Code only going a third of the way along the strip.

Using Arduino Project Guidance
1

Hi guys

I've wired together 122 push through 8mm neopixels powered through an Uno for an art project, but my strand test is only partially successful.

The colour changing only goes 30 pixels in and then stops. No idea why. The pixels are wired the correct way round and I've got continuity between the last working pixel and the next one so I'm stumped.

Has anyone got any ideas? Please see the attached photo if my description does not make sense. Thanks!

2

No photo attached.
No code attached.
Each neopixel can use 60mA when on full white. Uno can only power a limited number of them, 500mA if powered from USB port, maybe a little more, 600-700mA, if 7.5V is used into the barrel jack.
122 x .06A = 7.32A. You're going to need a bigger power supply.
Example:

3

Yes, thanks for that. I did attach a photo but it has not uploaded. The code is the adafruit strand test. I should have stated that I am running them through a power supply. I have alternatively tried powering the lights from a powersupply wired up through a block terminal and running the arduino off of a power supply (currently set to 6 v as its new and over volts). Both of those methods (and running off of USB) produce the same results. I've also tried a knock off mega I have and that would only light up the first 10 or so.

4

I've checked my power supply and it says 500 mA 6VA (max.), so just the same as USB. Think you are right. Many thanks for the link. I shall purchase immediately.

5

Okay, unfortunately Crossroads was not correct.

I've tried using an Adafruit 5v 10a supply and get the same issue: Code only runs along the first 30 or so lights. I'm using a mega now so it's not a RAM issue. Any one have any other ideas? Anyone?

6

(deleted)

7

I've never used neopixels, but they are individually addressable, right?

If so, I've got to assume that your code is not properly addressing the pixels beyond 30.

8

"I've never used neopixels, but they are individually addressable, right?"

Yes, you send out 3 bytes of data for each one in the string.
122 neopixels need 366 bytes to go out.