The power requirements for DotStars are pretty much identical to NeoPixels…in fact, we’ll simply refer you to the relevant page of the NeoPixel Überguide for pointers on estimating and routing power. In summary:
- Estimate up to 60 milliamps peak for each pixel at full brightness white.
- A ground connection is required between the microcontroller and strip, in addition to the signal lines.
- For long strips, try to add a power tap every meter or so. This prevents a brown-out effect toward the end of the strip.
- As with NeoPixels, adding a 1000µF (6.3V or higher) capacitor close to the strip (between 5V and GND wires) is a good idea, do it!
Another guide, this one about minimizing NeoPixel power draw, is also 100% applicable to DotStars!
Our LED suppliers sometimes make unannounced production changes to the wiring. Therefore, the best way to identify connections is a close visual examination of the strip.
First, look for arrows printed along the strip next to each LED. These show the direction of data moving down the strip…your microcontroller connects at the originating (“in”) end, the arrows point toward the “out” end. (In the photo above, our microcontroller would be located off the left side.)
Second, look for labels on the strip to identify the function and order of the four wires: ground, 5 Volts, data and clock…usually labeled GND, 5V, D or DI (data input) and C or CI (clock input). These will go to corresponding pins on your microcontroller and power supply.
Again, due to production variations, you can’t always count on wire colors or plug genders as a reliable indication of function, even if ordered at the same time. Take a close look to confirm before connecting anything.
The simplest wiring is if you can power the strip off of the microcontroller board itself. This is fine for small projects (one or two dozen DotStars max) because we don't light up a lot of LEDs at once.
- Connect the strip 5V pin to the board 5V
- Connect the strip GND pin to board GND
- Connect the strip CI (Clock input) and DI (Data input) to the board’s SPI SCK and MOSI pins (if using an SPI bus) or any two digital pins (if “bitbanging” the signals). We’ll explain this in more detail in the “Software” section of this guide.
For longer strips, when you need more than 1 Amp of current, you should power with an external 5V power adapter like so.
- Connect the strip 5V pin to the power adapter 5V
- Connect the strip GND pin to board GND and power adapter GND
- Connect the strip CI (Clock input) and DI (Data input) to two digital or SPI pins as explained above.
Important: three points are connected to ground: power supply, microcontroller and DotStar strip. If there’s no common ground between the microcontroller and strip, the LED’s won’t function properly.
DotStars are 5 Volt devices. They may respond to 3.3V signals, but this is not a guaranteed thing. If using a 3.3V controller (Feather, Raspberry Pi, etc.), add a logic level shifter to boost 3V logic to 5V…something like a 74AHCT125 on the data and clock pins.