Difference between cathode and anode RGB LEDs

If you aim to control individual RGB LEDs, you'll need a significant number of control pins. In this scenario, working with 506 LEDs means dealing with 506 elements that require control. The challenge lies in the manipulation of RGB LEDs due to their inherent complexity.

Imagine if RGB LEDs consisted of three separate diodes encapsulated together. That configuration would simplify the control process immensely. Take, for example, this model: RGB SMD LED.

Now, let’s crunch some numbers. If you used a MAX controller that manages 64 LEDs simultaneously, dividing 506 by 64 gives approximately 7.95. Hence, around 8 MAX controllers would be necessary for each color without the need for multiplexing to create yellow; you would simply activate blue and green together. The same applies if you want either red or green alone.

A single MAX controller operates 8 LEDs and requires a current of 160mA or more at 20mA per LED (which varies based on brightness). In this case, for combined Red, Green, and Blue, the total would be 16 * 160mA, translating to nearly 3A for the power supply. If you're using a 40mA setting (with the output pulsing at 800Hz), you'd require a 6A power supply.

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Another alternative is WSB (Write Serial Byte), an RGB LED variant featuring built-in controllers. By sending 3 bytes of serial data, it effectively manages the activation of the appropriate colors via 8-bit PWM for each channel. This significantly simplifies wiring, as you can create a long series of daisy-chained connections. Note that each WSB LED consumes 20mA for red or green individually, but it may draw up to 40mA for simultaneous blue and green operation. Consequently, the total requirement for a setup with 509 LEDs would be 5V at 20A.

For anyone seeking Arduino libraries for controlling these, Adafruit offers a variety of resources, perfect for sending 3 bytes per 506 LEDs once every second or at your desired display time.

LED Fundamentals: The Basics of High-Power LED Lighting

LEDs are ideal for various lighting applications, designed to emit substantial amounts of light from a compact size while maintaining high efficiency. Here at LEDSupply, we provide an extensive selection of LEDs suitable for different applications; however, the key lies in understanding their usage. LED technology differs from conventional lighting, and this post aims to clarify all you need to know about LED illumination: how to operate LEDs safely for optimal light output and longevity.

Defining an LED

An LED is a specific type of diode that converts electrical energy into light. For those unfamiliar, a diode is an electronic component that allows current flow in one direction only. Thus, an LED is designed to emit light when electricity flows through it in a singular direction—from the anode (positive side) to the cathode (negative side). The acronym LED stands for Light Emitting Diode. In essence, LEDs function as miniature light bulbs that demand significantly less power while producing high light outputs efficiently.

Types of LEDs

Generally, we offer two varieties of LEDs:

5mm Through-Hole & Surface Mount.

5mm LEDs

5mm LEDs come within a 5mm diameter lens and possess two slender metallic legs at the bottom. These are utilized in instances where lower light output is sufficient. Moreover, they operate at diminished current levels, capping at around 30mA, unlike Surface Mount LEDs that necessitate at least 350mA. All 5mm LEDs are sourced from leading manufacturers and are available in various colors, intensities, and lighting patterns. Through-hole LEDs are particularly well-suited for small flashlight applications, signage, and any projects involving breadboards as their leads facilitate easy use. For further information on setting up 5mm LEDs, reference our dedicated guide.

Surface Mount LEDs (SMD)

Surface Mount LEDs feature diodes that can be positioned on a substrate like a circuit board, protected by a silicon dome (see Figure 1). We supply high-power SMD options from top industry players, Cree and Luxeon. Both brands have their merits, with preferences often influenced by experience and personal insights. Cree typically boasts higher lumen outputs, marking itself as a leader in the high-power LED market, while Luxeon excels in color rendition and thermal management.

High-Power LEDs can be available as bare emitters (as illustrated in Figure 1) or mounted to a Metal Core Printed Circuit Board (MCPCB). These boards are insulated and equipped with conductive tracks to ease circuit connectivity. Our 20mm 1-Up and 3-Up starboard configurations are among our bestsellers. Moreover, we also provide QuadPods, which accommodate four high-power LEDs on a board slightly larger than the standard 20mm stars (as shown in Figure 2). Our high-power LED options can even be built in linear designs. The LuxStrip can hold six LEDs per foot and can be connected up to 10 feet long.

The Importance of Polarity: Wiring LEDs

Electronic polarity determines if a circuit is symmetric or asymmetric. As diodes, LEDs only permit current to flow one way. Without current flow, no light will be produced. Essentially, wiring an LED backward won't damage the entire system; it simply won't light up.

The positive side is identified as the anode, and the negative side as the cathode. Current flows specifically from the anode to the cathode, emphasizing the need to distinguish between them. For surface mount LEDs, connections are typically labeled; however, for 5mm LEDs, the longer lead signifies the anode (positive). Refer to Figure 3 for clarity.

Color Variations

One of the remarkable advantages of LEDs is the abundance of color options available.

White LEDs

Correlated Color Temperature (CCT) helps create varying white light at different temperatures, specified in degrees Kelvin (K). Lower temperatures, ranging from 3,000K to 4,500K, result in warmer to neutral white hues. In contrast, temperatures exceeding 5,000K are categorized as cool whites or "daylight white."

Colored LEDs

For colored LEDs, the wavelength measured in nanometers (nm) is crucial. Certain applications demand specific colors for visual impact, while others require distinct wavelengths for uses such as curing, growth, or accent lighting. Figure 4 depicts various wavelengths and their corresponding colors.

We strive to maintain uniform color temperatures and wavelengths across our brands and types of LEDs. Always check LEDs’ color or wavelength in the sub-section of product pages, or use the color filter in the LEDs dropdown on our homepage. In terms of white light, we offer options at different Kelvin ratings. For colored variants, we range from 400-660nm.

LED Brightness

Beyond color, LEDs shine due to their brightness, which becomes apparent in terms of lumens, the scientific unit used to measure luminous flux—the total amount of visible light an object emits. While 5mm LEDs often package this output in millicandelas (mcd), the viewing angle for these LEDs also impacts the perceived brightness they project.

Significance of Drive Current

The luminous output (lumens) of an LED correlates directly with the amount of current supplied. Measured in milliamps (mA) or amps (A), high-power LEDs typically run on currents upwards of 350mA. Different LEDs come with distinct current ratings, so taking note of these parameters is essential when selecting an LED and its driver.

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Assessing Brightness

The next step is to determine the appropriate LED and driver combination to yield the desired light output. We have conducted in-depth research, compiling brightness measurements for each high-power LED across varying drive currents. Note that these measurements pertain to 1-Up stars; for increased brightness, consider 3-Up configurations that provide triple the light within the same dimensions.

While the aforementioned resources can help ascertain LED light output, manually determining this is not a daunting task.

To succeed, information from the LED's datasheet is required. On all our LED product pages, you will find links to the respective manufacturer’s datasheet located at the bottom of the page.

Example: Calculating Cree XP-L Brightness at a Specific mA

In this scenario, we will analyze the Cree XP-L. First, locate the Flux Characteristics table (see Figure 5). We will address binning shortly, specified in the ‘Group’ column. For now, let’s assume we are utilizing a cool white XP-L belonging to the highest bin (v5). The highlighted value indicates the typical flux at a specified mA, along with typical lumen outputs for varying drive currents.

For this illustration, let us assume we want to run this LED using a mA BuckBlock LED driver. To determine the resulting brightness, locate the relative flux against current graph in the datasheet, which should resemble the nearby graph.

The arrow indicates the tested base output (100% relative flux). If we track the curve, we can identify a 75% increase in light output at this mA mark. Multiplying the 460 lumens by 1.75 indicates that the cool white XP-L operating at this mA yields approximately 805 lumens.

Finding the right LED and the corresponding lumen output needed while transitioning to LEDs can be challenging since traditional lighting measured output based on bulb wattage. LEDs boast much higher efficacy, rendering direct wattage measurements misleading, as a 50-watt LED can outshine a 50-watt incandescent. Figure 6 outlines how various incandescent bulbs compare regarding lumen output.

Viewing Angle and Optics

Our 5mm LEDs come with designated viewing angles, so you can easily find one that meets your requirements. Regarding surface mount LEDs, a wide angle of about 125 degrees is standard! The LED starboards are compatible and can be easily utilized with additional LED optics. These secondary optics focus and reflect the light from an LED into various patterns, such as spot, medium spot, wide spot, or elliptical/oval outputs.

As illustrated in Figure 7, 1-Up optics are cone-shaped and necessitate the use of an optic holder. In the case of our LED boards, optic holders possess four legs designed to fit into the star's grooves, while triple LED stars accommodate Carclo optics featuring three holes for optimal placement.

Powering LEDs

LEDs boast the highest efficacy among available lighting sources. Efficacy is a metric representing how effectively a light source generates visible light, expressed in lumens per watt. To determine this, one first needs to calculate the watts consumed by the LED. This involves multiplying the forward voltage (the voltage initiating current flow in a typical conducting manner) by the driving current measured in amps (it is essential to use amps rather than milliamps). Let’s examine the Cree XP-L 1-up LED as a prime example.

Assuming the Cree XP-L operates at mA, as illustrated in Figure 8, it yields a forward voltage of 3.15 at this current. Hence, calculating watts becomes a matter of multiplying 3.15 (forward voltage) by 2 A (in mA, this equals 2 Amps), resulting in a total of 6.3 watts.

Upon determining wattage, we can calculate the efficacy by dividing 742 lumens (the measured lumen count for this LED at mA) by 6.3 watts. Consequently, the efficacy of this Cree XP-L translates to 117.8 lumens per watt. While this measurement reveals a commendable efficacy rate, note that Cree iterates that the XLamp XP-L LED can achieve an outstanding efficacy of 200 lumens per watt operating at 350mA. Bear in mind that efficacy tends to drop as more current flows through an LED due to heat buildup, which diminishes efficiency. Achieving greater brightness might necessitate accepting this compromise; however, to maximize efficacy, running LEDs at lower currents is advisable. These calculations aid in determining your application's power requirements and potential energy savings in the future.

Insights on LED Drivers

Finding a suitable LED driver capable of supplying the necessary drive current to achieve the desired lumen output is paramount. An LED driver is an electronic component that manages the power supplied to an LED or strings of LEDs. The driver responds to the variable needs of the LED by maintaining a steady supply of power as the LED's electrical properties fluctuate with temperature changes. Think of this as akin to cruise control in a vehicle. As the car (LED) navigates through variations in elevation (changes in temperature), the cruise control (driver) ensures a constant speed (light), adjusting the fuel (power) usage accordingly. This precision is vital since LEDs necessitate specific electrical configurations for proper functionality. Insufficient voltage can yield low current, resulting in weak light output, while excessive voltage could lead to too much current, causing overheating and severe damage (thermal runaway). Always refer to the LED's datasheet to verify the recommended current to avoid such issues.

How Much Voltage is Necessary to Activate an LED?

This common query can be easily addressed. It all hinges on understanding your LED's forward voltage. For multiple LEDs wired in series, account for the cumulative forward voltages; for parallel circuits, only consider the forward voltage of the LEDs within each string. As a guideline, maintain at least a 2-volt overhead, as certain drivers, such as LuxDrive, require this for proper functionality. Thus, if the total forward voltage in a series is 9.55, a 12V supply is advisable. For offline drivers (AC input), simply note the rated output voltage and ensure coverage. Thus, an AC input driver rated from 3-12VDC would suit this application as well.

Heat Management

Calculating the wattage of your setup will also aid in determining the heat management measures necessary. Since high-power LEDs generate heat, excessive heat production can result in diminished light output and reduced lifespan, as elaborated here. We recommend employing heat sinks, accurately suggesting approximately three square inches for every watt of LED output. For higher wattages, seeking a heat sink designed specifically for the wattage in use is advisable.

LED Binning & Quality Considerations

As the LED industry progresses rapidly, comprehending the distinctions among various LED products is critical. Given the spectrum of prices, from economical to high-end, caution is warranted when selecting budget LEDs, as the old adage holds true—“you get what you pay for.” Budget options might work effectively initially, but their longevity and reliability often fall short due to inadequate testing.

At LEDSupply, we have meticulously selected the LEDs we offer. We prioritize stocking only premium brands and uphold rigorous standards regarding color temperature. Our substantial experience in this field has underscored the importance of quality manufacturing and effective binning of LEDs. During manufacturing, LEDs display performance variations around average values stipulated in their datasheets. Therefore, manufacturers class (bin) LEDs according to luminous flux, color, and forward voltage. We opt for bins representing the highest luminous flux (visible light) and minimal forward voltage to ensure we provide LEDs showcasing optimal efficacy. Many lower-quality LED products are poorly constructed and inadequately documented, leading to frequent project failures and fostering skepticism regarding the longevity of LEDs. Owing to our expertise and purchasing potential, we can provide top-tier products at competitive prices.

This guide serves as a valuable foundation for understanding LEDs and selecting suitable products. If further queries arise or if you want more information regarding a specific product or its applicability to your needs, we're here to assist. Please reach out via our contact page or call us at (802) 728- to discuss your requirements with our knowledgeable Tech Support Team.

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