I have a question about wire distance. I want to create my own front walkway lighting. I figure I can use either the neopixel stick or the neopixel jewel in a custom housing to line my walk way. Figure between 15 and 20 total housings. But they will have about 4 ft of wire between them. Is that a problem? I want to drive all of these from a single Micro in a small weatherproof enclosure. Can I do this spread so far apart, or will I need to make some compromises?
I have been able to do things like this. I use cat5e cable (data/ground on a twisted pair). Watch for power voltage drop across your distances as well
Peter,
Sounds very doable! Lets talk about power and data separately. The “neopixels” are the pseudo-name for the WS2811/WS2812. These do not have a clock signal, so the data line is limited to about 10-15ish feet before the signal potentially starts acting flaky. But everytime the signal hits a pixel, it gets re-transmitted and you are good for another 10-15ish feet. So your 4ft spacing sounds fine. Now lets talk about power. I would use 18awg or heavier cable to be physically robust for an outdoor application, but also to minimize voltage drop on the wire (voltage drop goes up as current goes up ala V=IR). So measure the voltage @ the beginning (aka 5v) and measure the voltage at the end when all the LEDs are @ white. Ideally you want it to be close to 5v. Down below 4v and the greens and blues start to dim and your colours shift.
I’m sure others will share more insight.
respect,
frenchy (Steve French)
http://www.voltvision.com
@Steve_French by using cat5e cable and 5v level shifters (if using something with 3.3v outputs) I’ve gone over 50’.
@Daniel_Garcia , nice! I’ve done that with WS2801, but not with WS2811/WS2812. So, when you did it, did you use one twisted pair for GND/Data? What about power? Did you have fresh power waiting for you on the other end or did you try to send power over the unused cat5 pairs? Some cat5 is 24awg and some is 28awg…either way there is definitely lots of considerations trying to send power over cat5! Regarding level shifters, I am experimenting with buffers/translators right now, but for some reason I just had the ridiculous thought of sticking a pixel on the front and making that be a level translator…hmmm…
I ran power separately - you’re pretty limited on the amperage you can get over cat5e so I haven’t experimented much with it yet.
Wow, that’s good to know. This might actually work fairly well. A TP connection and then a molded 18 AWG pair should probably be a pretty neat type of connection between each housing. I think in this case, the stick is perfect, and I plan to create a custom PCB for this, so it sounds like a simple setup altogether. As I look at the datasheet for this, I don’t see the max current for each one. I’m a bit of newbie for HW though and may not be used to reading it. I seem to remember that each 2812 is .6ma. Is that right? It’s a 15amp circuit, I’ll be driving it through a 5v brick, and I’d like to be able to drive each segment at 100% brightness if possible.
Sorry, that should have been 6ma per LED in my last post.
60mA, or 0.06A per LED.
If you’re interested in helping me test a tool to help you make these kinds of current draw and voltage drop calculations and have an iPhone, email me your Apple ID (ratkins at fastmail dot fm).
Sorry, but I do have an iPad (latest).
Like Robert said its 20mA per LED, which for full worst-case white is R+G+B = 20+20+20 = 60mA = 0.06A per pixel. It adds up fast, so always be aware. If you start to use more and more pixels, then perhaps your wire gauge needs to go up or else distribute your power supplies.