Powering 10 1m lengths of ws2812bs with 144leds per metre

Projects General Guidance
1

Hi,

I have tried to do as much research as possible but I am still scratching my head as to how I attack my project.
Which is to light up 10 fence posts each with a 1m strip of ws2812bs running 144 leds per metre.

I have chosen this strip as i would like to eliminate 'spotting' of the leds rebated into the posts, installed in a slim low profile channel with a milky diffuser.
I have tested 60led per m ws2812bs but led seperation is very apparent due to the closeness of the strip to the diffuser.

Please see attached layout sketch

Led posts sketch 1
Led posts sketch 11440×1340 113 KB

The posts are approximately 1.8m apart but split into a set of 7 posts one side of garden, and 3 posts at the other side of my garage, each cluster approximately 12m apart. The closest of 7 post cluster (post 7) is 5m from the mains socket and the closest of the 3 post cluster (post 8) is 7m from the mains.
Hope the basic sketch helps.

My questions are these,

1 Power distribution -

I already have in my possession 2 x 5v 60a switching power supplies.

Using 1/3 rule at 10a per strip (headroom) will I be able to use these supplies to feed all 10 posts with the distances metioned above?
Thinking in terms of post 1 being the furthest away from mains, could i power 1 to 5 of the 7 post cluster with one psu then 6 and 7 off 1 rail on psu 2 along with 8 to 10 running off rail 2 on psu 2?

What size fuse do i need to install on the mains leads going the 2 power supplies?

Where is the best location for the power supplies, for example near post 7 and post 8 are, or directly at the mains socket. The power supllies are non waterproof so i would have to consider enclosure locations
Is it acceptable to just inject power at each end of each 1m strip or will i need to power midstrip as well?

Is 2.5mm gauge cable enough to link the strips?

2 Control -

The main aim is to have the strips illuminate the garden upon motion detection /dusk to dawn timer but would also like to create a fade in and out and effects for parties.
I need each strip pixels to illuminate from led 1 to 144 at the same time on each post.

How is this achieved?

Motion trigger will be provided by a Phillips Hue outdoor motion sensor as I have a smartthings bridge, a hue bridge and IFTTT and alexa.

I have in my possession a sp108e wifi controller.

I know this can handle the number of leds but can it handle the motion to fade and how do I allocate the pixels?

If it cant be used which arduino would fit the bill?

I realise there are many questions, but feel they relate to the specific task and would appreciate any help with this project, however small.

Many Thanks,

Lex

2

If this were my project, I would run a 6mm (10 gauge) power bus to the base of each post and daisy chain the LED strips. (Data-out of strip 1 feeds data-in of the next strip.) You can use a 0.5mm (22 gauge) wire for the data.

You will have 1440 LEDs. If they are all turned on, full white, then plan on 60ma per LED. Or 86.4 Amps. In my experience, 60ma is overkill for planning. Light up a strip with full intensity white and measure the current it actually draws. I guarantee that it will be less than 8 Amps that the 60 ma per LED "rule of thumb" calculates.

I would use a 30A supply for post 8-10 and a separate 60A supply for the remaining posts. Make sure they share a common ground.

(Almost) any Arduino can handle 1440 LEDs, but you need 3 bytes per LED for the the LED array, so I suspect that you would have memory limitations with the Uno. I have run Christmas displays of 800 LEDs using a Wemos D1 Mini.

Fuses. Why? Most people misunderstand fuses. A fuse protects upstream. I don't have this particular PSU but the ones I have purchased from Bangood already have a mains fuse on them. (Probably required by import rules).

3

Why are you so concerned about this?

The reason for using individually addressable LEDs such as the WS2812 is to have different colour patterns, which is quite a different concern than providing uniform illumination.

This project is very ambitious. You have problems with power reticulation of large currents at low voltages where small drops cause colour distortion, and with data integrity of the rather high frequency control signal over significant distances. And while we do not know what your present controller will actually provide, it is true that the more basic Arduinos have memory limitations for so many LEDs.

Do you really want each post to show a unique pattern?

4

If the data lines are daisy-chained, then this is no problem for an Arduino. Our Christmas display is an LED tree; basically a cone of 24 strings or 48 LEDs for a total of 1152 LEDs. The strings are wired in serpentine structure (bottom to top, top to bottom, repeat 12X). I have coordinated patterns for each string.

5

Thanks for the fast response Steve,

Ive taken your advice and purchased a 6mm twin and earth cable as main bus feed and the 2.5mm earth will used for data.

If i want each post to show the same pattern can i not just connect the data in on each strip at one end so it thinks it has only 144 leds to sequence?

6

Thanks for the response Paul B,

I dont need each post to show different patterns.

I would like to be able to sequence the leds to brighten and fade up 1 to 144 to full over the course of a few hours and cycle colours. Each post showing the same sequence.
The project is about lighting my garden but could be useful for testing arduino programming, and increasing my knowledge.
I do believe that it is ambitious, but in todays modern society, where we have wonderous groundbreaking technology, i find it funny that wiring up 10 fence posts classes as an epic build.
I do however appreciate the challenge and understand its problems.

Do i need to be utilising a 1000f cap infront of the first led on each string?

7

Given the distances between the posts and particularly between the clusters, I would think twice about running 5V at many Amps over such long distances.
Let's also hope for no lightning strikes in your area; you might get a unique pattern on each post, but only for a few microseconds and then absolute darkness.

I wouldn't call it 'epic', but the laws of physics and the inherent challenges of outdoor environments just haven't changed all that much over the past century or so. What has changed tough is that we want to run power-hungry devices with sensitive data lines under those conditions. It's more complex than you may realize if you want to do this in a way that it will still work 1 or 2 years from now.

So for starters I'd try to prevent having to run low voltage across long distances and instead fiddle about with a higher bus voltage with local (per post, per cluster) DC-DC converters to keep losses a bit low. Or perhaps even supply each post or cluster with plain old 115VAC and run a ground bus along with it so everything references to the same GND level. Then figure out a way to maintain signal quality of the data line across those posts, which will require a combination of protection (think ESD & induction from nearby lightning strikes) and perhaps repeaters (on top of the ones integrated in the WS-candies, although they might suffice; you'll have to try).

Also spend a few minutes, if you can, thinking about how EMI plays a role in this. You may not realize this, but radio amateurs or even emergency services nearby (within a couple dozens of miles) may not be fond of a massive ring of high-current PWM-ed copper acting as a basically uncontrolled antenna emitting all sorts of crap all over the place.

This is one of those projects that you can do the simple way and call it a day, or you can do it properly.

8

That is why I recommended a 6cm (12 gauge) power bus between the posts.
If he hadn't purchased all the parts, 12V LEDs would have been the better choice.

9
  1. Draw a schematic. We don't use "earth" the same way.
  2. NO! You cannot connect the data lines in parallel. The LEDs are represented by an array in software. You write the pattern you want to display in the array then call the .show method. So if you have 144 LEDs on a pole and you want to duplicate the pattern on the next pole you just copy the section of the array.
10

Yes, that will at least keep power loss / voltage drop manageable over those distances. It's kind of a brute force approach though. Not necessarily wrong, but also not necessarily elegant IMO. Plus, what I said about the EM noise that contraption will make will still apply. Sure, at higher voltages it will also be an issue, but a little less so. If I were to do this, I'd go for higher voltages.
In fact I'm working on an RGB led array of 250-400W which will be pwm controlled; it'll run off 48V to keep noise somewhat manageable. An earlier version of the devices (100W at around 32V) already gives some very nasty radio interference on standard FM broadcast bands. It's not pretty. Imagine what an order of magnitude higher current will do, with line segments of various lengths. It's broad spectrum radio noise generator of pretty epic proportions (so epic after all, Haha!)

11

Should not be too much of a problem for a couple of reasons.

The power and return - or data and return which is much less of a concern insofar as the data is intermittent - are running as a paired transmission line which should not radiate RF.

Each LED has a suppression capacitor.

And the PWM of each LED is not synchronised with others or should not be to any significant extent, so the overall RF signal will be reduced to a very low level of broadband noise.

Using the same data to all posts does somewhat reduce complexity but still poses a need for buffering. It would be worth considering using RS-422 (RS485) drivers and receivers with "twisted pair" for the data.
12

Due to the power converters, not the WS2812s!

What do you mean? You can connect each post array to the same data, it will need buffering. Each post will display the same pattern.

13

No, in that particular case the leds were/are monolithic and the current sources don't have any inductors; each led array is essentially driven with close to its nominal voltage with the excess few volts dissipated in a semiconductor. I haven't done thorough analysis on it, but it seems to me the supply lines to the leds act as an antenna and emit harmonics of the pwm frequency + switching noise (ringing).
But I agree OP's solution may not have to be very problematic, especially if the cables are buried or even better shielded cables are used. Still, there's going to be noise, and I guesstimate it will be significant.

14

Koraks,

EMI is something I honestly did not factor in or even consider. Very grateful for your input.

Would I be better treating the project as 10 seperate strips individually powered and individually controlled. Would running a 10 way power distribution to 10 smaller psus be a more sensible option.

15

Would I gain any advantage using swa armoured.

At the moment i am looking at using 40mm waste pipe buried approx 100mm below the front of the posts to distribute cabling. I could potentially foil and braid the cables inside it if it helped with interference.

The psus, leds and controllers are all spare parts from a previous project.
The 6mm twin and earth is returnable, so could change to swa.

16

Yes, I think that would keep noise down considerably. If you basically run every pole off 115VAC and use a small PSU (doesn't have to be particularly huge since it'll only power one pole each) you're cutting down considerably on electrical noise. It also means you won't have to use shielded cable to cut down electromagnetic noise and you can get away with much thinner wires, so the cable will be much cheaper as well. It might not offset the costs of the 10PSU's, but it might in fact be quite close. A simple 115VAC-5V 10Amp PSU costs something like $10 if you get them from China. Maybe you can even find a better / cheaper deal; you'd have to check.
As a compromise you could also run posts that are close to each other from a single PSU so you only need a handful of PSU's (but they'd have to be bigger since they'll be powering several posts each). It'll still replace the 12 meter cables with less heavy 115/230VAC cables (I see you mention meters, so maybe you're in a 230V part of the world :wink: ).
When using several AC-DC power supplies, do make sure you run a separate ground wire that connects the posts to each other and to the control unit so everything references to the same ground. So yes, SWA armoured might come handy for sure.
Of course you can always use the 6mm + earth (so is that 3 conductors total?) for lower currents as well if you have the cable anyway. It'll be overkill of course, but otherwise than costs won't have technical drawbacks.

17

HAM radio operators would be up in arms every Christmas if your hypothesis were correct. Nothing this noisy in the RF spectrum could escape the attention of the FCC (in the U.S.).

18

I very seriously doubt there would be any significant RF noise running a bus from one or two separate PSUs. In fact, putting a 110V PSU at each pole would very likely increase the potential for RF noise, since the PSU is most often the source of the noise.

Also running 110V underground to each pole would (at least in the U.S.) require an electrical permit from the town and THW rated cable in a conduit rated for buried electrical use. The conduit may not, according to the NEC (National Electrical Code) contain both 110V and data wires. Then the power supplies at each pole would have to be in a sealed waterproof box.

Of course, when you invite the electrical inspector, you may also be triggering an inspection from the building inspector to make sure your poles ae properly installed.

So, running 110V to each pole would raise the cost of the project by at least $200 per pole.

I stand by my original post that running a 6mm (12 Gauge) power bus from pole to pole is the most efficient method of powering the LED strips.

Put one of these at the base of each pole with a blank cover (sold separately):

carlton
carlton600×600 29.5 KB

For a permanent, profession solution, I would run 1/2" electrical PVC from box to box, but for low voltages the conduit is not required. And not cheap.

19

Yes,

Im in the good old uk.
6mm twin and earth cable has 3 conductors, 2 6mm2 7 strand cores and a single strand 2.5mm2 core. Ive 50m
I could use this cable to distribute power to the psus.

20

Big (expensive) mistake.