Hi,
I work on an artistic installation with 30 000 leds (may be 42 000 futures)
This is not for a video screen so I do not need a high refresh rate. (This point remains to be determined)
As much for piloting a limited number of leds I understand well how to go about, as much for a project of this magnitude I have some doubts and therefore prefer to call the experts.
Which controller do you think should be used?
According to my research, the best solution would be several teensy connected. Am I right?
How to determine the number of teensy?
What are the alternatives?
First determine how bright you’ll be driving each LED. At full brightness they can draw as much as 60mA each. So 0.06A * 42,000 = 2520A @ 5V. If you use 120V to 50A power supplies, you need 51 of them. Then you’ll need to wire them such that you inject 5V power every hundred LEDs or so.
If you use WS2812s your refresh time will be 1.26 seconds to write to the whole strip as a single unit (800kHz data). You’ll have to use multiple processors to do better than that. If you use APA102s you can write data a lot faster (many MHz).
Thanks James.
I considered the energy part and the need to regularly power the LEDs.
On the other hand I did not consider the constraints related to the rate of transfer of information.
How do you get the delay of 1.26 seconds?
Is it in the case of using a single output for all 30,000 (42,000 LEDs)? Because if I understood correctly, the use of several outputs in parallel allows to inject the control signal at several points and thus to reduce this time.
According to my research the leds APA102 have a rate of 4Mhz therefore almost 3.2 times faster but I do not know what to think because I have difficulty to interpret the datasheet I consult. What parameter should we look at?
If I understand correctly, it takes 3 bytes per led therefore between 90 kb and 120 kb of memory between 2 and 3 teensy 3.x.
Is it possible to chain several teensy? I understand that yes but I do not find where I read it.
Are there controllers with enough memory to handle as many leds and arduino / fastled compatible?
Hi Simon, you can read about Teensy information at http://www.pjrc.com they do have an octows2811 shield which can chain 3 Teensy boards together. You can also find usefull information / project in Youtube, keyword octows2811, you’ll find a way to control the led via pc software (live) thru USB. If you want to control that much of LEDs, what kind of IC you wanna use? 1 LED/pixel or 3 LEDs/pixel? WS2812 and APA102 are single pixel/LED type. Therefore, u will need more controllers.
@Joni_Law Hi, I’ll need RGB led.
At this time, I don’t know what IC I’ll use. I just like use FastLed libraries because it seem very usefull and simple to make animations. So I’ll need one IC (or more chained IC) who is able to drive very lot of led and who is Arduinon compatible.
I’ll deeply search on youtube for more exemples.
Hi Simon. For 30K-45K count of LEDs, in my opinion, I’ll use a pc based software like Madrix (commercial) or Glediator/Jinx (free) paired with suitable controller (can be DMX/SPI). Madrix do have both solutions. Using arduino based, we gotta do a lot of programming in order to get good effects result. Say for example you’re going to use ws2812b LED strip (there are other LED fixtures out there) per meter 60 LED. 30000/60 = 500 meter of LED strip
30000 also = 30000 x 3 bytes (CRGB) = 90000 bytes. Which is not possible to use an Arduino Uno or alike. Whereby using Teensy 3.2 https://www.pjrc.com/store/octo28_adaptor.html
You have limitation of around 8864 pixel per board, and maximum of 3 boards supported as written on their page. So, my conclusion is supporting that much of LEDs not to say cannot, but difficult to achieve and must spend a lot of effort to do effect programming. Good luck.
@Joni_Law Yes, my project will be based on 500 meter of 60 LED / m but it’s not final because it must fit into my budget.
The project is in gestation therefore according to the cost I will reduce the necessary length or the density of LED / m
I came across Glediator a few days ago but I did not deepen the subject because it did not seem to meet my expectations. I will take a closer look.
thank you for your advice
@Matthieu_Simon it also depends on what kind of animation you want to do (e.g. CPU load/frame). One way to distribute the load is to use stateless frame generation. I have an experimental framework at https://github.com/maruel/dlibox/tree/master/go/anim1d that enables coordinated autonomous actors to generate blended frames without external coordination beside a “clock”. Everything in integer calculation so it works well even on a single-core 700Mhz RPi1 (tested). It’s kind of a “competitor” of FastLED in some way but for higher power CPUs since it requires linux for now. It can then be driven directly by an rPi or (maybe?) a series of FT232H connected to a PC.
https://twitter.com/marcaruel/status/793441115756236800 shows 4 independent workers coordinated over MQTT and triggered via motion sensors and timers but I’ve yet to try the “chunk X of strip Y”. The code is very “1D oriented”, which may be a bit limited if you plan to create 2D or 3D displays.
