SparkFun Forums

[gormly]

For the sparkfun project: Addressable RGB LED Music and Sound Visualizer.

I would like to build this project to see how it works, get my hands dirty and get into this kind of stuff. It's a simple 1 meter visualizer. Cool but not what I truly want.

My ultimate goal is to create a floor lamp style music visualizer. It will output white (or white-ish) light when I want to use it as a lamp and then do it's thing to the music when I want it to. To do this, I will need to power and control at least 5 meters of addressable LEDs. Unfortunately my knowledge of power and how it relates is what is holding me back. Component layout, soldering, programming, I have a handle on all of that, what I want it to DO is not the problem, how to power it properly is.

But first things first, this project lacks a power supply in the tutorial, or the add to cart list of items. It states on the red board page that you can "Check out the related items below for a compatible wall-wart power supply.". However, the only power supply I see is a 9V 650ma. The projects red board specs says any power supply in the range of 7-15VDC. Does this mean the board takes in 7-15 but outputs 5V? I assume yes. I know this may seem like a silly question but I am a power newb.

Is that the appropriate power supply? Is it that "easy"? Just calculate?

I checked online calculators and it seems like one meter strips can be powered by anything pretty much, the 9V at 650ma puts out 5.85 watts so enough to power the suggested 1 meter 60 led strip they provide in the project (yes?). I also checked amazon for cheaper addressable strips (because the 5 meter here is really expensive) and many comment say you need 10 or more watts to power that many LEDs. This is where I am stuck for the floor lamp idea. I am not sure how to calculate what I need and I am also not sure if simply changing the power supply would be "enough". Is it plug and play in that sense?

So two questions:

1. If I buy and build this specific project step by step, do I also buy that particular power supply, the 9V 650ma?
2. If I swap the 1 meter strip for the 5 meter, can I simply use a different power supply?

I am completely lost when it comes to power and its kind of embarrassing, I pride myself on being at least average in the smarts department, any help would be appreciated.

[darrellg]

Sparkfun has many fine tutorials, but I find that the Adafruit tutorial on this subject is superior. You can find it at https://learn.adafruit.com/adafruit-neo ... e?view=all. It addresses the areas you are asking about.

[gormly]

Thanks darrellg

The Adafruit tutorial is focused on NeoPixels and Arduino and lots of power information, which is good. I could confidently know what I could power with that setup arduino/neopixel. It also made me realize that you can't just add a beefier power supply and make it work (not to the arduino controller board I mean)

I also "get it" now, the 5V pin is the absolute power source for the led strip if powered by the controller board, so there is a ceiling of how many leds which depends on the draw at full brightness for each pixel/led. Whew!

However... this isn't an Arduino and it's not a neopixel strip and I seem to be lacking the same information that article gives for this project.

For example, the article you linked for me states "The Arduino can continuously supply only about 500 milliamps to the 5V pin" That's just 2.5 watts, not enough to power what I want according to the specs on the various strips on amazon because that is the ceiling of the audrino, for something longer or with more LEDs I would have to power the strip separately (so two power cords?.. yuck) if using an Audrino.

So what does the sparkfun red board 5v pin output? Is it the same? 500ma?

I am confused... LOL.

Is there a spec sheet I am missing that shows what the output of the sparkfun board 5V pin is? I like to know what the maximum length/num of leds I could use would be.

[darrellg]

The Redboard is going to supply about the same as an Arduino Uno. There is a linear voltage regulator on the board that converts the input voltage to 5V, but it has a limited capacity and will not power anywhere close to the number of LEDs as you plan on using.

The best and safest way to power your project is to use two power supplies. The strips can be powered from a separate, high current supply, while the board uses a 7-15V low current supply. As long as the grounds are connected together, your project will work great.

You can use one high current 5V supply to power everything by connecting it to both the strips and the 5V pin of the board, but if your supply loses regulation and the voltage exceeds about 5.5V, it will damage the micrcontoller. Most of the Arduino documentation says not to power your board this way for that very reason.

[gormly]

Thank you again, you have solved the riddle for me. I wanted to power a long strip, enclose it in a nice base (I have other skills lol) and use one single power cord all nice and neat. Now that I understand it (sort of) I get it. Unless you're truly a professional or electrical engineer, or the project has low power requirements, these projects will always just be "projects".

>You can use one high current 5V supply to power everything by connecting it to both the strips and the 5V pin of the board, but if your supply loses regulation and the voltage exceeds about 5.5V, it will damage the micrcontoller.

I assume this means that if you strip the transformer plug, splice the wires and connect a wire from the power supply directly to the pin on the board and bypass the power connector on the board.. yes?

It seems like there should be a legit type splitter of some sort or a way to power both from one power supply, bare wires to the LED but a plug to the female power socket on the board? That solves that issue no? (but not using the "pin" on the board but rather the plug socket which I assume has regulated protection from spikes coming from a dubious power supply.

Not sure if I am explaining it right. But the gist is, connecting to the board pin is bad.. connecting it to the power in socket is OK... yes?

[darrellg]

When I do it that way, I put the board in a project box and add a panel mount power jack. I can't seem to find one on the Sparkfun site, but they do have this: https://www.sparkfun.com/products/10288.

You do have to connect the 5V supply directly to the 5V pin on the board instead of the power connector. Do so bypasses the on-board regulator, which requires a couple volts above the target voltage to operate, hence the 7-15V requirement. As long as you use a quality, regulated supply, it should be safe.

[gormly]

darrellg, thanks for responding, I appreciate the time you are giving me here and it's all coming together for me

>When I do it that way, I put the board in a project box and add a panel mount power jack.

I get what you are saying, but that still leaves an issue I am unsure of. Perhaps you can help me with that? The amperage.

Over the course of the last few days I have put a lot of time into trying to learn all of this stuff. I kind of see now how I could use one power supply and a regulator to provide a stable 5V to the sparkfun pin, but it's the amps that deliver power needed to the LEDs

So my thought is 5V 10A Power supply to plug of barrel jack connector then:
barrel jack connector > to a Pololu 5V Step-Up/Step-Down Voltage Regulator > Sparkfun 5V input Pin
barrel jack connector > split to LEDs

But what about amps? Does it matter in any of this? I think I get it but not sure, amps are there but they must be asked for..or "drawn" yes?

To power a long LED strip, it seems I might need a 5V power supply with as much as 10A. With 10A I could power more than enough LEDS for my project idea.

So if I connect that 5v 10A power supply to the barrel jack connector and through the regulator will the spark fun board be "safe" from the amps? The LEDs will only draw what they need and the spark fun board will also?

[darrellg]

If you are using a regulated power supply, there should be no need for the Pololu 5V Step-Up/Step-Down Voltage Regulator.

Each device will only use as much current as it needs. You could have a power supply with 5V 1000A capability, and the board will only use what it needs.

The current required by your LED strips will depend on how many LEDs there are, how many are lit at a time, the brightness setting in your program, and the colors you are using. With RGB devices, if you only use red, green or blue, then only one junction at a time will be lit. If you use cyan, magneta, or yellow, two junctions will be lit (red+green is yellow, red+blue is magenta, green+blue is cyan), if you use white, then all three junctions will be lit. Each junction can use up to 20mA at max brightness, which is 60mA when showing white at max brightness.

If your strip is more than a couple meters long, you may find that the LED on the far end don't show the right colors. That would be because the traces on the strip have enough resistance to cause the voltage to drop enough that the LEDs won't operate correcly, especially the blue ones which have a higher voltage drop. You can feed the power from both ends to fix that.

[gormly]

>If you are using a regulated power supply, there should be no need for the Pololu 5V Step-Up/Step-Down Voltage Regulator.

I thought of adding that regulator because you let me know that power issues could hurt the board if connected through the pin and not the power connector, like a 5.5v instead of 5v, so I figured just to make sure...

"but if your supply loses regulation and the voltage exceeds about 5.5V, it will damage the micrcontoller. Most of the Arduino documentation says not to power your board this way for that very reason."

But I get it. A decent 5V supply should be just fine.

I was kinda worried about the amps mostly, like using a 5V 10 amp power supply, splicing it off to the 5v on board and also the LEDs. That "solves" the problem. 5V goes to the pin and draws whatever amps it needs and the rest up to it's limit can power the LEDs. I assume as long as the LEDs do not draw more than say 9.5 amps, nothing "bad" will happen. So I will make sure the length/number of LEDs does not exceed the need. 60mA per led assumed. 9500/60 gives me 150 or so LEDS (at full white brightness).

I think I get it, I am going to try out this project as is on their tutorial and then experiment slowly.

I REALLY appreciate your knowledge on this, thank you very much. This is all stuff I didn't know just a few short days ago.