WS2812B Light Strip Project (now with Video!)

[james2k2]

Hi All,

Another project from me again! This time, just asking for a bit of advice.

I'm looking at making a large distributable LED strip project using the WS2812B units. The strips will be housed in a frosted lens rigid aluminium chassis at 50cm each in length (15 LED's per strip). This allows for any heat dissipation that may occur and the frosting gives it good light dispersion.

I've built one and am happy with the finish and is controlled using a DMX to WS2812 converter.
Video (Please turn down your speakers/headphones... the music is rather sudden!)


I've considered using something called Fadecandy if I want a bit more control as well. For this reason I am looking at the interconnects between the bars. I am thinking of using a 4-pin connector: 1 - +V, 2 - -V, 3 - Data In, 4 - Data Out. Then having 'Y' style cables to connect them together, or I have the option to just hook them up individually (The Fadecandy has 8 outputs of 64 LED's each, therefore my config would be 4x Light bars per channel).

The other option would be to use 2x XLR type connectors on each bar as these are cheap, readily available, and can be bought in good length ready made cables for not much. My only gripe is that those connectors are very bulky and the light bars are very small in width and height.

Any suggestions on this project, or indeed any improvements you can think of?

Thanks. :-)

[xuio]

Sounds nice. Could you post some pictures? I am working on a similar project.

RJ11/RJ45 are nice connectors for such projects, only problem is the current. I am using rj11 connectors for data and standard barrel jacks for power.

For longer distances you could consider transmitting the signals via LVDS. You can use cheap rs485 transmitters for this.

Moritz

[james2k2]

Thanks for your input!

I will post a pic or video of the first bar I've made with the controller at some point soon :-)

Thinking about RJ45... POE spec suggests a maximum of 51W using all 4 pairs over Cat5. So my opinion is to use 3 pairs = 38.25W, which at 5V means 38.25W / 5V = 7.65A (I = P / V). My target was 5A per 'string' (5 of my 50cm Bars at 0.9A each for full white brightness), so in theory this works. And the super cheapness and abundance of Cat5/6 cabling and connectors makes it a good choice.

Please correct me if my calcs above are wrong!

[dom0]

Contacts are rated by RMS current, not by power.

PoE uses 48 V (nominal) and the allowed current is 500 mA or something like that. 0.5 A seems reasonable to me for the cabling (conductors are 0.2 mm² or so), 5 A definitely not.

As for the connectors I'd suggest mate-n-lock or similar connectors ; RC people also have plenty of compact low-voltage high-current connectors.

[james2k2]

Thanks for your reply. Are you suggesting 0.5A for the whole thing then, or per contact?

Edit: I missed the RC bit. Can you give me a connector type to look up please? I've checked out the likes of Mini-XLR, but the costs far outweigh the project need.

Edit again: I just realised Mate-n-Lok was a connector type! Haha. Anyway, those aren't suitable for my need. I'm wanting something where a cable run as a whole is readily available (instead of me making it). Because some situations may require only a 30cm link between bars, and some may be 5m between bars. This type of unit I'm trying to build can already be bought and they appear to use these connectors: http://www.pmdx.com/Images/4Pin-PlugAndJack_800.jpg

Cheers. :-)

[dom0]

Here's a thread discussing the current rating of typical RJ45 connectors: https://groups.google.com/forum/#!topic/sci.electronics.design/TPGrRTJjReA

Seems like PoE uses at least two pairs, which would imply only 300 mA or so per contact.

Sub-D might be an option, too. Reasonable size and contacts are typically rated for 1 A per contact or more (industrial grade connectors).

[dom0]

http://www.pmdx.com/Images/4Pin-PlugAndJack_800.jpg

These look like CB microphone connectors to me

[james2k2]

Well I've been looking at some PoE injectors and there are plenty rated at 48V, 500mA = 24W. I need just over 22W for my needs, so surely this is suitable still? And don't forget, this is absolute peak brightness on white. Nominal current is usually only about 40% of that.

What about those 4 pin CB connections? Anybody know where I can get them cheap in the UK?
Opinions?

Thanks so far everybody by the way! I will get a video up shortly.

[Corporate666]

Well I've been looking at some PoE injectors and there are plenty rated at 48V, 500mA = 24W. I need just over 22W for my needs, so surely this is suitable still? And don't forget, this is absolute peak brightness on white. Nominal current is usually only about 40% of that.

What about those 4 pin CB connections? Anybody know where I can get them cheap in the UK?
Opinions?

Thanks so far everybody by the way! I will get a video up shortly.

See above what dom0 said.

You are talking about power, but that is not how connectors are rated.  You need to consider the current.

48V/500mA = 24W that is not the same as 5V/5A = 25W.  Just because the wattages are about the same, doesn't mean you can run 5A through a small gauge wire @ 5V that would be fine with 0.5A at 48V.


As for pre-made cabling... check this category on Digikey

http://www.digikey.com/product-search/en/cable-assemblies/circular-cable-assemblies/1573006

Narrow your search to the 4 position ones (circular, DIN, Mini-DIN) and that will show what's easily available pre-made.

[james2k2]

I guess my issue more than anything is the cost of connectors. With the Mini XLRs, the cost weight of the project is connectors alone (no cabling) costing twice as much as the actual LED's and Controller boards!

LED's are £9.99 per metre from a UK supplier, or I can get them super cheap from eBay China for about £29 for 5m.
The Aluminium Tubes are £3 each, and even come with a bar of white led's that I can use elsewhere!

The connectors are coming in around £1.92 average each and I need lots of them (30 or so for just 5 bars and controller).

Anyway, as promised a video of my first bar prototype: https://youtu.be/QkjDezahnbI Apologies for the poor quality, it's something I just threw together.

[james2k2]

What about using USB cables? Apparently that has a maximum handling of 5A.

And as a test, I set all the LEDs to white at full brightness and measured 750mA current usage. So 5 bars would only be 3.75A peak. I would obviously want some wiggle room on that so would still provide a 5V/5A supply for each chain.

I've not found much in the way of round din connectors that seem to suit my need/budget on digikey.

Edit: I'm beginning to think it may be easier to do what somebody suggested of running separate power/data cables. Apologies if I'm becoming frustrating. I guess a specification would help: low mass with minimal insertion/separation force (clip acceptable) and small size.

Failing this, I could just do it the same way other commercial products do it.. a single cable going to each bar from a central controller. There will likely be no more than 10 bars as this is a good maximum on DMX (450 channels out of 512). This also means I can use a single big power supply in a central location.

[dom0]

What about using USB cables? Apparently that has a maximum handling of 5A.

Not by a long shot. Quality USB connectors are rated at ~1.5 A and most cables are dimensioned to use as little copper as the spec permits (i.e. permissible voltage drop over the entire length of the cable).

I didn't find any solid numbers for the cheap (20 cents or so each) 9 pin D-sub connectors, but I'd trust them to maybe 1 A per contact (given that high quality ones are rated for 5+ A) ; using 4-5 contacts for supply, two data, two to three + shell for return it might work out fine. And they're dirt cheap. But you wouldn't of course use null modem cables or something like that, those are data cables and not designed for power, i.e. small conductors.


Aaaand I might repeat the mate-n-lok suggestion, they're rather cheap, safe (latch) and quickly assembled (crimp).

[james2k2]

Ok, I've decided! I'm going to go for a separate cable from controller to each bar.
This means less than 1A required to each bar.

With this in mind, are the mate-n-lok connectors still the best option in your opinion?

[Corporate666]

Is this a commercial project or something home-brew? 

If the latter, I guess I am not sure what the problem is with having 2 cables?  You could heat shrink them together and just have 2 connectors on the end.  You could use a couple of barrel power jacks of different sizes so that they can't be connected incorrectly, and pre-assembled barrel power cables are available in lots of different lengths and you can buy junk Chinese ones on eBay for cheap money.

If it's a commercial project, you have to carefully consider user stupidity.  Using a cable or connector that is made for someone else will often result in a user trying to plug that cable in.  So for example if you used USB (and you shouldn't), someone, somewhere will try to plug it into a USB socket.  Or if you use modular connectors, someone will try to plug a network cable into it.  If it's a commercial project, you should spec something suitable.

Another question - what do you need 4 wires for?  You say power, ground, data in and data out.  I don't quite understand that in the context of WS2812 LED's... DI and DO are the same line, just to feed one chip from the next.  Unless I am missing something, I don't see why you would need both in a cable? 

If indeed you only need 3 pins, you can get 3-pin XLR cables cheap on eBay

http://www.ebay.com/itm/10-lot-pack-6ft-xlr-male-to-female-3pin-MIC-Shielded-Cable-6-ft-microphone-audio/151614526862?_trksid=p2047675.c100009.m1982&_trkparms=aid%3D777000%26algo%3DABA.MBE%26ao%3D1%26asc%3D20131227121020%26meid%3D2432685db68d46c9b71553354726a5cf%26pid%3D100009%26rk%3D1%26rkt%3D1%26sd%3D301163946499

[james2k2]

Hi Corp666.

It is a homebrew, but would likely be used as part of my mobile disco rig.

This is one reason why originally I was looking at either 4 pin xlr, or 4 pin dc din (like pictured previously). But the cost of those tends to outweigh the worthwhile-ness of the project, as it is purely for effect rather than dancefloor coverage.

Well my dmx to ws2812 converter only has the one output, so the data daisy chain needs to continue I believe? So my opinion is that the 4th wire will bring DO back to the controller and connect to DI on the next output.

Another option I mentioned earlier was using Fadecandy instead of DMX and then have individually controlled lines to each output, which would then allow me to use 3 pin connectors and save some cost. This would also give me the advantage of upping the resolution of my pixels to say 30 in a tube rather than 15, and is practically unlimited on the number of boards I can use to create bigger displays.

[Corporate666]

Hi Corp666.

It is a homebrew, but would likely be used as part of my mobile disco rig.

This is one reason why originally I was looking at either 4 pin xlr, or 4 pin dc din (like pictured previously). But the cost of those tends to outweigh the worthwhile-ness of the project, as it is purely for effect rather than dancefloor coverage.

Well my dmx to ws2812 converter only has the one output, so the data daisy chain needs to continue I believe? So my opinion is that the 4th wire will bring DO back to the controller and connect to DI on the next output.

Another option I mentioned earlier was using Fadecandy instead of DMX and then have individually controlled lines to each output, which would then allow me to use 3 pin connectors and save some cost. This would also give me the advantage of upping the resolution of my pixels to say 30 in a tube rather than 15, and is practically unlimited on the number of boards I can use to create bigger displays.

Ok - I see what you are trying to do.  You mentioned previously about Y cables and keeping your current below 5A per string, then you mentioned DI and DO wires so it was all a bit confusing.

Are you specifically trying to make it so that a pattern continues from the end of one string to the start of the next?  Or are you just connecting them that way for some other reason?  You can run multiple strips from the same output of your controller (you may have to terminate with some resistance to avoid signal reflections), and each strip would then do the same thing.

If you want the pattern from one strip to "roll off the end into the next", then is there a reason you wouldn't just connect them with 3-pin XLR cables and daisy chain from one to the next?  XLR's will handle 10A with appropriate gauge wire, and they can be had on eBay for cheap money ($20 for 10 pre-made cables in the link I posted).  Running each strip back to a central connection but connecting them in serial seems like a really inelegant way to do it.  Not to mention you'll need to be connecting wires to both ends of your strips inside the tubes and possibly sending that data over some pretty long wires.

You also mentioned a Fadecandy.  I looked that up and it has 8 separate channels... you can't just use that and connect each tube to a separate channel?  If your tubes are 0.5M using the 30 LED per meter WS2812 strips, you're looking at around 1A per strip... you're getting into some pretty beefy power requirements if you used all 8 channels on a Fadecandy.  Not to mention that's 40 watts of LED light.  That's, as we say in the USA, a "metric shitload", probably on par with 150-200 watts of incandescent light.  . 

[james2k2]

Thanks for your reply.

Yes, I apologise for my indecisiveness and general confusing mindset.

I suppose my main issue is budget as I am trying to save for more important things, but really want to finish this project and ultimately don't have the funds to try and try again if I don't like something.

Obviously, the rest of my rig uses XLR already for the DMX cabling which is why I was avoiding that, but as you say it fits my ultimate criteria of being super cheap and readily available as well as carrying plenty of current. 10A would allow for all 10 bars to be daisy chained no problem as well so your point of elegance is spot on.

With Fadecandy you configure your layout in software. I've already spent extensive time playing with it and seeing my options and ultimately ended up being able to stream the video output from VJ software to the Fadecandy server using Spout which was great. My idea for this was to have a single bar of 15 LED's connected to each output and essentially have an 8x15 grid. The software layout would then handle where each row and column begins and how many led's there are per output.

I would still need to run cables from one end of each tube to the other and have both input and output though as I really need the tubes to be able to hang neatly as well. This as where the 4-pin connector and Y cables kind of came in, if you get my thinking.

Also, I didn't realise (until you mentioned it) how bright this would be total once all bars were complete! I like bright. :-)

[james2k2]

Hi again all!

Just thought I'd update everybody on the progress of this project. I've finally chosen a connector. There's some IP65 connectors available that are targeted at these types of LED strips, rated to 10A. They are these:

They can be got for £10 for a pack of 10 pairs with 20cm cables on each - perfect! I will buy 2 sets of these so I can make my own extensions if required. I'll then obviously need 2 more pairs to make the initial cable run. (A female cord out my controller box secured with a grip grommet, then the initial cable run)

I've decided to go for the snaked approach to interconnecting so a cable on each end of the tube - means I can daisy chain them neatly, or hang them without the need for the extensions under normal circumstances.

Control will be via my Enttec Open DMX unit, controlled from JINX! on my laptop with the DMX to WS2811 driver I have.

The power will come from one of those metal chassis PSU's like this:


Via an IEC like this:

I just need a bit more advice. I was going to colour code all my spades, so blue for N, red for L and Yellow for GND/EARTH. But obviously the connector colours usually indicate the gauge of wire used in them. So how would you go about this? Use all the same colour spades with different colour wire?

Also, I've never used or seen up close one of those PSU's, so what size spade forks/disconnects should I be using?

Any other advice or pointers you may have?

[LukeW]

I was going to colour code all my spades, so blue for N, red for L and Yellow for GND/EARTH. But obviously the connector colours usually indicate the gauge of wire used in them.

For reliable/safe engineering you should ensure that all the crimp terminals are the right ones - correct sized for the gauge of wire used.

Choose appropriately colored wire for your mains circuits, eg. brown and blue and green/yellow, and it doesn't matter that all the insulated crimp terminals will be red, or whatever. That's the way I would do it.

Or, to be extra neat, you could put heatshrink over the sleeves of the crimp terminals. You don't really need to, but you can if you want to. But brown heatshrink is not something you see every day.

[Corporate666]

It's been a while so I don't remember the exact setup, but you said in the original post something about five 0.5 meter strips (0.9A per strip) for each channel, then 8 channels.  So that would be 4.5A per strip, 36A for the whole lot, 180 watts.

If you are now planning to daisy chain each strip to the previous/next, just keep in mind that the total current is going to be flowing through the first strip in the chain - and the traces on that flex PCB definitely won't handle 36A.

I am not sure what they're rated for, but you mentioned 15 LED's for 1/2 meter, which would be 150 leds for 5 meters (and I've seen 5 meter reels of WS2812 LED's).  At 60mA per LED on white, that's 9 amps for the whole strip - which is probably really pushing it for the trace width and copper thickness on those strips.

Anyway, just keep in mind the total current draw through the first strip.

[remixed123]

Hi James,

Not sure how far you got along with this project. But I have just posted details that provide you everything you are looking for, plus it also has Apps so you can control the lights in various ways, including synchronising with music.

Check out the post here - https://www.eevblog.com/forum/projects/lightserver-rgb-intelligent-lighting-project-app-control-works-with-ws8212b/

If you have already progressed, then perhaps the source code would be interesting, as there are lots of algorithms for effects and other useful functions for color manipulation.