This Simple Device Tests SMD WS2812B LEDs

WS2812B individually addressable RGB LEDs are incredibly useful, because they’re much easier to control in large quantities than traditional common-cathode and common-anode RGB LEDs, while also requiring on a single microcontroller pin for data. But they can be a bit less reliable, as they contain their own tiny driver chips. There is nothing worse than soldering a bunch of SMD WS2812B LEDs onto a PCB, just to find that some of them are bad. To identify those faulty units before soldering them, Gokul KB (AKA gokux) designed this simple device for testing SMD WS2812B LEDs.

Gokux likes to salvage WS2812B LEDs from strips and modules, so it isn’t uncommon to end up with bad units. Maybe they were already faulty or maybe they were damaged during removal. In either case, Gokux wanted to sort out those duds quickly and easily. This tester, designed for 5050 size WS2812B LEDs, is perfect for the job.

The tester has four nice, big copper pads, so placing the LED with tweezers is easy. Whenever the device is on, it runs the testing code. That code (a sketch for the Arduino IDE) performs two tests. The first is cycling through red, green, and blue, in order to check the functionality of each of the actual LEDs inside the WS2812B package. The second is performing the same cycle on a second WS2818B LED, connected after the first in the chain and mounted permanently on the PCB. That is important for verifying that the tested LED’s driver chip is passing along data as it should.

The hardware for this is about as straightforward as it gets. Gokux designed a PCB using Flux.ai, which is browser-based software that includes some AI tools to streamline the process. That PCB hosts the permanent LED, the pads for the test LED, and pads for the castellated pins on a Seeed Studio XIAO SAMD21 development board. A minimalist 3D-printed enclosure, designed in Autodesk Fusion 360, provides some protection and only requires a pair of M3 screws to assemble.

This may be a niche tool, but it is inexpensive to build and would be very useful to makers that use a lot of WS2812B LEDs in their projects.