Question about putting together a custom PCB to help me clean up my new

Electronics FastLED Archive
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#1

Question about putting together a custom PCB to help me clean up my new light project. I have 4 windows each with a 4m strip of Neopixels, running from a Mega with FastLED. My question is, using ExpressPCB (or any board service I guess) to build a custom PCB, how big do the +5v power traces need to be for each strip? Has anyone done this? Can anyone help me? I don’t think a 4m strip would draw that much power, but voltage drops and overheating a trace are a concern (it’s under my couch in the living room). Note that they may be running all white, but brightness will be 75% or less most of the time (they are very bright otherwise), and generally, they will just be blinking some representation of holiday colors. Well, on the 4th, one window will be white 100% of the time in a flag layout (less bright though).

Thoughts? I really just want to do this with cheap stuff from Fry’s and Adafruit, but don’t want to burn down the house, or watch the lights fade or blink out due to a voltage drop.

#2

If I understand, you have 4 windows with 4 strip each for a total of 15 strips but how many LEDs per strip ?

#3

:slight_smile: 4X 4 = 15 !?!?
Sorry twas a typo ! :slight_smile:

#4

16 total, at 30 per strip. Sorry, there are 120 per strip, for a total of 480 in the system.

#5

I guess you meant 120 per window… :wink:
and 480 LEDs total for the room.

With every pixel full on white = 480 X 60ma = 28,8 Amps !!!

I would design for that maximum myself but if you are 100% sure that you would never exceed 75%… it is your choice.

Have a look here… ttp://http://www.smps.us/pcb-design.html

It is gives very nice guidelines about PCB design, if you are going to do it yourself.

#6

Thank you for the link. I’m pretty sure based on the Neopixel descriptions that < 500 will no draw 30 amps. I suspect it’s far less than that. But, I need to figure out the specifics before I do this. I’m hoping someone else has done something similar and can provide feedback on experience.

#7

I just checked Adafruit’s specs and for a single 30 LED 1Meter strip they specify ~ 2 Amps so if you multiply this by 16 strips…

#8

Yeah, you’re right. They say 10A for 10m, but I think they assume you aren’t going to run white full bright ever. Crud, that’s a lot of power.

#9

I do have experience with PCB design and have some experience with multi RGB LED projects… and of course it is likely to be far less current in a typical animation but…

you are concerned with voltage drop and heat and I would recommend that you design with maximums in mind.

Please remember you will be sticking this under a couch in your living room !!!

#10

OK a few suggestions/guideline…

  1. For power traces on a PCB, make them as wide as you can in the space that you have available.

  2. You can always solder a low gauge wire on top of the power copper traces on the PCB to beef-up its current handling capacity.

Here’s another link to wire gauges and current carrying capacity…

http://www.engineeringtoolbox.com/wire-gauges-d_419.html

#11

That was the suggestion from the guys here at work. And ExpressPCB has some guidelines that seem awfully small, but the added wire would work just as well. Thanks for the help.

#12

I did not look into the ExpressPCB guidelines but would assume they describe individual power traces to small components and ICs not a heavy current distribution scheme.

#13

Well, I suspect this comes up a lot, so they do. http://expresspcb.com/ExpressPCBHtm/Tips.htm

#14

Well… you indicated that their guidelines seem awfully small but I see now that they do provide a sensible PCB design guideline for heavy power traces.

Good luck with your design and make sure you show off your work when it is ready !

#15

Yeah, thank you for the help and sounding board. I actually have a pretty sensible plan now I think. Can’t wait to get it put together.