Most of these LEDs come in a 5050 housing (5x5mm SMD) and have a WS2811 controller chip in them. There are also some other versions. Here we describe some of them.
WS2812 / WS2812S
This is the first version of the integrated WS2811 IC into the LED (as far as xopr knows). It has six pins (see the ASCII LED diagram): (top N/C, middle VDD, bottom VSS) ⋮[ #]⋮ (top VCC, middle DI, bottom DO: notch)
This is the improved version with only four pins (see the ASCII LED diagram): (top VCC, bottom DO) :[ #]: (top DI, bottom, GND: notch) (top view, the # is where the chip is)
Also known by Adafruit as DotStars.
Currently, we haven't played with it yet.
interfacing with 3.3v logic
The 5V logic doesn't accept 3.3v signals by default; there are two ways to get around this:
- under-volt your LEDs (tested with about 3.75v, and the input logic accepts 3.3v
- add a level converter.
- You will often see a mosfet (BSS138 or 2N7000, which work bidirectional) or TTL logic (like the 74LS245 octal bus transceiver, or just an AND or OR gate), but since we only need a 5v output connected to a high impedance input, we can use an NPN transistor for this. (reference: ,  and )
- Connect the:
- collector of a bc547 via a 4k7 resistor to 5v
- same collector to the DI of the LED
- base of the transistor via a 10k resistor to 3.3v
- emitter to your 3v3 output