3

I am looking at Adafruit to purchase some LED strips for a mod for my computer case, and want to power it with an Arduino.

I am looking at the Uno, but the Mega looks good too. I hear the Uno is good because if the chip fries, you can just replace it easier than the Mega's chip. I did hear that the Uno chip had issues, but that was a 2013 post.

Anyways, I am essentially looking to connect about a foot of 144 leds/m to the front of my case, and connect that to the Arduino. I will then be lining the inside of my case with about 12-15" per side (x4 sides) of 60 leds/m so I wanted to connect that to another part of the Arduino.

I read that each led takes something like 6mA or 60mA each, so that is what we should watch for. I was trying to search for this question that others asked, but people were looking to connect a lot of strips, and needed relays and whatnot, so I wanted to make sure the Arduino itself could power about 1.5 to 2 meters of Led strips in at least 2 different strip configs (or whatever you want to call them).

I also am curious if there will be an issue programming each strip setup or, if it just is a little more work to get it setup?

Since this is a computer cause led setup, I'm not sure if I should go USB power, or a wall charger? What is the recommended approach for something like this?

I will definitely be reading up more tutorials and all that important stuff, but I want to buy the stuff now since I realized there's a cyber Monday deal going on, so I don't want to miss out...

Any help is appreciated, thank you!

5

Yes, the current draw is the main factor here. That's not really an Arduino issue though, as I will enlighten you about later on when I talk power supplies.

I assume, since you don't mention what the LEDs are, that you are talking about strips of WS2812 "NeoPixel" LEDs (the ones where you can control the colour of each and every individual LED).

I would recommend keeping all the LEDs as one single strip. That doesn't mean you can cut the strip into segments, just join the ends to each other using wire in one chain. That way you just have one chain to deal with in the Arduino. Running multiple chains can be somewhat more resource hungry and I'm not even sure it's possible on an Arduino. So keep it all as one long chain split into chunks and re-joined with wire.

Now for power. Your computer has a big powerful power supply in it. That gives a very good regulated 5V supply with many many amps available. More than enough to run hundreds of LEDs. By all means run the Arduino from USB (makes for easy programming - inspect your motherboard, it may well have an internal USB connector that would be ideal (I know mine has). And then run the LEDs themselves off the +5V direct from the computer's power supply. A spare hard drive power connector could be good for that.

  • Thanks for the information. I'm not sure if there are different kinds, but I'm looking at these adafruit.com/products/2328 I'm not sure if the Dotstars are needed over the Neopixels, but they aren't that much more expensive I guess.... So multiple chains aren't a good idea for this? Is there anything that can run them? I'm just not sure if a I can connect 144 and 60 led strips together? Also where would I add in the second power connection since ti seems after a meter things start to get dimmer? For the psu I pull off one of the 5v+ plugs from lets say the 6 pin molex/sata – XaolingBao Dec 1 '15 at 0:59
  • and then connect it up somewhere on the Arduino (will find out obviously). I was hoping I could connect it directly to the MB, so that's good. So I run the Arduino off of the usb, but I run the LEDs from a 5V+ rail? I figured I ran the LEDs right from the Arduino? I also read that I could connect multiple Arduinos together with something like the wifi or another shield? Would that be a smarter approach, but Idk if I need to spend another 25$...? Thoughts? Thanks! – XaolingBao Dec 1 '15 at 1:01
  • They look similar to the WS2812 but I think they are "lighter" on the MCU, so you should be able to have multiple chains. Connect the +5V direct to the LEDs +5V, the LED's ground to both the Arduino ground and the PSU ground, and the LED's data line(s) to the Arduino. Power the Arduino from USB. – Majenko Dec 1 '15 at 1:05
  • Hmm so you think the dotstars will be good then ? So I would need some sort of wire splitter or something or how do I connect all of this jazz to the Arduino? I'm not sure what "necessary items" I need to buy.... How can I figure out if I 100% can use multiple chains or not? I'm not sure if there is anything on ADafruit's site, or if I should check the forums or what not... Thoughts? Thanks! – XaolingBao Dec 1 '15 at 1:10
  • Dotstars look good, yes. You don't need any fancy wire splitters, just some wire cutters and electrical tape will do the job. A soldering iron is probably needed too. I haven't used the Dotstars so I can't say for sure if you can do multiple chains or not - best look at the manual, libraries, examples, and see if anyone else on here has first hand experience of working with them. I'm sure someone else can chime in. – Majenko Dec 1 '15 at 1:36
1

The important thing to understand here is that there are two things going on:

  1. Powering the LEDs – that's the big power draw and it makes a ton of sense to do that off of the computer power supply.

  2. Controlling the LEDs – that'a a very small load, using one (NeoPixel et al.) or two (DotStar et al.) pins on the Arduino. So there is no need to do anything fancy, you should have more than enough drive in the Arduino pin(s) to handle the LED control.

You might want to take a look at the FastLED library (or head directly to the GitHub repo) it explicitly support multiple strands of LEDs (and interchangeably supports a whole slew of LED type including NeoPixels and DotStars. I think, but haven't tried, you could support multiple strands of NeoPixels by creating several instances and giving each instance its own pin.

DotStars come (if you get a "finished" end) with a connector that has all four wires (Vcc, Gnd, data, and clock) as well as two additional wires for "bulk" power. But if you don't get a finished end you would just solder to the pads that are at each cut point. You probably want to power the strip(s) in parallel – feeding them from each end so that the LEDs at the end don't see too much of a voltage drop.

  • Thanks for the tips, much appreciated. I was confused thinking the power was directly from the Arduino. I've seen peopel use the PSU itself, so I guess I just rip out one of the 5V+ and a ground from the LEDs to the Arduino and PSU? The issue I'm having is I'm going to be using some 144 LEDs/m and some 60 LEDs/m, so I'm not sure if they are compatible, or what...? Thoughts/ Thanks! :) – XaolingBao Dec 1 '15 at 3:00
  • Yes, that's right – either use a spare disk drive connector or put in a wye connector to tap one. I'd be surprised if you didn't have spare. The 144 LED/m and the 60 (and 30) LED/m tapes are all compatible. For the strips that you want to run the same "program" chain their data lines together. If you want to control a strand separately, give it its own data line (on the DotStars I'm not sure if you can use a common clock with individual data lines for segments with different programs, but it seems like that might be possible. – dlu Dec 1 '15 at 3:07
  • I have a few 4 pin molex connectors from my previous build, but I noticed the pSU I'm looking at has a 6 pin molex/Sata, so I'm not sure what that's about compared to the 4 pin... There is the 4 pin connector thing on Adafruit's site, but it's out of stock for now :(. Would it be better to get one of those or...? I feel like I have a lot to read up on! I'm also hoping to turn on the Arduino when my comptuer turns on. Not sure how difficult that is. I'm looking at one of the Keypads, so it would be interesting to turn it on with a keycode :)! – XaolingBao Dec 1 '15 at 3:10
  • The wires should be color coded, one of the easier things to do would be to cut off the Molex connector and go directly to the strip (or just pick a connector that you can easily get (like spade or bullet quick connects). If you power the Arduino via USB from the computer it will power up with the computer. – dlu Dec 1 '15 at 3:14
  • Yeah, I believe red is 5V+? I'm not sure I follow what you mean by "cutting off the molex connector" do you mean just taking out the red wire or..? I'll look up the quick connects though. I could power the Arduino from the wall and then have the computer be turned on from the Arduino right? Thanks! – XaolingBao Dec 1 '15 at 3:26
0

The other answers you have here cover the points well, just to offer my $0.02.

Using a wall adapter

It's really not necessary to use a separate wall adapter and you'd be adding another layer of complexity unnecessarily. So don't bother. Also with a wall adapter you would have to consider grounding it to the computer's power supply, not necessarily an issue, but not required if you use internal power.

Powering your LEDs

your computers power supply is more than capable of handling EVERYTHING you've mentioned (unless you're already maxing it out, which I doubt).

Just make sure that you're powering the LEDs directly from the computer's power supply, and not from the (arduino) board itself, since that 5v is limited to 500mA from the USB connector, and definitely don't drive the main power from a data pin (I'm sure you know that—but just in case :P)

If you do split the strip (running two strips shouldn't be a problem) be sure to provide power where ever you can, ie each end, even in the middle. It will aid in providing even power throughout the strip.

Powering the Arduino

I'd be running the Arduino off it as well, either grab a header cable off the board that has an end you could plug into your arduino and mount it inside, or feed a USB cable through the back and use one of the extra external USB ports. A bonus of running it outside would be you could physically reset the board by unplugging it :) or simply turning it off by doing the same.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.