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Topic: LED/MIDI to light up a series of sculptures (Read 1 time) previous topic - next topic


Dec 13, 2016, 09:53 pm Last Edit: Dec 13, 2016, 10:45 pm by Erik1234
I'm working on a fairly complex project for a beginner, and I really need some help! I'm embedding 100 WS2811 rgb LEDs in ceramic sculptures and using a MIDI interface together with a sequencer to write a light display that synchronizes with sounds. Everything triggers with a sensor when you sit in front of the piece and randomly selects one of ten positions in the sequencer.
I have written the code, and it works fine for my 8-LED prototype powered via Arduino by USB, but now it needs to be scaled up, and that means powering it externally.

6amps should be enough current for the lights as well as the Arduino (max 60mA per rgb LED). It's easy enough to find a 12v 6a AC/DC converter and 12v works with the Arduino. The LEDs want 5v, so I need to step down the 12v.

1.  Should I use one converter that can handle 6a, or should I use 3 that can handle less current, and divide the LEDs into sections? (shown in the schematic)

I'm learning so much new stuff that I don't even remember right now why I drew it like that, maybe someone can tell me? The thing is that the different sections of LEDs have to be spread out. I think I read that the buck converter should be as close as possible to the load.

2.   How should I connect the ground together? The MIDI part of the circuit takes 5v from the Arduino, can that go to the main ground wire or should it go to ground via the Arduino ?

3.   I use one large capacitor next to the power plug. What size should it be? The calculations made me very confused, gut feeling says 1000uF. I don't know exactly how clean the signal has to be (% rippel), but I guess cleaner is better especially with these rgb LEDs that send a lot of data on one pin? Then as I divide the LEDs into sections I put a smaller 100nF one per section (sizes are between 10-20 LEDs per section).

So those are a couple of things I would really like to know the answer to, but please feel free to look at the drawing and come with other comments! I tried to be specific, but really I just want to break down and cry and let someone with actual knowledge deal with this mess :) It's my first schematic, not sure I have done it right. Attaching also a Fritzing diagram that shows my intentions if the schematic doesn't make sense.

Finally, somewhat unrelated, I will need to pull cables from the Arduino to the lights, which are sitting around 160-190cm (5-6ft) away. Then there will be 10-20cm (5-10inches) between each light (I can't use strips, the distances between lights have to be irregular), and the max number of lights on one data pin is 40.

4.   Is it reasonable to expect the data to arrive correctly to the LEDs or am I kidding myself? How many LEDs can I power with one AWG20 jumper wire? Do you think I need to put one on each end of a 20 LED section? In that case, is one ground cable enough or it needs to be two as well?

omg, I have a million questions, but this is a start. I really hope you can help me! Thanks!

Edit: Here's the prototype in action https://www.youtube.com/watch?v=Tu9M32QbaDs

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