Everything about LEDs: Learn the basics of LED lighting and how to power!
May 21 2019
LEDs are appropriate for many lighting applications, they are designed to produce a lot of light from a small form factor while maintaining fantastic efficiency. Here at LEDSupply there are a variety of LEDs for all kinds of different lighting applications, the trick is knowing how to use them. LED technology is a tad different than other lighting that most people are familiar with. This post is here to explain everything you need to know about LED lighting: how to power LEDs safely so you get the most light and the longest lifetime possible.
What is LED?
An LED is a diode that converts electrical energy into light. For those who don't know, a diode is an electronic device that works only in one direction. Basically, an LED is an electronic device that emits light when current flows from an anode (positive pole) to a cathode (negative pole) in one direction. The principle diagram of the light-emitting diode LED is an acronym for "large flight e mitting d IODE. Basically, leds are like tiny light bulbs that require less power to light up and are more efficient at producing high-light output.
The LED type
In general, we provide two different types of LED:
5mm through hole and surface mount.
5 mm LED
A 5mm LED5mm LED is a diode in a 5mm diameter lens with two thin metal legs at the bottom. They are used in applications that require less light. The 5mm LED can also operate at a much lower drive current, with a maximum output current of about 30mA, while the SMT LED requires at least 350mA. All our 5mm leds come from top manufacturers and offer a variety of colors, intensities and lighting modes. Through-hole leds are suitable for small flashlight applications, signage and anything else you use with your breadboard, as they can easily be used with their leads. Check out our guide to setting up 5mm leds for more information about these tiny light sources.
Surface mount LED (SMD)
Led bare emitter
Figure 1 - naked emitter
A surface mount LED is a diode that can be placed on the substrate (circuit board) and protected by a silicon dome above the diode (see figure 1). We provide high power surface mount LED from industry leaders Cree and Luxeon. We think both are excellent, which is why we end up carrying them. Some people prefer one, but have experience and know what to look for. Cree tends to have higher lumen output and is a market leader in high-power leds. Luxeon, on the other hand, has excellent color and heat control.
High power LED as a bare emitter (as shown in figure 1) or mounted on a metal core printed circuit board (MCPCB). Circuit boards are insulated and contain conductive tracks to facilitate circuit connections. Our 20mm 1-Up and 3-Up star design is the best-selling product. We also provide QuadPod, which can accommodate four high-power leds on a circuit board slightly larger than 20mm star (see figure 2). All of our high-power LED options are also available with a linear design. The LuxStrip can accommodate 6 leds per foot and is easily connected to a 10-foot length.
LED Star MCPCB configuration
Figure 2 - MCPCB options
Polarity is important: connect the LED
The electronic polarity indicates whether the circuit is symmetrical. Leds are diodes, so allow current to flow only in one direction. When there is no current, there is no light. Thankfully, this means that if we connect one LED back, it won't burn the entire system, and it won't happen.
The positive pole of an LED is an anode and the negative pole is a cathode. Current flows from the anode to the cathode and never in the other direction, so it is important to know how to distinguish the anode from the cathode. For surface-mounted leds, this is easy because the connections are marked, but for 5mm leds, for longer leads that are the anode (positive pole), see figure 3 below.
LED polarity interpretation
Figure 3 - find the anode and cathode of the LED
One of the great things about leds is that you get different choices and different light.
Correlation color temperature (CCT) is the process of producing different white light at different temperature. The color temperature is expressed in degrees kelvin, which is a temperature scale where zero occurs at absolute zero, and each degree is equal to one kelvin. The lower temperatures from 3,000K to 4,500K tend to be the warmer neutral white. Higher temperatures of 5,000K + are cool white, also known as "daylight white."
For color, what really matters is the nanometer (nm) wavelength. For some applications, visual effects require color, but sometimes certain wavelengths are required for curing, growth, coral tank lighting, and more. For a concept of what wavelength and temperature produce certain colors, see figure 4.
LED color and wavelength map
Figure 4 - LED color and color temperature
We try to provide a similar color temperature-wavelength for each brand and type of LED. You can always find the color or wavelength of the LED in the subsection of the product page, or even search by color from the LED drop-down menu on the home page. In white, we carry 3000K, 4000K, 5000K and 6500K. In terms of color, we carry 400-660nm.
The LED brightness
LED is not only famous for its color, but also much brighter than other light sources. It is sometimes difficult to distinguish the brightness of an LED because it is measured in lumens. Lumens are the scientific units that measure the flux of light or the amount of visible light from a light source. Note that 5mm leds are usually listed in milliampere (MCD). For 5mm leds, their viewing Angle also affects the light output they emit, as shown here.
Why move forward on current issues...
The amount of light (lumens) an LED emits depends on the amount of electricity it provides. The current is measured in milliamperes (mA) or amperes (A). High-power LED can withstand current of 350mA to 3000mA. The current rating of the LED will vary, so be sure to track this when selecting the LED and driver.
To determine the brightness
Now comes the tricky part, selecting the LED and driver combination that will output the desired light. We have done a lot of basic work here, after measuring the brightness of each high-power LED with different driving current. Note that these are measurements for 1-up stars, so if you want more light, 3-up leds are a good choice because they are three times the amount of light in the same footprint.
The above resources can always be used to determine the LED light output, but manual lookup is not difficult.
To do this, you need to get information from the LED data table. On all of our LED pages, we link to the manufacturer data sheet at the bottom of the page.
Example: look for the brightness of Cree xp-l at 2100mA
In this example, we use Cree xp-l. First, find the Flux Characteristics table (figure 5). We will discuss the sizing of the markup in the "group" column later, but we assume that we will use the cold white xp-l from the highest partition (v5). The number highlighted is a typical @1050ma flux, which is the current when measuring xp-l. On the right are typical lumens of 1500,2000 and 3000mA driving currents.
LED flux diagram
Figure 5 - LED flux diagram
For this example, suppose we want to run the LED using the 2100mA BuckBlock LED relative flux chart driver, we need to find what the light output looks like. When driving the unlisted intermediate drive current, find the relative flux and current diagram in the data sheet that looks like the figure on the right.
The arrow is the test (base) output (100% relative flux). The curve reaches 2100mA. After that, we found that the light had increased by 75%. Taking 460 lumens from above and multiplying by 1.75, we can see that the cold white xp-l running at 2100mA emits about 805 lumens.
Switching to an LED can be difficult to find the LED and lumen output you need. This is because light is always measured by the wattage of the bulb. Leds are much more efficient, which makes it almost impossible to measure in this way, since a 50-watt LED will be significantly brighter than a 50-watt incandescent. In figure 7, we show the different incandescent bulbs and the number of lumens they output. This helps to better understand the light expected of an LED and whether it is as much as the old lighting.
Incandescent lamps convert to lumens
Figure 6 - lumen power of incandescent lamp
Angle and optics
Our 5mm LED already lists the views of each LED, so just search for one that suits you. In the case of our surface mount leds, most of them emit very wide angles at 125 degrees! Fortunately, LED star plates are compatible and easy to use LED optical devices. These secondary optical devices are used to focus light, and they can reflect light from LED to point, middle point, wide point or oval and oval patterns.
As shown in figure 8, the 1-up optical device is tapered and requires optical element holder. In the case of our LED panel, the optical bracket has four legs and can sit in a star-shaped groove. The three LED stars are also compatible with the Carclo optical components, and have three holes in the circuit board for mounting the optical components' supporting feet.
LED lenses and optical devices
Figure 7 - LED optical devices and supports
How to power LED
Leds are known to have the best performance of any other light source. Efficacy is a measure of the amount of visible light produced by a light source, also known as lumen per watt. In other words, how much light do we get? To find this, first look for the power of the leds you're using. To find watts, you need to multiply the forward voltage (the voltage at which the current begins to flow in the normal conducting direction) by the driving current of the ampere (note that it needs to be in amperes... Not milliamperes. Let's look at the Cree xp-l 1-up LED as an example.
Look for LED forward voltage
Figure 8 - LED forward voltage
Suppose we run the Cree xp-l at 2000mA. As can be seen from figure 8, the forward voltage under this driving current is 3.15. Therefore, in order to find watts, we multiply 3.15 (forward voltage) by 2 A (2000mA = 2 amps) and get 6.3 watts.
So now to find out, we just need to divide 742 lumens (this LED has a lumen test of 2000mA) by 6.3 watts. As a result, the Cree xp-l is 117.8 lumens per watt. This is very effective, but it is also noted that Cree says the XLamp xp-l LED has a break-through efficiency of 200 lumens per watt with a running current of 350mA. It's nice to know that when you put more current into the LED, the efficiency goes down, because it adds heat, which makes the LED less efficient. Sometimes you need to accept this, if you need the LED to be very bright, but if you want the best effect, then you should run the LED at a low current. This helps you determine how much power your application needs and to achieve energy savings in the future.
More information about LED drivers
This means that you need to find an LED driver that can drive the LED at the current you need to get the lumen you want. LED driver is an electronic device used to adjust the power supply of LED or LED string. When the LED's electrical characteristics change with temperature, the driver responds to the LED's changing needs by providing constant power to the LED. A good analogy to understand this is the cruise-control car. As the car (LED) moves through hills and valleys (temperature change), the cruise control system (driver) ensures that it maintains a steady speed (light) and thus regulates the required gas (power). Drivers are important because leds require a very specific power supply to work properly. If the voltage supplied to the LED is below the required voltage, very little current will flow through the junction, resulting in insufficient light and poor performance. On the other hand, if the voltage is too high, too much current can flow to the LED, and it can overheat and seriously damage or fail completely (heat runaway). Always make sure to check the LED data sheet to understand the recommended current to avoid these problems.
How much voltage does it take to light the LED?
This is a common problem that is actually fairly easy to understand. What you need to know is the LED forward voltage. If you have multiple series leds, you need to consider all the forward voltages, and if you have a parallel circuit, you only need to consider the forward voltages for each string of leds. See here for more information on wiring Settings. Maintaining at least 2 volts of overhead is a good idea because some drivers (such as LuxDrive drivers) require this driver to work properly. Therefore, if the total forward voltage of the series circuit is 9.55, the 12V power supply should be safe. For off-line drivers (ac input), you only need to know their rated output voltage and ensure coverage, so ac input drivers with an output range of 3-12vdc are also suitable for this application.
Finding the power of sytsem can also help you understand the required heat control. Because these leds are high-power, they generate heat, which can be very bad because you can learn here. Too much heat causes leds to produce less light and reduce their life. We always recommend using radiators, and like to say that leds use about 3 square inches per watt. For greater power, I recommend looking for a recommended number of watts for the running radiator.
LED grading and quality
With the LED industry now growing at a very fast pace, it is important to understand the differences between leds. This is a common problem because leds can range from very cheap to very expensive. I'm careful about buying cheap leds because you always get what you pay for. Yes, leds may work well at first, but because of poor testing, they usually don't last long or burn out quickly.
LEDSupply's leds are all handpicked. We only stock the best brand and color temperature. Our extensive experience in the industry has helped us understand the importance of high-quality LED manufacturing and packaging. In the manufacture of leds, there are performance variations near the mean in the technical data sheet. For this reason, manufacturers use leds for flux, color, and forward voltage. We choose the case with the highest luminous flux (visible light) and the lowest forward voltage, because this ensures that we have the most efficient LED. A large number of LED products are manufactured cheaply and without proper records, which leads to many failed projects, and then leads people to think that leds are not actually as durable as they say. With our experience and our purchasing power,
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