Something is maxxing out my current and it's not my PSU

I have a multi strip setup:

144 LED/m - 1m
300 LED/m - 5m
2ft extender
144 LED/m - 1m
1ft extender
144 LED/m 1m
144 LED/m 1m

I had these guys hooked up to a 5v 3a PSU with a wago clip splitting the pixelblaze from the strip prior to connection. I am opnly powering the LED strips via the 3 std 3 pin header, not the ‘spare’ pos and neg cables.

I started noticing flickering on the last 3 strips when working at highter brightness, so I tried subbing out the PSU for a 5v 5a PSU. Same problem.

Running a meter on the ground, it looks like the draw is never getting above 2a. Is this related to the extension cables? Some inbuilt limitation of PB I am not aware of? Voodoo?

Hey Kevin!

Wow, that’s quite a lot of LEDs for even a 5 A power supply! If I understand you correctly, you’re using something like WS2812 LEDs.

A single WS2812 can typically pull 50 mA at full white, so to completely power all (144+300*5+144+133+133) = 2054 LEDs, you’d need a 103 A power supply! In an ultra-long run like you have planned (and especially without power injection, which is where you re-connect the 5V power occasionally, typically every 250-300 LEDs), the voltage will drop so low below 5V after the first 300 LEDs or so that it becomes unable to draw more current. There’s not enough voltage left to even push more amps through everything, so you aren’t seeing more than 2A of draw.

If you’re OK running this at a very low brightness level (5A / 103A => ~5%) and having slow frame rates of 7-10 frames per second (only subtle/slow animations), this setup might work as long as you reconnect power between strips. How often you re-inject depends on how bright you want to run them. Colored patterns will draw about half what a full-white pattern would.

For best performance, many people choose to run no more than 500 pixels per “channel” (gives 30-40 FPS; Draws ~6A at 25% max brightness). A Pixelblaze has one channel, or you can get an output expander with 8 channels and consider a wiring setup that’s more like a spider. This will also boost your frame rate probably around 2X to 15-20 FPS.

If spider wiring isn’t easy, or you want smooth animation frame rates of 30-50 FPS, I’d suggest buying 4 Pixelblazes if that’s in budget, and using the forthcoming Sync feature to make them all do the same thing.

*I haven’t heard of 133/m LED strips, you probably meant 144, but I left the math at 133 and it won’t change my answer much.

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Yes, 144 led/m!

I don’t know why power injection didn’t occur to me. I use that on my hardwired strip lighting in my ceiling - and that’s 24v! Will try some injection along the way and see how that helps. Thanks.

On that note…do you have to inject both pos an neg? Or will something like this work?

Yes, you have to inject both! The electrons flow through the ground wire just the same. If you just inject +5 then the ground will be a nice warm bottleneck.


Ok, well here’s another ZANY 240v question…

Could I inject via a seperate PSU (not directly connected to the PB or the initial strip) if they are powered by a common circuit? (ie return to 240v ground, if not 5v ground)

In my house (230V/50Hz), I have 3x300 WS2812B LED strips in a horseshoe (see Color twinkles on walls and ceiling - YouTube) with 5V 8A (power+ground) at the start, end, and middle (connected to both junctions). I am pretty sure that the 3 power supplies are not all on the same circuit breaker, but everything works fine and has not yet ignited. :face_with_peeking_eye:

It seems to me that sharing the DC ground is best, but with a good AC system … electrons are electrons.

You definitely need to connect the GND / negative side between multiple power zones. If there is any difference at all between each zone’s negative side levels, it can cause the relative data signals between the LEDs to swing outside of their limits and would flicker at best, and quite possibly damage the LED.

Your power supplies are probably isolated from other power supplies plugged in to the wall, so there isn’t usually a default shared reference for the negative side. You really don’t want power going through a true earth ground between power systems.

Voltage drop affects both positive and negative side. The positive side drops, while the negative side rises! This can create an imbalance even with an otherwise shared negative side at the power source(s) between zones. Even when injecting power for both positive and negative, you want to keep a continuous GND connection between each zone/LED that are connected with data.

The best practice for injecting power with multiple supplies is to leave GND / negative connected between zones, but disconnect the positive side so that each zone has a single power supply providing power.

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