Large Neopixel Project Help

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grandeswag
 
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Large Neopixel Project Help

Post by grandeswag »

Hi, I'm building a large music visualizer using neopixels. I have a 20x30 neopixel grid built. Only about half of the pixels light up with my current set up just using the strandtest code. I'm using a Teensy 3.1. I have a 5v 40A powersupply, power leading to many spots from the supply to the neopixels. If my hardware is no good, I also have access to beaglebone black rev B and C, and a raspberry pi.

any ideas?
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davidl13
 
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Re: Large Neopixel Project Help

Post by davidl13 »

Please excuse my ignorance but will the Teensy actually drive 600 NeoPixels?

(I'd keep a close eye on the voltage and current from the supply.)


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pburgess
 
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Re: Large Neopixel Project Help

Post by pburgess »

A Teensy 3+ should have no trouble with huge numbers of pixels.

Two things:
1. Have you tried connecting the Teensy to a data input further down the line? (Running the same code is fine.) Idea is to see if there's a bad pixel causing the trouble, or something else.
2. Do you have (or can you sketch) a schematic of your power distribution? How many connections to the strip are there, and what's the wire gauge?

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paulstoffregen
 
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Re: Large Neopixel Project Help

Post by paulstoffregen »

davidl13 wrote:Please excuse my ignorance but will the Teensy actually drive 600 NeoPixels?
Yes, 600 is actually a fairly small project. Teensy 3.1 can pretty easily do far more.

A few months ago, I personally verified 4320 LEDs (an array of 90 by 48) can be driven easily at video speed, while also playing 44.1 kHz (mono) 16 bit audio, using only a single Teensy 3.1, with the Octo28 shield for signal outputs and SD shield for a SD card to hold the data (no PC was used). It was demo'd at Maker Faire in San Mateo last May. Here's a detailed blog article about that 4320 LED project.

http://community.arm.com/groups/embedde ... faire-2014

600 may seem like a lot if you're used to regular Arduino. For Teensy 3.1, it's actually a pretty small number.

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paulstoffregen
 
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Re: Large Neopixel Project Help

Post by paulstoffregen »

Good power wiring is critically important for LED projects. For a small strip or just a couple NeoPixel rings, you can get away with just a couple power wires. But for hundreds or thousands of LEDs, you really must run lots of power wires. Merely running a few small power wires to 600 LEDs is not enough. Poor power delivery will cause any big LED project to fail.

Please watch the video of that 4320 LED project. At 0:27 you can see the back side. There's also a photo about 1/3rd the way down that lengthy page. You can see that project used 48 pairs of red/black on both sides, for a total of 192 wires for power delivery from the 6 power supplies to the LED array. I believe that project used #20 size wire.

A pair of power wires should be connected directly from the power supplies to each strip. For long strips (like the 90 pixel length in that huge project), you need to connect both sides. For you shorter 20 LED strips, connecting to just one side is probably adequate. But you MUST run many separate power paths to feed power to your LED array, so all the LEDs get a low impedance power source. It may seem excessive, but you really should run 30 separate pairs of wires, from every individual strip directly back to the power supply.

DO NOT route the power in a serpentine path like the data. Think of the power and data separately, not "flowing together".

You should also design your system so the Teensy ground and LED power ground meet at or near the LED data inputs. LEDs should always have their power wires kept as reasonably short as possible and run directly to the power supply (never to the Teensy first).

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