help in understanding the ws2811 led

[mortonkopf]

hi all,
can anyone explain this please, as I think I need to forget about using the ws2811 led for this particular project.

I have built two POV batons, one with ws2811 leds and one with LPD6803. The 6803 leds seem to progress from one colour to the next one sent seamlessly, without going to off. The ws2811 leds, on the other hand seem to reset by switching all colour off and accepting the new one. This gives a speckled effect rather than a flow of colours. Is this something inherent in the led (the 50us LOW)?

holly pov is ws2811, and other one is a lower density baton using lpd6803


regards
mortonkopf

 

[PaulStoffregen]

I do not believe it's related to the 50 us reset time.

The 50 us is simply the minimum no-communication time needed before the WS2811 will recognize more communication as being new, rather than simply continuing your prior communication. It's not a special signal sent to the WS2811, but merely the absence of any communication.

You can send no communication for much longer than 50 us, even hours or days or indefinitely. The LEDs stay on during that time. The WS2811 is not psychic. It's can't predict the future. It doesn't know if you're going to start new communication in 50 us or a month later.

This effect might be related to the relatively low PWM frequency the WS2811 uses. That's unrelated to the communication. Unfortunately, there's also nothing you can do to change it, other than use a different type of LED chip.

 

[mortonkopf]

Paul, thanks for the quick response, as you can tell, I looking at a steep learning curve. I love the idea of psychic leds though.

On further reading, I found on the Adafruit site regarding the ws2811 / neopixel "The refresh rate is relatively low (about 400 Hz), and color displays in fast motion may appear “speckled.”

all the best
mortonkopf

 

[ac17]

What about the newer ws2812b strips?

 

[dgarcia42]

the WS2812B has the same issue - 400hz refresh rate. Most of the folks I know doing POV type stuff are using the LPD8806 (which has something like a 2.4khz refresh rate, give or take, not to mention a 20Mhz data rate).