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How many leds? #288
Forgive me if you see this question for the 100th time but I didn't find it in FAQ, neither in wiki.
So the question is, how many ws2812b leds can I control? I mean what is really the maximum length?
Thank you for answering.
This doesn't relate to the FastLED library, so it would be better discussed on the FastLED Google+ group - http://fastled.io/+
That said, your biggest issue is going to be voltage drop on the strip, and that will depend on how bright you're running the LEDs and how many are on simultaneously. You can always inject power along the strip in segments with heavy cable from a large PSU, or via several "point of load" power supplies. Just make sure to keep a common ground connection.
With the WS2812B and similar LEDs, the data signal itself is regenerated by each LED chip, so that isn't generally an issue.
With enough LEDs, your next bottleneck will be either memory capacity of your microcontroller, or the time to send each data frame (depending on your desired update rate).
The application on your uC will crash - sometimes "randomly" sometimes reliably - when it has too little SRAM to hold the datait needs to work on.
The amount of SRAM available for LEDs depends on what else the controller is doing that also requires SRAM buffers or "chunks" such as :
Arduino Leonardo, Micro, Uno, Nano only has 2.5 kByte of SRAM,
Required framerate - mostly to keep the animations or video frames looking smooth
Power supply rating ( and cabling used )
How many leds is a complex question - it depends on the amount of ram on the hardware that you have (e.g. about 600 on a given arduino, more like 10-15,000 on the teensy). It also depends on what kind of frame rate that you want. It takes 30µs to write out a single led's worth of data, so the absolute maximum number of rgb led updates per second that you can do is about 33,000 (or, if you're doing 8-way parallel output 260,000ish). Of course, that's assuming spending 100% of your time writing led data.
Re: maximum length - there really isn't one. Because each WS2811/WS2812 re-generates the signal, in theory you can have as long of a chain as you want (as long as you inject power regularly, see below - or every 100 or so). Voltage drop is the reason why you need to inject power at various points - but because of the signal regeneration happening at each chip, you don't have to worry about voltage drop/signal degradation as a function of length.
Thanks for informations
But I don't understand, How to calculate the number of LED WS2811 that can be put on a microcontroller ?
Can you help me for this calculation, with the size of RAM, the speed of the µC ?
And for my application, I need to receiv data with the 1.31 protocol and I find this takes place in RAM ?
thanks and soory for my level in english ..
First off, I am a complete newbie so thanks for any insight and help.
I am putting together a Christmas Light Display using Arduino's. Part 1 is 16 Solid State Relays being controlled with Vixen through an Arduino Mega. Part 2 is strips of Mukungit WS2811 Pixels. I just got the LED Strips last night and I copy and pasted some code for PixelFlex to get them to interact with Vixen and it mostly worked. I know now (after reading this thread) that one issue is that I was using an Uno because it's what I had laying around and I could tell it wasn't as responsive as I would like. Another problem is that some of the Pixels in the middle of the strip stayed lit and were not controlled with the rest of the pixels. I imagine that this is a symptom of me copying and pasting code that was not the right thing. When ran a simple chase code all of the Pixels responded appropriately so I know that the strand of pixels is fine.
Now, for the big question... Each strand has 300 Pixels and I would like to run 8 strands. Furthermore, I would like to run them all independent from each other. How many of what controllers would you recommend to control these? From this thread I am getting the feeling that a DUE might be the right answer for me but will one do it? I'm good with power, I'm just lost when it comes to coding and the processing speed of Arduino's. I bought the book "Programming Arduino" and am working my way through that.
yes, I know I need to start small.... but that's not my style. That's why I am starting to work on my Christmas Display at the end of September. Thanks in advance!
ajensen2 - check out the controllers from SanDevices. I started my Christmas display using Arduinos and have transitioned to the SanDevices E6804 controller. It is awesome and has good fusing on each output for protection. Also check out xLights software too. I am right now switching from Vixen to xLights. Good luck.