LED Project Design Guide

THIS PAGE IS A WORK IN PROGRESS

A basic tutorial on building your own LED light or LED art project. This is not meant to be a one-stop guide, but a local source for basic questions and terminology.

Controller

A controller comes in different types, the controller needs to be compatible with the LEDs or pixels that are being used.

Constant Voltage: Most common type, does not regulate current and provides a consistent voltage, usually the output is PWM controled to vary the channel intensity. Used to control LEDs such as 12 volt LED strip or modules.

Constant Current: A less common type, regulates the output current to a constant selectable value, voltage is consistent but can be higher than the LED's rated voltage. used to control high-wattage LEDs, or smaller LEDs such as 5mm or 10mm types.

Pixel Controller: Becomming more common, these types of controllers are used to talk to smart/addressable pixels, such as WS2812, WS2801, APA102. These controllers do not control the LEDs directly like other controller types, but rather produce a data signal that is received by the pixels and decoded into light intensity for the colored LEDs within the pixel.

LED And Pixels

The most important part of a LED project, the LED didoes. LEDs are available in all sorts of types, currents, voltages, and configurations. Anything from a SMD single color LED to high-wattage RGBW LEDs mounted on heatsinks. Each LED, whether it is a module or a single loose LED requires careful selection of controller and especially current limiting.

Standard LEDs: Covers SMD packages and epoxy cast packages like 3mm, 5mm, 10mm. These types of LEDs come in a variety of light colors, packaging, and lenses. SMD types usually have a clear lens that adjusts the viewing angle of the LED. Epoxy cast packages come in different sizes, in either clear, diffused white, or colored lneses. Colored lenses do not affect the color of the LED, clear lenses change the LEDs viewing angle. These types of LEDs commonly use 20mA to 100mA.

High Wattage LEDs: These types of LEDs are large and bright, and normally mounted on an aluminium heatsinks(commonly called stars), that are then thermally attached to even larger heatsinks. They require high currents and produce a lot of extra heat that must be dissipated through a heatsink to prevent damage and degraded life expectency. These types of LEDs should only be controlled with a constant current controller or regulators, using resistors produces too much power waste to be effective.

Smart or Addressable Pixels: The most recent development in LEDs, these are usually contain RGB or RGBW LEDs with an integrated driver. The pixels don't get powered by the controller but rather receive a digital data signal that the pixel converts into light intenstiy values. Multiple pixels can be chained together one after the other to create longer strands. Each pixel in the strand can be individaully controlled through the data protocol. Pixels come in different chipsets, each chipset requires a different data protocol and has different features and capabilities. Look online for additional information. And visit the LED Pixel Chipsets page for supported chipsets supported by NLED.

Current Regulation

LEDs can not limit the current that flows through them, given the opportunity they will draw so much current they will burn up the diode. No LED should be powered up with out current regulation, LED pixels have internal current regulation and are powered directly from the power supply.

Constant Current: The best way to limit current, it is the most power effiecnet and safest way to power LEDs. Constant-current regulators come in many sizes and capabilities, they come as small as SOT-23 SMD sized for current regulation as low as 10mA, or larger multi-component circuits that can produce high currents. The constant-current regulator must have the same output current(or less) as the LEDs require, some are output a fixed current, some methods have adjustable output currents.

Resistors: Suitable for low current standard LEDs, quick and cheap, just add a resistor in series with the anode from V+, or in series with the cathode to DC GND. See online calculators for help choosing resistor values for various LED forward voltages.

Power Supplies

Power supplies should provide the correct voltage for your LEDs or pixels, commonly pixels use only 5 volts, but some may use 12 volts. While standard LEDs or high-wattage LEDs will use voltages dependant on how the LEDs are arranged(series or parallel) and how many are connected. Series LEDs use more voltage than a single LED, but the same current. Parallel LEDs(not recommended usually) require less voltage but higher currents. A power supply's voltage should match the LEDs requirement exactly(unless using constant current controller) to prevent damage or inconsistent light output. But the amperage can be higher than required, a power supplies amp rating is the maximum it can provide, so it is fine to use a 3A PSU for 1A worth of LEDs.

A very basic/simple calculation for your projects current consumption with LED pixels: # of Pixels x 60mA = maximum current draw(in mA, divide by 1000 for amps)

Wiring and Connectors

An often over looked component for a project, the wires and connectors used to put everything together is equally important as the other project components. Under rated wires or connectors can cause power distribution issues which can result in inconsistent color between LEDs or pixels. Proper power distribution and routing can greatly affect the quality of the project.

Wiring: As a general rule, use the heaviest gauge wire that is reasonable for the project, especially on the main power runs, such as from the PSU to the LEDs. If there is a long wire run between LEDs or from the power supply, those are the areas that should have the thickest wire. Thicker wire results in a lower resistance for the wire run, voltage levels will drop as it is transmitted throug wires, thicker wiree has less reistance so therefore less voltage drop. Bad power routing causes LEDs and pixels to be dimmer than expected. It is especially noticable when a long pixel strand is powered, the end(s) closest to the power supply will be at full intensity, while the pixels further down the strand and further away from the power supply are noticiably dimmer, affecting the color consistency. It is very noticable on certain projects and must be avoided. The best method is to inject power into the pixel strand as often as possible, these injection points are nothing more than a direct connection to the power supply or power distribution point with heavy gauge wire that prevents voltage drop. Not easy to do all the time, NLED has a few products to make power injection easier. Products Webpage

Connectors: A common bottle neck and often not considered. All connectors, whether it is wire-to-board or wire to wire have limits on how much current they can pass through before negative effects such as heating and voltage drop become an issue. If an under-rated connector is used, it can cause issues like lower voltage and limited current draw, which can dim LEDs or make them not function at all. Voltage ratings are less important as they are usually a few hundred volts, not an issue with low voltage DC. The actual current ratings of connectors is specified by the manufacturer. The common JST(-SM) connectors commonly used for LED pixels are rated for 3 amps, which equates to about 50 RGB pixels. Common tube jacks(2.1x5.5mm or similar) have ratings between 2 amps and 5 amps. For high current applications, like power supply connection and large runs, connectors like XT-30(30 Amps) or XT-60(60 Amps) with heavy wire are recommended.

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