What is the highest value of NUM_LEDS? I need 5400...

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What is the highest value of NUM_LEDS? I need 5400…

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@Tomasz_M ​ Have a look at this post:
https://plus.google.com/114844607488015640212/posts/iHiofCd84pe

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There are a few limitations:

  • Each LED takes three bytes of RAM, so there’s a hard limit based on what microcontroller board you choose and how much RAM it has. An Arduino UNO has 2,048 BYTES of RAM. A Teensy 3.1 has 64K bytes.

  • Transmitting data to each LED takes some time. If you had (bog forbid), 5,400 slow WS2811 “NeoPixels” in one string, you could only update them about six times per second. If you use fast APA102 “DotStar” LEDs, you can update about 20X more times per second.

  • Calculating the animation design for 5,400 pixels will also take more CPU time than calculating animations for a smaller number of pixels. You’re going to want an ARM-based microcontroller, like the Teensy 3.1.

  • And then there’s power. Each pixel draws up to 30 milliamps. Even if we assume just a meager 20ma per pixel, 5,400 pixels will draw over 100 Amps at five volts, and you have a serious power challenge.

Let me pose this question to you: What’s the largest project you’ve done so far? Is this idea you have about the same scale? Is this new idea 10X bigger than your previous largest? 100X bigger?

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Hah!

Well, I have confidence that you can get there! Everyone else who’s ever done thousands of LEDs has started off with just a few…

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I need more and more and more :slight_smile:

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You’re among friends here.

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Hi @Tomasz_M ,
As was pointed out to you earlier, you will need to very carefully design your power supply and distribution to make 5,400 RGB LEDs work !
Please note that Mark’s assumption of 20ma per pixel is only that… an assumption… If you ever want or need to light up all 5400 RGB LEDs full brightness white you may actually need closer to 60ma per pixel, that is 20 ma per color on each pixel so 5400 LEDs X 3 colors(R-G-B) X 20ma per color = 324 Amps.
I really hope you have some solid understanding of power distribution issues. If not, come back with a lot more details about your project…
What type of RGB LED are you using or planning to use ?
What physical layout are you planning ?
EX: a 2D array 54 X 100 ??
What kind of animation ?
How often will you need to update your display? That is the FPS you would need ?

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7 x PMR-4V320WDAA ?

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@Tomasz_M That is only a 4.2V output !?!?!

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I am currently building a 150x24 matrix and have plans to build a 750x24 one!
I am using Teensy 3.1’s with OctoWS2811 adapters and overclocking to 144MHz. The DMA means that I still get to use the cpu time while the led data is being streamed. For power I use multiple 300w 5v PSU’s with bridged grounds.
For the larger matrix I am going to have to use three teensy’s synced together. I have developed a method using the pull down mode of the digital inputs and a diode to make an OR gate, it requires 2 pins on each board. I use the same software on each board and use 2 more digital pins so that they self ID on startup and shift their matrix window accordingly. In trials for the larger matrix I can achieve around 50 frames per second which is fine for my use :slight_smile:

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