; the electronic components run cooler. This not only extends the life of LEDs but also increases the life of the phosphor coating that is used to produce white light.
Helps designers create ambient lighting presets to create mood settings.
Increases flexibility in usage of space. A brightly lit space for reading or an office space can turn into a presentation/conference area by dimming.
Increases productivity by enabling individual control of lights in order to reduce eye strain and fatigue, or to improve concentration.
Heat management is critical for the performance of LEDs. Increasing heat in LEDs has the following effects in performance characters:
The two-phase heat technique is a cooling technique that uses the advantages of both active and passive cooling methods.
It works on the principle of evaporation and condensation. The process requires disposable heat to initiate the process that happens in a hermitically sealed tube that is filled with a minute quantity of liquid. The system has cooling fins around the tube to dissipate heat. This system offers high reliability, zero operation costs and is not orientation dependent.
The following are types of optical systems of LEDs:
Here are few of the ways in which glare can be reduced from LEDs:
Unlike conventional light sources that reduce in output and eventually fail, LED products do not normally suddenly fail. Instead, the light output reduces over time.
The normal convention is to measure the life from when the output has reduced by 30%, i.e. when there is 70% light output remaining. This is often quoted as the L70 life and is measured in hours.
The thermal management of the LEDs. If LEDs come on a standalone chip, appropriate heat sinks have to be designed to prevent premature failure of LEDs.
The electrical stress: Running LEDs at currents higher than specified make the LED run hot. This can happen with wrongly matched drivers. For example, if the driver produces 700mA but the LED needs 350mA, this will put stress on LED and reduce its lifespan.
Higher ambient temperatures than the ones that the LED is rated for will reduce its expected life.
LEDs produce light by direct conversion of electrical energy to light energy.
On the other hand incandescent light sources produce light by heating a filament until it grows red hot. Linear and compact fluorescent lamps use a UV discharge plus a phosphor to produce the light. HID lamps use the ionization of gases in a discharge tube which in turn produce photons.
With the further increase in performance characteristics of LEDs and the advent of OLEDs the application sector of LEDs has expanded. Below are some of the new uses of LEDs:
Luminous walls and ceilings
Transparent walls and partitions that turn opaque at different times of the day.
Solar powered fabrics
LEDs do not directly produce white light. There are two ways in which white light is produced from LEDs as below:
Using a blue LED with a phosphor coating to convert blue light to white light by a process called fluorescence.
Combining red, blue and green LEDs to produce white light. White light is produced by varying the intensities of the individual red, blue and green chips.
The following are the different types of RGB LEDs:
These are chemical symbols used for materials used in the manufacturing process of the LEDs to generate specific colors.
AlGaAs - Aluminium Gallium Arsenide used to generate red and amber portions of the visible spectrum.
AlInGap - preferred chip technology using Aluminium, Indium, Gallium and phosphorous to produce red, orange and amber colors.
InGaN - Indium, Gallium and Nitrogen to produce green, blue and white colors.
Apart from CRI, R-values and CQS, color consistency is also a measure of the quality of light. The color consistency can be evaluated at several levels as follows:
There are several possible reasons why this happens:
The remote phosphor process offers:
Here are the various terminologies for developmental stages of LED in chronological order:
The advantages of SMD over DIP LEDs are:
The basic types of chip LEDs are:
LED modules may be available in the following forms:
The chip on board (COB) package enables mounting of the package directly onto a heat sink instead of relying on a LED board manufacturer.
In many designs the heat sink is designed to be a part of the luminaire housing design, which reduces the number of components in the system.
The development of more stable mains voltage AC LED drivers is leading to solutions that can reduce wiring requirements and overall dimming cost.
Here are the general LED lighting facts:
These are some LED lighting benefits:
Staring straight into a strong LED Light with a high color temperature (expressed in Kelvin) at a close distance for a long period of time can possibly damage the retina. Normally, the discomfort experienced will require to avert or close the eyes, preventing any damage.
These are the factors in play:
The journal article (Photochem. Photobiol. 89, 468-473) shows the experiments exposing human eye cells to light intensity of 5 mW per square centimeter for twelve hours, which leaves noticeable damage behind. However, for a typical white LED spectrum, this intensity level corresponds to staring directly into a 100-Watt-equivalent light bulb from about 10 centimeters away, for twelve hours straight.
LED street lighting and circadian rhythm
No. If properly designed and applied, LED lighting will provide its advantages and you can avoid potential unwanted side effects.
If you apply the right light, in the right place, at the right time, for the right situation, LED light can positively impact public safety and liveability while also offering savings on energy and maintenance. Philips Lighting solutions are carefully designed for local applications taking into account the right optics and light intensity to benefit from the LED advantages and mitigate negative effects like circadian disturbances and glare.
Well-designed LED street lighting
There are several good examples from the current Philips Lighting customers including:
Preventing light pollution
The impact of Color temperature
Color temperature is measured in Kelvin, it’s a mathematical calculation derived from the Spectral Power Distribution (SPD) of a light source. It allows for a wide variety of specific color combinations. LED lighting is available with various combinations of Correlated Color Temperature (CCT) and Color Rendering Indexes (CRI), which can result in various effects on vision. The color temperature is defined in degrees Kelvin, a warm light (yellowish) is around 2700K, moving to neutral white at around 4000k, and to cool white (bluish) around 5000K or more.
To demonstrate why it’s important, for example, in many outdoor applications, protecting the public with lighting that promotes alert drivers and a safe environment may be the highest priority. In those cases, the recommended color temperature is deployed with considerations for the space and those in it.
Does indoor LED lighting have a dark side?