Determine How Much Light You Need
The number and type of LEDs that you select for your application will of course depend on a number of factors unique to your requirements, including:
- The size of the area to be illuminated.
- The illuminance (brightness) that you need.
- The light color that you need.
To estimate the total lumens that you will need, select a similar light source from the table below and multiply the value in the Lumens per Watt column by the total wattage of the lamps you would typically use.
For example, if you would normally use two 12" fluorescent lamps that are rated at 8 watts each with a lumens output of 60 LPW, then you will need select LEDs that can generate 960 lumens to produce the same amount of light.
Lumens per Watt (LPW)
12 - 18
50 - 100
|Metal Halide Lamp||
65 - 115
|High Pressure Sodium Lamp||
85 - 150
|Low Pressure Sodium Lamp||
100 - 200
Next, you need to determine the color that you need. LEDs are available in a wide variety of colors and temperatures of white light. If a specific color is not available, then it is even possible produce a specific color or temperature by mixing the output of different color LEDs.
Normally color mixing requires specialized controllers and is probably beyond the scope or need of most applications, but you can still do some basic mixing simply by selecting different color LEDs. This will require a bit of experimentation, however.
Number Of LEDs
The number of LEDs that you will need will be based on the total lumens that you need for your application. As each color LED has a different lumens output your first need to decide what color LEDs you are going to use. Then using the lumens ratings of the LEDs you have selected, determine how many LEDs you will need to achieve the level of lighting that you need.
As you browse our online catalog of LEDs, you will find that there are a lot to choose from. So where should you start?
First, we recommend that you stick with our pre-mounted Rebel LEDs. Un-mounted Rebel LEDs require specialized tools and skills to solder them to their mounting bases, while mounted LEDs only require basic soldering skills and standard bench top soldering tools.
Whenever possible try to stick with the 20mm single star LEDs. These LEDs are not only easy to work with, but cooling is much easier than the Tri-Star LEDs. There is also a much larger lens selection for the 20mm single star LEDs.
If space is at a premium, then the single 10mm square LEDs may be a good option.
You need to determine what type of optic or lens will be needed for each LED. The output from an LED typically has a beam angle of about 120 degrees, which is usually far too wide and unfocused for most applications. To focus and direct the beam you need to mount a lens in front of each LED. These lenses are sometimes called secondary optics, as they are used in addition to the integrated lens on the LED. (The primary optic.)
Selecting lenses is not an exact science, so you may need to do some experimenting to determine what beam angle you need for your application.
Powering The LEDs
LEDs are not like incandescent or flourescent lighting and have specialized power requirements. So before you continue review this page to learn more about how LEDs need to be powered.
For long life, color stability and low heat generation, we recommend that you limit the drive current to your LEDs to 700mA whenever possible. Even though most Rebel LEDs are rated to operate as high as 1000mA, running LEDs at these power levels requires a cooling system that can be challenging to design and build.
Like the LEDs, we also offer a large variety of 700mA power drivers to choose from. Which one you should use will of course depend on your specific requirements, but as a starting point you may want to check out the 3023-D-E-700 driver. This DC driver is dimmable and comes with an integrated wiring harness - making it easy to connect the driver to your power supply, the LED and a potentiometer for dimming the LEDs.
Depending on the input voltage that you have available and the LEDs that you are powering, a single driver can power up to 7 series connected Rebel LEDs at 700mA. You will find more details about using BuckPuck drivers, including a number of electrical schematics in the driver documentation.
In addition to the LED driver, you will also need a DC power supply. Most folks just use a standard DC wall adapter. The power from the wall adapter goes directly into the LED driver, which in turn regulates the output current for the LED(s). We do not offer DC power supplies or wall adapters.
Quite a bit of heat is produced inside an LED that must be removed and dissipated, making heat management a very important part of your design consideration. You cannot operate high power LEDs without providing some means of removing and dissipating the heat.
Cooling is usually achieved by mounting the LED directly to a finned aluminum heat sink, and in the case of confined environments, using one or more cooling fans to extract the heat from the enclosure. You will find a detailed article here that provides more details about how to cool high power LEDs.
LEDs are usually mounted directly to a finned heat sink. The best way to do this is with double sided thermally conductive tape. You can also use thermally conductive epoxy, or even screws and nuts, but thermal tape is clean, neat and much easier to use.
LEDs are not waterproof or moisture resistant, so if you will be using the LEDs in an outdoor or damp location you will need to mount the LED assemblies into some sort of moisture resistant enclosure.