1ST Neopixel Project Help

[jward448]

All,

I am working on my first Neopixel project and could use your help specifying it. Here are the reqs:

Need to control 70-75 Neopixel LEDs. They need to be spaced roughly 12" from each other.
We'd like to use a wifi enabled raspberry pi as the primary control compute interface connected to a fadecandy connected to the LED chain.
Each pixel will be responsible for lighting up a cloth covered 12"x12"x12" triangular panel in a geodesic dome. I'm not sure we'll get enough light and be able to diffuse it enough to completely light that large an area but budget constraints keep us from just throw more LEDs at it.

-Other than the fade candy and the pixels themselves are there any other things you'd recommend we buy from Adafruit?
-Are there concerns about the distance between the pixels on the bus? If so, can it be mitigated?
-Any powersupply recommendations? It would be ideal if we can just hook a DC-DC PS to a 12V, high amperage battery and have it run all day.


This dome will be part of an interactive display that will be used to encourage teens in STEM.

Any guidance is greatly appreciated!

James

[mikemeaney]

It's doable. In my own testing I've strung two pixels the width of a sofa without issue. NeoPixels buffer the signal they out put meaning that the signal (for the most part) is just as good at the last pixel is just as good at the first.

Also neopixels are INSANELY BRIGHT. I'm often covering them put paper or pointing them at the wall.

[mikemeaney]

Also, use a 5v. Supply. 12v will destroy your pixels

[adafruit_support_mike]

Absolutely right on both points above!

WRT power, each NeoPixel uses up to 60mA, so 75 of them would use a maximum of 4.5A. In practice, we've found that you can usually make projects work with 1/3 of the maximum current.. you only use maximum current when the pixels are putting out white light at full intensity, which isn't very interesting. Once you start mixing colors and changing the brightness, the current consumption falls.

A 2A @ 5v power supply should be enough to run your NeoPixels:
https://www.adafruit.com/products/276

One point to note: we suggest putting a power connection about every 30 pixels.

Each pixel only gets as much current as the ones before it have allowed to go past, so the voltage along the VCC wire drops slightly as it passes each pixel. Even small losses add up though, and eventually your colors get 'red shifted' because there isn't enough voltage for the blue and green pixels to draw full power.

Putting a new connection to the power supply about every 30 pixels keeps the line losses small enough that all the pixels work as they should.

[OsmarTakeuchi]

Following this subject, where I have almost a similar configuration (in totally different application), this 12" distance among each of pixels would bring any addressing problem due to noise over the line or weak digital signal coming from the Arduino?

[mikemeaney]

The WS218x data sheets are rather ambiguous about the distance between each pixel. Best advice is to try to stick to safe and sane (less than 12") leads. The data sheets are rather emphatic though about them re-buffering the signal from one pixel to the next, therefore mitigating the issue of data loss of long runs. Provided that there are pixels really no more than a foot apart. Like I said, I ran two pixels across a sofa for a few hours just as a test without issue. :/

[jem_j85]

I was wondering if there is a way to adapt the Gemma Hoop Earrings code from the x16 neopixel rings to the x12 neopixel ring. I have the x12 neopixels ring and used the same code posted in the learning center but no dice. Any advice would help. Thank you

[Franklin97355]

the same code posted in the learning center but no dice. Any advice would help

How have you changed it for your hardware? and what do you mean by "no dice" just what happens and what messages do you get?