WS2812 RGB LED questions

Using Arduino Project Guidance
#1

My questions are simple.

  1. Is there any way I can have an arduino detect how many LEDs are in set of WS2812 addressable led strips.

  2. Does anyone else run into the issue of the LEDs quickly flashing a random color? It only ever happens when connecting power, I managed to reduce the issue about 90% but the other 10% of the time one or more of the leds flash a random color. Any ideas world?

Dragono

#2

1 maybe if you could come up with a way to determine the current flow and divide that by 60ma when all the LEDs are 255,255,255.
2 never had that problem.

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#3

dragono:

  1. Is there any way I can have an arduino detect how many LEDs are in set of WS2812 addressable led strips.

If you connect the data out line from the last LED in the strip back to the Arduino, it would be possible to monitor the signal coming back from the strip. If the strand were 15 LED long and the program sent commands for 20 LEDs, the data out pin of the last LED would send the data for the last 5 LED which wasn't used by the strip.

dragono:
2. Does anyone else run into the issue of the LEDs quickly flashing a random color? It only ever happens when connecting power, I managed to reduce the issue about 90% but the other 10% of the time one or more of the leds flash a random color. Any ideas world?

I've seen this. I think it's caused by noise on the data line as the lights are powered up.

If the LEDs were being continuously refreshed with new data, the random colors shouldn't last very long.

#4

dragono:
I managed to reduce the issue about 90% but the other 10% of the time one or more of the leds flash a random color.

How did you manage that?

BTW: You connected GND of the Arduino to GND of the strip, didn't you?

#5

Instructions with the LED strip said to add a200-500 OHM resistor inline with data wire. And yes I have ground them together.

#6