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Arduino code works on smaller Neopixel strip only
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Arduino code works on smaller Neopixel strip only

by acutair on Wed Nov 06, 2019 5:01 pm

Hey folks,

I've got a simple "glow/fade" sketch running on an Arduino Nano clone, powering a small strip of Neopixels (8 LEDs). The code works fine.

When I attach a longer Neopixel strip (58 LEDs), I get power (from a separate DC power supply), but the code doesn't have any effect on the strip.

I adjusted the number of LEDs in the code. Everything's connected appropriately to the longer strip: 5V and ground have a 1000 uF capacitor across them and the Nano's attached to the “in” end of the data line (there's a little arrow on the strip).

Am I missing something obvious?

Andre

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Re: Arduino code works on smaller Neopixel strip only

by adafruit_support_bill on Wed Nov 06, 2019 5:09 pm

If you post some photos showing your soldering and connections we can take a look.

What are you using for a power supply for the strip?

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Re: Arduino code works on smaller Neopixel strip only

by acutair on Thu Nov 07, 2019 2:27 pm

Here are the connections, showing data and power:
Imageconnections

My data line isn't soldered to the Nano (yet) because I'm going back and forth between the larger strip and a much smaller, 8 LED strip. But the data connection works fine for the smaller strip, so I'm confident the connection to the Nano is ok.

Here are the labels on the strip, showing +5V (red), ground (white), and data in (green):
Imagelabels

The power supply is a 5V / 8A with a terminal block adapter.

Thanks!

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Re: Arduino code works on smaller Neopixel strip only

by adafruit_support_bill on Thu Nov 07, 2019 2:40 pm

I don't see any ground connection to the processor.

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Re: Arduino code works on smaller Neopixel strip only

by acutair on Thu Nov 07, 2019 3:46 pm

adafruit_support_bill wrote:I don't see any ground connection to the processor.


I'm powering the Nano via USB, so it's grounded through that connection.

EDIT: I'm reviewing the uberguide, though, and see a diagram that shows the processor getting ground from the same source as the neopixel strip >>
Image

Is that required with the longer strip? How come it works on the shorter strip w/o that ground?
Last edited by acutair on Thu Nov 07, 2019 4:00 pm, edited 1 time in total.

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Re: Arduino code works on smaller Neopixel strip only

by adafruit_support_bill on Thu Nov 07, 2019 3:49 pm

You need a direct ground connection from the processor to the strip for a signal reference.

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Re: Arduino code works on smaller Neopixel strip only

by acutair on Thu Nov 07, 2019 4:02 pm

Ah ... ok, I think I understand why the smaller strip works now: it's getting power (+5V, gnd) and data all from the nano. So the "signal reference" is already in place, yes?

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Re: Arduino code works on smaller Neopixel strip only

by adafruit_support_bill on Thu Nov 07, 2019 4:08 pm

Yes. Having a direct signal ground is even more important for longer strips since the power supply ground can get quite noisy. That is why we usually recommend running power and ground directly to the strips, then signal and ground between the strip and the processor.

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Re: Arduino code works on smaller Neopixel strip only

by acutair on Thu Nov 07, 2019 5:53 pm

Ah ha! It works!

Thank you so much for the education.

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Re: Arduino code works on smaller Neopixel strip only

by adafruit_support_bill on Thu Nov 07, 2019 5:55 pm

Good to hear it is working. Thanks for the update.

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