Newbie advice

M

momentous

New member
Hi there,

I don't know whether I am posting in the right place, but here goes.
This is my first year building a Christmas light project.
I am running FPP on a Raspberry Pi and would like to connect two 5m WS2812b LED Strips to it.
Each strip has 300 pixels on it and each metre requires 18 watts, so the 300 pixels need 90 watts in total, I think anyway.

My questions are:

- What power supply would you recommend?
- How would I wire my power supply with the two strips and Pi?
- Would I have to split power along the strips due to the voltage drop on 5v?

Thanks,
M
 
The Vdd pin to the strip needs 5v. We can fly you some links to some power supplies (Meanwells seem to be the most popular for outdoors), but ultimately, as long as you get it 5v plus-or-minus 0.3v, you're covered. Your USB charger on your cell phone is 5v, and you already have that. For your data pin, the 3.3v coming straight from the Pi will suffice (for now).

I believe for 5V, 300 pixels, 5 meters strips, you need to connect your 5v to Vdd and the ground to ground on both ends of the led strip i.e. both beginning and the end. You might get away with just connecting the beginning, but you also might not, and you really don't want to debug that right now. Of course, if you did use your cell phone charger, that only supplies 2.1A, and your strip is 18w. One charger can only power one strip.

Don't connect the 5v pin on the Pi to the led strip. Data pin comes from the Pi. Vdd comes directly from the power supply. Ground comes from both the Pi AND the power supply. Don't sweat connecting ground from the Pi on both ends. Beginning only for that will suffice.

I'm sure others here will typo-check this, to make sure I typed it right.

For $25, you can buy a smart receiver which will make your initial bringup phase easier,.and eventually you might want that anyway. What it does is take the Pi out of the picture, so you're not dealing with software issues. Or risk screwing up the Pi with a wiring mistake.
 
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Thanks very much for the reply.
It is greatly appreciated.

If I wanted to add LED strips in the future, would it be worth sticking with multiple USB chargers or upgrading to a better power supply?
If so, would I need multiple power supplies for each strip supplying ~20A, or should I just have one?
 
A single 300 pixel strip is going to draw around 18A when all 300 pixels are on at white with 100% brightness. That USB charger mentioned above will likely be good for supplying power to the Pi, but you are going to need something a lot beefier to supply power to the LED strips.
 
Note that my advice is primarily for getting started. Getting that strip to respond to your commands and sequences is your light bulb moment (pun not intended, but I ike it...). I almost never use a cell phone charger outdoors for real (although I've done it in stageplays quite often). The idea was, you already have one. You would invest the money in a more legit power supply after you have something known to work.

I'm surprised no one commented on my suggestion about the smart receiver (which could be easily misunderstood). For $25 you could also buy a Pi hat for pixels, which would make getting started easier in different ways. People have probably filmed tutorial videos for how to use pixel Pi hats.



That all-important just-get-it-to-work moment is the hardest. Expanding and scaling it gets easier after that. More expensive, but easier.
 
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