Lost on what I need....help?

I’ve been doing some research but I am a little lost here.
I purchased for trial and error a NodeMCU, 10amp 5v PSU, and a 5M LED Strip (5v, 60 LED/M).

I managed to get the NodeMCU flashed and figured that out. I realized though I think I underestimated the amperage needed.

Goal is to have LED strip lights around the fascia of the house – I measured I need about 60 feet. I read that I could just put power injection after every strip so (4x 5M strips). For Christmas and Halloween basically. Long run it would be great to tie it to music, but step by step…

What size PSU do I need to accomplish this goal, or am I not going about this the right way? Should I split up the plan into two separate nodeMCU’s? Should I plan to downsize to 30 LED/M strips?

Just a little lost with so much information out there for a first timer. Any guidance would be great.

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Rough rule of thumb:

All of this is based on the worst case of all LEDs at 100% White.

At Max brightness (full White) an RGB LED draws ~0.3W.
For 20m (66 feet) at 60LED/m => 1200 LEDs.
1200 LEDs x 0.3W/LED => 360W
If they’re 5V LEDs you’re talking about 360W/5V => 72A
For 12V LEDs, that’s 30A

The strips typically will transport about 5A of current before they exhibit too much drop so you add injection points to keep the voltage across the strip stable. For 5V LEDs, that’s 5Ax5V=>25W or 25W / .3W/LED => 83 LEDs. For 12V, you get get about 200 LEDs.

You add injection points as needed to match these levels.

You’ll want to check the specs (or better yet, measure) your LED’s to be sure what you need.

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Thanks. So can I use a single power supply to add the injection points along the line, or do I need multiple power supplies? if I can use a single say 60amp PSU, can a single wire be ran in parallel and T into each new strip?

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It’s your call how you provide the power, either single or multiple.
The typical advantage of multiple supplies is to place them along the strip as near to the injection points as you can manage.
That lets you use smaller wire for injection runs.
Plus it may be easier/cheaper to get 3 x 20A supplies rather than 1 x 60A.


ok thanks that is helpful. So now I need to understand what gauge wiring I need to accomplish this.

The LED strip says they are 5v 12amp 60W max draw. So using that with 2 strips = 120W max draw. How do I figure out what gauge wiring I need to avoid voltage drop and keep everything safe with my total distance being ~35ft on the front of the house I wanted to try this on?

Take a look at the voltage drop calculators in the KB.

They’ll give you an idea of the drop for wire of a given size when you know the max current and distance.

Maybe I am not calculating it correctly, I tried a few different ones online and end up with it saying I need 0 gauge wire which doesnt seem right.

This one I used the following:
LED Strip Length (ft): 16
Voltage (V): 5
Power Draw (W/ft): 12
Wire length (ft): 20


The total amperage draw of your 16 ft LED strip is 38.40 Amps, which is below the recommended safe amperage limit of 41 Amps for 12 AWG wire.

The total voltage drop across the 20 ft of 12 AWG wire is approximately 1.220V.
Your power source of 5V will be dropped down to 3.780 V

Does that sound right? So 8 or 10ga wire is what I need to run for 20ft? Just seems really thick for a short run, but maybe thats what it is? Or am I grossly overthinking the power draw 600 LED’s will do in the real world?

Your LEDs take somewhat more power (I went with 0.3W/LED, yours come in at 0.4W) than my previous calcs, according to the mfg. specs.
If those specs are correct correct (and you’d have to measure a live string’s usage to know differently) your voltage drop calculations are correct. You’re starting to see the issues around setting up a large # of LEDs, power is something to figure out correctly.

That being said, there are a number of ways to make things a little easier to handle.

  1. The total current you need is set by the total # of LEDs you’re trying to power. But you can split the total current into smaller (and easier to handle) chunks with power injection. Think about splitting your 36’ string (I rounded up to make the math simpler) as 4 x 9’ strings. You use 4 wires from your power supply, each taking 1/4 of the total so the wires can be smaller. If that doesn’t make things manageable enough you can split into 1/6ths at 6’ or 1/8ths at 4.5’

  2. Move your power supplies so they’re closer to middle of the strips. If you use 2 power supplies and position them near the middle of the “left” and “right” halves of your string, you’ll shorten the length of the injection lines. Ideally you put the supplies right near the center of the each strip then the injection lines are as short as possible. That may not be possible so you might end up with a bunch of shorter injection points and 1 or more long ones. The shorter the run, the smaller (and cheaper) the wire you can use.

  3. All of this is “worst case” with your LEDs at 100% White, you won’t likely run that way continuously.
    For a static Xmas display, if you ran a pretty R-G-B pattern you’d be at 1/3 the max power. Other patterns will come out differently. For effects the draw is less predictable and excessive drop will cause random changes to the LEDs. That’s why you generally do your power calcs based on 100% white.

  4. When doing injection lines, they don’t have to be (and most often won’t be) equal lengths. That means you do drop calcs on each line separately. If you split your string evenly, each injection will handle the same current, but they’ll have different lengths and can be different size wire if required.

Personally, I like to try and split the strips so that 18AWG wire is feasible. In your setup, that would mean split into 1/8ths and keep the wire length down to 10’ or less. If that doesn’t work out for all the points, use the “middles” technique and supply as many as you can with 18AWG and go up to 16AWG for the longer runs.

Remember when you inject, it doesn’t need to be at the end of a strip. Think about injecting in the middle of a strip so power goes “left and right” to supply legs evenly.
And lastly, remember to fuse the injection wires suitably. A wire that can handle 10A maximum needs a 12A fuse.

ok thanks that is helpful – So the long-term plan is to extend this run further along the house ~60ft total…I figured I could just start with a short run first, figure this all out then add later, but it appears this might not be a good plan.

Now I understand the gauge wiring a little better, maybe I should repurpose these 5V strips to something else and go with 12V 30LED/M strips for the longer runs I want to do then? Would that help with reducing the gauge thickness of the wire, thus easier to hide/manage?

In general 12V LEDs take a little less than 1/2 the current for the same Wattage output so that does make the wiring easier in general.

As you can see from the drop calculators, the 3 things that affect drop are:

  1. Wire size, the bigger the wire the lesser the drop.
  2. Wire length, the shorter the wire the lesser the drop.
  3. The current being carried by the wire, the smaller the current (more injections, or higher voltage) the lesser the drop.

Reorganizing your power supplies so you can do more but shorter injections is often a good way to minimize this stuff. Thinking about how you can route your power wires separately from the strip is also helpful. And lastly, it’s often helpful to use a very short (5-10 cm) length of 18AWG wire attached to the larger injection wire when needed. That’s often easier to solder on the strip compared to 14 or 12 AWG.