What Have I Missed?

Max Kabilafkas

Apprentice elf
Joined
Dec 19, 2020
Messages
55
Hi all

Playing around with my new controller and lights, trying to figure out how it all works, and I feel like I have missed something in regards to power.

I currently have a Meanwell RSP - 320 - 5CC power supply (https://www.power-supplies-australia.com.au/MEAN-WELL-RSP-320-5CC) powering my PixLite 16 controller. It outputs 300W of power.

I have 10 strings of 5v pixels (https://www.aliexpress.com/item/32844995715.html?spm=a2g0s.9042311.0.0.423b4c4ddQYnO9) which I daisy chained together and plugged directly into the controller for testing. According to the datasheet, each pixel pulls 0.3W and therefore each string of 50 pixels should pull a total of 15W. These 10 strings daisy chained together should pull 150W then.

How come then when I did my test, only 4-5 of the strings lit up? And of those, only the first two did not have reduced brightness? Aren't I way under the 300W threshold, even with the 0.85 efficiency calculation?

Thanks
 

Notenoughlights

400,000+ twinkly lights
Joined
Oct 16, 2016
Messages
641
Location
Christchurch, New Zealand
Have you included power injection into the strings?
Every 50 to 100 leds on 5v need power injected in order to keep them at full brightness the whole way along.
The power supply may be able to supply the current required to run your 10 daisy chained strings, however the wires the pixels are attached to can not carry that full current, hence the need to add power into the strings further along the line.

You may also need to make sure you have your controller set to output data to the 500 nodes attached to the output.

Highly suggest the 101 manual that will go through the basics of power injection https://auschristmaslighting.com/threads/1889/
 

Max Kabilafkas

Apprentice elf
Joined
Dec 19, 2020
Messages
55
Right, I thought I would only need power injection when I went above the 300w my current power supply can provide.

Does each point of power injection need to come from a dedicated power supply? Or can one power supply inject power at multiple locations?
 

Notenoughlights

400,000+ twinkly lights
Joined
Oct 16, 2016
Messages
641
Location
Christchurch, New Zealand
You can inject power from the same supply, when you start introducing additional power supplies you need to be wary of how you wire each string to the next. You can not carry the positive from one string to the next when powering the next in line string from another power supply.

The 300W is the total load the power supply can handle.
 

Nojoy

Full time elf
Joined
Aug 9, 2020
Messages
110
Don't forget that each string of 50 pixels also draws ~2.77Amps at full brightness on white (assuming ws2811) A Pixlite 16 ships with 4 Amp fuses on each output and each output is rated to a maximum of 7.5Amps (different fuses required to exceed 4 Amp per output). so while your power supply may be able to support up to 60A total, each individual output cannot support more than 84 pixels at full brightness in terms of the Amps being drawn before the fuse should blow.
Distributing the pixels across the outputs, lowering the brightness and power injecting directly from power supplies can all increase the total pixels you can run.
Recommend http://www.da-share.com/calculators/led-strip-string-current/ to work out current/amp draw
 

TerryK

Retired Elf
Joined
Feb 9, 2020
Messages
655
Location
West Central Ohio
Right, I thought I would only need power injection when I went above the 300w my current power supply can provide.

Does each point of power injection need to come from a dedicated power supply? Or can one power supply inject power at multiple locations?
There are various schemes of power injection. Injecting power from a single supply to multiple points is one of the easiest to implement and understand and is thus probably the most used method.
Dedicated supplies could be done but efficient matching of a supply to its load will be difficult. Depending upon if one implements a single or double feed, amperage into an injection point will at the maximum be either 5 or 10 amp give or take a bit. To be efficient one would need to use supplies rated at a bit more than the either 5 or 10 Amp. The amperage limitation is due to the string AWG wire size.

It may be easier if you think in terms of current rather than watt and/or (suppy) efficieny. The supply you mentioned is rated at 60 Amp. Working properly, as long as it supplies up to the 60 amp and maintains the 5 Volt it matters little what its rated wattage or efficiency is. Same for the pixels, think how many pixels at how much current each at the drive level you want/need.
 
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