Teensy LC plus neopixels... (noob alert).

Searching through the forums haven't turned up an answer to this simple+newbie question:

On the Teensy LC home page it says:

"Teensy-LC provides a 5V output to directly drive WS2812/NeoPixel LEDs"

then it says:

"A 74LV1T125 buffer is connected to pin 17, with the increased output voltage available on another pin"

Here are the questions:

- what is the simplest circuit to explore WS2812 strips with Teensy-LC?
- can I do this with power from the USB alone?
- bonus question: how many LEDs could I hope to power off usb alone?

Any replies are greatly appreciated!

Hi.

WS2812's can draw up to ~ 60mA each at maximum brightness on all elements (eg, red blue and green cranked right up to 255, producing a very bright white).
USB can provide up to 500mA, - 100mA for teensy + some headroom leaves you with about 400mA to play with.

If you limit your brightness to a quarter (still produces bright colours), you can get around 400 / (60 / 4) ~= 26 LEDs.

The circuit is as simple as providing 5v to the strip on its Vin line from Vin on the teensy, connecting ground and finally connecting the data in on the strip to the 5v buffered pin on the teensy (I can't remember which pin that is precisely).

For software, I recommend the FastLED library that comes packaged with teensyduino.

Hope this helps. =)

Hi Cosford, indeed it does! Thanks!

For future newbies: it seems that the 74LV1T125 is built-in on the Teensy LC board (cool!)..
And the output pin is on the "right side of the board" next to pin 12. Software that writes to pin 17
also triggers higher-voltage results on this special pin.