Problem with some patterns / adding more power - 1020 apa102's

Hello everyone, would like some advice on a setup i have running.

I have 3 x 4m + 1 x 5m APA102’s total 1020 pixels currently powered by one Alitove 5v-15A arranged along my roof in the following configuration:

PBv3.3+[4m]+[4m]**+[4m]+[_5m]

Many patterns work fine, but with some, like the “custom sequence” around the middle-to-end, i start getting what looks like signal degradation that makes the end LEDs only red, and some flickering red. I’m just not 100% sure if the degradation is being caused by mathematical issue with that specific pattern accommodating the large number of pixels, due to vdroop, or the lack of any NULL Pixels for data/clock signal boosting…

Currently, the Alitove is plugged in where the **'s are above. I have a second power i want to add but i’m not sure where the optimal location is to plug it in. Where would you recommend connecting them both? The Alitove is currently also powering the PB as well.

I know there is definitely a need for more power, since i have to run the brightness at around 80% max or else there are some patterns that if I go 100% immediately starve the PB of enough power to operate, and it’s wifi radio doesn’t work. As for “Null Pixels”, if you think not having them is causing the problem, are they something i need to make myself or can i purchase them?

Thanks,

Ryan

Hi Ryan! Welcome to the forums!

This definitely looks like a voltage drop issue.

For this many LEDs, you’ll probably want at least one more 15A supply, and you’ll want to run your LEDs closer to 50% brightness.

My recommendations are based on the idea that you want to be able to accidentally run some all-white code (I’ve done this with a single typo!) and not have anything blow or brown out.

Imagine you were bent on running them at 100% brightness. The rule of thumb for the no-brown-out current draw is 60mA per pixel (real world is a little less, but it’s best figured by measuring your specific pixels after being wired up). Using this rule of thumb means 1020 LEDs* .06 A = 61A. You could decide to run 60A worth of current (such as a Mean Well LRS-350-5), but this is likely more pain than it’s worth for several reasons, including the work of running robust power injection wires and building an enclosure for the supply. The most compelling reason to not aim for 100% power is that LEDs at 50% of max current consumption don’t look half as bright as running them at 100% - test for yourself, but it feels more like 75% of full brightness due to how our eyes scale down our perception as real light intensity increases.

So, if you’re like me and you really love those 15A Alitove supplies for their convenience with barrel jacks, my suggestion would be to run in one of these power configurations (notice there’s two **’s for where you’d connect your two supplies):

PBv3.3+[4m ]+[4m ]X+[4m ]+[_5m ]

Or

PBv3.3**+[4m ]+[4m ]X+[4m ]**+[_5m ]

The new “X” is important - it’s where you snip or otherwise disconnect the red +5V Vdd wire between those sections of strip. This prevents your Alitoves from competing with each other, since they’re not designed to be bridgeable power supplies.

The last thing to check is the clock speed you’re driving them at in the Pixelblaze Settings page. For longer runs, you need to reduce the clock speed. I’d start at 2MHz and then adjust it up or down till you find the fastest clock that doesn’t flicker your brightest/whitest patterns.

Hope this helps! Good luck.

3 Likes

Awesome Jeff. Thank you so much for the post and all the dat!
Yeah, i’m already doing 2MHz. I’ll give the second configuration you suggested a try when i have time. So, you don’t think I would need any of the “NULL Pixels”?

Thanks again,

-Ryan

I don’t think so. I’ve tried a few from time to time (as well as a SPI signal amplifier), and they never really helped. Also, I think they are mostly a tool for unclocked pixels like the WS2811, whereas yours are the better clocked kind.