When searching the Digi-Key website for LED assemblies, you may come across three different types - LED engines, LED modules, and Chips On Board (COBs). The needs of your specific project will determine what the best LED assembly is for you.
An LED engine is what one might think of as a ‘complete’ LED assembly. Engines come with integrated current limiting circuitry and are as plug-and-play as this particular product type can reasonably get. One supplies power to an LED engine and they get light. This allows the system designer to focus their efforts elsewhere and consolidate all of their lighting circuitry into a single component, but it does cost the system designer some flexibility, as current level through an LED controls brightness.
An LED module is an LED assembly made with discrete LEDs that does not include integrated current limiting circuitry. These devices are simpler and usually less expensive than LED engines as well as affording a system designer the flexibility to control current to their lighting circuit themselves, but it does require the system designer to implement external circuitry around the LED module to ensure no overcurrent reaches and burns their LEDs. Because they’re made up of discrete LEDs, an LED module can be built in a wide variety of form factors such as light bars, or even made into flexible light strips that can conform to anything you need to illuminate.
A Chip On Board, or COB, is similar to an LED module, save that it incorporates multiple LED dies into a single package to create one homogenous lighting system. These are the Big Shiny devices that can generate tremendous light levels, acting as a single massive LED to produce all the light. Like modules, COBs do not incorporate current limiting circuitry and require this circuitry be supplied externally. Because a COB incorporates multiple dies into a single large package, they cannot typically be made into long light strips or bars, instead providing a greater level of illumination from a single source than many modules.
For more information on selecting the proper LED for your project, please check out some of our other articles on LED selection and design:
LEDs and LED Drivers
Choosing the Correct Resistor for Your LED
How to test an LED