Monster WS2812B strips

bte2

Hi all, I am just finishing up a pontoon build and I was thinking about using some strips for general-purpose lighting as well as entertainment effects. I am looking at 30 LED/meter waterproof strip x 10 meters for a total of 300.

I understand that I need to divvy up the sections to reinforce the power traces, but before I even get started I thought I'd pitch it out to the brain trust to see if anyone has any thoughts about controlling them with a propeller.

They have strips with 144 of them per meter, and I'm trying to figure out how in the world a person would control such a beast- just 2 meters of it is a whopping 288 LEDs to control.

Inasmuch as the installation goes, I plan on welding a piece of aluminum angle along the top rail pointing downward with the LED strip also pointing downward but hidden from view by the angle stock.

Anybody have any thoughts on how to control a jillion of these things? BTW, I found 100w DC-DC converters on eBay for like $15.

Thanks in advance :-)

Mike Green

I can start you with some general principles and hope that someone with more practical experience can give you more specific advice. You're talking about a lot of power. Figure up to 50mA per LED ... 1.5A per meter. You're going to want to be careful about how quickly you change the colors and intensity of a group of LEDs to limit the transient changes in supply current.

Each LED reconditions the signal headed onwards, so you don't have to worry too much about signal degradation for long strings ... as long as the supply voltage doesn't sag too much with changes in the supply current draw. You may want some kind of driver IC depending on the distance and conditions between the Propeller and the start of each string of LEDs.

Duane Degn

Powering the strips will likely be the challenge. Adafruit has lots of information about powering lots of WS2812B LEDs.

The Propeller won't have any trouble controlling 288 LEDs. You should use some sort of level shifter to boost the Prop's 3.3V logic up to 5V.

I don't know if you've seen the thread I started where I show some of the WS2812 projects I've worked on.

http://forums.parallax.com/discussion/149822/fun-with-ws2812-b-leds

I used WS2801 LEDs in this one.

[ur]http://forums.parallax.com/discussion/147963/mood-enhancing-leds[/url]

Duane Degn

Here's a link to the Adafruit Uberguide.
https://learn.adafruit.com/adafruit-neopixel-uberguide

Here's a four channel level shifter.
https://www.adafruit.com/products/1787

I've successfully used the above chip to convert the 3.3V signal from the Prop to 5V which the WS2812B LEDs appear to prefer when they're powered with 5V. The WS2812B LEDs can be controlled with 3.3V logic if they're powered from a 3.3V source. High current 3.3V power supplies aren't as common as the 5V variety.

Peter Jakacki

Any 74HCT gate will work, you don't need anything special there and it is really only ever driving a single WS2812 as they are all daisy chained, unless of course you create multiple chains. So a common as mud 74HCT04 etc will be fine as you can have two in series to "buffer" or else it's nothing to change the software to drive an inverter so that you could have 6 channels. But certainly run that at 5V or even 5.5V if you can trim it to help overcome the voltage drop that results especially when running many of them at full bright white setting. Don't try to do this with a linear regulator though but don't worry as there are plenty of 5V power packs available these days but you may have to isolate the power to sections if you use more than one supply.

Tachyon has the WS2812 driver built-in, very fast, and it is very easy to interact with bunches of these LEDS.
BTW, Tachyon would only take 9ms to update a single string of 300 LEDs so that means a refresh rate of over 100Hz if you wanted.

Tubular

Here's a prop module I designed up that can drive 20 strips or so. The DIP prop chip is on the back of all the 3 pin headers. Its possible to drive 4 or 5 (@100 MHz) strips per cog using interleaved pasm

You can get 16 amp (80 watt) dc-dc converters ("point of load") easily - I used a $13 Murata one from digikey but they follow a fairly standard pinout.

I think I did boost the prop up to running off 3v6. To be honest I've never really struck issues driving at 3v3, but others have. Its important the prop circuit doesn't conduct the hefty ground current of the leds.

Also attached is a 'christmas star' that had 288 of those high density leds and worked fine.

bte2

Thanks for the responses! I have been working since I posted so I will look into some of the ideas now. My aim is to lay out the strips in such a way as to come up with a meaningful numbering/naming scheme and at first can some routines in. Later I plan on making a console to make them up on the fly but for now I just want to get some lights working reliably. I still have quite a bit of thinking to do I'll probably lay it out on the floor this winter and install it next spring.

Thanks again!

JonnyMac

My favorite level shifter for the WS2812 and similar devices (it's good for servos, too) is the TC4427. In fact, my friend Matt uses the circuit so often with the Propeller Mini (you can see his picture in the September issue of Nuts & Volts) that he asked me to make him a little PCB.

bte2

JonnyMac, per your advice in your column, I have been using the 4427 a lot and am very pleased with the results. In fact, it is precisely because of your column that I use Propellers in the first place, and I use a lot of them now.

In case you ever wonder, thank you. Seriously :-)

JonnyMac

bte2 wrote: »

JonnyMac, per your advice in your column, I have been using the 4427 a lot and am very pleased with the results. In fact, it is precisely because of your column that I use Propellers in the first place, and I use a lot of them now.

In case you ever wonder, thank you. Seriously :-)

Thanks. I'm glad you enjoy the column. I love Propeller programming and hope that I can convey that joy and teach others that may be laboring with less fun devices.