Hello, I've just bought 12 strips with 300 LED each for 3600 leds total.

Hello, I’ve just bought 12 strips with 300 LED each for 3600 leds total. The plan is will start playing with it in the next weeks, are there any links suggested for that kind of number of leds? I’m thinking to go for a teensy 3.1 but I’d like to hear from other experiences.

PS. the goal is to create a 75x48 display

Are you going to be writing your own animations that run on the controllers themselves, or are you going to be piping the animation in from a connected PC of some sort?

If you’re not writing your own animations that will execute on the controllers themselves, but rather piping in pixel data from a computer, I’d recommend taking a look at Fadecandy for a controller. https://github.com/scanlime/fadecandy https://learn.adafruit.com/led-art-with-fadecandy/intro
(The Fadecandy is descended from the Teensy3!)

If you’re going to write your own animations, I’d definitely head for a Teensy3.1 for that scale.

Tell us more about the project you have in mind?

And what kind of LEDs are these? WS2811/WS2812B? Or something newer (or older)?

You will need (some) beefy power supplies which are capable to give you 216A at full white. And a decent plan how to distribute the power. Oh…and maybe sunglasses for testing :wink:

Thanks for the prompt replies.

I’d like to write the animations inside the controller, to reduce the number of components involved.

The first installation that I have in mind will likely only use a subset of the leds and hardly ever at full brightness, so I’ll probably go for (much) less beefy PSUs than the 216Amps suggested.
Leds are going to be screened by a canvas so I’m hoping to make it without sunglasses too (as always on a budget, LOL).

Frame rates are also not a concern, (we are thinking to produce an interactive artwork that invites people to feed a growing plant, so it’s not going to be whizzing fast), but of course I’d like to keep the option for high frame rates if feasible with limited electronic complexity.

I’m not 100% sure what type of leds I’ve got.
On the order they are listed as WS2811/WS2812B, and I have not investigated the difference yet.
They work with the NEOPIXEL setting of the library (3 pins).

Big question: in principle, can I attach them all to a single Teensy 3.1 if I don’t mind frame-rate issues?
This seems to be possible in terms of memory, but I’ve not bought a teensy yet to see what it means for speed and I have questions in terms of signal degradation over the data line.

Hi @Claudio_Benghi , of course you can attach all these LEDs to a single Teensy3.1

I would strongly suggest that you also order the OCTOWS2811 adapter at the same time you get that Teensy. It is plug&play with the Teensy, it will allow you to have 8 outputs in parallel and it provides the necessary logic level conversion from the Teensy 3.3V operating voltage to the strips 5V.

Hi again @Claudio_Benghi , you should have no worries about signal degradation over the data line unless you have exceptionally long length of data wire between strips.

As pointed out though, with that many strips and LEDs, solid power distribution will be the key to a successful project. Do not cut corners there, make sure that with you do not have any significant voltage drop anywhere on the strips when they are driven at full brightness white.

Do post some pics and videos when you have all that going… have fun !!!

Be sure to not drive the entire length serially. Put several strips into parallel. Otherwise your frame rate is going to be terrible. I have nearly 800 LEDs on a single pin on a Teensy and while its doable, I am thinking about rewiring the whole project to reduce the longest length to only 300 or so and it should significantly help the frame rate.

Thanks, right now I’m thinking to use the Teensy with the OCTOWS2811 (as suggested by +JP Roy) to cater for voltage conversion.
This makes 450 pixels per pin (8 pins available on the octo).
I was surprised at the amount of current these strips can draw… at full brightness it’s over 200Amps, I’m thinking to go for 50% of that if I keep brightness under control (several of my leds will be off most of times).
It seems all straightforward, next steps are to put them together nicely in the physical setup and look at how to achieve the animation patterns.

The problem with small PSUs is: even if you run only low AVERAGE brightness levels it is still a PWM which draws the FULL possible current for a very short moment. So use at least massive capacitors to limit the (massive but temporary) volage drops in order to have your leds always working properly. (It took me (painfull) weeks to understand this simple logic…)

You could get 4x 5v 70Amp power supplies. I have a price list from ScottLED says $16.13 a piece. So $64 plus shipping, which I would venture would put it up to $150 is pretty reasonable to light that. If you are running your PSUs at 100% all the time, I am certain the life will be shorter than running them at <80% all the time… Or run 3 PSUs with one as backup.

@Justin_Eastman @Stefan_Petrick thanks for the power tips. I’ve asked ScottLED and I’m waiting for their quotation… I was hoping for the power components to be a little less imposing (I need to find a place to hide them), but maths does not lie, they need to be beefy.

Hi @Claudio_Benghi ,

If you can afford them and you have the room to mount them, Ideally you should get
PSU’s that will supply the maximum current possible AND maybe even some more !!

That being said, if you are concerned with costs and/or PSU mounting space, I would not worry about only getting PSUs that can cover your calculated maximum average current draw plus 10 or 20% safety margin.

To add to Stefan’s PWM explanation, each device has it’s own internal PWM frequency, about 400hz. They are not synchronised and with so many LEDs, that peak current will tend to average out over the whole assembly. Small decoupling capacitors close to each device as found in most of these WS2812 strips should take care of peak local current demands.

If you know that you will always set your maximum brightness to 50%, then you can use that to safely decrease your PSU current specs.

If you know that your display will never have all LEDS ON simultaneously, you can also use that data in your PSU maximum current calculations.

If you know that you will never have all LEDs on white at the same time, you can again use that info to decrease your PSU current specs.

I need my $$$ to buy other toys so if I ‘know’ that I can use a 100 amp PSU for a build, I will not go out and purchase a 200 Amp PSU !!

I am just about to start putting together a 150 x 24 matrix! Definitely go for the Octo board, they work fantastically and due to the DMA output method, give more time for your code to run. To stop signal issues just remember to use twisted pair from the RJ45 direct to the strips. You can also set the Teensy 3.1 to 144MHz overclock which is working well for me and should easily achieve 50+ frames/sec. I have also put on GitHub my matrix, text & sprite classes if they are of use.